[Index]
Monthly Global Tropical Cyclone Summary January 2007
[Summaries and Track Data] [Prepared by Gary Padgett]
| Tropical
Cyclones
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Monthly Global Tropical Cyclone Summary January 2007 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
JANUARY, 2007
(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.)
SPECIAL NOTE: Very happily, John Diebolt of Tucson, Arizona, now has his
tropical cyclone website up and running again and has begun once more to
produce graphic images depicting the tracks of all tropical systems for
which I prepare a tabular track in the companion cyclone tracks file.
These can be accessed at the following URL:
http://www.tropicalcyclone2005.com/>
Scroll down the chart to the month of interest and click on the green
bar under "Operational Track Image" for the desired system.
The tabular track of positions and intensities may also be obtained
from the above website, or from the other archival sites listed in
the Author's Note in the closing section of this summary.
*************************************************************************
JANUARY HIGHLIGHTS
--> Southwest Indian Ocean activity picks up late in month
--> Two short-lived tropical cyclones form in South Pacific Ocean
*************************************************************************
EXTRA FEATURE - INDEX TO EXTRA FEATURES FOR 2006
Beginning in May, 2000, I began including with each monthly summary
an extra feature which I called the Feature of the Month. Beginning
with July, 2005, I suspended these as a regular monthly item, but have
since included some extra features as time permits. Following is an
index to the Extra Features for 2006.
JAN - INDEX TO MONTHLY AND EXTRA FEATURES FOR 2005
FEB - A COMPARISON BETWEEN THE AUSTRALIAN CYCLONE SEVERITY SCALE
AND THE SAFFIR/SIMPSON SCALE
MAR - WESTERN HEMISPHERE TROPICAL CYCLONE NAMES for 2006
APR - none
MAY - none
JUN - A REVIEW OF THE 2005-2006 TROPICAL CYCLONE SEASON
FOR THE SOUTHERN HEMISPHERE
JUL - ADDENDUM TO JUNE SUMMARY - East Coast LOW of 27 June
AUG - ADDENDUM TO JULY SUMMARY - System South of Nova Scotia on 17 July
SEP - SOUTHERN HEMISPHERE TROPICAL CYCLONE NAMES
2006 - 2007 SEASON
OCT - ADDITIONAL ATLANTIC TROPICAL STORM ADDED
NOV - none
DEC - A REVIEW OF THE 2006 TROPICAL CYCLONE SEASON
FOR THE NORTHERN HEMISPHERE
*************************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for January: No tropical cyclones
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for January: No tropical cyclones
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for January: 1 tropical depression **
** - classified as a tropical depression by JMA only
Northwest Pacific Tropical Activity for January
------------------------------------------------
No tropical storms or typhoons formed in the Northwest Pacific basin
during the first month of 2007. However, there was an interesting
system followed during the first week of the month in the South China
Sea north of Borneo and far to the southeast of southern Vietnam.
According to C. P. Chang, Naval Post-graduate School, Monterrey, the
well-defined vortex was induced by horizontal shear and terrain effects.
These are typically weak with only moderate vorticity. There was enough
convection associated with the vortex that at 0000 UTC on 5 January, JMA
classified the system as a weak tropical depression near 5.0N/111.0E.
By 1800 UTC the system had moved westward to near 6.0N/108.0E. Six
hours later JMA reduced the system to a low-pressure area, still moving
slowly westward. The final reference to the LOW was at 07/1200 UTC
when it was placed near 4.0N/105.0E. No wind estimates were given, but
peak winds likely did not exceed 20 kts. This system was not referenced
in any STWOs issued by JTWC.
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for January: No tropical cyclones
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for January: 1 tropical disturbance
1 severe tropical storm **
1 intense tropical cyclone ++
** - system formed late in December and continued on into January
++ - system formed late in January and continued on into February
Sources of Information
----------------------
The primary sources of tracking and intensity information for
Southwest Indian Ocean tropical cyclones are the warnings issued by
the Tropical Cyclone Warning Centre on La Reunion Island, part of
Meteo France (MFR), and the Regional Specialised Meteorological Centre
for the basin. However, tropical cyclones in this region are named
by the Sub-regional Tropical Cyclone Advisory Centres in Mauritius and
Madagascar with longitude 55E being the demarcation line between their
respective areas of naming responsibility. The La Reunion centre only
advises these agencies regarding the intensity of tropical systems.
References to sustained winds imply a 10-minute averaging period unless
otherwise stated.
In the companion tropical cyclone tracks file, I occasionally
annotate positions from warnings issued by the Joint Typhoon Warning
Center (JTWC) of the U. S. Air Force and Navy, located at Pearl
Harbor, Hawaii, when they differ from MFR's coordinates by usually
40-50 nm or more. The JTWC warnings are also the source of the
1-minute average maximum sustained wind values included in the
tracks file. Additionally, information describing details of
satellite imagery and atmospheric circulation features included in
the narratives is often gleaned from the JTWC warnings.
Southwest Indian Ocean Tropical Activity for January
-----------------------------------------------------
As the month opened Tropical Storm Clovis was gathering strength
as it passed just east of Ile Tromelin on its way to a rendezvous with
the eastern coast of Madagascar on 4 January. The report on Severe
Tropical Storm Clovis may be found in the December, 2006, summary.
Bulletins were issued for two numbered disturbances in the Southwest
Indian Ocean during January. Early in the month (6 January) a LLCC with
some associated deep convection formed in the central Mozambique Channel
off the west coast of Madagascar a few hundred miles west of the city of
Antananarivo. Outflow was favorable but shear was high due to an upper-
level trough to the southwest impinging on the disturbance. The LOW
drifted erratically southward through the Channel without significant
development. At 08/0600 UTC MFR issued the first of only two warnings
for Tropical Disturbance 06 with 10-min avg winds estimated at 25 kts,
locally reaching 30 kts in the eastern part of the system. The final
bulletin at 08/1200 UTC noted that intensification was not expected
due to an unfavorable environment and that the system was forecast to
make landfall as a weak disturbance between Toliara and Itempolo in
southwestern Madagascar within the next 12 to 24 hours. Dvorak estimates
from JTWC peaked at only T1.5/1.5, but SAB did return a T2.0/2.0 rating
at 07/2030 UTC, suggesting that 1-min avg winds could have been 30 kts,
in agreement with MFR's classifications of T2.0/2.0. A track for this
system was included in the companion cyclone tracks file and a graphic
is available on John Diebolt's website.
Late in the month another tropical cyclone began to take shape over
the west-central South Indian Ocean west of Diego Garcia and developed
into the rather intense Tropical Cyclone Dora. A report on Dora follows.
INTENSE TROPICAL CYCLONE DORA
(MFR-07 / TC-10S)
28 January - 12 February
-------------------------------------------------
A. Introduction and Storm Origins
---------------------------------
Forming at the end of January and operating until nearly the middle
of February, the long-lived Dora was the herald of a rather significant
outbreak of tropical cyclones across the Southwest Indian Ocean. Four
named storms were to follow during February with three reaching tropical
cyclone (i.e., hurricane) intensity and two of those becoming intense
tropical cyclones (10-min avg winds of 90 kts or higher). Dora followed
a rather zigzagging south-southwesterly track from deep in the tropics
to the west of Diego Garcia to extratropical transition far to the south
of the Mascarenes. Winds peaked at 100 kts on 4 February while the storm
was centered more than 200 nm northeast of tiny Rodrigues Island, but
had weakened to about 50 kts by the time Dora made its closest approach
to the island, lying 90 nm to the east at 0000 UTC on 6 February.
A graphic displaying the track of Intense Tropical Cyclone Dora may
be found at the following link:
http://www.tropicalcyclone2005.com/>
Scroll down to the chart for January, 2007, and click on the green bar
under "Operational Track Image" on the line for Dora (10S).
In the daily STWO for the Southwest Indian basin on 26 January, JTWC
noted that an area of convection had persisted approximately 235 nm west
of Diego Garcia. Weak convective banding was present on the northeastern
and southwestern peripheries of the LLCC. The disturbance was located
in a region of low vertical shear and favorable diffluence aloft, so the
potential for development was upped to 'fair' on the 27th. At 0600 UTC
on the 28th MFR issued their first bulletin for Tropical Disturbance 07,
located about 350 nm west of Diego Garcia. Deep convection was flaring
over a well-defined LLCC and bands of convection were wrapping into the
southern semicircle of the disturbance; hence, JTWC upped the development
potential to 'good'. By 28/1800 UTC Tropical Disturbance 07 was located
about 340 nm west-southwest of Diego Garcia and tracking slightly east of
due south at 6 kts. MFR estimated the winds at 25 kts, locally reaching
30 kts, but JTWC issued their first warning on TC-10S, estimating the
1-min avg MSW at 40 kts.
Equatorward outflow was excellent, and by early on the 29th a poleward
outflow channel was developing and the system began to show signs of
further intensification. MFR upgraded the disturbance to a 30-kt
tropical depression at 29/0600 UTC, and six hours later Mauritius
christened the developing system Tropical Storm Dora--a name contributed
to the regional list by Mozambique. Dora was then located about 500 nm
southwest of Diego Garcia, and moving steadily to the south-southwest
along the southwestern periphery of a near-equatorial ridge to the
northeast.
B. Synoptic History
-------------------
After earning a name, Dora intensified rather quickly to a severe
tropical storm, reaching 50 kts by 0000 UTC on 30 January, but then the
system intensified more slowly, not reaching tropical cyclone intensity
until 0600 UTC on 1 February. (JTWC had upgraded Dora to hurricane
intensity at 1800 UTC on 30 January.) The storm was then located
approximately 375 nm northeast of Rodrigues Island and moving southeast-
ward at 5 kts. Dora was caught in a weak steering environment between
a mid-level ridge to the northeast and another ridge to the south. After
reaching tropical cyclone status, Dora's intensity increased only slowly,
possibly due to stable air introduced by a trough passing to the south.
Dora's track turned to the south-southwest on 2 February due to the
influence of a competing subtropical steering ridge anchored over
Madagascar and extending eastward to the south of the storm. Around
this time Dora underwent an eyewall replacement cycle, resulting in a
large eye and an "annular" appearance.
Outflow was good and Dora continued to slowly strengthen, reaching a
peak intensity of 100 kts (10-min avg) with an estimated CP of 930 hPa
at 03/1200 UTC while centered about 250 nm east-northeast of Rodrigues
Island. (JTWC's peak 1-min avg MSW of 115 kts is in good agreement with
MFR's.) The storm's motion became westerly at a slow crawl on the 3rd
as the battle between the near-equatorial ridge and the subtropical ridge
continued. After peaking in intensity Dora began to weaken rather
quickly as a building anticyclone to the southeast began to inject cooler
and drier air into the cyclone's center. At 03/1800 UTC the estimated
MSW was 100 kts--twenty-four hours later Dora was a minimal 65-kt
tropical cyclone and was downgraded to a 60-kt severe tropical storm at
05/0000 UTC.
However, after this point the intensity leveled off and Dora's MSW
hovered around 50-55 kts for another day and a half. The very slow
westerly motion continued and the tropical storm reached its closest
point of approach to Rodrigues Island around 0000 UTC on 6 February when
the center lay about 90 nm to the east of the island. The MSW at this
time was estimated at 50 kts. Following its CPA to Rodrigues, Dora's
track became generally southwesterly for the remainder of its life,
although still with a few wobbles. The primary steering mechanism
became a subtropical ridge situated to the southeast of the tropical
storm. As Dora tracked into higher latitudes it encountered increasing
vertical shear and drier air and had weakened to a 40-kt tropical storm
by 06/1800 UTC. JTWC continued to weaken the system, but MFR bumped
the winds back to 45 kts at 08/0600 UTC. The storm by this time was
beginning extratropical transition and the slight intensification was
likely due to baroclinic influences.
JTWC issued their final warning on Dora at 09/0600 UTC, noting that
a well-defined LLCC remained but the system had lost all its deep
convection. At the same time MFR classified Dora as an extratropical
gale with the strongest winds (locally up to 50 kts) occurring far to
the south of the center due to a gradient with the subtropical HIGH.
Dora at this time was located approximately 400 nm south-southwest of
Rodrigues Island and moving southwestward at 5 kts. RSMC La Reunion
continued to issue warnings on the extratropical system for another
three days as it accelerated southwestward, gradually curving to the
south. The final reference by MFR was at 1800 UTC on 12 February when
the weakening gale was located over 1000 nm to the southwest of Reunion
Island.
C. Damage and Casualties
------------------------
No reports of damage or casualties are known to have resulted from
Intense Tropical Cyclone Dora.
(Report written by Gary Padgett)
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for January: 1 tropical cyclone of gale intensity
1 monsoon LOW ("landphoon")
Sources of Information
----------------------
The primary sources of tracking and intensity information for
Northwest Australia/Southeast Indian Ocean tropical cyclones are
the warnings and advices issued by the Tropical Cyclone Warning
Centres at Perth, Western Australia, and Darwin, Northern Territory.
References to sustained winds imply a 10-minute averaging period
unless otherwise stated.
In the companion tropical cyclone tracks file, I occasionally
annotate positions from warnings issued by the Joint Typhoon Warning
Center (JTWC) of the U. S. Air Force and Navy, located at Pearl
Harbor, Hawaii, when they differ from the Australian centres' coor-
dinates by usually 40-50 nm or more. The JTWC warnings are also the
source of the 1-minute average maximum sustained wind values included
in the tracks file. Additionally, information describing details of
satellite imagery and atmospheric circulation features included in
the narratives is often gleaned from the JTWC warnings.
Northwest Australia/Southeast Indian Ocean
Tropical Activity for January
------------------------------------------
A tropical LOW formed south of Indonesia at the end of December and
remained quasi-stationary for a couple of days. Some gales on the
northern periphery were noted on 1 January, and by the next day had
increased in coverage to the point that the system was named Tropical
Cyclone Isobel. Isobel tracked generally southward and inland near Port
Hedland on the 3rd. During a post-storm review it was determined that
Isobel had not met all the criteria for an official tropical cyclone
as practiced by the Australian TCWCs. By the definition used by the
BoM warning centers, a system has to have gales wrapped around more than
50% of the center for at least 6 hours to qualify as a tropical cyclone.
This information came from Andrew Burton of BoM Perth, and he notes that
such hair-splitting is not normally employed in operations, but comes
into play during preparation of "best tracks" and official post-storm
summaries. (Thanks to Andrew for the enlightenment on this issue.)
A report follows on "Tropical Cyclone" Isobel, and another on a very
interesting and significant over land monsoon LOW which wandered about
central Australia for well over a week, bringing heavy rains and gale-
force winds to some areas. Both reports were authored by Simon Clarke.
TROPICAL CYCLONE ISOBEL
(TC-07S)
31 December � 3 January
-------------------------------------------
A. Storm Origins
----------------
The fleeting life of Isobel can be traced back to a concentrated
cluster of thunderstorm activity located approximately 180 nm S of
Bali, Indonesia, and 550 nm NNW of Port Hedland, Western Australia,
as early as 29 December 2006. This thunderstorm activity struggled to
consolidate, being affected by strong upper-level westerly winds.
However, by 1 January 2007, it was clear to BoM Perth that there was
the potential for the tropical LOW to consolidate and develop further,
with a track forecast to take the system southward toward the Pilbara
coast of Western Australia.
B. Synoptic History
-------------------
As the system commenced its rapid path to the SSE, the Perth TCWC
noted within its advisories and warnings that the system consisted of
multiple low-level circulations and was therefore basing its advices
on the projected location of the consolidating centre of organising
thunderstorm activity. The system was named Isobel at 02/0600 UTC when
located near 15.0S/119.3E (approximately 310 nm N of Port Hedland) as
convection consolidated close to the most dominant LLCC. Development
of the overall system was further enhanced by a strong poleward outflow
channel. The system accelerated on a S to SSE path, reaching 13 kts
just prior to landfall as a result of a strengthening southerly
steering current on the northwestern periphery of a high-amplitude
trough situated off the western coast of Australia.
The system may have achieved its peak intensity of 982 hPa and 45 kts
(10 min-avg) at 02/1200 UTC while located approximately 250 nm N of
Port Hedland. However, this figure may be re-examined in further
post-analysis scrutiny.
Isobel eventually crossed the coast to the north of Pardoo
(approximately 20.0S/119.3E) at 12 noon WST (03/0400 UTC), and at
this time possessed little more than a weak, ill-defined centre with
the central pressure estimated to be 990 hPa. For that reason the
strong squally winds and heavy rains normally associated with a
typical tropical cyclone were not reported close to the centre. The
highest winds associated with Isobel were actually reported at Barrow
Island: some 230 nm to the west of the landfall location. Isobel was
downgraded 3 hours after landfall as the overall system became
embedded and absorbed into the developing deep trough that was forming
over the southwestern part of Western Australia at the time.
C. Storm Effects
----------------
Isobel was responsible for shutting down offshore oil production for
a period prior to landfall. However, the disruption was short-lived.
Localised and highly variable rain totals were recorded, including a
6-hour total of 141 mm at Mandora, just to the east of the landfall
location (up to 3:00 pm on the 3rd). However, aside from this there
were no significant direct impacts associated with the system.
Isobel will probably be better remembered for injecting a significant
slug of tropical moisture to fuel the developing deep trough /low-
pressure system over the eastern Goldfields of Western Australia.
Eventually this new mid-latitude LOW pressure system (988 hPA) went
on to produce severe gales and significant rainfalls in what was
described in the local media as "once-in-a-generation" storm over
parts of southern Western Australia.
The damage bill from the collision of the moisture slug from �ex-
Isobel� and the deep trough is estimated to be in the tens of
millions (AUD), primarily concentrated in the Esperance to
Ravensthorpe area. More than 100 homes were damaged, several boats
were destroyed, trees were felled and 35 metres of bridge on the
South Coast Highway, the main road linking Esperance to Perth, was
washed away. A Department of Agriculture and Food spokesman said an
estimated 20,000 head of sheep and cattle had died from exposure and
drowning in the wild weather. Mining activities in the south were
also severely disrupted. A region around the West Australian coastal
town of Esperance was declared a Natural Disaster Area.
Some long standing one-day rainfall records fell and a comprehensive
summary of the event can be found at the following link:
http://australianweathernews.com/news/2007/070104.SHTML>
The low-pressure system eventually tracked to the SE, passing over
Tasmania on 6�7 January, producing strong winds and useful rain.
There were no reports of human injuries or deaths associated with the
combined system.
D. Additional Discussion
------------------------
Post-analysis of the tropical system that was named Isobel reveals
that it really never was a tropical cyclone at all. The system
consisted of a series of multi-centred low-pressure circulations that
never had the opportunity to consolidate into a central dominant
cyclonic core prior to landfall. Therefore, it seems that Isobel's
demotion was predicated upon a structural issue and not a wind speed
issue. (See basin introductory paragraph above for some late-received
information clarifying this matter.)
It should be noted that Dvorak classifications from SAB and AFWA
reached T3.0/3.0 on 2 January, and JTWC's rating at 02/1730 UTC
reached as high as T3.5/3.5. JTWC's peak 1-min avg MSW for Isobel was
40 kts, but no warning was issued at the synoptic hour nearest their
peak Dvorak numbers, i.e., 02/1800 UTC.
(Report written by Simon Clarke; last paragraph added by Gary Padgett)
MONSOON LOW
12 - 22 January
-----------------------------------
A persistent monsoon LOW developed from a surge in the monsoon that
had become established over the Kimberley/Top End region of Australia by
12 January. On 13 January a weak tropical LOW developed overland in the
Kimberley region of Western Australia and tracked slowly to the
southwest. Tropical cyclone advisories were issued as the LOW approached
the western Kimberley Coastline. However, by 14 January the LOW switched
to an east-southeasterly path, taking the system inland into central
Australia while it continued to deepen over land. The monsoon LOW
proved to be particularly resilient as it tracked into the Northern
Territory late on 16 January, subsequently moving through the central/
southern half of the Northern Territory to the north of Alice Springs
(17 � 20 January) before eventually entering far western Queensland near
Bedourie, and thence turning onto a north-northeasterly track toward the
inland region to the south of Mount Isa (20 � 21 January). The LOW
thereafter curved back to the west and quickly dispersed upon
re-entering the Northern Territory. The entire lifespan of the system
was in excess of ten days.
The Australian continent experiences such persistent summer monsoonal
low-pressure systems from time to time and the term �landphoon� has been
unofficially coined for these weather systems. The LOW, for all intents
and purposes, appeared to have the cloud structure of a tropical cyclone
in satellite imagery and produced areas of strong to gale force winds.
However, it did not develop a tight inner core or eye wall. The movement
of the LOW could be tracked in radar imagery as it passed to the north of
Alice Springs where it reached its minimum estimated CP of 995 hPa.
On 19 January, Birdsville Airport AWS recorded 340/37-kt to 42-kt
gusts (QNH 1001.7 hPa) while the LOW was centered about 220 km away.
Even farther out from the centre, Ballera Gas Field AWS recorded
350/33 kts sustained, probably as a consequence of thunderstorm activity.
The LOW drew in significant tropical moisture initially though the
Kimberley region and the adjacent areas of the northwestern Northern
Territory before it swept into the southern half of the Territory, much
of South Australia, western parts of Victoria and the far west of
Queensland. During the period 18�21 January most of these areas
recorded monthly rainfall in the highest decile, although the BoM notes
that few records were set.
Through South Australia and western Victoria the rains were enhanced
by the slow approach of a frontal system which generated a broad area of
slow moving thunderstorms. Localised flash flooding occurred at several
locations in the Pastoral Districts and northern Agricultural Districts
as a result. Some notable rainfall totals in South Australia included
Hawker: 125.4 mm to 9 am on 20 January and 173 mm for the week ending
9 am Monday 22 January. Corny Point: 107 mm to 9 am on 20 January and
Parawa: 105.4 mm to 9 am also on 20 January. Arcoona homestead, near
Woomera, recorded 143 mm in the 24 hours to 9 am on 20 January, with much
of this falling in a 4-hour period from 11 am to 3 pm on 19 January.
Arcoona had accumulated a total of 190 mm for the week ending 9 am Monday
22 January. South Australia had its ninth-wettest January on record
(73% above normal).
The LOW eventually dumped much-needed rainfall into the Channel
Country, Warrego and Central West of Queensland, causing flooding in
many inland river systems. In Queensland, Bedourie's January total of
296.4 mm is the highest monthly total recorded in its 61 years of record,
(January average: 32.1 mm). Cluny received a monthly total of 483 mm,
the highest in its 68 years of record (January average: 37.2 mm).
Bedourie, with 169.1 mm, and Cluny, with 229 mm, also reported their
highest daily rainfall totals on record. A number of stations had more
rain during this event than they received in all of 2006.
(Report written by Simon Clarke, with significant statistical information
provided by BoM)
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for January: 1 tropical LOW **
** - system eventually became a tropical cyclone in early February
Northeast Australia/Coral Sea
Tropical Activity for January
-----------------------------
Much of the southern Northern Territory and western Queensland were
under the influence of a persistent and well-organized monsoon LOW for
several days around mid-month. The LOW, however, formed in the Kimberley
region of Western Australia and a report on the system, written by Simon
Clarke, may be found in the above section of this summary covering the
Western Australian region. At the end of the month a tropical LOW began
to take shape just north of the eastern Top End. During the first week
of February this system was seen to wander aimlessly around over the
Gulf of Carpentaria for several days. By the 5th the LOW was headed
eastward toward the southern Cape York Peninsula when it began to
strengthen and was named Tropical Cyclone Nelson. A report on Nelson
will be included in the February summary.
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for January: 1 tropical depression
2 tropical cyclones of storm intensity
Sources of Information
----------------------
The primary sources of tracking and intensity information for
South Pacific tropical cyclones are the warnings and advisories
issued by the Tropical Cyclone Warning Centres at Nadi, Fiji (for
waters north of latitude 25S), and Wellington, New Zealand (for
waters south of latitude 25S). References to sustained winds imply
a 10-minute averaging period unless otherwise stated.
In the companion tropical cyclone tracks file, I occasionally
annotate positions from warnings issued by the Joint Typhoon Warning
Center (JTWC) of the U. S. Air Force and Navy, located at Pearl
Harbor, Hawaii, when they differ from the Southern Hemisphere
centres' coordinates by usually 40-50 nm or more. The JTWC warnings
are also the source of the 1-minute average maximum sustained wind
values included in the tracks file. Additionally, information
describing details of satellite imagery and atmospheric circulation
features included in the narratives is often gleaned from the JTWC
warnings.
South Pacific Tropical Activity for January
--------------------------------------------
RSMC Nadi, Fiji, issued warnings on three tropical systems during the
month of January following a month-long quiet period in the tropical
South Pacific. Two of the three systems became named cyclones of near
hurricane intensity. The first, a non-developing system, is described
here--reports follow on Tropical Cyclones Zita and Arthur, written by
Simon Clarke. Track graphics for all three disturbances may be found
on John Diebolt's website.
Tropical Depression 06F formed on 9 January a couple hundred miles
east of the Samoan Islands. For a few days the depression remained
quasi-stationary and meandered about aimlessly in the same region. By
the 14th a decided motion toward the south and east had become apparent
with the center passing very near Palmerston Island on the 14th while
moving eastward. By the 15th the depression accelerated off to the
southeast but became quasi-stationary again the next day near the Austral
Islands, where it meandered around for another couple of days before
weakening. Deep convection was associated with TD-06F, but the system
remained in a highly-sheared environment throughout its lifetime. Gale
warnings were issued by Nadi for a week-long period from the 10th through
the 17th for a band of peripheral gales which accompanied the depression,
mainly to the north and east of the center. By 15 January northwesterly
shear had increased to 35-40 kts and the convection had become removed
far to the north and east of the center--at this juncture RSMC Nadi
classified the system as an extratropical depression. It seems highly
likely that much of the apparent erratic motion of this depression was
due to relocations of the diffuse LLCC. Interestingly, both of the
cyclones which followed during the latter week of January pursued similar
tracks to TD-06F, forming in the vicinity of Samoa and moving initially
eastward, then curving southward west of French Polynesia to the vicinity
of the Austral Islands.
TROPICAL CYCLONE ZITA
(TD-07F / TC-08P)
17 � 26 January
-----------------------------------------
A. Storm Origins
----------------
Tropical Cyclone Zita (TD-07F/TC-08P) was the third tropical cyclone
to form in the South Pacific for the 2005/06 season, developing after
a nearly two month-long hiatus in tropical cyclone activity in that
basin.
Zita was first identified as a slow-moving and poorly-organised
tropical depression (TD-07F) as early as 17 January near 12.0S/174.0W
(approximately 130 nm NW of Savai�i Island, Western Samoa). TD-07F
was centrally located along an active ITCZ which had been established
across the central South Pacific for several days prior. Two other
clearly identifiable depressions developed at about the same time as
pre-Zita, including TD-06F to the west which slid away rapidly to the
SSE as a highly sheared extratropical system, and TD-08F to the east
which later developed into Cyclone Arthur soon after Zita�s demise
(see separate report).
B. Synoptic History
-------------------
Initially TD-07F was in a favourable environment for further
development with upper-level divergence persisting at 250 hPa with
minimal shear. At 22/2100 UTC the depression was upgraded to cyclone
status near 14.4S/156.7 (approximately 275 nm WNW of Bora Bora,
Tahiti) and named Zita. The cyclone moved to the SE at 14 kts on an
accelerating path through a weakness in the subtropical ridge opened
up by TD-06 to its SSE. Zita initially gained strength at a rapid
pace with a CDO developing over the LLCC and cold convective bands
wrapping tightly around the centre. Zita reached a peak intensity of
maximum 10 min-avg winds of 60 kts and a CP of 975 hPa at 23/1200 UTC
near 17.3S/153.8W, or about 250 nm WNW of Papeete, Tahiti, close to
Maupihaa Atoll. However, the cyclone soon entered a region of cool
SSTs and high vertical wind shear and its convective top was soon
drawn to the SE away from the LLCC.
Zita passed close to the North Austral Group of islands while
weakening, eventually crossing 25S and entering the open southern
ocean and Wellington�s AOR. Zita was downgraded at 25/0000 UTC near
29.0S/150.0W (approximately 780 nm S of Papeete) as it transformed
into an extratropical storm. The remnant storm persisted for another
24 hours while moving rapidly to the SSW.
The peak 1-min avg MSW estimated by JTWC during Zita's lifetime was
60 kts at 0600 UTC 23 January.
C. Storm Effects
----------------
There were no significant reports of damage associated with Zita
despite passing through a series of small island groups along its
path. Some localised light damage was reported on Rurutu and
Rimatara including several trees uprooted and flooding along coastal
roads.
(Report written by Simon Clarke)
TROPICAL CYCLONE ARTHUR
(TD-08F / TC-09P)
21 � 28 January
-------------------------------------------
A. Introduction and Storm Origins
---------------------------------
Tropical Cyclone Arthur (TD-08F/TC-09P) was the fourth tropical
cyclone to form in the Southwest Pacific for the 2005/06 season, and
like its predecessor, Zita, was a short-lived storm that essentially
followed the same track that Zita had taken a few days earlier.
The pre-Arthur disturbance was first identified as a tropical
depression (TD-08F) on 21 January near 11.9S/176.4W (approximately
235 nm WNW of Savai�i Island, Western Samoa), moving to the ESE at
5 kts. Initial development was hindered by diurnal variations and
strong upper-level wind shear which produced an elongated pattern of
convection. The depression gradually accelerated to the ESE, passing
to the north of the main Samoan islands. By 24/0000 UTC convection
had begun to organise around the LLCC with convective tops cooling
and upper-level outflow improving. Gale-force winds initially
developed in the NE quadrant (between 30 to 90 nm from the centre)
and these slowly wrapped in toward the centre.
B. Synoptic History
-------------------
The depression was upgraded to cyclone status and named Arthur at
24/1200 UTC. At this time Arthur was located near 14.7S/165.6W
(approximately 300 nm E of Pago Pago, American Samoa), moving to the
ESE at 21 kts under the influence of a westerly steering field.
Arthur intensified rapidly under a CVA region with strong divergence
and minimal shear. Cold convective bands wrapped tightly into the
centre as outflow developed in all quadrants. A banding eye formed
and was observed to contract in satellite imagery.
Peak intensity was attained at 25/0000 UTC (maximum 10-min avg winds
of 60 kts and a CP of 975 hPa) near 15.7S/160.8W, or about 520 nm WNW
of Bora Bora, Tahiti. The peak intensity was sustained for little
more than 6 hours as increasing upper-level northwesterly wind shear
began to displace the CDO away to the SE of the LLCC. Before reaching
Tahiti, the weakening cyclone veered away from its east-southeasterly
track and onto a southeasterly path and into Wellington's AOR. The
combined effects of cooler SSTs and strong upper-level wind shear put
an end to Arthur as a tropical cyclone at 27/1200 UTC near 31.0S/145.0W
(approximately 820 nm SSE of Papeete, Tahiti). The remnant storm
continued to accelerate toward the SE at 25 kts and was last referenced
in Wellington�s warnings near 40.0S/130.0W at 1800 UTC on 28 January.
The peak 1-min avg MSW estimated for Arthur by JTWC was 65 kts, in
good agreement with Nadi�s 10-min avg estimate of 60 kts. All the
satellite agencies except for AFWA peaked at T4.0/4.0, while AFWA
reached T5.0/5.0 at 1730 UTC on the 24th.
C. Storm Effects
----------------
There were no significant reports of damage as a result of Arthur.
However, in tandem with Zita, the cyclone produced a prolonged period
of heavy rain in parts of French Polynesia, causing a number of
landslides and some associated damage to houses on the main island of
Tahiti and neighbouring Moorea. Gusty winds and heavy sea swells
were reported as the cyclone passed through the Austral Islands and
into the open southern ocean.
(Report written by Simon Clarke)
*************************************************************************
SPECIAL FEATURE - SOURCES OF TROPICAL CYCLONE INFORMATION
The purpose of this section is to list some websites where many and
varied types of tropical cyclone information are archived. Many readers
will know about these already, but for the benefit of those who don't,
I wanted to include them.
(1) Aircraft Reconnaissance Information
---------------------------------------
Various types of messages from reconnaissance aircraft may be
retrieved from the following FTP site:
ftp://ftp.nhc.noaa.gov/pub/products/nhc/recon/>
Information regarding how to interpret the coded reconnaissance
messages may be found at the following URL:
http://www.nhc.noaa.gov/reconlist.shtml>
Links are also included to websites with further information about the
U. S. Air Force 53rd Weather Reconnaissance Squadron and the NOAA Air-
craft Operations Center.
(2) Archived Advisories
-----------------------
All the advisory products (public advisories, forecast/advisories,
strike probabilities, discussions, various graphics) issued by TPC/NHC
are archived on TPC's website. For the current year (using 2004 as an
example), the archived products can be found at:
http://www.nhc.noaa.gov/archive/2004/index.shtml>
Links to tropical products archives for earlier years are available at
the following URL:
http://www.nhc.noaa.gov/pastall.shtml>
JTWC warnings for past storms are archived on the NRL Monterrey website:
http://www.nrlmry.navy.mil/tc_pages/tc_home.html>
On the NRL site, the link to past years can be found in the upper left
corner of the screen.
I am not aware at the moment of any other TCWC which archives all
its tropical cyclone warning/advisory products for public access, but
if I learn of any, I will add them to this list.
(3) Satellite Imagery
---------------------
Satellite images of tropical cyclones in various sensor bands are
available on the NRL Monterrey and University of Wisconsin websites,
courtesy of Jeff Hawkins and Chris Velden and their associates. The
links are:
http://www.nrlmry.navy.mil/tc_pages/tc_home.html>
http://cimss.ssec.wisc.edu/tropic/tropic.html>
On the NRL site, the link to past years can be found in the upper left
corner of the screen. For the CIMSS site, a link to data archives is
located in the lower left portion of the screen.
Additional tropical satellite imagery, along with looping ability for
composite microwave imagery for the Western Hemisphere north of the
equator, can be found at:
(1) For the Eastern North Pacific:
http://www.ssd.noaa.gov/PS/TROP/trop-epac.html>
(2) For the Atlantic, Gulf of Mexico and Caribbean Sea:
http://www.ssd.noaa.gov/PS/TROP/trop-atl.html>
I'm sure there are other sites with available imagery available, and
as I learn of them, I will add the links to this list.
*************************************************************************
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 August, 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
from the archive sites listed below. (Note: I do have a limited e-mail
distribution list for the track files. If anyone wishes to receive
these via e-mail, please send me a message.)
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. Back issues can be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Michael Pitt, Chris
Landsea, and John Diebolt):
http://australiasevereweather.com/cyclones/>
http://www.typhoon2000.ph>
http://mpittweather.com>
ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
http://www.tropicalcyclone2005.com/>
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.metoffice.gov.uk/weather/tropicalcyclone>
TROPICAL CYCLONE REPORTS AVAILABLE
JTWC now has available on its website the Annual Tropical Cyclone
Report (ATCR) for 2005 (2004-2005 season for the Southern Hemisphere).
ATCRs for earlier years are available also.
The URL is: https://metocph.nmci.navy.mil/jtwc.php>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 2006 Atlantic and Eastern North Pacific
tropical cyclones; also, storm reports for all the 2006 Atlantic
and Eastern North Pacific cyclones are now available, as well as
track charts and reports on storms from earlier years.
The URL is: http://www.nhc.noaa.gov>
A special thanks to Michael Bath of McLeans Ridges, New South Wales,
Australia, for assisting me with proofreading the summaries.
PREPARED BY
Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327
Kevin Boyle (Northwest Pacific)
E-mail: [email protected]
Simon Clarke (Northeast Australia/Coral Sea, South Pacific)
E-mail: [email protected]
*************************************************************************
*************************************************************************
|
Document: summ0701.htm
Updated: 14th March 2007 |
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