[Index]
Monthly Global Tropical Cyclone Summary July 1999
[Summaries and Track Data] [Prepared by Gary Padgett]
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Cyclones
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Monthly Global Tropical Cyclone Summary July 1999 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
JULY, 1999
(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 activity increases but average intensity quite weak
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for July: 1 tropical depression
NOTE: Much of the information presented below was obtained from the
TPC/NHC discussion bulletins issued with every regular advisory. All
references to sustained winds imply a 1-min averaging period unless
otherwise noted. Also, some information on Tropical Depression #2
was obtained from the preliminary report on this system already
available on TPC/NHC's website.
Atlantic Activity for July
--------------------------
No named tropical storms or hurricanes were noted in the Atlantic
basin during July, but there were a couple of significant tropical
weather systems. The first was Tropical Depression #2 which formed
from a tropical wave that had left the coast of Africa on 20 Jun. The
wave reached the extreme western Caribbean Sea on 30 Jun and a broad
area of mid-tropospheric turning was noted. The wave moved onto the
Yucatan Peninsula on 1 Jul and a weak LOW moved out into the Bay of
Campeche early on the 2nd. During the day deep convection became
better organized and a tropical depression had formed by 1800 UTC
about 200 nm southeast of Tampico, Mexico. The depression continued
moving west-northwestward and the center had crossed the coast about
35 nm south-southeast of Tuxpan by 0400 UTC on 3 Jul. Reported
rainfall totals ranged from 105 to 317 mm. There were no known
casualties or significant damage.
The second significant tropical weather system of July was a
tropical wave which left the coast of Africa on the 3rd and moved
rapidly westward across the Atlantic. The wave had reached the
eastern Caribbean Sea on 8 Jul when it was investigated by U. S. Air
Force Reserves Hurricane Hunters. The reconnaissance flight found
flight-level and surface winds in excess of 45 kts in squalls, mainly
west of the wave axis. This unusual wave was propagating westward
at 20-25 kts--faster than the environmental easterly flow. As the
wave approached Honduras early on 10 Jul it was becoming better
organized. A reconnaissance flight found a weak low-pressure area
just inland over northeastern Honduras with strong, gusty winds to
the north and northeast of the LOW. Deep convection with cloud
tops colder than -80 C had developed in bands within 120-240 nm of
the center with weak to moderate convection near the surface center.
Upper-level cirrus outflow had also become better defined. The
surface LOW skimmed along the northern Honduran coast and inland
over southern Belize and Guatemala. The system almost became a
tropical depression and would likely have done so were it not for
the fact that the area of minimum pressure remained inland or right
along the coast. This tropical wave subsequently crossed Central
America and moved out into the Eastern Pacific where it developed
into a tropical depression (TD-03E).
This tropical wave was likely prevented from developing into a
tropical cyclone due to its very rapid translational speed. No doubt,
relative to the wave axis, a circulation existed, but in order to
qualify as a tropical cyclone a complete circulation must exist for
a stationary point on the earth's surface--evidenced by a westerly
wind on the equatorward side of the disturbance. Such strong
gale-bearing tropical waves are not common, but they do occur
occasionally in the Atlantic. A strong wave passed through the
central Caribbean in September, 1992. Easterly winds to around 50 kts
were reported by ships and a reconnaissance flight on the northern
side of the disturbance when it was south of Hispaniola, but on the
south side of the wave only easterly winds were reported. The
tropical waves which produced Hurricanes Camille of 1969 and Erin of
1995 both contained sustained winds well above tropical storm force
before a surface circulation had become established. In each case,
when the surface circulation did develop, the system was upgraded
immediately to a tropical storm.
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for July: 3 tropical depressions
1 tropical storm
1 hurricane
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. Some information was
obtained from preliminary storm reports located on TPC/NHC's website.
Northeast Pacific Activity for July
-----------------------------------
One rather strong hurricane (Category 3 on the Saffir/Simpson
Scale) plus four weak, short-lived systems roamed tropical Northeast
Pacific waters during July. Beatriz became the region's second
hurricane of 1999 and the first to become a major hurricane, but
the storm remained far from any populated areas. The other four
systems were quite weak and short-lived with Calvin being the other
named storm during the month, and a minimal tropical storm at that.
Due I suppose to the relative inactivity in the Atlantic and North-
east Pacific basins during July and early August, the staff of TPC/NHC
found time to prepare some preliminary reports for all the Northeast
Pacific systems in July except for Hurricane Beatriz. I have used the
analyzed Best Tracks from the preliminary storm reports on the other
systems in the companion cyclone tracks file document. Tropical
Depression 03E developed from the very active tropical wave which
crossed the Atlantic, Caribbean, and Central America during early and
mid-July. (See the section of this summary covering the Atlantic
basin for a description of the early history of this system.) The
tropical wave emerged into the Eastern Pacific on 13 Jul and was
upgraded to a depression at 0600 UTC on the 14th when it was centered
about 225 nm southwest of Manzanillo. The system at one point had
a very large, impressive area of deep convection, but after the
depression had formed it remained very ill-defined. TD-03E moved
generally westward and dissipated around 15/1800 UTC about 450 nm
southwest of Cabo San Lucas. After 1200 UTC on 14 July, the official
Best Track positions differ by almost 100 nm from the operational
warning positions, and the final advisory position at 15/1200 UTC
is almost 200 nm south of the Best Track location for that time.
Tropical Depression 04E formed on 23 July from a tropical wave which
had entered the Pacific on 15 July. At 0000 UTC on the 23rd the
center was about 1300 nm west-southwest of Cabo San Lucas. The
depression moved generally westward and into the Central North Pacific
region on 24 Jul, dissipating about 725 nm east-southeast of Hilo,
Hawaii, by 25/0000 UTC.
A tropical wave which left the African coast on 5 July, immediately
behind the active wave which ultimately spawned TD-03E, crossed the
Atlantic and Caribbean and eventually reached the Eastern Pacific where
by 26 July it began to show increased convective organization. The
first advisory on TD-06E placed the center about 1100 nm southwest of
Cabo San Lucas at 1800 UTC on 26 Jul. The depression moved northwest-
ward and encountered vertical shear which did not allow the system to
intensify into a tropical storm. The depression had dissipated by
28/0000 UTC.
Hurricane Beatriz (TC-02E)
9 - 16 July
---------------------------
Hurricane Beatriz developed from an area of disturbed weather near
the Gulf of Tehuantepec which was first mentioned by TPC/NHC on 6 Jul.
The disturbed area drifted westward, slowly becoming better organized,
and was upgraded to a tropical depression at 0600 UTC on 9 Jul when it
was centered approximately 275 nm southwest of Acapulco, Mexico. The
depression exhibited good outflow in all quadrants, and with Dvorak
intensity estimates of T2.5 and T3.0 from TAFB and SAB, respectively,
was upgraded to Tropical Storm Beatriz only six hours later. Tropical
Storm Beatriz (Spanish form of Beatrice--pronounced "bay-ah-TREECE")
continued moving westward and slowly intensified. A U. S. Navy
FNMOC scatterometer pass indicated a wind of 41 kts about 150 nm
northeast of the center around 1800 UTC on 10 Jul.
Beatriz was upgraded to a hurricane at 1200 UTC on 11 Jul when the
center was estimated to be about 575 nm south-southwest of Cabo San
Lucas. By 12/0000 UTC cloud tops of -65 to -70 C were wrapping
three-quarters of the way around the eye, and the MSW was estimated
at 85 kts. The hurricane exhibited good banding features and outflow
was well-developed in all quadrants except the northwest. Beatriz
apparently underwent a concentric eyewall cycle during the 12th. By
1800 UTC the storm displayed a well-defined eye 21 nm in diameter and
T-numbers from TAFB and SAB were up to T5.5, so the MSW was increased
to 100 kts, making Beatriz the first major hurricane (Category 3 on
the Saffir/Simpson scale) in the Eastern Pacific this season. Six
hours later the eye had become even tighter and the intensity was
set at 105 kts--the maximum reached by Beatriz--with an attendant
estimated central pressure of 956 mb. Objective T-numbers were
ranging around 5.6-5.7 during this time. At peak intensity Hurricane
Beatriz was located about 775 nm southwest of Cabo San Lucas on the
southern tip of the Baja California Peninsula.
Hurricane Beatriz to this point had been moving on a course just
north of due west, but now the storm began to turn to more of a west-
northwesterly course. By 0600 UTC on 14 Jul Beatriz was nearing the
25 C SST isotherm, the eye was becoming ragged and convective tops
were warming, so the MSW was decreased to 95 kts. Twenty-four hours
later an eye was still visible, but the storm was beginning to weaken
rapidly. Beatriz was downgraded to a tropical storm at 16/0000 UTC
as satellite imagery showed the low-level circulation to be de-coupling
from the mid- and upper-level convective circulation. Six hours
later there were no convective tops colder than -50 C and a
scatterometer pass found no winds higher than 30 kts except for perhaps
near the center where there was no data available. Since Dvorak
estimates were slightly higher, the MSW was set at 40 kts for the
0900 UTC advisory, but the storm was downgraded to a dissipating
depression six hours later since all that remained was a tight swirl
of low clouds. Dvorak numbers still supported minimal tropical storm
intensity, but, as Lixion Avila pointed out in a Discussion Bulletin,
the Dvorak estimates were constrained by rules which were not designed
for weakening swirls over cool Eastern Pacific waters. The final
advisory placed the dissipating system about 1300 nm west-southwest
of Cabo San Lucas at 16/1800 UTC.
Tropical Storm Calvin (TC-05E)
25 - 27 July
-------------------------------
Tropical Storm Calvin was a "one-day wonder" which barely qualified
as a tropical storm. The parent tropical wave left the African coast
on 9 Jul and entered the Eastern Pacific on the 20th. A mid-level
circulation was evident on the 23rd, and an elongated low-level center
formed within the ITCZ on 24 Jul but did not exhibit enough organized
convection to warrant depression classification. The first visible
satellite images on 25 Jul revealed a low-level circulation center
located on the northwest edge of a cluster of deep convection, so
the disturbance was classified as a tropical depression. The first
warning position, at 25/0600 UTC, placed the depression's center
about 575 nm south-southwest of Cabo San Lucas. During this period
the Pacific Ocean north of 16N and between 115W and 140W was dominated
by a large, upper-level trough which was responsible for fairly
strong northwesterly shearing over the region.
Dvorak estimates from TAFB and SAB had reached 35 kts by 0600 on
26 Jul, so the depression was upgraded to Tropical Storm Calvin.
However, the shearing persisted and Calvin soon began to weaken and
was downgraded back to a depression only 12 hours later when satellite
intensity estimates were 35 kts, 30 kts, and 25 kts, respectively, from
TAFB, SAB, and AFGWC. This system moved on a west-northwesterly track
through most of its existence, turning more to the northwest on 27 Jul.
The 27/0300 UTC advisory noted that there had been a recent burst of
convection near the center with the suggestion of a convective band
extending from the east to the south of the center, but this feature
did not persist for long. By 1500 UTC the weak low-level center
appeared to be weakening into an open wave. The final Best Track
position on Calvin, at 1200 UTC, places the dissipating center about
800 nm west-southwest of Cabo San Lucas.
One interesting aspect of Tropical Storm Calvin is that
operationally, Calvin was carried as a tropical storm only from 0600
UTC to 1800 UTC on 26 Jul, but according to the official Best Track,
the tropical storm portion of the system runs from 25/1200 UTC through
26/0600 UTC. However, the Best Track's MSW never rises higher than
35 kts, which was the highest operationally assigned value.
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for July: 1 tropical depression
3 tropical storms **
1 typhoon
** - two of these were classified as tropical storms only by JMA;
JTWC carried them only as tropical depressions.
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. Also, as
announced earlier in a separate posting, a column of 10-min avg MSW
is included--the values being obtained from either PAGASA's or JMA's
advisories. A special thanks to Michael V. Padua, owner of the
Typhoon '99 webpage, 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 and 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
-----------------------------------
It was a month of interesting discrepancies between the various
warning centers in matters of tropical cyclone classification. JTWC,
which normally has the more liberal warning criteria, named only two
tropical storms while JMA classified two other systems as tropical
storms that were treated as only tropical depressions by JTWC. And
during the early stages of Tropical Storm Neil, PAGASA had upgraded the
disturbance to Tropical Storm Helming before JTWC had even initiated
tropical depression warnings! One system was carried as a tropical
depression by JTWC that was not warned on by any other agency (at least
to the author's knowledge). This system, TD-08W, formed on 21 Jul
about 200 nm north-northeast of Okinawa and moved generally northward
and into the southwestern tip of the Korean peninsula. A track is
given for this depression in the Global Tropical Cyclone Tracks file
for July. Since two of the tropical depressions were treated as
tropical storms by JMA, I will give them individual coverage below.
Tropical Storm (TC-07W / TS 9904)
15 - 18 July
----------------------------------
The first unnamed tropical storm of July (as per JMA) can be traced
to an area of disturbed weather which was located about 600 nm east-
northeast of the Northern Marianas Islands on 13 Jul. By the 14th a
very weak low-level circulation center was exposed to the northeast of
a area of convection. The convection was drifting to the southwest
and had good outflow aloft, and the Tropical Weather Outlook from JTWC
indicated the possibility of a new center forming under this
convection. JTWC issued the first tropical depression warning at
0000 UTC on 15 Jul, placing the low-level center about 500 nm east-
northeast of the northern tip of the Marianas. The warning indicated
that intensification of the depression was being hindered by some
shearing as a result of its being caught between two subtropical
ridges, one to the east and one to the west. The next warning
relocated the depression's center to the north-northwest somewhat.
Beginning around 1800 UTC on 15 July, TD-07W began moving on more of
a west-northwesterly course which it maintained throughout most of its
life. The depression was steered primarily by a subtropical ridge
to its east-northeast, and remained in a moderate shearing environment
created by an upper-level LOW to its northeast. JMA upgraded the
depression to a tropical storm with 35-kt MSW (10-min avg) at 1800 UTC
on 16 Jul and maintained it as a tropical storm for 30 hours. JTWC
initially forecast the system to reach tropical storm status, but
by 17/0000 UTC the forecast no longer called for this since the low-
level center had become completely exposed 80 nm north-northwest of
the strongest convection.
Late on the 17th the system began moving on more of a northerly
track in response to a passing trough to the north. Vertical shear
increased and the depression began to rapidly dissipate. The final
JTWC warning at 18/0600 UTC placed the dissipating center about 400 nm
south-southeast of Tokyo.
Discrepancies in warning positions between JMA and JTWC were greater
than normal, and may give a clue as to why JMA happened to classify
this disturbance as a tropical storm. Most of the time, especially
during the tropical storm stage, JMA's position was generally about
70-80 nm southeast or south-southeast of JTWC's position. Since this
system experienced mainly northwesterly shear, the main convective
mass was usually southeast of JTWC's placement of the low-level center
of circulation. If JMA's analysts were consistently assessing the
low-level center to be nearer or under the deeper convection, then
it is not surprising that they considered the system to be stronger
than did JTWC.
Tropical Storm Neil/Helming (TC-09W / STS 9905)
21 - 28 July
------------------------------------------------
A Significant Tropical Weather Outlook (STWO) from JTWC on 19 Jul
mentioned a symmetrical area of convection located east of Luzon
but there was no low-level circulation apparent. PAGASA initiated
depression advisories on this disturbance at 0000 UTC on 21 Jul
when it was located roughly 300 nm east-southeast of Cabo Engano
(the northeastern tip of Luzon), naming the depression Helming. The
system moved very little over the next couple of days, drifting very
slowly northwestward. PAGASA upgraded Helming to a tropical storm
the next day when the center was estimated to be about 250 nm east-
southeast of Cabo Engano. By the 23rd PAGASA was reporting the
MSW (10-min avg) to be 45 kts; yet the SWTO from JTWC on that day
indicated a completely exposed low-level center about 100 nm north of
the nearest deep convection with maximum winds in the area estimated
at only 15-20 kts. This obviously represents a major disagreement
between warning centers in interpretation of satellite imagery.
PAGASA had dropped the winds back to 35 kts on 24 Jul, but the SWTO
from JTWC indicated that convection had increased in areal coverage and
a 24/0000 UTC surface analysis indicated a low-level circulation center
might be present underneath the convection. A Formation Alert was
issued at 24/2130 UTC and JTWC initiated depression warnings at 0600
UTC on 25 Jul when the center was estimated to be located about 200 nm
south-southwest of Okinawa. At the same time PAGASA increased the
10-min MSW to 40 kts. The tropical cyclone at this time was located
in a very active monsoon trough which extended from the South China
Sea, across Luzon, and northeastward to a point southeast of Okinawa.
The system to be known as TD-10W / TS 9906 was taking shape at this
time within the trough in the South China Sea.
The cyclone continued generally northward, steered by a subtropical
ridge to its east. The center passed only about 20 nm east of Okinawa
around 25/1800 UTC per JTWC's track (about 70 nm east per JMA's track).
Kadena AB reported a sustained wind to 16 kts with gusts to 23 kts and
a pressure of 986.4 mb as the system passed by. JTWC's MSW estimate
was 30 kts at this time, while interestingly, JMA's 10-min avg MSW
estimate was 50 kts--approximately equivalent to a 1-min avg MSW of
60 kts. The system was upgraded to Tropical Storm Neil at 26/0000
UTC, but JTWC's assigned MSW never rose higher than 40 kts. JTWC
upgraded the system to a tropical storm based upon animated satellite
imagery which indicated convection to the north of the center had
consolidated and was wrapping around the center. Satellite current
intensity estimates (received by JTWC) were around 30 kts, but
apparently some synoptic reports indicated higher winds.
After passing Okinawa Tropical Storm Neil turned to a course just
west of due north in the direction of South Korea. The convection
began to weaken as the storm moved over cooler SSTs. Neil passed just
east of Cheju Island and moved over the extreme southwestern tip of
South Korea around 0600 UTC on 27 Jul. The weakening system skimmed
up the western coast of South Korea and made a final landfall about
20 nm southwest of Seoul around 28/0600 UTC. There was no significant
convection associated with the system at this time, and scatterometer
data and synoptic reports indicated winds no higher than 15 kts.
Tropical Storm (TC-10W / TS 9906)
26 - 27 July
----------------------------------
The second unnamed tropical storm of July (as per JMA) was a short-
lived system which formed in the northern South China Sea and quickly
made landfall in southeastern China just east of Hong Kong. The daily
STWO issued by JTWC first mentioned an area of convection on 21 Jul,
located in the northern South China Sea west of Luzon. A mid-level
circulation was detected but was not reflected at the surface. By the
23rd a small, low-level center was noted embedded in the monsoon
trough. The next day some anticyclonic flow was developing over
the region and convective organization was becoming slightly better.
Synoptic data at 25/0000 UTC indicated possible multiple circulation
centers in the South China Sea.
JTWC issued the first tropical depression warning at 1800 UTC on
26 Jul, placing the center about 120 nm south-southwest of Hong Kong
and with MSW set at 25 kts. Six hours later the system had moved
northeastward and was located about 65 nm south-southeast of Hong
Kong. JTWC still estimated the MSW to be 25 kts, but JMA upgraded
the system to a tropical storm with 40-kt MSW (10-min avg). By
0600 UTC on the 27th the center of the tropical storm was almost
on the coast of China about 60 nm east-northeast of Hong Kong. JMA's
position at this time was slightly farther north and east. This
was the last bulletin from JTWC, but JMA issued advisories through
1800 UTC, keeping the storm at 35 kts as it trekked north-northeastward
through southeastern China. It is not known to the author whether or
not JMA's MSW estimates were based upon synoptic reports.
Typhoon Olga/Ising (TC-11W / TY 9907)
28 July - 3 August
--------------------------------------
A STWO issued by JTWC at 0600 UTC on 25 Jul mentioned that an area
of convection south of Guam was becoming better organized, and the
25/0000 UTC surface analysis indicated that a low-level circulation
center might be forming. The SWTO for the next day, however, placed
the primary area of convection almost 600 nm to the west, and there
was no further indication of a circulation forming. JTWC issued a
Formation Alert at 0230 UTC on 28 Jul, and this appears to be related
to the previously mentioned disturbance. High-resolution visible
satellite imagery depicted a low-level center, and PAGASA initiated
tropical depression advisories at 0600 UTC, naming the depression
Ising. Ising's center was east of the southern Philippines, about
430 nm east of Surigao, a city on the northern tip of Mindanao.
Tropical Depression Ising began moving on a north-northwestward
course which it followed for a couple of days, steered by a
subtropical ridge to the northeast. Organization increased and JTWC
initiated warnings at 29/0000 UTC. By 1800 UTC deep convection east
of the Philippines was forming into a spiral band feeding into the
depression. JTWC upgraded the system to Tropical Storm Olga at this
time based on satellite intensity estimates of 30 kts and extrapolation
of ship reports. PAGASA also upgraded Ising to a tropical storm at
1800 UTC. Olga/Ising's center was located at this time about 550 nm
east-northeast of Catanduanes Island in the Philippines.
Olga/Ising continued moving north-northwestward until it crossed
20N around 1200 UTC on the 30th; then the storm turned to more of a
northwesterly track. The storm continued to slowly intensify,
with PAGASA upgrading it to a typhoon at 31/0600 UTC when the center
was estimated to be about 275 nm southeast of Okinawa. JTWC followed
suit six hours later. Olga was initially forecast to become a rather
intense typhoon, but its development was limited somewhat by dry air
entrainment--the drier air likely resulting from subsidence associated
with a TUTT. By 0600 UTC on 1 Aug the dry air entrainment ceased
and Olga displayed a small, completely-formed eye. The typhoon had
intensified slightly, reaching a peak MSW of 75 kts shortly before
passing over the island of Okinawa. Typhoon Olga passed directly
over Okinawa around 1200 UTC, causing it to weaken slightly, but it
soon regained its 75-kt winds after exiting the island.
By 2 Aug Olga's motion turned to more of a northerly course as
a mid-latitude trough to its west deepened. The typhoon also began to
accelerate. Olga passed just west of Cheju Island around 03/0000 UTC
as it slowly weakened, due primarily to cooler SSTs. Olga passed near
the southwestern tip of South Korea and then raced northward in the
Yellow Sea, just brushing the western coast of South Korea. At
0600 UTC Kunsan AB reported gusts to 48 kts with a pressure of 984 mb.
The storm was downgraded to a tropical storm at 1200 UTC with the low-
level center displaced 112 nm from the nearest convection. By 1800
UTC, when JTWC and JMA each wrote the last advisory, Olga was inland
over North Korea and rapidly losing tropical characteristics.
Press reports located by the author indicate that 63 persons were
killed or missing in South Korea from floods, landslides, and other
rain-related accidents. Olga's passage through the country came on
the heels of several days of torrential rains, and widespread flooding
was reported throughout much of the nation. About 8500 homes were
submerged in the floodwaters, and 25,000 persons were homeless.
Agricultural losses were significant too--98,800 acres of rice paddies
were reportedly washed away. Heavy rains associated with the
storm also fell on North Korea, leading to widespread flooding there.
The author has not received any information about the effects of
Typhoon Olga during its passage over Okinawa. If anyone has any
reports of the typhoon's passage over the island, please send them to
me and I will include them in next month's summary.
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for July: 1 tropical depression **
** - classified as a depression by IMD only
NOTE: The tracking and intensity information for North Indian Ocean
Basin tropical cyclones is based primarily upon operational warnings
from the Joint Typhoon Warning Center of the U. S. Air Force and Navy
(JTWC) at Pearl Harbor, Hawaii. Occasionally some information may
be gleaned from the daily Tropical Weather Outlooks and other bulletins
issued by the Indian Meteorological Department (IMD), which is the
WMO's RSMC for the basin.
The MSW are based on a 1-min averaging period, which is used by
all U. S. civilian and military weather services for tropical cyclone
warnings. For synoptic observations in the North Indian region,
both 10-min and 3-min average winds are employed, but IMD makes no
attempt to modify the Dvorak scale for estimating tropical cyclone
intensity; hence, a 1-min avg MSW is implied. In the North Indian
basin JTWC usually does not initiate warnings until a system is
well-organized and likely to attain tropical storm status within
48 hours.
North Indian Ocean Activity for July
------------------------------------
The Indian Meteorological Department (IMD) classified one system
as a depression during July. A low-pressure area formed in the
northern Bay of Bengal on 26 Jul, and by 0300 UTC on the 27th had
organized into a tropical depression about 100 nm south-southeast of
Calcutta. The depression subsequently moved west-northwestward and
inland into Orissa State near Dhiga early on 28 Jul. The system
became somewhat better organized and was classified as a deep
depression by IMD (basically meaning 30-kt winds). By 1200 UTC the
system was inland and dissipating about 50 km northwest of Ranchi.
This disturbance was mentioned by JTWC in their daily STWO's for the
North Indian Ocean but was not classified as a tropical depression.
***********************************************************************
SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E
Activity for July: No tropical cyclones
***********************************************************************
AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E
Activity for July: No tropical cyclones
***********************************************************************
SOUTHWEST PACIFIC (SWP) - 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 included in the July, 1998 summary.
I will include this glossary from time to time, primarily in "lean"
months without a lot of tropical cyclone activity to cover. But if
anyone missed receiving it and wishes to obtain a copy, send me an
e-mail privately and I'll forward 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: jul99.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: jul99.sum, for
example.
Back issues can also be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Tom Berg, and Michael
Pitt):
http://australiansevereweather.com/cyclones/>
http://www.geocities.com/capecanaveral/6825>
http://www.hcane.com/tropcl.html>
http://www.qisfl.net/home/hurricanemike>
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 new website
the complete Annual Tropical Cyclone Report for 1997 (1996-1997 season
for the Southern Hemisphere). Also, tracks only for the 1998 tropical
cyclones are currently available.
The URL is: http://199.10.200.33/jtwc.html>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 1998 Atlantic and Eastern North Pacific
tropical cyclones; also, preliminary storm reports for all the 1998
Atlantic and Eastern North Pacific cyclones are now available.
The URL is: http://www.nhc.noaa.gov/1998.html>
Prepared by: Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)
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Document: summ9907.htm
Updated: 4th January 2007 |
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