[Index]
Monthly Global Tropical Cyclone Summary December 1998
[Summaries and Track Data] [Prepared by Gary Padgett]
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Cyclones
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Monthly Global Tropical Cyclone Summary December 1998 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
DECEMBER, 1998
(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.)
***********************************************************************
DECEMBER HIGHLIGHTS
--> One of the most intense Australian cyclones on record strikes
the Northern Territory and Western Australia
--> Central Philippines struck by another typhoon
--> Kingdom of Tonga damaged by South Pacific cyclone
***********************************************************************
CORRECTION TO OCTOBER (AND NOVEMBER) SUMMARY
In the October summary I listed the URL to a website prepared by
NCDC which contained extensive information on the effects of Hurricane
Mitch. I made an error in the website address and attempted to correct
it in the November summary. Well, I goofed again! Megan McKay has
informed me of my mistake and sent the correct URL. It is:
http://www.ncdc.noaa.gov/ol/reports/mitch/mitch.html>
Thanks to Megan for sending me the correct address, and my apologies
to anyone who was frustrated in trying to connect to the site.
***********************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for December: 1 hurricane
Hurricane Nicole (TC #14)
24 November - 2 December
--------------------------
Hurricane Nicole formed in the eastern subtropical Atlantic in late
November and was active into the first couple of days of December.
In fact Nicole was at its peak intensity of 75 kts as the month of
December opened. Since the storm formed and ran most of its course
during November, the complete history of Nicole was described in the
Global Summary for November.
***********************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for December: No tropical cyclones
***********************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for December: 2 tropical depressions
1 tropical storm
1 typhoon **
** - This based upon JTWC's and PAGASA's classifications--JMA did not
classify Faith/Norming as a typhoon.
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
'98 webpage, for sending me the PAGASA tracks. Also some information,
primarily on the pre-depression stages of the various cyclones, was
taken from the Monthly Report of the RSMC, Darwin, Northern Territory,
Australia. A special thanks to Leanne Hollis for forwarding that
report to me.
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.
Typhoon Faith/Norming (TC-24W / STS 9815)
8 - 14 December
------------------------------------------
A Formation Alert was issued by JTWC very early on 8 Dec for a
tropical disturbance deep in the tropics in the western Carolines.
The first depression warning was issued at 0600 UTC locating the center
about 300 nm east-southeast of Palau. A band of convection located
about 470 nm to the north of the system was producing some winds to
gale force, but these were not directly associated with the depression
and were not included in the intensity or wind radii. The depression
moved fairly quickly on a northwesterly course at about 16 kts,
slowly strengthening and passing about 100 nm north of Palau at
09/0000 UTC. The system was upgraded to Tropical Storm Norming by
PAGASA at 1200 UTC on 9 Dec, and was named Tropical Storm Faith by
JTWC six hours later. Faith/Norming at this time was centered about
300 nm west-northwest of Palau. (One of the JTWC warnings mentioned
that Faith's northwestward heading was partly due to self-propagation
effects often exhibited by large cyclones. For those who have access
to it, Dunn and Miller's classic book _Atlantic Hurricanes_ includes
an interesting discussion of this effect [pp. 193-194 in the Revised
Edition published in 1964]).
After crossing the 10th parallel, Faith/Norming turned to more of a
west-northwesterly course. Early on 10 Dec the storm rapidly
intensified, reaching minimal typhoon strength by 1200 UTC when located
just off the coast of Samar in the Philippines and about 315 nm south-
east of Manila. The typhoon's translational speed was about 19 kts
when it reached the islands. The center of Norming appeared to track
across the islands of Samar and Masbate, just south of Sibuyan, across
the southern tip of Tablas, just south of Mindoro, through the Calamian
Group, and finally clipping the northern tip of Palawan as it exited
into the South China Sea. By 11/1800 UTC Faith/Norming was located
about 300 nm southwest of Manila and had reached its peak intensity
of 90 kts (1-min MSW) as reported by JTWC. PAGASA did classify
the storm as a minimal typhoon with 65-kt MSW (10-min avg), but JMA's
highest 10-min MSW estimate was 60 kts. This was quite a large
discrepancy between the two for a cyclone of this intensity--usually
the delta MSW between the two centers doesn't reach 30 kts until a
system is approaching supertyphoon intensity.
After clearing the Philippines Typhoon Faith sailed on westward
across the South China Sea, gradually slowing down and turning to a
west-northwesterly course as it approached the Vietnamese coast due
to the effects of a passing mid-latitude trough which weakened the
subtropical ridge somewhat. The storm began to experience increased
windshear by 1500 UTC on 12 Dec and slowly weakened. Faith made
landfall in Vietnam just north of Nha Trang as a tropical storm with
60-kt winds around 0000 UTC on 14 Dec. Once inland the storm began
to quickly dissipate.
Norming/Faith moved swiftly through the Philippines but left a trail
of death and destruction in its wake. The latest casualty figures
available to the author indicated at least 11 were known dead and 70 or
more missing. A passenger vessel, MV Aida, capsized off Pandan on a
voyage from Palawan to Libertad, Antique. Three were killed;
20 passengers were rescued but 30 were still reported missing. Damage
was heavy in Aklan province--the provincial engineer initially
estimated damage to infrastructure at 50 million pesos, damage to
agriculture at 13 million pesos, and to fishery resources at 43 million
pesos. Flooding was severe in some areas, and the typhoon's winds
uprooted many trees and toppled power poles.
More detailed information on the effects of the typhoon in the
Philippines can be found on the following website addresses:
http://www.inquirer.net/issues/dec98/dec12/news/news_6.htm>
http://www.inquirer.net/issues/dec98/dec13/news/news_9.htm>
(Thanks to Michael Padua for forwarding this information to me.)
Tropical Storm Gil (TC-25W / TS 9816)
9 - 13 December
--------------------------------------
Short-lived Tropical Storm Gil developed from another monsoon
system in the South China Sea between Borneo and southern Vietnam.
JTWC issued a Formation Alert at 0530 UTC on 9 Dec, and the first
warning on a new depression was issued at 1200 UTC with the broad
center estimated to be located about 300 nm southeast of Ho Chi Minh
City. The warnings were prompted by the receipt of a 10-min wind
report of 20 kts. The depression moved slowly westward and gradually
became better organized with convection mainly located along the
western periphery of the large, broad circulation. JMA classified
the system as Tropical Storm 9816 at 10/0000 UTC with 35-kt MSW
(10-min avg). JTWC upgraded the depression to Tropical Storm Gil
at 0000 UTC on 11 Dec based on scatterometer data indicating winds to
35 kts around a well-developed but exposed low-level circulation
center. (It is interesting to note that JMA downgraded the system to
a depression at the very same time that JTWC upgraded it.)
Gil's life as a tropical storm, however, was very brief. JTWC
downgraded Gil back to a depression only six hours after naming it.
The system had become even more sheared, satellite intensity estimates
were only 25 kts, and scatterometer data no longer supported tropical
storm intensity. Gil moved westward, passing just south of the
southernmost tip of Vietnam. There was a flare-up of convection late
on the 11th--an oil platform reported a gust to 45 kts in the area of
convection. The slowly weakening depression drifted west-southwestward
across the Gulf of Thailand and moved into the Malay Peninsula in
southern Thailand where it dissipated.
Tropical Depression (TC-26W)
17 - 19 December
-----------------------------
A Formation Alert was issued by JTWC at 17/1100 UTC for a tropical
disturbance located in the central Philippines. This disturbance had
been mentioned in a Tropical Weather Outlook the previous day when it
was located in a low-latitude trough near 6N, 132E. The first
tropical depression warning on the system was issued at 1200 UTC on
the 17th locating the broad center about 175 nm south-southeast of
Manila. This large monsoon depression moved generally northward
through the Philippines, passing near Manila around 0000 UTC on 18 Dec.
MSW were never reported as higher than 25 kts, and the system had lost
its identity west of northern Luzon by 13/0000 UTC with its remnants
being absorbed into a broad monsoon trough to the south.
JTWC appears to have been the only warning center classifying this
system as a tropical depression. PAGASA and JMA simply referred to it
as a low-pressure area.
Tropical Depression (TC-27W)
19 - 22 December
-----------------------------
The final tropical depression of 1998 in the Northwest Pacific basin
developed in the South China Sea as part of a large monsoon gyre. Ship
reports of 25-30 kt winds were the basis for JTWC initiating warnings.
The center of the loosely-organized system was located about 500 nm
west-southwest of Manila at 0600 UTC on 19 Dec. The depression moved
in a general north-northeasterly direction throughout its life. Early
on the 20th convection consolidated and deepened somewhat. By 0900 UTC
the low-level circulation was partially exposed on the southwest edge
of the main convective area. A secondary circulation was noted
developing in the base of the broad monsoon trough. Late on 20 Dec
there were some ship reports of winds to 30 kts.
As the depression moved farther north, it began to enter a high
shear environment. By 21/2100 UTC ships were reporting winds to only
25 kts along the western periphery. The depression was located along
the northern edge of the large monsoon gyre in the South China Sea.
Several low-level circulations were seen farther south within the
monsoon circulation. The last JTWC warning, issued at 22/0000 UTC,
located the dissipating center about 225 nm southeast of Hong Kong.
As with the previous depression, neither PAGASA nor JMA classified
this system as a tropical depression--only as a low-pressure area.
***********************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for December: 1 tropical cyclone of hurricane intensity
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) on the island of Guam. For weaker systems not in warning
status by JTWC, information gleaned from the twice-daily issuances
of the Indian Meteorological Department (IMD) was used to complete
the tracks. These bulletins usually give analyzed center positions
at either 0300 or 0600 UTC and 1200 or 1500 UTC.
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.
Tropical Cyclone (TC-08A)
13 - 17 December
--------------------------
The final tropical cyclone in a somewhat above-normal year for the
North Indian Ocean began to take shape off the southern tip of India
on 7 Dec. A broad low-level circulation with an associated area of
convection was located on that date near 9N, 79E and drifting
westward into the Arabian Sea. By the 11th vertical shear had lessened
and the system began to get better organized. JTWC issued a Formation
Alert on 12 Dec, and the first warning was issued at 13/0000 UTC. The
center was estimated to be about 600 nm south-southwest of Bombay and
drifting generally northward. MSW were increased to 45 kts at 0600 UTC
based upon ship reports. The system at this time was still rather
large and loosely-organized.
The cyclone continued moving slowly north-northwestward and steadily
strengthened, reaching hurricane force at 15/0600 UTC when located
450 nm west-southwest of Bombay. The storm began to move on a more
northwesterly track, gradually turning into a straight westerly course.
The cyclone was originally forecast to make landfall in Oman as a
hurricane, but by the 15th the forecast had changed due to an expected
increase in vertical shear. This expected increase in vertical shear
indeed materialized as the subtropical ridge to the north strengthened
while upper-level flow continued out of the southwest. TC-08A began
to weaken significantly as it plodded toward the southern Arabian
peninsula.
On 16 Dec some ship reports of 35-kt winds were received, so the
system was maintained as a tropical storm. Early on the 17th the
storm turned a little more to the west-northwest, passing about 135 nm
south of Masirah Island around 0300 UTC, and made landfall later that
day in Oman as a minimal tropical storm. Once inland the system
quickly dissipated.
***********************************************************************
SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E
Activity for December: No tropical cyclones
***********************************************************************
AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E
Activity for December: 2 tropical LOWs (depressions)
1 tropical cyclone of gale intensity
1 tropical cyclone of storm intensity
1 severe tropical cyclone (very intense)
The primary source of information for Australian Region tropical
cyclones are the warnings and bulletins issued by the three TCWC's
at Perth, Darwin, and Brisbane. Information gleaned from JTWC's
warnings is used as a supplement for times when it was impossible to
obtain Australian bulletins and for comparison purposes. Additionally,
some information came from the Monthly Report of the RSMC at Darwin,
Northern Territory. References to sustained winds should be
understood as being based on a 10-min averaging period unless
otherwise noted.
Mr. Matthew Saxby, a tropical cyclone enthusiast from Queanbeyan,
New South Wales, Australia, is going to assist me with collecting
information and preparing tracks for tropical cyclones in the
Australian Region. Some of the information contained in the narratives
is based upon information forwarded to me by Matthew. A special
thanks to Matthew for his assistance.
Tropical Cyclone Billy (TC-05S / TC-03U)
1 - 6 December
-----------------------------------------
Disturbed weather just off the northwestern Australian coast was
mentioned in daily Tropical Weather Outlooks by both JTWC and Perth
as early as 20 Nov. Weak diffuse LOWs would form and then weaken,
primarily in the area from 13S to 16S, and between 114E and 125E.
By the 30th the area had become so disorganized that no general
coordinates were given. However, on 1 Dec a new LOW center had
formed near 14S, 120E along the tail end of a shear line associated
with a decaying frontal boundary. The environment had become more
favorable and the LOW was given some potential for development.
Perth began issuing bulletins at 02/1600 UTC. The LOW was located
about 180 nm northwest of Broome at this time.
With favorable upper-level divergence and weak vertical shear, the
system began to intensify as it was steered to the southwest by north-
easterly winds associated with a high pressure ridge to its southeast.
The LOW was upgraded to Tropical Cyclone Billy with 35-kt MSW at 1000
UTC on 3 Dec when it was centered about 200 nm north-northwest of Port
Hedland. Billy intensified fairly quickly, reaching its peak
intensity of 60 kts by 0400 UTC on 4 Dec when it was located about
140 nm north of Karratha, and maintained this intensity for 18 hours.
Radar imagery at 0900 UTC from Dampier indicated a 13-nm diameter eye.
On this basis JTWC reported the 1-min MSW as 65 kts in a couple of
warnings.
Tropical Cyclone Billy began to experience increased vertical shear
later in the day and began to weaken quite rapidly. Perth issued the
final warning on Billy at 0400 UTC on 5 Dec when it was centered about
115 nm north-northwest of Mardie or about 170 nm north-northeast of
Exmouth. The cyclone still had 40-kt winds at this time but was
forecast to weaken. JTWC continued to issue warnings until 06/1200 UTC.
At 05/1500 UTC scatterometer data indicated 1-min MSW of 45 kts. The
low-level center had become exposed by 2100 UTC. Billy continued to
weaken, and winds had fallen below gale force by the time the center
moved inland near Onslow around 0600 UTC on 6 Dec.
Tropical Cyclone Thelma (TC-06S / TC-04U)
3 - 15 December
------------------------------------------
JTWC first mentioned a weak tropical disturbance in the Arafura Sea
on 3 Dec. The system was located north of Arnhem Land in Australia's
Northern Territory about 250 nm east-northeast of Darwin. From its
innocuous beginnings this disturbance was destined to grow into the
most intense tropical cyclone to menace Darwin since the incredibly
destructive Cyclone Tracy, which destroyed almost all of Darwin's
buildings and left 66 people dead on Christmas Eve, 1974; and would
also become the most powerful cyclone to threaten the Top End of
Western Australia this century.
The weak LOW drifted slowly slightly north of west, very gradually
becoming better organized. By 6 Dec the system was located about 150 nm
north of Melville Island or about 200 nm north of Darwin. The LOW
began to intensify quite rapidly, becoming Tropical Cyclone Thelma at
0430 UTC on the 6th. Thelma drifted very slowly southward as it
intensified, later curving to the south-southwest. The cyclone
clipped the northwestern ends of the Tiwi Islands north of Darwin
(Melville and Bathurst) as it was reaching Category 5 on the
Australian cyclone scale--pretty much the equivalent of a Saffir/
Simpson Category 5. An advice from Darwin related that gusts to about
110 kts were likely being experienced on the islands.
Thelma began moving on more of a southwesterly course as it reached
its first peak intensity of 120 kts MSW and an estimated central
pressure of 925 mb. The cyclone made its closest approach to
Darwin at around 0600 UTC on 8 Dec when its eye was centered about
100 nm west-northwest of the city. As the eyewall approached the
Tiwi Islands its diameter was 19 nm, but had shrunk to 10 nm by
08/2100 UTC as the storm reached its first peak intensity of 120 kts.
(JTWC's peak 1-min avg MSW reported was 135 kts, which is in excellent
agreement with Darwin's 10-min value.) A press report indicated that
winds gusting to near hurricane force in Darwin brought down at least
12 trees on houses, powerlines, and a car. During a six-hour period
on the 8th, 100 mm of rain was recorded at Darwin. No injuries
were reported from the Tiwi Islands or Darwin.
Thelma weakened slightly on 9 Dec as it trekked southwestward across
the mouth of the Joseph Bonaparte Gulf, but regained its 120-kt MSW
on 10 Dec prior to making landfall. This fluctuation in intensity
perhaps was due to an eyewall expansion and contraction cycle--the
JTWC warning at 10/0900 UTC mentioned this. Tropical Cyclone
Thelma made landfall on the Kimberley coast as a Category 5 cyclone
around 2200 UTC on 10 Dec. Based on the last advice from Darwin and
the first from Perth as that office assumed warning responsibility,
wind gusts of 160-175 kts likely were experienced on the coast.
Thelma's landfall occurred about 75 nm (140 km) northeast of Kuri Bay
or about 180 nm (330 km) northeast of Cape Leveque. This location
is also about 80 nm (145 km) west of Kalumburu.
The cyclone was moving south-southwestward at the time of landfall.
By 11/0400 UTC the MSW was down to 75 kts as Thelma passed only about
50 km (27 nm) northeast of Kuri Bay. The weakening storm turned to
more of a southwesterly, then west-southwesterly, course which kept
it moving roughly parallel to the coast. By 13/1000 UTC Thelma had
reached a point about 110 km south-southwest of Broome, or only about
25 km south of La Grange. Perth had by this time downgraded the
cyclone to a tropical LOW with 30-kt winds while JTWC was still
carrying the system as a minimal tropical cyclone with 35-kt winds
(1-min avg). Thelma was able to maintain its low-level organization
quite well overland due to a favorable atmospheric environment with
good upper-level support and moist inflow from the coast. The center
of Thelma reached the coast around 1600 UTC on the 13th and moved
back offshore; however, the system never strengthened significantly.
At 14/0400 UTC the center was about 30 nm (55 km) northwest of Wallal.
Thelma drifted westward for a day or so, then turned to the south
and moved inland once more about 70 nm east-northeast of Port Hedland
at 1600 UTC on 14 Dec and began to dissipate.
Very fortunately Thelma made landfall in a very sparsely populated
portion of the Western Australian coastline. Emergency officials
attempted to evacuate the population of the Kalumburu community located
about 3055 km north of Perth which was expected to bear the brunt of
Thelma's fury. They were able to evacuate about 120 people, but about
180 were left behind. Most of those took refuge in an old monastery
which had 60 cm-thick stone walls. None of the press reports mailed
to me by Matthew mentioned any fatalities due to Cyclone Thelma. If
I learn of any later, I will report them in a future summary.
After making landfall for the final time, Thelma produced heavy
rains which led to flood warnings for the De Grey River and adjacent
streams in Western Australia. Marble Bar recorded 91 mm between
9AM and noon on 15 Dec, and 106 mm between 9AM and 3PM. Nullagine
recorded 83 mm in the same six-hour period.
Tropical LOW
7 - 13 December
---------------
An area of concentrated convection near 9S, 88E was mentioned in
the Significant Tropical Weather Outlook by JTWC on 3 Dec. The
TCWC at La Reunion issued one advisory on this area (calling it "A3")
at 1200 UTC on the 4th. Over the succeeding days the area drifted
eastward into the Australian Region and slowly became better organized.
The Perth TCWC initiated bulletins on the tropical LOW at 1000 UTC on
7 Dec when the system was located roughly 175 nm west-northwest of
Cocos Island. 10-min MSW were estimated at 25 kts, which represents
the maximum for the system. The weak LOW sat essentially stationary
for about 48 hrs and became less organized. Perth discontinued
6-hourly bulletins at 08/0400 UTC but continued to mention the LOW
in the daily Tropical Cyclone Outlooks for the central Indian Ocean.
The remnants of the LOW drifted eastward to a point about 150 nm
north-northwest of Cocos by 0400 UTC on 13 Dec.
Low-pressure areas were a persistent feature on the charts from
the beginning of the month of December within the monsoon trough
in the South Indian Ocean. There is a distinct possibility that
the above-described LOW was the same discrete center which eventually
developed into Tropical Cyclone Cathy. But because there is a 3-day
and 300 nm gap between the last position I have available on this
LOW and the LOW which was the precursor of Cathy, I have chosen to
treat them as distinct systems.
Tropical Cyclone Cathy (TC-10S / TC-05U)
16 - 30 December
-----------------------------------------
A weak tropical LOW was mentioned in the Tropical Cyclone Outlook
for the central Indian Ocean issued by Perth at 0400 UTC on 16 Dec.
The system was placed near 9S, 102E, or about 350 nm northeast of
Cocos Island. This LOW possibly was a continuation of the Tropical
LOW described above. The disturbance remained quasi-stationary for
several days without much organization.
By 24 Dec the system had become better organized and had shifted
several hundred miles to the south, or else a new center had formed.
JTWC issued a Formation Alert, and Perth began issuing 6-hourly
bulletins at 1000 UTC with the center estimated to be about 250 nm
southeast of Cocos. JTWC began issuing warnings later that day
after a scatterometer pass indicated 35-kt winds (1-min avg) around
the center. The system continued to gain in organization and Perth
named the LOW Tropical Cyclone Cathy at 1000 UTC on Christmas Day when
it was about 275 nm due south of Cocos Island. Maximum 10-min winds
were estimated to be 45 kts. Satellite imagery from around 1500 UTC
indicated cold-air stratocumulus being drawn into the circulation on
the south side. The organization of the cloud pattern had improved
but the intensity of the convection had decreased.
By early on 26 Dec the low-level center was becoming exposed.
Cathy was being steered westward by a subtropical ridge to its south,
but southerly mid-level winds were blowing the convection northward.
The cyclone continued to weaken and Perth issued its final warning
at 2200 UTC when the center was located about 325 nm west-southwest of
Cocos Island. JTWC carried the weakening system in warning status
for another 24 hours. Visible satellite imagery on the afternoon of
the 27th indicated that the convection was completely sheared away
although the low-level center was still well-organized. The remnants
of Cathy continued on westward into the central Indian Ocean. The
last mention of this system by Perth, in a Tropical Cyclone Outlook,
placed the remnant LOW near 13.5S, 84.5E at 0200 UTC on 30 Dec. No
advisories were issued on this LOW by any of the warning centres in
the Southwest Indian region.
Tropical LOW
26 December - 2 January
-----------------------
NOTE: The narrative summary for this system was largely written by
Matthew Saxby. I have primarily just performed some editing.
The last significant tropical disturbance of 1998 in the Australian
Region was first noted by JTWC over the Gulf of Carpentaria in its
25/0600 UTC Significant Tropical Weather Outlook. During the next two
days it moved westward, slowly deepening, until by 27 Dec it was over
the Limmen Bight (the southwest corner of the Gulf). The following day
the disturbance moved over southeast Arnhem Land, but though it
remained over land it continued to intensify slowly. After 28 Dec it
moved southeastward, and at 29/0600 UTC was located at 17S, 139E, or
over land just east of the Queensland/Northern Territory border. The
disturbance remained in this general area for the next day or two; then
on 30 Dec moved over water and began to develop further. At 2100 UTC
on the 30th the Brisbane TCWC issued a Tropical Cyclone Watch for
portions of the southern Gulf coast. The depression was located at
this time about 90 nm northwest of Mornington Island and moving south-
east. The LOW turned to the south-southeast shortly afterwards,
passing about 40 nm west of Mornington Island. The Watch was cancelled
when it became apparent the center was moving back inland. The system
began to break-up over northwestern Queensland and had dissipated by
0600 UTC on 2 Jan. At the time the Cyclone Watch was issued on 30 Dec
the LOW had a central pressure of 996 mb, so the MSW would likely have
been in the 25-30 kt range.
The main impact of this system was very heavy rains over much of the
state of Queensland. Many centres reported 24-hour totals exceeding
150 mm on 31 Dec-01 Jan. One station reported 285 mm but the location
is unknown. Widespread rainfall became prevalent over all the state
except for the southwest corner on 1 and 2 Jan as moisture from the
system streamed southward from the Gulf. This rainfall activity was
enhanced in southern Queensland and northeastern New South Wales by
interaction with an upper-level trough which brought rain and shower
activity as far south as Sydney on New Year's Day. Rainfall readings
of 50-100 mm were still common over central and northern Queensland
(mainly inland) as late as 3 Jan. Widespread flooding resulted from
the heavy rains with rivers in the Gulf region being severely affected.
Also some of the river systems which feed into Lake Eyre from north-
western Queensland reached flood stage, with many streams still
flooding as late as 24 Jan--a situation which could continue for weeks
or even months.
An interesting aspect of this system was the phenomenally low
daytime temperatures which accompanied the rain. Many centres in
northwestern Queensland recorded record low and near-record low January
maxima on 1 Jan. Longreach made headlines with a maximum of only
21 C--16 degrees below normal and a record low January maximum.
Temperatures in southern Queensland were somewhat below normal, but not
as severely (6 C below normal in Brisbane). Curiously, although
northern and central coastal areas received heavy rainfall, their
temperatures were only slightly affected.
At least one death can indirectly be attributed to the storm, due to
a car driving off a winding mountain road in heavy rain and thick fog
north of Brisbane.
***********************************************************************
SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E
Activity for December: 2 tropical depressions **
1 tropical cyclone of hurricane intensity
** - This is based upon the classification by the Nadi, Fiji, Tropical
Cyclone Warning Centre which has official WMO warning
responsibility for the South Pacific north of 25S and between
160E and 120W. By JTWC standards both of these systems met the
criteria for tropical storms.
NOTE: Most of the information presented below was taken from the
operational warnings and advisories issued by the Fiji TCWC at Nadi
and from the Monthly Summary for December prepared by the staff of
the Nadi centre and sent to me by Alipate Waqaicelua, Manager, Forecasting.
A special thanks to Alipate for sending me a copy of the summary.
Also, a special thanks is due to Steve Ready of the Wellington office
for forwarding me some cyclone damage and casualty figures from
Tahiti and Tonga.
References to sustained wind imply a 10-minute averaging period
unless otherwise noted. Also, the basic definition of a cyclone in
WMO Region 5 (Australia and the South Pacific) has the unique
requirement that a depression must have gale-force winds more-or-less
completely surrounding the center before the system is named as a
tropical cyclone. Hence, often (as in the case of the two depressions
this month) gales of 35-40 kts may be present in one or two quadrants
but the system is not considered a tropical cyclone.
Fiji this season has initiated their own numbering scheme for
tropical disturbances (01F, 02F, etc) that form in the Nadi AOR. Some
of the numbered disturbances never warrant depression status. The
first numbered disturbance of this cyclone season, 01F, was a weak and
short-lived disturbance north-northwest of Samoa on 4 Dec. It moved
from near 9.5S, 174.0W at 1500 UTC to near 8.5S, 175.0W by 1800 UTC.
MSW were estimated to be only 20-25 kts. Only two warnings were issued
on this system by Nadi, and no track is given in the accompanying
Cyclone Tracks file.
A significant amount of the material presented below on Tropical
Depression 02F (TC-08P) and Tropical Cyclone Cora was taken directly
from the informative summary sent to me by Alipate.
Tropical Depression (TC-07P)
14 - 17 December
-----------------------------
A Significant Tropical Weather Outlook issued by JTWC on 11 Dec
mentioned an area of disturbed weather near 6S, 165E. During
subsequent days the disturbance drifted westward across 160E into
the eastern portion of the Brisbane region. Broad troughing with
several centers of lower pressure extended southward and eastward
from near 10S, 155E. By late on 14 Dec a LOW near the southeastern
end of this trough had become better organized and Fiji mentioned this
as a tropical depression at 2100 UTC located about 410 nm west-
northwest of Noumea, New Caledonia. Since the system was practically
on the boundary between Brisbane's and Nadi's respective AOR's (19.5S,
159.7E) and moving southeast, Nadi assumed warning responsibility for
the depression; therefore, I am including it as a Southwest Pacific
basin system. But because the depression had originated in Brisbane's
AOR, the Fiji TCWC did not assign it an "F" designator; hence, the
reference to it by the JTWC number.
JTWC initiated warnings on the system at 15/0900 UTC due to a ship
report of 34 kts at 0000 UTC. Bulletins from Nadi alluded to gales
being present in the southern and eastern quadrants, but since they
were not surrounding the center, the depression was not named as a
tropical cyclone. The depression moved southeastward roughly parallel
to and several hundred miles southwest of New Caledonia. By 0600 UTC
on 16 Dec the system was about 250 nm southwest of Noumea and had moved
across 25S and into the AOR of the Wellington, New Zealand, office.
The depression turned to the south and accelerated as it began to lose
tropical characteristics. It passed about 210 nm west of Norfolk
Island at 1700 UTC, and had become extratropical about 400 nm west-
northwest of New Zealand's North Cape by 0500 UTC on 17 Dec.
Tropical Depression (TD-02F / TC-08P)
22 - 24 December
--------------------------------------
This system was very interesting in that it had many features of
a cold-cored, baroclinic depression. The first warnings were issued
by Fiji late on 21 Dec when the LOW was quasi-stationary about 300 nm
south-southwest of Tahiti. Gales of up to 35 kts were forecast to be
occurring within 150 nm of the center in the southeastern semi-circle.
As the system began moving further to the southeast it was being
continually subjected to strong vertical shear which exposed the low-
level circulation well northwest of the deep convection. At this time
there was considerable divergence in Dvorak T-numbers from various
centers but with most running from 2.5 to a weak 3.0.
The depression began to move to the southeast later on 22 Dec and
accelerated rapidly on 23 Dec. The system moved out of Fiji's warning
AOR shortly after 1800 UTC on the 22nd. Convection was also rapidly
developing around the center and most satellite analysts were agreeing
on an embedded center pattern with a current intensity number of 3.5.
Wellington did not issue any tropical cyclone warnings on this system
as gales were believed to be occurring only in the southeast quadrant.
NPMOC's peak 1-min MSW reported was 50 kts at 23/1200 UTC. The system
became completely extratropical and the last warning from Pearl Harbor
placed the LOW about 900 nm south-southwest of Pitcairn Island.
Even though the center of the depression remained about 300 nm from
Tahiti, a zone of convergence associated with the system brought some
very heavy rainfall to the island. Steve Ready passed along some
figures he'd obtained from Jacki Pilon, Director, Meteo France, Tahiti.
On 19 Dec the Faa'a airport meteorological station recorded 366 mm;
Papeete high school Lamenais (a climatological station) recorded
508mm; and another station (Tiare #2) reported 550 mm. (Presumably
these are 24-hour totals.) One death was reported with three persons
missing. There were some landslides but no injuries. Nine houses
were destroyed with more than 100 damaged or flooded; also many bridges
and roads were damaged.
The information from Jacki contained the interesting observation
that the heavy rainfall was not caused by intense convection. Winds
were weak to moderate at the surface and almost nil at the cloud
level, and the station radiosounding showed saturation up to 500 mb
only. The clouds were visually of stratiform shape and appeared to
be quite warm on satellite pictures, but nonetheless caused very high
precipitation rates.
Tropical Cyclone Cora (TC-03F / TC-09P)
21 - 28 December
----------------------------------------
The Nadi TCWC began monitoring a disturbance over the Northern Cooks
on 18 Dec which was embedded in the South Pacific Convergence Zone.
The disturbance was drifting slowly west-southwestward but convection
was not organized very well and was being influenced by diurnal
effects. The system continued to drift farther west-southwest to just
north-northwest of Samoa by 21 Dec where it began to show increased
signs of intensification. An AWS on American Samoa (WMO 91766)
reported 1-min avg winds of 32 to 42 kts with a minimum pressure of
1002 mb. This prompted Nadi to issue the first gale warning on the
system at 21/0600 UTC.
Over the next three days the depression continued to drift towards
the west-southwest, slowly showing significant improvements in
convective organization. The center passed a short distance to the
south of Wallis and Futuna Islands. Late on 23 Dec the depression
seemed to stall, describe a tight loop, and then began to move slowly
to the south-southeast. Tropical Cyclone Cora was christened at
0600 UTC on 24 Dec when it was located about 300 nm east-northeast of
Nadi. Cora was headed at this time for Tongatapu (Tonga's largest
island) on which is located the capital, Nukualofa.
Cora developed rapidly after being named, reaching storm intensity
(47 kts) around 1200 UTC and hurricane intensity by 25/0900 UTC when
it was located about 150 nm northwest of Tongatapu. An NPMOC warning
at 0900 UTC indicated that the convection associated with Cora extended
as far as 400 nm from the center. The hurricane reached its peak
intensity of 75 kts (90 kts 1-min MSW from NPMOC) at 25/1800 UTC when
just northwest of Nukualofa. The eye seems to have made its closest
approach to the island of Tongatapu around 0300 UTC on 26 Dec when
it passed a short distance to the northeast. This placed the capital
very near to the eyewall region, but fortunately it was the right
front side. (In the Southern Hemisphere winds are normally stronger
on the left front side with respect to the direction of motion due
to the clockwise rotation of the winds.)
After passing Tonga Cora began to accelerate, first towards the
east-southeast, but finally southeastward and out of Nadi's AOR.
The weakening hurricane passed about 300 nm south of Rarotonga
around 1800 UTC on the 27th. Wellington assumed warning
responsibility after 0600 UTC but within 24 hrs Cora was deemed
extratropical. By 28/2300 UTC the extratropical storm was almost
1000 nm south of Tahiti and moving on further into the colder South
Pacific Waters.
The lowest pressure recorded at Nukualofa was 959.5 mb at 26/0400
UTC and a peak gust of 70 kts was recorded at 26/0454 UTC. Most of
the damage was to agriculture, with root crops being the hardest hit.
A few houses had damaged roofs and power was disrupted due to lines
being downed. According to some figures received from Steve Ready,
the overall damage estimate was placed at $19.6 million in Tongan
dollars (equivalent to $12 million U.S. dollars). Cora was less
damaging to Tonga than Tropical Cyclone Hina in March of 1997.
***********************************************************************
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 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
December as an example: dec98.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: dec98.sum, for
example.
Back issues can also be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, and Tom Berg):
http://australiansevereweather.com/cyclones/>
http://www.geocities.com/capecanaveral/6825>
http://www.hcane.com/tropcl.html>
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>
The preliminary storm reports for all the 1997 Atlantic and Eastern
North Pacific tropical cyclones are available on the Tropical
Prediction Center's website: http://www.nhc.noaa.gov> . These
reports include the analyzed best-track for each cyclone. The staff
of JTWC is also working on an on-line version of their Annual Tropical
Cyclone Report for 1997. It is still under construction, but the
best-track files are already available for 1997 Northwestern Pacific
and North Indian Ocean cyclones. The URL is:
http://www.npmocw.navy.mil/npmocw/prods/jtwc.html>
Prepared by: Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays)
***********************************************************************
***********************************************************************
|
Document: summ9812.htm
Updated: 18th March 2008 |
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