Tropical Storm TOMAS Forecast Discussion
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000
WTNT41 KNHC 021452
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
1100 AM EDT TUE NOV 02 2010
TOMAS HAS CERTAINLY BECOME BETTER ORGANIZED SINCE YESTERDAY...WITH A
LARGE AREA OF DEEP CONVECTION AND INCREASED BANDING SEEN IN
CONVENTIONAL SATELLITE AND MICROWAVE DATA. HOWEVER...THE STORM HAS
CHANGED LITTLE IN ORGANIZATION SINCE THE RECONNAISSANCE AIRCRAFT
REPORTED SFMR SURFACE WINDS OF 45 KT AROUND 0800 UTC. THEREFORE...
THE INITIAL INTENSITY IS HELD AT THAT VALUE...WHICH IS IN LINE WITH
THE LATEST DVORAK T-NUMBERS OF 2.5 AND 3.5 FROM SAB AND TAFB...
RESPECTIVELY. THE NEXT AIR FORCE HURRICANE HUNTER AIRCRAFT IS
SCHEDULED TO INVESTIGATE TOMAS THIS AFTERNOON.
WESTERLY SHEAR CONTINUES TO RELAX AND THE MID-LEVEL ENVIRONMENT
APPEARS TO BE MOISTENING. THESE ATMOSPHERIC CONDITIONS...COMBINED
WITH HIGH OCEANIC HEAT CONTENT...FAVOR INTENSIFICATION DURING THE
NEXT FEW DAYS...WHICH IS SHOWN BY MOST OF THE GUIDANCE. IN
FACT...THE SHIPS RAPID INTENSIFICATION INDEX GIVES A 48 PERCENT
CHANCE OF A 30-KT INCREASE IN WIND SPEED DURING THE NEXT 24 HOURS.
THE OFFICIAL FORECAST HAS BEEN ADJUSTED UPWARD FROM THE PREVIOUS
ADVISORY AND IS NOW AT OR JUST ABOVE THE HIGH END OF THE INTENSITY
GUIDANCE. AFTER A FEW DAYS...LAND INTERACTION...DRIER AIR...AND
SOME INCREASE IN SOUTHERLY SHEAR IS LIKELY TO CAUSE WEAKENING.
THE INITIAL MOTION ESTIMATE IS A LITTLE SLOWER THAN BEFORE...270/9.
A TURN TO THE WEST-NORTHWEST AND NORTHWEST WITH A DECREASE IN
FORWARD SPEED IS FORECAST DURING THE NEXT 24-48 HOURS AS A STRONG
TROUGH MOVES EASTWARD ACROSS THE GULF OF MEXICO. AS A RESULT...
TOMAS IS EXPECTED TO TURN NORTHWARD AND NORTHEASTWARD BEYOND 48
HOURS IN DEEP-LAYER SOUTHWESTERLY FLOW ON THE EAST SIDE OF THE
TROUGH. SEVERAL OF THE GLOBAL MODELS SUGGEST THAT THE TROUGH WILL
NOT COMPLETELY CAPTURE TOMAS AND THERE REMAINS A LARGE DISAGREEMENT
IN THE FUTURE POSITION OF THE CYCLONE AT DAYS 4 AND 5. THE OFFICIAL
FORECAST IS OF LOW CONFIDENCE DURING THAT TIME PERIOD AND IS NEAR A
CONSENSUS OF THE GFS...GFDL... UKMET...NOGAPS...AND ECMWF MODELS.
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...IT APPEARS
THAT THE TROPICAL CYCLONE WILL POSE A SIGNIFICANT THREAT OF HEAVY
RAINFALL OVER HAITI AND THE DOMINICAN REPUBLIC LATER IN THE WEEK.
Tropical Storm TOMAS Forecast Discussion
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000
WTNT41 KNHC 030242
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
1100 PM EDT TUE NOV 02 2010
SATELLITE IMAGES INDICATE THAT OVERALL CONVECTION HAS DECREASED
DURING THE PAST SEVERAL HOURS...THOUGH A CURVED BAND HAS BECOME A
LITTLE BETTER-DEFINED RECENTLY. MICROWAVE DATA SUGGEST THE CENTER
IS ON THE SOUTHEASTERN SIDE OF THAT BAND...AND REMNANTS OF THE OLD
MID-LEVEL CIRCULATION CAN BE SEEN NORTHWEST OF ARUBA. SATELLITE
INTENSITY ESTIMATES VARY FROM 35-55 KT...AND NO CHANGE WILL BE MADE
TO THE INITIAL WIND SPEED OF 35 KT. AN AIR FORCE HURRICANE HUNTER
WILL BE IN THE AREA IN A FEW HOURS TO CHECK ON THE STATUS OF TOMAS.
LARGE-SCALE ENVIRONMENTAL PARAMETERS APPEAR TO BE RATHER FAVORABLE
FOR FUTURE INTENSIFICATION WITH LOW SHEAR AND VERY WARM WATER FOR
THE NEXT FEW DAYS. IT IS UNCERTAIN...HOWEVER...IF TOMAS CAN TAKE
ADVANTAGE OF THESE CONDITIONS. A LOOK AT GLOBAL MODEL CROSS-
SECTIONS SHOW A TILTED VORTEX INITIALLY...WITH THE GFS/UKMET
SUGGESTING A MORE FAVORABLE VERTICAL VORTEX STRUCTURE FOR
STRENGTHENING IN A DAY OR TWO. THE ECMWF MODEL...WHICH WAS ONE
OF THE FEW MODELS THAT PREDICTED THE WEAKENING OF TOMAS IN THE
EASTERN CARIBBEAN...HAS A QUITE DIFFERENT SCENARIO WITH A GOOD DEAL
OF TILT REMAINING FOR THE NEXT FEW DAYS AND ONLY A MODEST INCREASE
IN WINDS UNTIL AFTER THE TROPICAL CYCLONE LEAVES THE CARIBBEAN.
WITH SUCH DIVERGENCE IN THE GUIDANCE...THE NEW FORECAST IS ABOUT
THE SAME THE PREVIOUS ONE...A LITTLE HIGHER THAN THE MODEL
CONSENSUS.
AN UNCERTAIN INITIAL MOTION ESTIMATE IS 280/7. A CONTINUED
SLOW-DOWN OF THE TROPICAL CYCLONE IS LIKELY AS RIDGING WEAKENS TO
THE NORTH OF TOMAS. A DEEP LAYER LOW ENTERING THE GULF OF MEXICO
IS EXPECTED TO ACCELERATE AND TURN TOMAS TO THE NORTH AND NORTHEAST
ON THURSDAY. WHILE THE MODELS TAKE VARIOUS SPEEDS AND ROUTES TO
GET THERE...THEY REMAIN FOCUSED IN THE DIRECTION OF SOUTHWESTERN
HAITI. THE NHC FORECAST IS ADJUSTED SLIGHTLY TO THE RIGHT OF THE
PREVIOUS FORECAST DURING THE FIRST COUPLE OF DAYS...AND GENERALLY
LIES TO THE SOUTHEAST OF THE MODEL CONSENSUS. THE HWRF AND GFDN
HAVE A RATHER DEEP AND INTENSE CIRCULATION...WHICH APPEAR TO BE
OUTLIERS AND BIASING TVCN...THE VARIABLE CONSENSUS MODEL...TOO FAR
TO THE NORTH.
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...IT APPEARS
THAT THE TROPICAL CYCLONE WILL POSE A SIGNIFICANT THREAT OF HEAVY
RAINFALL OVER HAITI AND THE DOMINICAN REPUBLIC LATER IN THE WEEK.
Vortex Data Message
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000
URNT12 KNHC 021849 CCA
VORTEX DATA MESSAGE AL212010
A. 02/18:21:50Z
B. 13 deg 26 min N
074 deg 22 min W
C. 850 mb 1474 m
D. NA
E. NA
F. 349 deg 12 kt
G. 219 deg 35 nm
H. 1007 mb
I. 18 C / 1510 m
J. 19 C / 1520 m
K. 3 C / NA
L. NA
M. NA
N. 1345 / 8
O. 0.02 / 7 nm
P. AF300 0821A TOMAS OB 10 CCA
MAX FL WIND 30 KT NW QUAD 17:44:20Z
MAX OUTBOUND FL WIND 28 KT N QUAD 18:34:00Z
RAINING AT THE FIX POSN CALM BELOW
SFC WNDS LGT AND VAR INBOUND LEG
RELIED ON TEMP RISE FOR FIX
;
Tropical Depression TOMAS Forecast Discussion
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000
WTNT41 KNHC 030840
TCDAT1
TROPICAL DEPRESSION TOMAS DISCUSSION NUMBER 21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
500 AM EDT WED NOV 03 2010
AN AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING TOMAS A COUPLE
OF HOURS AGO FOUND AN ILL-DEFINED AND ELONGATED CIRCULATION WITH NO
TROPICAL STORM FORCE WINDS AT EITHER THE 925 MB FLIGHT LEVEL OR THE
SURFACE. BASED ON THIS INFORMATION...TOMAS IS BEING DOWNGRADED TO
A TROPICAL DEPRESSION AT THIS TIME. THE PERIPHERAL CLOUD PATTERN
CONTINUES TO SHOW ORGANIZATION WITH FRAGMENTED OUTER BANDS...BUT
THERE IS LITTLE CONVECTIVE ORGANIZATION NEAR THE ESTIMATED CENTER.
THE WEAKENING OVER THE PAST 24 HOURS IS DIFFICULT TO EXPLAIN.
PRECIPITABLE WATER ANALYSES FROM THE UW/CIMSS DO NOT SUGGEST MUCH
OF AN INTRUSION OF DRY AIR INTO THE CIRCULATION. THE CIRRUS
MOTIONS FROM SATELLITE IMAGES SHOW A FAIRLY WELL-DEFINED OUTFLOW
PATTERN...ESPECIALLY OVER THE NORTHERN SEMICIRCLE. THIS WOULD
NORMALLY BE CONSISTENT WITH LIGHT VERTICAL SHEAR. AMSU
AREA-AVERAGED WIND SHEAR DERIVED BY CSU/CIRA...HOWEVER...INDICATE A
RECENT INCREASE IN MID- TO UPPER-LEVEL SHEAR OVER TOMAS. THIS IS
EXPECTED TO BE TEMPORARY AS GLOBAL MODELS PREDICT DECREASING SHEAR
OVER THE NEXT COUPLE OF DAYS. THE INTENSITY FORECAST CONTINUES TO
CALL FOR TOMAS TO RESTRENGTHEN INTO A HURRICANE BEFORE REACHING
LAND. GIVEN THE ERRATIC BEHAVIOR OF THIS TROPICAL CYCLONE THUS
FAR...THIS IS A LOW-CONFIDENCE INTENSITY FORECAST. THE NOAA G-IV
JET IS CURRENTLY CONDUCTING A SYNOPTIC SURVEILLANCE MISSION AROUND
TOMAS WHICH SHOULD GIVE A BETTER ASSESSMENT OF THE DYNAMIC AND
THERMODYNAMIC ENVIRONMENT.
THE HURRICANE HUNTERS FOUND A BROAD AREA OF LIGHT WINDS SURROUNDING
THE LOCATION OF THE MINIMUM PRESSURE...SO THERE IS SIGNIFICANT
UNCERTAINTY IN THE CENTER POSITION AND INITIAL MOTION. OUR BEST
GUESS AT THE LATTER IS 285/4. THE TRACK FORECAST IS BASICALLY
UNCHANGED FROM THE PREVIOUS ADVISORY. TOMAS IS EXPECTED TO TURN
NORTHWARD AND NORTHEASTWARD OVER THE NEXT FEW DAYS IN RESPONSE TO
THE STEERING FLOW AHEAD OF AN APPROACHING MID-TROPOSPHERIC TROUGH.
BY THE END OF THE FORECAST PERIOD...GLOBAL MODELS SHOW THIS TROUGH
LIFTING OUT AND LEAVING TOMAS BEHIND OVER THE SUBTROPICS FOR A FEW
DAYS. ACCORDINGLY...THE OFFICIAL TRACK FORECAST SHOWS A TURN TO
THE RIGHT WITH DECREASING FORWARD SPEED BY DAY 5.
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE TROPICAL
CYCLONE WILL POSE A SIGNIFICANT THREAT OF HEAVY RAINFALL...
FLOODING...AND POTENTIAL MUD SLIDES OVER HAITI AND THE
DOMINICAN REPUBLIC LATER IN THE WEEK.
Tropical Storm TOMAS Forecast Discussion
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000
WTNT41 KNHC 040249
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
1100 PM EDT WED NOV 03 2010
DATA FROM NOAA AND AIR FORCE RESERVE HURRICANE HUNTER MISSIONS
INDICATE THAT THE LOW-LEVEL CENTER OF TOMAS IS STILL NOT QUITE
ALIGNED WITH THE MID-LEVEL CENTER. THEY HAVE MOVED CLOSER TOGETHER
DURING THE DAY...HOWEVER...AND A 2219 UTC SSMI/S MICROWAVE PASS
SHOWS CONSIDERABLY MORE BANDING THAN THIS SYSTEM HAS HAD DURING THE
PAST FEW DAYS. THE INITIAL WIND SPEED WILL REMAIN 40 KT...WHICH IS
NEAR THE FLIGHT-LEVEL AND SFMR MAXIMA REPORTED BY NOAA.
THE LARGE-SCALE ENVIRONMENT IS FAVORABLE FOR STRENGTHENING OF TOMAS
WITH LIGHT SOUTHWESTERLY SHEAR AND WARM WATERS. IN FACT...ALL OF
THE RELIABLE MODELS THAT DO NOT MOVE TOMAS OVER A SIGNIFICANT
PORTION OF HAITI MAKE THE CYCLONE A HURRICANE WITHIN 36-48 HOURS.
THE SHIPS RAPID INTENSIFICATION INDEX ALSO SHOWS A 62 PERCENT
CHANCE OF A 30-KT INCREASE WITHIN THE NEXT 24 HOURS...THOUGH THIS
MODEL WAS TOO HIGH YESTERDAY. THIS SYSTEM HAS BURNED US BEFORE BY
DOING THE EXACT OPPOSITE OF THE GUIDANCE...BUT GIVEN THE IMPROVED
MICROWAVE PRESENTATION...I AM INCLINED TO RAISE THE FORECAST A
LITTLE BIT TO HURRICANE STATUS. THE NEW FORECAST IS NEAR OR
SLIGHTLY BELOW A COMPOSITE OF THE GFDL...SHIPS...AND LGEM MODELS.
WEAKENING IS FORECAST AT THE END OF THE PERIOD AS THE TROPICAL
CYCLONE INTERACTS WITH A COLD FRONT AND VERTICAL WIND SHEAR
INCREASES.
THE CURRENT MOTION REMAINS 330/5...THOUGH THIS IS MORE UNCERTAIN
THAN NORMAL WITH THE NHC INITIAL POSITION ON THE NORTHEASTERN SIDE
OF THE BROAD LOW-LEVEL CIRCULATION. A WEAK RIDGE TO THE EAST OF
TOMAS IS STEERING THE STORM FOR NOW...BUT A RATHER STRONG DEEP
LAYER LOW OVER THE GULF OF MEXICO IS EXPECTED TO CAUSE THE TROPICAL
CYCLONE TO TURN TOWARD THE NORTH TOMORROW...AND THE NORTH-NORTHEAST
BY EARLY FRIDAY. TOMAS SHOULD BE ACCELERATING AS IT PASSES NEAR
HAITI AS THE MID-LATITUDE LOW APPROACHES. ONLY COSMETIC CHANGES
WERE MADE TO THE NHC FORECAST WITH THE MOST RELIABLE MODELS STILL
FOCUSED ON A TRACK TOWARD SOUTHWESTERN HAITI. AT DAYS 4 AND
5...THERE ARE SOME INDICATIONS FROM THE MODELS THAT THE GULF OF
MEXICO LOW WILL LEAVE TOMAS BEHIND TO THE EAST OF THE BAHAMAS...AND
THE OFFICIAL FORECAST IS SHIFTED TO THE RIGHT AT THAT TIME.
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE TROPICAL
CYCLONE WILL POSE A SIGNIFICANT THREAT OF HEAVY RAINFALL...
FLOODING...AND LIFE-THREATENING MUD SLIDES OVER HAITI AND THE
DOMINICAN REPUBLIC DURING THE NEXT FEW DAYS.
Vortex Data Message
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000
URNT12 KNHC 032341
VORTEX DATA MESSAGE AL212010
A. 03/23:14:30Z
B. 14 deg 24 min N
075 deg 44 min W
C. NA
D. 5 kt
E. 201 deg 2 nm
F. 318 deg 7 kt
G. 260 deg 50 nm
H. EXTRAP 1004 mb
I. 24 C / 359 m
J. 24 C / 362 m
K. NA / NA
L. NA
M. NA
N. 134 / 1
O. 0.02 / 2 nm
P. AF301 1121A TOMAS OB 22
MAX FL WIND 31 KT E QUAD 20:47:20Z
MAX OUTBOUND FL WIND 14 KT NE QUAD 23:35:50Z
SLP EXTRAP FROM BELOW 1500 FT
;
Vortex Data Message
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000
URNT12 KNHC 040615
VORTEX DATA MESSAGE AL212010
A. 04/06:04:40Z
B. 15 deg 34 min N
076 deg 02 min W
C. 850 mb 1410 m
D. 41 kt
E. 074 deg 68 nm
F. 140 deg 36 kt
G. 069 deg 80 nm
H. 999 mb
I. 17 C / 1523 m
J. 19 C / 1522 m
K. 16 C / NA
L. NA
M. NA
N. 12345 / 8
O. 0.02 / 2 nm
P. AF309 1321A TOMAS OB 05
MAX FL WIND 36 KT E QUAD 05:34:30Z
RADAR DEPICTED 12 NM LONG BAND NE OF CTR
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000
WTNT41 KNHC 040841
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
500 AM EDT THU NOV 04 2010
SATELLITE PICTURES SUGGEST THAT THE CLOUD PATTERN OF TOMAS HAS NOT
CHANGED SIGNIFICANTLY DURING THE LAST SEVERAL HOURS. HOWEVER...
DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE
THAT THE PRESSURE HAS FALLEN TO 997 MB WITH MAXIMUM SURFACE WINDS
OF 41 KT. DESPITE THE AIRCRAFT DATA WHICH ARE INDICATIVE OF SLIGHT
STRENGTHENING...THE VORTEX HAS BEEN TILTED IN THE VERTICAL BASED
UPON COMPARISON OF EARLIER NOAA AND AIR FORCE AIRCRAFT DATA.
GIVEN THE SIGNIFICANTLY LOWER CENTRAL PRESSURE FROM THE AIRCRAFT...
THE INITIAL INTENSITY IS INCREASED TO 45 KT FOR THIS ADVISORY.
THE CURRENT MOTION ESTIMATE REMAINS 330/06. THE FORECAST PHILOSOPHY
REGARDING THE TRACK OF TOMAS IS UNCHANGED. TOMAS SHOULD BE STEERED
NORTH-NORTHWESTWARD TO NORTHWARD AROUND A LOW- TO MID-LEVEL RIDGE
LOCATED OVER THE WEST CENTRAL ATLANTIC TODAY. AFTER THAT...TOMAS
SHOULD BEGIN TO ENCOUNTER AN INCREASING SOUTHWESTERLY FLOW
ASSOCIATED WITH AN ANOMALOUSLY DEEP MID- TO UPPER-LEVEL TROUGH
MOVING ACROSS EASTERN NORTH AMERICA AND TURN NORTHEASTWARD WHILE
ACCELERATING. EVEN THOUGH THE SYNOPTIC REASONING HAS NOT CHANGED
FROM THE PREVIOUS PACKAGE...THE OFFICIAL FORECAST TRACK IS SHIFTED
TO THE LEFT ON ACCOUNT OF THE MOST RECENT AIRCRAFT CENTER FIXES.
ALTHOUGH LARGE-SCALE FACTORS OF MODERATELY LOW SHEAR AND WARM WATERS
ARE FAVORABLE FOR FURTHER INTENSIFICATION OF TOMAS...THE VERTICAL
TILT OF THE VORTEX AND THE BROAD NATURE OF THE CIRCULATION MAY
ARGUE AGAINST A RAPID INCREASE IN STRENGTH. INTERESTINGLY...THE
SHIPS RAPID INTENSIFICATION INDEX THAT HAD BEEN SHOWING THE
POTENTIAL FOR A 30-KT INCREASE WITHIN THE NEXT 24 HOURS IS NOT AS
HIGH AS IT WAS BEFORE. THE NEW NHC FORECAST IS SIMILAR TO THE
PREVIOUS ONE AND ASSUMES THAT THE LARGE-SCALE ENVIRONMENT SHOULD BE
CONDUCIVE ENOUGH TO ALLOW FOR STENGTHENING DURING THE NEXT 24-36
HOURS. BEYOND 36 HOURS...STRONG AND INCREASING SOUTHWESTERLY SHEAR
OVER THE WESTERN ATLANTIC IS FORECAST TO CAUSE WEAKENING...PERHAPS
AT A MORE RAPID PACE THAN INDICATED IN THE CURRENT FORECAST. THE
NEW NHC FORECAST IS REDUCED FROM THE PREVIOUS ONE AT LATER FORECAST
TIMES GIVEN THE STRONG FORECAST SHEAR.
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST
SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE IS HEAVY RAINFALL...
WHICH COULD PRODUCE FLASH FLOODING AND LIFE-THREATENING MUD SLIDES
OVER HAITI AND THE DOMINICAN REPUBLIC DURING THE NEXT COUPLE OF
DAYS.