[Index]
Monthly Global Tropical Cyclone Summary July 2000
[Summaries and Track Data] [Prepared by Gary Padgett]
| Tropical
Cyclones
[Index] |
Monthly Global Tropical Cyclone Summary July 2000 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
JULY, 2000
(For general comments about the nature of these summaries, as well as
information on how to download the tabular cyclone track files, see
the Author's Note at the end of this summary.)
***********************************************************************
JULY HIGHLIGHTS
--> North Pacific quite active
--> Twin typhoons affect several East Asian nations
--> Rare Central North Pacific storm forms
--> Hawaii affected by dying Eastern Pacific hurricane
***********************************************************************
***** Topic of the Month for July *****
SEASONAL STATISTICS FOR THE EASTERN NORTH PACIFIC
The material presented below was compiled by John Wallace, a student
at the University of Texas in San Antonio. John became very interested
in tropical cyclones during the exceptionally active 1995 Atlantic
hurricane season, and as he puts it, "started me on a crash course in
tropical meteorology readings"--much the same experience I had had
30 years earlier, although it only took the very average 1963 season to
get me started. John relates that after coming across the annual
seasonal summary articles in _Weatherwise_, he was surprised to learn
that the Northeast Pacific basin usually saw much more tropical cyclone
activity than the Atlantic; yet, only rarely did one find articles
written about tropical cyclones in this basin.
At about the same time, John became familiar with the seasonal
forecasts of Dr. Gray and the CSU team and decided that the Net
Tropical Cyclone (NTC) activity index was an ingenuous way to measure
the overall "punch" (or lack thereof) of a season's activity. So John
gained access to the Best Track database for the Northeast Pacific
and tabulated some statistics for this basin and calculated the NTC
and Maximum Potential Destruction (MPD) according to Dr. Gray's
formulae. The remainder of this article is as I received it from
John with some minimal editing by myself.
-----------------------------------------------------------------------
The first version of this table, with commentary, was completed in
mid-1999. In it I used a 1975-1997 baseline and used "Named Tropical
Cyclone Days" instead of Gray's canonical Named Storm Days--similar,
except that the depression stage was included. As I didn't know the
formula, I didn't calculate Maximum Potential Destruction (MPD). Gary
Padgett was the first to review it, and he commented favorably though
he considered it unwise to include the depression stage of storms. He
also stated that reconnaissance data gave NEP data high reliability
going back to 1971. I had limited the first study to the beginning of
the use of the Dvorak technique (1975). Finally, he explained how to
calculate MPD and Hurricane Destruction Potential (HDP).
Buoyed by the new info, but also disheartened by its imperfections,
I let the project rest for awhile, and when I resumed it I got rid of
cyclone days and replaced it with storm days, extended the baseline
back to 1971 and forward to 1999, and included the MPD. Unfortunately,
HDP was too tedious to calculate with the available tools.
A full description of the eight parameters in the table below would
needlessly lengthen this article. Definitions can be found on the
Colorado State University Tropical Meteorology site:
http://typhoon.atmos.colostate.edu/forecasts/2000/august2000/
definitions.html>
I will, however, simply explain the abbreviations:
NS: Named Storms (includes unnamed storms added in post-analysis)
H: Hurricanes
IH: Intense Hurricanes
NSD: Named Storm Days
HD: Hurricane Days
IHD: Intense Hurricane Days
MPD: Maximum Potential Destruction
NTC: Net Tropical Cyclone Activity (%)
Eastern North Pacific Seasonal Parameters
1971 - 1999
YEAR NS H IH NSD HD IHD MPD NTC
1971 18 12 6 83.75 38.50 6.00 122 111
1972 12 8 4 80.25 33.75 4.50 82 85
1973 12 7 3 61.75 28.50 7.25 89 78
1974 17 11 3 62.00 22.25 2.50 94 79
1975 16 8 4 68.25 26.75 5.50 90 85
1976 14 8 5 58.00 22.50 9.75 95 89
1977 8 4 0 20.50 5.25 0.00 31 23
1978 18 13 6 97.25 48.25 14.75 128 138
1979 10 6 4 33.75 13.75 3.25 72 56
1980 14 7 3 48.25 22.75 2.75 71 66
1981 15 8 1 57.00 18.00 1.00 68 58
1982 19 11 5 93.25 37.25 7.50 115 111
1983 21 12 8 109.50 47.50 16.00 151 150
1984 18 12 6 95.50 44.25 14.50 133 133
1985 22 12 8 101.75 44.50 8.50 140 134
1986 17 9 3 62.00 28.25 6.75 89 86
1987 18 9 4 69.25 24.75 7.75 102 92
1988 13 6 2 54.75 21.00 3.50 76 61
1989 17 9 4 67.25 27.25 5.75 95 88
1990 20 16 6 120.25 58.25 20.25 157 166
1991 14 10 5 86.25 44.00 14.00 102 119
1992 24 14 8 135.00 57.00 18.25 172 172
1993 14 10 8 79.25 45.50 15.25 137 130
1994 17 9 5 89.25 35.75 18.00 135 123
1995 10 7 3 51.75 22.25 9.00 75 74
1996 9 5 2 32.00 13.00 3.25 54 46
1997 17 9 7 72.50 33.50 15.00 138 120
1998 13 9 6 62.75 33.00 10.75 98 102
1999 9 6 2 46.50 23.50 6.00 57 61
Avg. 15.6 9.3 4.6 73.3 32.0 9.0 104 100
The NTC was calculated using the 1971-1999 averages of NS, H, IH,
NSD, HD, IHD. The rounded averages of 16 NS, 9 H, 5 IH, 73 NSD, 32 HD,
and 9 IHD were used for the calculations; the difference between the
rounded and decimal answers was found to be negligible. These figures
only include storms that formed (or were classified as such) east of
140W, and for the entire lifetime of the storm--storms of Central North
Pacific origin are not included. For all the parameters, the average
NEP season has an NTC roughly 170% of the 1950-1990 Atlantic value. An
interesting coincidence that I noticed is that there are several years
in which the MPD and NTC match, or nearly so: 1972, 1983, 1984, 1986,
and 1992 are some examples.
-----------------------------------------------------------------------
As John notes above, he included only storms forming in the Eastern
North Pacific proper (i.e., east of 140W), but in the NSD, HD, and IHD
parameters included the entire lifetime of each storm, regardless of
whether it was east or west of 140W (or 180 for that matter). I
calculated two alternate sets of statistics for the basin:
(1) including only storms forming east of 140W and including only the
portion of tracks east of 140W for the various days parameters
(2) including all storms forming east of 180 and including only the
portion of tracks east of 180 for the various days parameters
I found that my NTC1 values were just about all within 10% of John's
except for 1992 and 1994 with the latter year showing the greatest
divergence. This was due to the large number of ENP cyclones forming
farther west than normal and moving into the CNP, most notably Category
5 hurricanes Emilia, Gilma, and John. But my NTC2 parameter matched
John's almost exactly for 1994. My NTC2 parameter was most different
from John's NTC in 1992, no doubt due to my inclusion of the intense
CNP hurricanes Ekeka and Iniki. The only other year in which my NTC2
showed a difference of more than around 10% was 1988; due most likely
to John's omission of CNP Hurricane Uleki.
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for July: No tropical cyclones
Atlantic Activity for July
--------------------------
No warnings were issued on any tropical systems in the Atlantic
basin during July. A fairly vigorous disturbance noted over Africa
on 7 Jul had moved off the coast by 0000 UTC on 9 Jul and displayed
a quite well-organized cloud pattern somewhat similar to the monsoon
depressions of the Western Pacific. However, this system did not
develop any further. (Thanks to Mark Lander for supplying some
satellite imagery of this disturbance.) For a two-week or so period
around mid-month strong upper-level westerlies spread over much of
the tropical cyclogenetical region of the Atlantic--likely related to
circulation anomalies in the Southern Hemisphere--and no tropical
wave had much of a chance to develop. By late in the month the shear
had relaxed and a tropical wave crossing the Atlantic from around the
27th through the 30th displayed a fairly tight swirl of low and middle
clouds but could not generate enough sustained central convection to
allow further development.
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for July: 2 tropical depressions
2 tropical storms **
1 hurricane
** - One of these storms weakened in the Central Pacific but later
redeveloped into a tropical storm in the Northwest Pacific basin
NOTE: Much of the information presented below was obtained from the
TPC/NHC discussion bulletins issued with every regular advisory (CPHC
for locations west of 140W.) All references to sustained winds imply
a 1-min averaging period unless otherwise noted.
A special thanks to John Wallace for writing up most of the report
on Tropical Storm Upana-Chanchu. I added an introductory paragraph
and wrote the portion covering the redevelopment of the system as
Chanchu in the Northwest Pacific basin.
Northeast Pacific Activity for July
-----------------------------------
Tropical cyclone activity had been just about normal in the North-
east Pacific basin during June, although Carlotta's intensity was very
unusual for June but not unprecedented. However, July was a little
less active than average with only two named storms and one hurricane
forming east of 140W in the Eastern North Pacific proper--only half of
the normal 4 storms and 2 hurricanes. In addition to these cyclones,
a rare Central North Pacific tropical cyclone formed--the first named
storm on record to form in that area during July since the era of
satellite coverage began.
At the end of June a westward-moving disturbance more than 1000 nm
west-southwest of Cabo San Lucas became quite well-organized and was
on the verge of being classified as a tropical depression on 1 Jul.
However, the thunderstorm activity became somewhat sporadic and no
advisories were issued at the time. The TWO for 1000 PDT on 2 Jul also
indicated that the system was likely to become a tropical depression
within the next 24 hours, but once more the trend toward increased
organization levelled off and the system subsequently weakened.
In addition to the two named storms (Daniel and Emilia), plus Upana
in the Central Pacific, advisories were issued by TPC/NHC for two
tropical depressions in the Eastern Pacific. The first of these,
TD-04E, formed from a tropical wave that left the African coast on
20 Jun. The wave tracked uneventfully across the Atlantic for the
next ten days. Upon entering the Eastern Pacific on the 30th, a weak
tropical LOW formed along the wave axis. Development was apparently
hindered by a well-defined upper-level LOW to the north. Conditions
slowly improved as the LOW tracked westward, and it was upgraded to
TD-04E at 2100 UTC on 6 Jul when it was located approximately 900 nm
southwest of Cabo San Lucas, Mexico. However, the depression soon
entered a hostile environment and had fallen apart by around 1500 UTC
on the 7th. (Thanks to John Wallace for writing up some information
on TD-04E.)
TD-05E likely developed from a tropical wave which was identified
on 9 Jul in the eastern Atlantic southwest of the Cape Verdes. This
wave had entered the Pacific by 18 Jul and a 1010-mb LOW formed on the
wave axis on 20 Jul. The LOW passed south of Socorro Island on the
21st, still continuing to show increased convective organization.
Advisories were commenced on TD-05E at 2100 UTC on 22 Jul when it was
centered about 375 nm west-southwest of Cabo San Lucas. However, even
as it was upgraded the depression was beginning to move over cooler
SSTs, and by 23/0300 UTC was already over 24 C water. The convection
that had been present earlier quickly vanished and the depression was
declared dissipated at 1500 UTC on the 23rd.
Tropical Storm Upana-Chanchu (TC-01C/12W / TS 0007)
20 - 30 July
----------------------------------------------------
Upana: a Hawaiian name, is the transliteration of Urban
Chanchu: submitted by the colony of Macau, is the Macanese word for
pearl
The first Central North Pacific tropical cyclone to be named in
three years was a rather insignificant system to have had so many names
and numbers. There seems to be pretty good evidence that the
development just west of the Dateline on 28 Jul was a re-development of
the former Upana, but perhaps there was sufficient enough doubt at the
time that the responsible JTWC forecaster decided to assign a new
number when that agency initiated warnings on the depression. It
should be pointed out that the official policy of the ESCAP/WMO Typhoon
Committee regarding "Dateline crossers" is that the original name
assigned by either NHC or CPHC will continue to be applied whenever a
cyclone moves west across the 180th meridian. However, warnings on the
earlier Tropical Storm Upana had been dropped for several days, and
with a new number assigned by JTWC, it seems likely that JMA decided
assigning a new name was the best policy to follow in this case.
Upana was the first Central Pacific storm on record to form in the
month of July since good satellite coverage began in 1966. An
unofficial contender for the title is Tropical Storm Emilia of 1982:
the best track data indicates tropical storm intensity was reached just
west of 140W. However, that figure is probably due to the vagaries of
best track data versus real-time warnings since there is often an
adjustment. In any case, Upana was the first official July storm
forming in the CPHC's area of responsibility and receiving a Hawaiian
name. Upana was also the first Central Pacific storm to form in almost
three years--since Paka in 1997.
The origin of Upana can be traced to a well-defined tropical wave
that tracked off the African coast on 28 June. It initially had a
strong mid-level circulation, but this quickly dissipated, and the
disturbance tracked uneventfully across the Atlantic. Even in the
Pacific, the wave showed no signs of organization until it reached
138W, whereupon it transformed into a tropical LOW on 17 July.
The LOW's organization increased steadily, and was sufficient to
warrant its upgrade to Tropical Depression One-C at 0300 UTC on
20 Jul roughly 800 nm southeast of Hilo, Hawaii.
The depression formed under a rare set of favorable conditions; its
low latitude kept it just south of strong westerlies to its north as
well as south of the cooler waters that usually weaken tropical
cyclones east of Hawaii. The westward track was influenced by the
strong subtropical ridge to its north which ensured it would present no
threat to the Hawaiian Islands. Shear was favorably low, and SSTs were
adequate; steady intensification seemed likely. A slightly improving
satellite presentation warranted One-C's upgrade to Tropical Storm
Upana at 2100 UTC on the 20th, roughly 650 nm south-southeast of Hilo.
After its upgrade, Upana intensified only slightly over the next day
to a 40-kt MSW with a CP of 1006 mb by 0900 UTC on the 21st. This was
to be Upana's peak intensity, and was maintained for only a day. The
storm generated strong, but ragged and ill-defined, convection, a fact
exacerbated by its unusual westward track through the ITCZ. Upana's low
latitude did not favor much intensification, and as the 21st wore on
its organization steadily decreased as shear began to impinge on the
system. Upana dropped below storm strength at 2100 UTC on the 22nd
about 700 nm south-southwest of Lihue. Its dissipation seemed certain;
the LLCC was exposed and devoid of deep convection. Surprisingly, the
depression underwent a minor intensity fluctuation on the 23rd as
strong convection redeveloped over the center. As shear was relatively
low and Upana was entering warmer waters, re-intensification to
tropical storm status was forecast. This, however, did not happen.
The LLCC remained difficult to locate and the track was adjusted
southward early on the 24th as the circulation dissipated and
convection collapsed. The final advisory on Tropical Depression Upana
was issued at 0900 UTC on 24 Jul with the center located roughly 425 nm
south-southwest of Johnston Island. It is worth noting that the
depression may in fact have dissipated earlier and redeveloped
completely--a scatterometer pass near 0500 UTC on the 23rd indicated
an open wave with no closed circulation.
No damage or casualties are known from Upana; it was never less than
550 nm from Hilo. Following the issuance of the last advisory from
CPHC, the post-Upana disturbance was not mentioned in the STWOs from
Honolulu except that the Outlook for 4PM Hawaiian Standard Time on
26 Jul carried a short note that the remnants of Upana had moved
west of the Dateline. A STWO issued by JTWC at 26/0600 UTC mentioned
an area of convection located about 900 nm east of Kwajalein and moving
westward. The next day satellite imagery depicted improving
organization around a LLCC and a 26/2205 UTC TRMM pass revealed a
partially-exposed LLCC with deep convection sheared just east of the
center. A Formation Alert was issued by JTWC at 1330 UTC on the
27th, and warnings on TD-12W were begun at 28/0000 UTC.
The depression was located about 500 nm east of Kwajalein or 300 nm
east-northeast of Majuro when the first warning was issued. The
system initially moved slowly to the west-northwest and gradually
became better organized. At 1800 UTC on the 28th JTWC upgraded
the depression to a 35-kt tropical storm located roughly 470 nm east-
northeast of Kwajalein. This position represented a relocation of
about 60 nm to the north-northeast of the previous warning position.
JMA had also decided the system met tropical storm criteria and
assigned the name Chanchu to the tropical cyclone. After being named
Tropical Storm Chanchu moved primarily on a slow northward track.
The 29/0000 UTC JTWC warning brought yet another relocation of 60 nm
to the north-northeast of the previous position. Satellite intensity
estimates were 35 and 45 kts so the MSW was increased to 40 kts--the
maximum for the storm. (JMA's peak 10-min avg wind estimate remained
at minimal tropical storm intensity of 35 kts.)
Convection continued to organize around the LLCC for the next few
hours and the 40-kt MSW was maintained through 0600 UTC. Chanchu was
a small tropical storm with gales covering an area only about 100 nm
in diameter. By 29/1200 UTC convection had weakened considerably and
Chanchu's winds were dropped to 35 kts. Recent scatterometer and
SSM/I passes did not reveal a LLCC. The final JTWC advisory was
issued at 1800 UTC, placing the dissipating storm at a location about
500 nm north-northeast of Majuro. A SSM/I pass at 1824 UTC as well
as another QuikScat pass did not show any evidence of a LLCC although
low-level convergence was indicated. The weakening depression was
forecast to track northwestward and dissipate within twelve hours.
Hurricane Daniel (TC-06E)
23 July - 5 August
--------------------------
For information on the origins of Atlantic and Northeastern Pacific
tropical cyclones, I usually rely on a file created and maintained by
John Wallace of San Antonio, Texas. John scans the Tropical Weather
Discussions issued four times daily by TPC/NHC for the Atlantic and
Eastern North Pacific and maintains a running log of all the tropical
waves and LOWs referenced, naming the waves from phonetic alphabetical
lists he has selected to avoid confusion. The vast majority of such
waves can be traced back to western Africa or at least the eastern
tropical Atlantic, but in the case of the pre-Daniel disturbance,
John's log first references this tropical wave on 20 Jul when it was
already located in the Pacific south of southeastern Mexico. So if
this system had indeed originated on the Atlantic side of Central
America, there apparently was not enough information to clearly piece
together any possible earlier history of the wave. A 1009-mb LOW had
formed on the wave axis by 22 Jul when it was located several hundred
miles south of Manzanillo, Mexico.
The first visible imagery on 23 Jul indicated that the disturbance
had become organized enough to be classified as a tropical depression,
so advisories were initiated on TD-06E. At 1200 UTC the depression was
centered about 525 nm south-southwest of Manzanillo with 30-kt wind
estimates from TAFB and SAB. Infrared imagery showed cold cloud tops
to -80 C and outflow was good everywhere except on the eastern side.
Intensification proceeded steadily and the system was upgraded to
Tropical Storm Daniel on the second advisory. Six hours later the
MSW was upped to 50 kts based on 45-kt satellite estimates from the
three agencies and a report from ship PJPO of 26-kt winds and a SLP
of 1004.8 mb from a point about 100 nm northwest of the center. A
small, persistent cold CDO was positioned right over Daniel's center.
By 24/1200 UTC Dvorak estimates had reached 65 kts and a 0835 UTC
TRMM image depicted an eye-like feature, so Daniel was upgraded to
a hurricane at 1500 UTC when it was centered approximately 650 nm
south-southwest of Cabo San Lucas. The storm was moving to the west-
northwest at 15 kts and appeared to be rapidly intensifying.
By 0600 UTC on the 25th Daniel exhibited a classic appearance in
satellite imagery with a 15-nm eye embedded in cold cloud tops.
Intensity estimates from TAFB and SAB had reached T5.5, so the MSW was
increased to 100 kts at 0900 UTC, thereby making Daniel a Category 3
hurricane on the Saffir/Simpson scale. The hurricane was centered more
than 700 nm southwest of Cabo San Lucas and moving west-northwestward
fairly quickly at 18 kts. Hurricane Daniel reached its peak intensity
of 110 kts from 25/1800 to 26/0000 UTC with an estimated attendant CP
of 952 mb. After peaking Daniel's eye became less distinct and the
winds slowly decreased; however, the hurricane maintained an impressive
inner core convective structure. There was a burst of cold convection
(-80 to -82 C) in the southern eyewall on the morning of 26 Jul,
indicating that slightly cooler SSTs had not affected the intensity of
Daniel too much at that point.
The hurricane experienced some weakening on 27 Jul as it continued
westward, steered by a well-established mid-level ridge to the north.
The eye appeared to expand and the MSW was decreased to 90 kts. By
28/0000 UTC the storm presented the appearance of a very well-organized
hurricane with a round CDO and a distinct eye. T-numbers had reached
T5.5 with objective numbers peaking at T6.0. With the storm near
marginal SSTs, the MSW was set at 95 kts but the 0300 UTC discussion
noted that winds might be 100 kts. However, six hours later, even
with Daniel over SSTs near 25 C, the satellite signature had improved
to the point that winds were increased again to 105 kts. TAFB's
estimate as well as some objective Dvorak estimates were as high as
115 kts. Daniel at this time was moving slightly west-northwestward
at around 16 kts due to some weak southerly shear and a mid- to upper-
level trough passing to the north which acted to weaken the subtropical
ridge. By 1800 UTC on 28 Jul the hurricane was definitely weakening
and the MSW was decreased to 90 kts. Daniel was located about 875 nm
east-southeast of Hilo, Hawaii, and was approaching 140W, so warning
responsibility was handed to the Central Pacific Hurricane Center in
Honolulu.
After entering the Central North Pacific Daniel came under increased
shear aloft and continued to weaken. The MSW was lowered to minimal
hurricane intensity at 29/0600 UTC. The discussion from CPHC at
2100 UTC noted that some deep convection had redeveloped near the
circulation center, and with Dvorak estimates of T3.5 and T4.0 from
SAB and Honolulu, the hurricane intensity was maintained, even though
the latest scatterometer data did not confirm the presence of a closed
circulation. During the afternoon a reconnaissance airplane flew
into the storm and found a CP of 995 mb with estimated maximum surface
winds of 55 kts, so Daniel was downgraded to a 60-kt tropical storm
at 0300 UTC on 30 Jul. The storm was then located about 400 nm east
of Hilo, moving to the west-northwest. For the next day or so Daniel
pretty much held its own with winds fluctuating around 50-55 kts.
A reconnaissance flight around 1800 UTC on the 30th found winds to
50 kts and greater at flight level northeast of the center. The
LLCC was beginning to separate from the deep convection and Daniel
was beginning to move on a more westerly course that was projected to
take the weakening storm across the central Hawaiian Islands.
However, during the afternoon (local time) of 30 Jul, Daniel
strengthened slightly and took a jog to the right, likely due to deep
convection which had redeveloped to the north of the center pulling
the storm northward and allowing a greater influence from upper-level
winds with a southerly component. This jog was very significant in
that it more or less assured that Daniel's center would remain north
of the islands. A reconnaissance aircraft also indicated that the
eye had reformed with deep convection covering the LLCC once more.
The MSW estimate was upped to 55 kts in the 31/0300 UTC advisory.
This re-intensification did not last long as Daniel began to present
a sheared appearance. Winds were decreased to 50 kts at 0900 UTC and
to 45 kts six hours later. But by 31/1800 UTC, Daniel had pulled
another surprise and re-intensified significantly. The LLCC had once
more moved beneath the upper-level cirrus dense overcast and convection
was beginning to wrap around the center. CPHC increased the MSW
estimate to 60 kts--just shy of hurricane force. The storm was
centered roughly 125 nm northeast of Hilo at this time, still moving
basically on a west-northwesterly track. This strong pulsation was
apparently due to a favorable interaction with an upper-level trough
to the west. An eye became apparent as the convection wrapped around
the center. But, like the earlier intensification spurt, this one was
also short-lived. By early afternoon (local time) on the 31st, the
convection was collapsing and the eye feature had closed up.
Thereafter, Daniel slowly weakened as it moved to the west-northwest
and passed north of the Hawaiian chain. At 1200 UTC on 1 Aug the LLCC
(which was exposed) was about 130 nm northeast of Honolulu while the
nearest deep convection was about 100 nm to the north of the center.
The MSW was down to 45 kts by this time. A reconnaissance flight a
few hours earlier had found a CP of 1001 mb but maximum FLW of only
32 kts. During succeeding days convection would occasionally break
out along the storm's northern flank, the result of which was to pull
the system northwestward. Daniel gradually weakened over the next few
days, although some convection would occasionally flare up near the
LLCC despite its movement over cooler waters. The storm never really
showed any significant signs of re-intensification but the persistent
convection did serve to prevent Daniel from weakening as rapidly as
might be expected.
By 1200 UTC on 3 Aug the convection within the circulation had all
but collapsed and Daniel was downgraded to a tropical depression well
to the northwest of Hawaii. The depression continued moving to the
northwest until around 04/0000 UTC when it appeared to be turning to
the north as it "punched" through the subtropical ridge. The steadily
weakening depression moved generally northward along 170W but the
system stubbornly clung to life for another day or so by generating
a few sporadic thunderstorms mainly to the south of the center.
Finally, by 0600 UTC on 5 Aug all deep convection had ceased within
the LLCC and Daniel was declared dissipated about 600 nm northeast of
Midway Island. Except for some wobbles in the vicinity of Hawaii,
this long-lived and far-travelled hurricane followed a remarkably
smooth and regular track for its entire life.
Tropical Storm Emilia (TC-07E)
26 - 30 July
-------------------------------
The origins of the Eastern Pacific's fifth tropical storm of the
season were connected with a tropical wave first identified in the
east-central tropical Atlantic on 14 Jul. The disturbance propagated
westward, entering the Caribbean Sea on the 17th, and had emerged into
the Pacific Ocean by around 22 Jul. On that day a 1010-mb LOW was
noted south of El Salvador. The wave continued to move westward and
by the early morning of 25 Jul had become somewhat more organized.
Showers associated with the disturbance at this stage spread north-
ward and led to some locally heavy rains over portions of southwestern
Mexico.
By 1200 UTC on 26 Jul the system had become organized enough that
advisories were initiated on TD-07E. The depression was then centered
about 540 nm south of Cabo San Lucas. Although deep convection had
become less centralized over the previous six hours, the overall
convective pattern had improved. A 0748 UTC TRMM overpass indicated
a mid-level circulation in the 85 GHz channel that was about 60 nm
north of the LLCC as seen in the 37 GHz channel. Even though satellite
intensity estimates were below tropical storm strength at 1800 UTC,
later visible imagery revealed that an inner convective region had
formed with an outer band wrapped more than halfway around it. On
this basis the depression was upgraded to Tropical Storm Emilia on the
2100 UTC advisory.
While Emilia presented a very well-defined LLCC with a pattern
resembling a banding-type eye, the convection was neither strong nor
concentrated near the broad center. There were occasional bursts of
deep convection, and the MSW estimate reached 45 kts by 27/0600 UTC but
remained there until 1800 UTC when there was an improvement in the
organization of Emilia. Dvorak intensity estimates at 1800 UTC were
50 kts and 55 kts from TAFB and SAB, respectively, so Emilia's winds
were upped to 55 kts--the peak for the storm's history. The center
was located approximately 300 nm south-southwest of Cabo San Lucas at
this time. The storm maintained this intensity for about twelve hours
as it moved northwestward at 12 kts, but by 0600 UTC on the 28th had
begun to weaken. Most of the associated convection had dissipated,
and even though KGWC gave Emilia a 65-kt estimate with 55 kts from
the other agencies, the lack of convection and motion over cooler SSTs
suggested a lower intensity so the MSW was dropped to 50 kts. Some
deep convection subsequently returned to the central region of Emilia,
but northeasterly shear kept it from wrapping around the LLCC.
Since its inception Emilia had been moving on a fairly straight
northwesterly track, but upon reaching the 20th parallel, the weakening
cyclone turned abruptly to the west and followed a general westerly
course for the rest of its existence. The effects of shear and motion
over cooler waters caused the storm to begin weakening rapidly after
1200 UTC on 28 Jul. Winds were down to minimal tropical storm
intensity by 29/0000 UTC but were held there for about 18 hours due to
Dvorak estimates from KGWC, TAFB, and SAB of 35 kts, and also due to
the possibility of a convective flare-up during the diurnal maximum.
There was a flare-up near the center around 1200 UTC, but by the after-
noon of the 29th the convection had diminished and Emilia was down-
graded to a depression at 2100 UTC, and the final advisory was issued
at 0300 UTC on 30 Jul, placing the dissipating center about 625 nm
west-southwest of Cabo San Lucas.
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for July: 2 tropical depressions
4 tropical storms **
2 typhoons
** - One of these, Chanchu, was a redevelopment of Tropical Storm
Upana from the Central North Pacific. Another was a system for
which no warnings were issued by any TCWC but was considered
a tropical storm by Dr. Mark Lander of the University of Guam.
NOTE: Most of the information on each cyclone's history presented in
the narrative will be based upon JTWC's advisories, and references to
winds should be understood as a 1-min avg MSW unless otherwise noted.
However, in the accompanying tracking document I have made comparisons
of coordinates with JMA (Japan) and the Philippines (PAGASA) when their
positions differed from JTWC's by usually 40-50 nm or more. A special
thanks to Michael V. Padua, owner of the Typhoon 2000 website, for
sending me the PAGASA and JMA tracks.
In the title line for each storm I plan to reference all the cyclone
names/numbers I have available: JTWC's depression number, the
JMA-assigned name (if any), JMA's tropical storm numeric designator,
and PAGASA's name for systems forming in or passing through their area
of responsibility.
Northwest Pacific Activity for July
-----------------------------------
After a quiet June in which no tropical depressions or storms
entered warning status, the waters of the Northwest Pacific basin
became quite active indeed during the month of July. Five tropical
storms, including two which reached typhoon strength, were assigned
names by JMA. One of these originated with a disturbance from the
Central Pacific which had formerly been a tropical storm south of
Hawaii. In addition to these, another small TUTT-spawned tropical
cyclone formed early in the month but no warnings were issued for
this system by any TCWC. Dr. Mark Lander of the University of Guam
felt that this disturbance did reach minimal tropical storm intensity,
and he has provided me with a track for the cyclone which is included
in the accompanying tropical cyclone tracks file. In accordance with
a procedure I developed last summer, I have dubbed this system with
the Greek letter "Kappa". (I assign the next available Greek letter
to any system which (1) appeared to have exhibited nominal tropical
characteristics, (2) was not warned on by any TCWC, and (3) in the
opinion of some experienced tropical meteorologist, likely reached
minimal tropical storm intensity (1-min avg MSW of 34 kts or higher).)
This system, plus all the officially named tropical storms, will be
described in greater detail below. There were also two tropical
depressions identified during the month which did not reach tropical
storm intensity. The first of these, TD-07W (named Gloring by
PAGASA), formed on 12 Jul about 225 nm east of Catanduanes Island in
the Philippines. PAGASA and JMA began issuing bulletins on Gloring,
but JTWC did not initiate warnings until 0000 UTC on 13 Jul when the
broad center of the depression was about 115 nm north-northwest of
Catanduanes Island. The system moved generally in a westerly
direction, crossing central Luzon between around 14/0600 and 1800 UTC.
After emerging into the South China Sea, Gloring turned more to the
northwest and weakened with the final JTWC warning placing the center
about 250 nm northwest of Manila at 15/0000 UTC.
As Tropical Depression 07W (Gloring) was crossing Luzon, another
area of disturbed weather formed in the South China Sea to the west
of Luzon. This area slowly consolidated into a tropical depression
and JTWC initiated warnings on TD-08W at 0000 UTC on 16 Jul when the
center was located roughly 235 nm south-southwest of Hong Kong. The
depression moved on a north-northwesterly track which carried it
inland into China about 140 nm west of Hong Kong around 17/0600 UTC.
Based upon JTWC's warnings, winds never exceeded 25 kts in this system;
however, JMA reported the 10-min avg MSW at 30 kts. By 1800 UTC the
depression was dissipating inland in China north of Canton.
Tropical Cyclone "Kappa"
1 - 5 July
------------------------
NOTE: No warnings were issued by JTWC nor JMA on this system. All
the information contained below (except for some geographical
references which I calculated) was supplied to me by Dr. Mark Lander
of the University of Guam. A special thanks to Mark for sending me
the information and track for this system.
A small circulation formed in the eastern quadrant of a TUTT cell
on 1 Jul about 325 nm northwest of Wake Island. Over the next day or
so the small system tracked generally northward (or a little west of
due north) until it reached a point roughly 600 nm northwest of Wake
Island around 1800 UTC on 2 Jul. It then made a sharp turn to the
east and convection began to increase around the center. By 1800 UTC
on 3 Jul Mark estimates the MSW to have reached 35 kts with the
center located approximately 625 nm north-northwest of Wake Island.
Estimated peak intensity of 40 kts occurred around 04/1200 UTC when
visible satellite imagery showed a partially-exposed LLCC tucked
under the southwestern side of a CDO feature. "Kappa" continued to
move in a general easterly direction and began to weaken rapidly
on 5 Jul as it merged with an old frontal system. The final position
in Mark's track places the dissipating center about 700 nm north-
northeast of Wake Island at 05/1200 UTC.
Typhoon Kirogi (TC-05W / TY 0003 / Ditang)
2 - 8 July
-------------------------------------------
Kirogi: Korean word for a type of wild goose, submitted by the
Democratic People's Republic of Korea (North Korea)
After lying quiescent for over a month, the tropics of the Northwest
Pacific basin became quite active in early July. Two twin typhoons
were spawned on opposite sides of the Philippines with both moving on
northerly, roughly parallel, tracks. Typhoon Kirogi was the stronger
of the two and moved from its birthplace well east of the central
Philippines to near the Japanese island of Hokkaido, brushing the
southeastern corner of Honshu as it swept north-northeastward. An
area of convection developed on 30 Jun about 350 nm east of the
Philippine island of Mindanao. The convection persisted near a weak,
mid-level circulation near the axis of the monsoon trough which
extended from Mindanao eastward to Koror. CIMSS shear charts and a
200-mb analysis indicated a favorable environment for strengthening.
The disturbance remained quasi-stationary in the general area for
the next few days and slowly became better organized. A broad LLCC
was evident in visible imagery on 1 July. JTWC issued a Formation
Alert at 2300 UTC on 1 Jul as convection began to organize rapidly
about the LLCC. The first warning on TD-05W was issued at 02/0600
UTC with the center located about 525 nm east of Catanduanes Island
in the Philippines. PAGASA initiated warnings six hours later, naming
the depression Ditang. The developing system began moving on a slow
northerly track several hundred miles east of the Philippines. JTWC
upgraded TD-05W to a tropical storm at 02/1800 UTC and PAGASA followed
suit six hours later. The LLCC was still very broad but convection
was wrapping around the southern and western periphery. JMA upgraded
the depression to Tropical Storm Kirogi at 0600 UTC on 3 Jul with
maximum 10-min avg winds of 40 kts. JTWC's 1-min MSW was 45 kts, which
represents excellent agreement with JMA.
Both JTWC and JMA upgraded Kirogi to a 65-kt typhoon at 03/1800 UTC
with the storm centered roughly 450 nm east-northeast of Catanduanes
Island. Animated satellite imagery revealed increasing consolidation
with tightly-curved banding features. The storm exhibited good outflow
in all quadrants and was continuing to be steered generally northward
by a mid-level subtropical ridge to the east. Located within a
favorable large-scale environment, Kirogi quickly intensified into
a strong typhoon. JTWC's MSW estimate reached 100 kts at 0600 UTC
on 4 Jul with animated visible satellite imagery depicting a large,
rapidly intensifying system. Kirogi sported a 29-nm irregular eye with
a convective band evident as far as 230 nm to the north of the LLCC.
Kirogi reached its estimated peak intensity of 115 kts six hours later
with the center approximately 470 nm southeast of Okinawa. A SSM/I
pass at 04/0926 UTC depicted a 32-nm round eye with data from a TRMM
pass indicating that the strongest banding lay to the east and south.
Gales extended outward 165 nm to the east of the center and 115 nm
elsewhere, while 50-kt winds reached out 85 nm to the east and 55 nm
elsewhere. The estimated radius of 100-kt winds was 15 nm; hence,
Kirogi was a fairly large typhoon. JMA's estimated peak 10-min avg
wind was 85 kts while PAGASA reported 90 kts from 05/0000 through
05/1800 UTC.
The JTWC warning at 05/0000 UTC noted that convection was symmetric
around the 26-nm cloud-filled eye. Six hours later the MSW was still
reported as 115 kts, but animated satellite imagery showed that the
deep convection had weakened considerably over the past few hours.
Apparently a mid-latitude trough to the northwest was having an adverse
effect on Kirogi even though the outflow appeared to still be good in
all quadrants. A 05/0914 UTC SSM/I pass depicted virtually all of
the convective banding to be confined to the eastern half of the
typhoon. By 1800 UTC the storm was continuing to show signs of
weakening with the MSW lowered to 100 kts. The deepest convection
was located in the southeastern quadrant only. Kirogi was by this
time moving on a north-northeasterly heading from which it never
deviated. Winds had dropped to 85 kts by 06/0000 UTC and were down
to 75 kts (per JTWC) by 1200 UTC, but the storm's intensity then
levelled off and Kirogi maintained 75-kt winds for a day and a half.
The typhoon passed about 375 nm west of Iwo Jima around 0600 UTC
on the 6th. This location was also approximately 350 nm east of
Okinawa. By 1200 UTC Kirogi was beginning to accelerate some on
its north-northeasterly heading, and had also become quite a large
typhoon. Winds of 50-kts covered an area 300 nm in diameter while
gales covered an area almost 500 nm in diameter.
Even though Kirogi had lost much of its earlier punch, it remained
a well-organized typhoon with a ragged, cloud-filled eye visible much
of the time as it accelerated toward Japan. The JTWC warning at 0600
UTC on 7 Jul noted that animated satellite imagery revealed a 13-nm eye
with a band of heavy convection closing in to make a concentric eye-
wall. By 1800 UTC Kirogi was located about 90 nm south of Tokyo
and moving north-northeastward at 26 kts. The MSW were estimated
at 70 kts from both JTWC and JMA with a synoptic pressure report of
973 mb. A 200-mb analysis indicated that a mid-latitude trough was
situated about seven degrees west of the typhoon with southerly
divergent flow of 10-20 kts over the system. The weakening Kirogi
passed near Choshi on Cape Inubo as it brushed southeastern Honshu.
By 08/0000 UTC the storm was located approximately 80 nm east-
northeast of Tokyo with 65-kt winds and was beginning to transition
into an extratropical system, although a 07/2117 UTC SSM/I pass
indicated a CDO with the LLCC about 30 nm into the convection.
Thereafter, Kirogi continued to weaken as cold air advection and
cooler SSTs caused the convection to weaken. The storm continued
moving north-northeastward east of Honshu and by 1800 UTC on the 8th
had completed extratropical transition just southeast of the island
of Hokkaido.
While Typhoon Kirogi was gaining strength east of the Philippines,
a monsoon depression in the South China Sea, later to become Typhoon
Kai-tak, was slowly consolidating and was accompanied by a large
area of gales before any warnings were issued. Heavy rains during
this time led to disastrous flooding and landslides in the Philippines.
There were some press stories circulating which stated that Typhoon
Kirogi had struck the Philippines or had caused great damage to the
nation. This is erroneous--the typhoon was never closer to the
Philippines than about 450 nm and could not have had any significant
impact in the country.
However, Kirogi did leave behind some damage and fatalities in
Japan. There were three persons reported killed and some cities were
flooded and homes buried in landslides. At least 300 homes in
the Tokyo metropolitan area were flooded, and downed power lines led
to about 20,000 homes being without electricity for as long as four
hours. Before reaching Honshu the storm had struck the Izu island
chain south of Tokyo where a shrine festival hall and three homes
were demolished by landslides on the island of Kozushima. One press
report mentioned winds to 68 kts in Japan, but the location of this
report isn't clear, nor was it stated if it were a sustained wind or
peak gust.
Typhoon Kai-tak (TC-06W / TY 0004 / Edeng)
3 - 11 July
-------------------------------------------
Kai-tak: contributed by Hong Kong, China, is the name of the old
airport in Hong Kong which was closed in 1998
An area of persistent but disorganized convection developed on
2 Jul in the central South China Sea about halfway between Luzon and
Vietnam. A QuikScat pass and synoptic reports indicated that a broad,
weak circulation was associated with the convection. The area had
drifted northward some by 3 Jul, and a synoptic analysis and visible
satellite imagery revealed a developing LLCC. PAGASA initiated
warnings on Tropical Depression Edeng at 03/0000 UTC with the center
located approximately 425 nm south-southeast of Hong Kong. Edeng
moved slowly northeastward toward the northern tip of Luzon. JTWC
issued a Formation Alert at 03/2300 UTC with the LLCC estimated about
150 nm northwest of Manila. The system had exhibited improved
organization with a band of convection wrapping into the eastern
quadrant of the LLCC. Edeng was located in a favorable environment
for intensification underneath the axis of the subtropical ridge.
JMA began issuing bulletins on the system at 0000 UTC on 4 Jul with
the broad center located about 100 nm south-southwest of Laoag on the
island of Luzon. JTWC followed suit and initiated warnings on TD-06W
six hours later. The center of the depression remained quasi-
stationary over the next couple of days over or near northern Luzon,
thereby slowing its intensification, even though convection gradually
became better organized. At 1200 UTC on 5 Jul PAGASA upgraded Edeng
to a tropical storm with 35-kt winds centered about 35 nm north of
Laoag. Six hours later both JTWC and JMA had classified the system
as a tropical storm with JMA assigning the name Kai-tak. Even though
Kai-tak had developed slowly, once it moved out over the Luzon Strait,
the storm began to intensify rather quickly.
By 0600 UTC on 6 Jul the convection had increased in areal coverage
and had consolidated around the LLCC. MSW were estimated at 60 kts
by both JTWC and JMA, and Kai-tak was upgraded to typhoon intensity
at 1200 UTC by JMA. The center of Kai-tak was located approximately
150 nm northwest of Laoag at this time. (JTWC upgraded the storm to
a typhoon at 1800 UTC.) Typhoon Kai-tak remained quasi-stationary
in the Luzon Strait just off the northern end of Luzon for several
days. At 1200 UTC on 8 Jul, just before the by-then weakening typhoon
began to move decidedly to the north-northeast, the center of Kai-tak
was located only about 90 nm north of where it been 72 hours earlier
when it had first been upgraded to a tropical storm by PAGASA. From
comments in some of the JTWC warnings, it appears that Kai-tak's slow
motion was caused by the combination of a subtropical ridge building
in from the east of the storm and a ridge located to the north.
The typhoon reached its estimated peak intensity of 75 kts (per both
JTWC and JMA) from 07/0600 through 08/0000 UTC. Interestingly, PAGASA
reported a 10-min avg wind of 90 kts during this period which would
correspond to a 1-min avg MSW of about 105 kts. In the cyclone tracks
file, I normally use the higher 10-min avg MSW value that I have
access to, but in this case, I reported JMA's lower value since it was
much more in line with JTWC's MSW, although it should be pointed out
that a 75-kt 10-min avg MSW would imply a 1-min avg MSW of 85 kts.
By 0000 UTC on the 8th satellite imagery depicted weakening convection
around a 15-nm eye, possibly due to upwelling of cooler water as a
result of the very slow movement of the system. At this point JTWC
still forecast Kai-tak to take off toward the north and intensify,
but by 0600 UTC it was evident the typhoon had weakened considerably.
Virtually all the convection around the exposed LLCC had dissipated
and the MSW was decreased to 65 kts. There was still, however, a
fair amount of convection over the periphery of the storm.
Kai-tak was able to maintain minimal typhoon intensity for another
24 hours as it began to move north-northeastward toward southern
Taiwan. The storm scooted up the east coast of the island, being
located about 50 nm northeast of the southern tip of Taiwan at 0000 UTC
on 9 Jul. At this juncture some convection had begun to wrap in
towards the center and a banding eye was becoming evident, but this
trend was reversed, apparently due to interaction with the mountainous
island. At 0600 UTC Kai-tak was downgraded to a tropical storm
when it was located about 45 nm southeast of Taipei. (JMA had down-
graded the system twelve hours earlier.) By the time the storm was
passing Taipei it was moving northward at 18 kts, being steered by
a combination of a mid-level HIGH to the east and a mid-latitude trough
over southeastern China.
After brushing Taiwan Kai-tak continued rapidly northward with a
slight jog to the north-northwest toward eastern China with most of
the convection over the western portion of the system. As the storm
neared China there was an increase in convection north of the center.
Animated water vapor imagery showed good outflow to the north and
south of the center and a 200-mb analysis revealed upper-level
diffluence above Kai-tak. At 09/1800 UTC the storm was centered about
35 nm east-southeast of Wenchou and by 0000 UTC on the 10th was
skirting the Chinese coast about 50 nm south-southeast of Shanghai.
The MSW estimate was decreased to 45 kts at this time and the storm
continued to weaken as it pulled away from the coast and sped north-
ward into the Yellow Sea. By 0600 UTC Kai-tak's center was located
about 85 nm northeast of Shanghai and moving northward at 22 kts.
Convection was beginning to weaken and the storm was downgraded to a
depression at 1200 UTC and forecast to transition into an extratropical
system. The final JTWC warning at 11/0000 UTC placed the system in
the far northern reaches of the Yellow Sea just west of the northern
part of the Korean peninsula.
During the time that Kai-tak was brewing as a monsoon depression in
the South China Sea, gales existed for several days just south of the
system. This regime helped to bring very heavy rains to portions of
the Philippines which led to widespread damage and many fatalities.
Contrary to what was widely reported in the press, Typhoon Kirogi,
several hundred miles to the east, was not responsible for the
situation in the Philippines except that perhaps inflow into the
typhoon helped to enhance the monsoon a bit. In the 72 hours ending
at 0000 UTC on 6 Jul Baguio City had recorded 570 mm, the monthly
average being 1074 mm. (Thanks to Patrick Hoareau for sending this
information along.)
The number of fatalities is not altogether clear. One press report
indicated that 27 lives had been lost in the flooding and landslides in
the northern and central portions of Luzon. Over 400,000 persons were
driven from their homes by the flooding which left hundreds of villages
and many towns under 1 to 2 metres of water. Hundreds of houses were
damaged and in many cases totally destroyed. The water level behind
the Ambuklao and Binga dams came to within less than 1 metre of
reaching the spillover level. Crops (especially rice) and fishponds in
many areas were damaged.
An unusual tragedy in Manila claimed over a hundred lives. A city
garbage dumpsite, covering about 0.1 square miles in area but with
garbage piled up to seven stories high, was weakened by the heavy
rainfall and collapsed onto an area of shanties, huts, and lean-tos.
As the garbage slid over the homes, it caught fire, burning and burying
many people alive. Three days after the slide the number of dead was
placed at 137 with 150 or more still believed buried.
Tropical Storm Tembin (TC-09W / TS 0005)
17 - 23 July
-----------------------------------------
Tembin: Japanese word for balance (a weighing device)
Tropical Storm Tembin was a fairly weak tropical storm which formed
near the northern Mariana Islands in mid-July and moved almost due
northward, recurving just east of Honshu. An area of convection
developed on 16 Jul over the northern Marianas. Animated satellite
imagery and CIMSS products indicated that the region was under the
divergent quadrant of a TUTT with a possible anticyclone developing
over the convection. Synoptic observations indicated a weak LLCC.
JMA began issuing bulletins on a new tropical depression at 0000 UTC
on 17 Jul with the weak center estimated to be just west of the
northernmost Marianas. JTWC issued a Formation Alert at 0100 UTC,
noting that the disturbance had consolidated and was intensifying.
JTWC held off on initiating warnings since at 0600 UTC visible imagery
indicated that although the system was displaying increased
organization, the convection had weakened some. Satellite intensity
estimates were 25 kts but synoptic observations and satellite-derived
winds indicated that winds near the center were only around 15 kts.
JTWC began issuing warnings at 17/1800 UTC based upon satellite
intensity estimates of 25 kts and synoptic reports. Convection had
increased in areal coverage with a possible banding feature developing
to the southeast of the LLCC. The depression was in a diffluent region
created by an upper-level LOW to the southwest and an upper-level HIGH
to the northeast of the Marianas. The center of TD-09W was estimated
to be about 175 nm northwest of the northern Marianas or about 180 nm
southeast of Iwo Jima. Initial slow motion to the northwest had
changed to a northerly heading by 0600 UTC on the 18th. CIMSS data
indicated that an upper-level ridge to the east was migrating westward
over the depression. The system was forecast to continue moving north-
ward through a break in the low- to mid-level ridge. JTWC upgraded
the depression to a tropical storm at 18/1800 UTC with the center
positioned about 85 nm northeast of Iwo Jima. Six hours later JMA
also classified the system as a tropical storm, naming it Tembin.
JTWC upped the MSW to 45 kts at 19/0000 UTC based on a 10-min avg
wind report of 41 kts from a reliable vessel in the vicinity.
Convection was seen to fluctuate some, but by 1200 UTC animated
satellite imagery indicated that deep convection had strengthened and
become better organized around the LLCC. Tembin continued to march
basically in a northerly direction but never intensified beyond 45 kts.
By 1800 UTC on the 19th some limited westerly shear was impinging on
the system, keeping the LLCC on the western edge of the deep
convection, although good outflow was present over the eastern semi-
circle. By 20/0600 UTC the shear had increased to the point that the
LLCC was exposed with the deep convection sheared 18 nm to the north-
east of the center. (During this period JMA's maximum 10-min avg
wind estimate reached 40 kts which agrees closely with JTWC's 1-min
avg MSW estimate of 45 kts.)
Tropical Storm Tembin began to slowly weaken as it moved northward
and encountered increasing shear. Also, animated water vapor imagery
indicated some mid- and upper-level dry air getting pulled into the
southwest quadrant of the storm. Steered by a low- to mid-level HIGH
to the east, the weakening storm continued northward, then curved to a
north-northeasterly heading as it passed east of Tokyo. By 0000 UTC
on 22 Jul the LLCC had become completely exposed with associated
convection displaced about 120 nm to the south. A 200-mb analyis
indicated moderate upper-level northeasterlies extending over the
region. JTWC downgraded Tembin to a depression at 0000 UTC with the
weakening center located about 150 nm east of Tokyo. JMA wrote their
last advisory on the storm also at this time. Synoptic ship reports
of 27 kts and 32 kts within 60 nm of the LLCC with pressures near
996 mb supported an intensity of 30 kts, so JTWC continued to write
warnings on the weakening Tembin for another day or so. A 22/1200 UTC
ship report about 90 nm south of the LLCC indicated 27-kt winds and
a pressure of 1001 mb. Rapidly weakening convection was noted about
125 nm southwest of the center. By 23/0000 UTC there was no longer
any convection associated with the LLCC and JTWC issued the last
warning with the dissipating system just east of Hokkaido.
Tropical Storm Bolaven (TC-10W/11W / STS 0006 / Huaning)
20 - 31 July
---------------------------------------------------------
Bolaven: contributed by Lao People's Democratic Republic (Laos), is
the name of a plateau in the southern part of Laos
An area of convection developed on 18 Jul about 600 nm east of the
Philippines. Animated visible satellite imagery indicated persistent
convection in the low-level southwesterly convergent flow of the
monsoon trough while animated water vapor imagery showed an upper-
level LOW located north of the area with a trough extending southwest-
ward to the west of the disturbance. CIMSS wind analysis showed weak
divergence in the upper levels over the region. By 19 Jul the main
convective area had migrated or re-formed farther to the west--about
250 nm east of the Philippines. JTWC issued a Formation Alert at
0030 UTC on 20 Jul when visible imagery revealed the existence of an
exposed LLCC southeast of the deeper convection. The first warning
on TD-10W was issued at 0300 UTC. The well-defined LLCC was fully
exposed but the depression was forecast to move into an environment
of decreased vertical shear during the next 24 hours that should allow
convection to consolidate near the center.
This forecast, however, failed to materialize. Over the next three
days the depression moved on a general northwesterly course, steered by
a subtropical ridge to its northeast. Upper-level northeasterlies
impinging on the system constantly sheared the convection that did
develop away from the LLCC. PAGASA initiated warnings on the system
at 21/0000 UTC, naming it Huaning. Huaning's center was located
roughly 325 nm east-northeast of Catanduanes Island at this time.
PAGASA estimated the 10-min avg wind at 30 kts during this time but
JTWC's 1-min avg MSW estimate never rose above 25 kts. By 23/0000 UTC
the depression's center had, in JTWC's estimation, moved inland over
northeastern Luzon and warnings were terminated. PAGASA, however,
placed the center about 50 nm to the east-northeast of JTWC's final
position.
A STWO from JTWC at 23/0600 UTC mentioned that an area of convection
had formed about 140 nm east of Luzon within the monsoon trough. The
convection was persistent with an apparent mid-level circulation. A
23/0241 UTC TRMM pass depicted poorly-organized convection with no
clear indication of a LLCC. Synoptic analysis indicated linear
convergence across the region which was experiencing moderate vertical
shear. Another STWO issued at 2100 UTC indicated that the area of
convection was located about 70 nm east-southeast of Port San Vicente
on Luzon. There had been a flare-up of convection near a quasi-
stationary poorly-defined LLCC. Scatterometer and ship data indicated
a weak LLCC with a TUTT located just north of the area. The potential
for development was rated Fair. By 24/0600 UTC the main convective
area was centered about 60 nm north of Luzon and a Formation Alert was
issued. JTWC began writing warnings on TD-11W at 24/1800 UTC with the
system centered approximately 300 nm south-southwest of Okinawa.
In the meantime, during the hiatus in JTWC warnings, PAGASA
continued to carry the system as Tropical Depression Huaning. Their
23/0600 UTC position relocated the center about 80 nm to the southeast
of the previous warning position. The center as followed by PAGASA
remained quasi-stationary through 24/0000 UTC, then was relocated
at 0600 UTC to a position about 100 nm to the north. JMA also began
issuing bulletins on the system at this point. Since PAGASA treated
the system as one entity, I am following their lead here. Mark Lander
stated that he and Roger Edson had taken a close look at satellite
imagery of the system during this period and were in agreement that
TD-11W (later Bolaven) was a continuation of TD-10W. Mark indicated
that PAGASA's track made a nice fit between the end of TD-10W and the
point where JTWC picked up TD-11W.
The rejuvenated depression began to track north-northeastward on
25 Jul in the direction of Okinawa. Intensification was slow as the
depression was still experiencing some shear. At 25/1200 UTC the
convection appeared to be weakening with a QuikScat pass indicating
a trough without a closed circulation. However, six hours later
convection had begun to increase again in areal coverage and JMA
upgraded the depression to Tropical Storm Bolaven, located about
125 nm southwest of Okinawa. JTWC classified the system as a tropical
storm at 26/0000 UTC based on synoptic reports of 35 kts. The winds
were raised to 40 kts at 0600 UTC by both JTWC and JMA based on
synoptic reports of 37 and 42 kts near the center. (Satellite current
intensity estimates remained 30 kts at the time.) Convection was
increasing in organization and areal coverage, especially over the
southern part of the system. Bolaven's center was located about 40 nm
southeast of Okinawa at this time, still tracking northeastward.
However, the northeastward motion came to a halt at 1800 UTC as a
subtropical ridge to the east began to build westward.
For about 24 hours the storm moved slowly and erratically generally
toward the west. Animated visible imagery revealed that a 90-nm
irregular CDO had developed over the LLCC by 27/0000 UTC. With
satellite intensity estimates of 45 and 55 kts, JTWC increased their
MSW estimate to 50 kts--the peak value for the storm's history.
(Interestingly, JMA reported the maximum 10-min avg winds at 55 kts
for the next couple of days.) The JTWC warning at 27/1200 UTC noted
that impressive outflow remained over the eastern portion of the storm.
Bolaven was at this time located within a weakness in the ridge, and
its motion was also being influenced by a TUTT located just to the east
of the tropical cyclone. By 28/0000 UTC the storm was drifting north-
ward at 3 kts from a position about 100 nm east-northeast of Kadena AB,
Okinawa. This northward motion began to increase later on the 28th,
and Bolaven experienced some northerly shear but managed to hang on
to its intensity through late on the 29th.
By 29/0600 UTC the storm was located about 225 nm south-southwest of
Sasebo, Japan, and moving north-northwestward at 7 kts. Animated water
vapor imagery continued to depict good outflow except in the northern
quadrant; however, CIMSS analysis indicated moderate vertical shear and
northeasterly flow over the system. Bolaven was being steered by a
weak subtropical ridge to the northeast. At 0000 UTC on the 30th the
storm was centered approximately 115 nm south-southwest of Sasebo and
tracking northward at 8 kts. Convection was sheared 50 nm to the
south of an exposed LLCC and JTWC brought the MSW down to 40 kts. A
mid-latitude trough approaching from the west was enhancing the
steering flow, allowing the storm to accelerate northward. Bolaven
passed about 55 nm west of Sasebo at 0600 UTC as a minimal tropical
storm. At 1800 UTC the cyclone was moving north-northeastward from
a position about 45 nm south of Pusan, South Korea. Bolaven was
beginning to display some extratropical characteristics, but satellite
imagery indicated that convection had temporarily moved back over the
LLCC due apparently to a relaxation in the vertical shear. However,
by 31/0000 UTC Bolaven was weakening again after having brushed the
southwestern corner of South Korea and was downgraded to a tropical
depression by both JTWC and JMA about 55 nm north-northeast of Pusan.
Six hours later JTWC wrote their final warning as the convection had
become weak and elongated and the depression was merging with a mid-
latitude trough and accelerating northeastward in the Sea of Japan.
Tropical Storm Upana-Chanchu (TC-01C/12W / TS 0007)
20 - 30 July
----------------------------------------------------
Tropical Storm Upana was a rare Central North Pacific tropical
cyclone which blossomed briefly south and southwest of Hawaii. The
system weakened to below depression status and warnings were dropped
by CPHC. The residual disturbance continued westward and began to
show signs of re-intensification as it neared the Dateline. After
crossing into the Northwest Pacific basin, the system redeveloped
into a tropical storm and was named Chanchu by JMA. The full
history of this system is given above in the section of this summary
covering the Northeast Pacific basin.
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for July: No tropical cyclones
***********************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for July: No tropical cyclones
***********************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for July: No tropical cyclones
***********************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for July: No tropical cyclones
***********************************************************************
SOUTH PACIFIC OCEAN (SPA) - South Pacific Ocean East of Longitude 160E
Activity for July: No tropical cyclones
***********************************************************************
EXTRA FEATURE
In order to shorten the amount of typing in preparing the narrative
material, I have been in the habit of freely using abbreviations and
acronyms. I have tried to define most of these with the first usage
in a given summary, but I may have missed one now and then. Most of
these are probably understood by a majority of readers but perhaps a
few aren't clear to some. To remedy this I developed a Glossary of
Abbreviations and Acronyms which I first included in the July, 1998
summary. I don't normally include the Glossary in most months in
order to help keep them from being too long. If anyone would like to
receive a copy of the Glossary, please e-mail me and I'll be happy
to send them a copy.
***********************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
in the following manner:
(a) FTP to: hrd-type42.nhc.noaa.gov [140.90.176.206]
(b) Login as: anonymous
(c) For a password use your e-mail address
(d) Go to "data" subdirectory (Type: cd data)
(e) Set file type to ASCII (Type: ascii)
(f) Transfer file (Type: get remote_file_name local_file_name )
(The files will be named with an obvious nomenclature--using
July as an example: jul00.tracks)
(g) To exit FTP, type: quit
Both the summaries and the track files are standard text files
created in DOS editor. Download to disk and use a viewer such as
Notepad or DOS editor to view the files.
The first summary in this series covered the month of October,
1997. If anyone wishes to retrieve any of the previous summaries,
they may be downloaded from the aforementioned FTP site at HRD. The
summary files are catalogued with the nomenclature: jul00.sum, for
example.
Back issues can also be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael
Pitt, and Rich Henning):
http://australiasevereweather.com/cyclones/>
http://www.typhoon2000.com> OR http://www.geocities.com/taifun00/>
http://www.hurricanealley.net/>
http://www.qisfl.net/home/hurricanemike>
http://www.met.fsu.edu/gsc/Docs/Grads/henning/cyclones/>
Another website where much information about tropical cyclones may
be found is the website for the UK Meteorological Office. Their site
contains a lot of statistical information about tropical cyclones
globally on a monthly basis. The URL is:
http://www.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html>
TROPICAL CYCLONE REPORTS AVAILABLE
I have discovered that JTWC now has available on its website the
complete Annual Tropical Cyclone Report (ATCR) for 1999 (1998-1999
season for the Southern Hemisphere). Also, ATCRs for earlier years
are available also.
The URL is: http://199.10.200.33/jtwc.html>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 1999 Atlantic and Eastern North Pacific
tropical cyclones; also, preliminary storm reports for all the 1999
Atlantic and Eastern North Pacific cyclones are now available.
The URL is: http://www.nhc.noaa.gov>
Prepared by: Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)
***********************************************************************
***********************************************************************
|
Document: summ0007.htm
Updated: 29th December 2006 |
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