Tropical Cyclone Sheila [Invest 99P]

[HURAKAN]

Tropical Disturbance Advisory Number A2 issued from RSMC NADI
Apr 22/0148 UTC 2005 UTC.

TROPICAL DEPRESSION 15F [997hPa] WAS LOCATED NEAR 17.4S 170.6W AT
220000 UTC. POSITION POOR AND BASED ON GMS/GOES EIR AND VIS IMAGERY,
AND PERIPHERAL SURFACE REPORTS. DEPRESSION MOVING SOUTHEAST AT ABOUT
20 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR THE CENTRE ESTIMATED
AT ABOUT 30 KNOTS, POSSIBLY INCREASING TO 35 KNOTS CLOSE TO THE
CENTRE IN THE NEXT 6 TO 12 HOURS. EXPECT CLOCKWISE WINDS 30 TO 35
KNOTS WITHIN 30 MILES TO 120 MILES OF CENTRE IN THE SECTORS FROM
NORTHWEST THROUGH EAST TO SOUTH.

SURROUNDING CONVECTION HAS BEGUN TO WANE AFTER AN OVERNIGHT FLARE,
SUGGESTING DIURNAL INFLUENCES. DVORAK ANALYSIS BASED ON CURVED BAND
WRAP OF 0.4 RESULTING IN DT=2.5, MET=2.5 AND PAT=2.5. FT BASED ON
MET: T2.5/2.5/1.5/24HRS FOR A RAPIDLY DEVELOPING SYSTEM. 250HPA WINDS
HAVE INCREASED TO 35 TO 40 KNOTS ACROSS THE SYSTEM. CIMMS INDICATES
15F IS MOVING INTO 20 TO 30 KNOTS SHEAR, ALTHOUGH UPPER DIFFLUENCE
REMAINS GOOD. MOST GLOBAL MODELS SHOW A RAPID MOVEMENT TOWARDS THE
SOUTHEAST AND EVENTUAL ABSORPTION INTO THE MIDLATITUDE WESTERLIES IN
THE NEXT 36 TO 48 HOURS. IN THE MEANTIME, THE SYSTEM IS EXPECTED TO
MAINTAIN CURRENT INTENSITY OR EVEN WEAKEN IF ENVIRONMENTAL SHEAR
CONTINUES TO INCREASE.

THE NEXT TROPICAL DISTURBANCE ADVISORY ON 15F WILL BE ISSUED AROUND
220800 UTC OR EARLIER.



21/2022 UTC 16.6S 172.9W T1.5/1.5 99P -- South Pacific Ocean

AN AREA OF CONVECTION HAS PERSISTED NEAR 16.2S9 177.5W0,
APPROXIMATELY 260 NM EAST-NORTHEAST OF SUVA, FIJI. RECENT ANIMATED
WATER VAPOR SATELLITE IMAGERY REVEALS INCREASING CONVECTION OVER A
LOW LEVEL CIRCULATION CENTER (LLCC). UPPER LEVEL ANALYSIS INDICATES
AN ENVIRONMENT OF MODERATE VERTICAL WIND SHEAR AND GOOD EQUATORWARD
DIFFLUENCE. MAXIMUM SUSTAINED WINDS ARE ESTIMATED AT 15 TO 20 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED AT 1006 MB. THE POTENTIAL
FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE
NEXT 24 HOURS IS FAIR.

THE SYSTEMS SEEMS TO BE GETTING ITS ACT TOGETHER AND COULD DEVELOP INTO THE SOUTH PACIFIC'S NEXT SYSTEM IN 24 HOURS OR LESS.

[HurricaneBill]

The South Pacific can be funny sometimes. It'll be active, go quiet for a while, and then a storm will pop up at the last minute.

Occasionally, out of season cyclones occur in the South Pacific. Cyclone Gina formed in early June 2003 and reached Category 2 status with sustained winds of 90 kts.

[P.K.]

TC Sheila now.

Tropical Disturbance Advisory Number A3 issued from RSMC NADI
Apr 22/0843 UTC 2005 UTC.

TROPICAL CYCLONE SHEILA CENTRE [995hPa] WAS LOCATED NEAR 18.4S 168.8W
AT 220600 UTC. POSITION POOR BASED ON GOES9 EIR AND IMAGERY. CYCLONE
MOVING SOUTHEAST AT ABOUT 20 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS
NEAR THE CENTRE ESTIMATED AT ABOUT 35 KNOTS. WINDS ABOVE 33 KNOTS
WITHIN EXPECT WINDS OVER 33 KNOTS WITHIN 90 MILES OF CENTRE IN THE
SECTOR FROM NORTHEAST THROUGH EAST TO SOUTHEASTMILES OF CENTRE.

OVERALL ORGANISATION HAS INCREASED SINCE PAST 6 HOURS WITH
RE-DEVELOPMENT OF DENCE OVERCAST TO THE SOUTHEAST OF SYSTEM CENTRE.
SYSTEM APPEARS SHEARED WITH PARTLY EXPOSED LLCC ON THE WESTERN EDGE
OF CENTRAL DENSE OVERCAST. DVORAK ANALYSIS BASED ON SHEAR PATTERN
YIELDS DT OF 3.0, MET=PAT=3.0. FT BASED ON DT : T3.0/3.0/D1.5/24HRS.
SHEILA REMAINS IN A MODERATELY SHEARED ENVIRONMENT WITH 20 TO 25
KNOTS WESTERLY WINDS ALOFT [250 HPA]. UPPER DIFFLUECE GOOD IN EASTERN
REGION. OUTFLOW GOOD TO THE EAST AND NORTH BUT RESTRICTED ELSEWHERE.
SST AROUND 28 DEGREE CELCIUS. SYSTEM IS EXPECTED MOVE SOUTHEAST,
STEERED BY NORTHWESTERLIES AT MIDDLE LEVELS.
MOST GLOBAL MODELS SHOW A RAPID MOVEMENT TOWARDS THE SOUTHEAST
WITHOUT SIGNIFICANT DEVELOPMENT. SHEILA IS EXPECTED TO GRADUALLY
WEAKEN AS IT DRIFTS INTO STRONG SHEAR ENVIRONMENT DEPICTED BY CIMMS.

FORECASTS :
AT 12 HRS VALID AT 221800 UTC 21.3S 164.8W MOV SE AT 25 KT WITH 35 KT
CLOSE TO CENTRE

AT 24 HRS VALID AT 230600 UTC 24.3S 160.1W MOV SE AT 25 KT WITH 30 KT
CLOSE TO CENTRE

OUTLOOK :
AT 36 HRS VALID AT 231800 UTC 27.4S 155.5W MOV SE AT 25 KT WITH 25 KT
CLOSE TO CENTRE

AT 48 HRS VALID AT 240600 UTC 30.4S 150.8W MOV SE AT 25 KT WITH 20 KT
CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON SHEILA WILL BE ISSUED
AROUND 221400 UTC..

[hcane]

Details and a track map can be found at Hurricane Alley.

http://www.hurricanealley.net

[P.K.]

Gone.

Tropical Disturbance Advisory Number A5 issued from RSMC NADI
Apr 22/2000 UTC 2005 UTC.

TROPICAL DEPRESSION 15F [997hPa] [FORMER TROPICAL CYCLONE SHEILA]
CENTRE WAS LOCATED NEAR 20.2S 165.4W AT 221800 UTC. POSITION POOR
BASED ON LATEST GOES10 VIS IMAGERY. SYSTEM MOVING SOUTHEAST AT ABOUT
20 KNOTS. EXPECT CLOCKWISE WINDS 30 TO 35 KNOTS WITHIN 30 MILES TO
180 MILES OF CENTRE IN THE SECTORS FROM NORTHWEST THROUGH EAST TO
SOUTH.

LLCC REMAINS EXPOSED WITH MAJOR CONVECTION DISPLACED ABOUT 2 DEGREE
TOWARDS THE SOUTHEAST. DVORAK ANALYSIS BASED ON SHEAR PATTERN YIELDS
DT=1.0 MET=PAT=1.5. FT BASED ON MET: T1.5/2.0/W1.0/24HRS. SYSTEM
REMAINS UNDER STRONG SHEARED ENVIRONMENT WITH 40 KNOTS WINDS ALOFT
[250HPA]. OUTFLOW RESTRICTED IN ALL QUADRANTS. 15F IS RUNNING INTO
MORE STRONGER SHEAR AS IT MOVES SOUTHEAST.


THIS WILL BE THE FINAL ADVISORY ON THIS SYSTEM.