Tropical Storm TOMAS Forecast Discussion
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000
WTNT41 KNHC 010841
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 13...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
500 AM AST MON NOV 01 2010
CORRECTED MOTION TO 260/12
WESTERLY VERTICAL SHEAR...WHICH APPEARS TO BE PRIMARILY DUE TO THE
DIFFERENCES BETWEEN THE LOWER- AND MID-TROPOSPHERIC FLOW...
CONTINUES TO IMPACT TOMAS. CONSEQUENTLY THE CYCLONE REMAINS HIGHLY
DECOUPLED AS THE LOW-LEVEL CENTER IS DISPLACED MORE THAN 100 N MI
WEST OF THE DEEP CONVECTION. SFMR OBSERVATIONS FROM AN AIR FORCE
RECONNAISSANCE AIRCRAFT INDICATE THAT THE INTENSITY HAS DECREASED
TO NEAR 45 KT. ADDITIONAL WEAKENING IS LIKELY AS 20 TO 25 KT OF
SHEAR SHOULD CONTINUE AFFECTING THE TROPICAL CYCLONE FOR ABOUT
ANOTHER 24 HOURS. THEREAFTER...THE SHIPS/LGEM GUIDANCE INDICATES
THAT THE SHEAR SHOULD RELAX WHICH WOULD ALLOW FOR TOMAS TO REGAIN
STRENGTH. THE OFFICIAL INTENSITY FORECAST FOLLOWS THIS SCENARIO
AND IS CLOSE TO THE CONSENSUS OF THE NUMERICAL INTENSITY GUIDANCE.
THIS IS WELL ABOVE THE LGEM GUIDANCE AND BELOW THE MORE AGGRESSIVE
GFDL MODEL FORECAST. IT SHOULD BE NOTED THAT THERE IS CONSIDERABLE
UNCERTAINTY AS TO HOW STRONG TOMAS WILL GET IN THE LATTER PART OF
THE FORECAST PERIOD.
AIRCRAFT AND SATELLITE FIXES INDICATE THAT THE MOTION IS JUST
SLIGHTLY SOUTH OF DUE WEST OR 260/12. A WEAKENING LOW- TO
MID-LEVEL RIDGE TO THE NORTH OF THE STORM SHOULD PRODUCE A
GENERALLY WESTWARD MOTION WITH DECELERATION OVER THE NEXT 48 HOURS
OR SO. IN 72 TO 96 HOURS...THE GLOBAL MODELS DEPICT A LARGE
AMPLITUDE MID-TROPOSPHERIC TROUGH MOVING EASTWARD ACROSS THE GULF OF
MEXICO. THE FLOW AHEAD OF THIS FEATURE SHOULD TURN TOMAS NORTHWARD
AND NORTH-NORTHEASTWARD WITH AN INCREASE IN FORWARD SPEED. THE
OFFICIAL FORECAST IS SOMEWHAT SOUTH OF THE PREVIOUS ONE IN THE
EARLY PART OF THE FORECAST PERIOD MAINLY DUE TO THE SOUTHWARD SHIFT
IN RECENT FIXES. AS NOTED EARLIER...THERE IS SOME AGREEMENT
AMONGST THE TRACK MODELS ON THE GENERAL TRAJECTORY OF TOMAS DURING
THE LATTER PART OF THE FORECAST PERIOD BUT THERE ARE STILL
SUBSTANTIAL DIFFERENCES IN THE PREDICTED FORWARD SPEEDS. DUE TO
THE UNCERTAINTIES ONE SHOULD NOT FOCUS ON THE EXACT FORECAST
TRACK...PARTICULARLY THE TIMING OF THE 4 AND 5 DAY POINTS.
Vortex Data Message
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000
URNT12 KNHC 010840
VORTEX DATA MESSAGE AL212010
A. 01/08:08:30Z
B. 13 deg 45 min N
067 deg 29 min W
C. 850 mb 1461 m
D. 34 kt
E. 277 deg 21 nm
F. 032 deg 27 kt
G. 277 deg 37 nm
H. 1003 mb
I. 17 C / 1540 m
J. 22 C / 1536 m
K. 6 C / NA
L. NA
M. NA
N. 1345 / 8
O. 0.02 / 2 nm
P. AF300 0521A TOMAS OB 14
MAX FL WIND 47 KT NE QUAD 05:45:50Z
MAX OUTBOUND FL WIND 43 KT N QUAD 08:21:30Z
Tropical Storm TOMAS Forecast Discussion
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000
WTNT41 KNHC 020234
TCDAT1
TROPICAL STORM TOMAS DISCUSSION NUMBER 16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
1100 PM EDT MON NOV 01 2010
THERE HAS BEEN NO APPRECIABLE CHANGE TO THE STRUCTURE OF TOMAS OVER
THE PAST SEVERAL HOURS. DEEP CONVECTION HAD DIMINISHED AT ONE
POINT THIS EVENING...BUT A LINEAR BAND HAS RECENTLY RE-DEVELOPED
ABOUT 60-90 N MI EAST OF THE LOW-LEVEL CENTER. THE INITIAL
INTENSITY IS HELD AT 40 KT...WHICH IS CONSISTENT WITH SATELLITE
ESTIMATES OF T2.5/3.0 FROM TAFB AND T2.6/2.7 FROM THE OBJECTIVE
ADT. ALTHOUGH WEST-SOUTHWESTERLY SHEAR CONTINUES TO IMPACT THE
CYCLONE...IT IS EXPECTED TO DECREASE IN 24-36 HOURS. IN
ADDITION...THE MID-LEVEL RELATIVE HUMIDITY IS EXPECTED TO
INCREASE...AND TOMAS WILL BE MOVING OVER A REGION OF INCREASED
OCEAN HEAT CONTENT. ALL THESE FACTORS SUGGEST THAT TOMAS SHOULD
RE-STRENGTHEN...AND THE INTENSITY MODELS ARE IN GENERALLY GOOD
AGREEMENT THAT IT COULD BECOME A HURRICANE AGAIN BY DAY 3. THE
PREVIOUS FORECAST IS IN LINE WITH THE NEW INTENSITY GUIDANCE...AND
NO CHANGES WERE REQUIRED ON THIS ADVISORY.
RECENT MICROWAVE IMAGERY SUGGESTS THAT TOMAS HAS CEASED MOVING
SOUTH OF DUE WEST AND NOW HAS AN INITIAL MOTION OF 270/10. TRACK
GUIDANCE INDICATES THAT TOMAS...IN ITS WEAKENED STATE...SHOULD
CONTINUE TO MOVE WESTWARD IN THE LOW-LEVEL FLOW FOR THE NEXT 36
HOURS OR SO. ONCE THE CYCLONE BEGINS TO STRENGTHEN...THE DEEPER
VORTEX SHOULD BE STEERED NORTHWARD AND THEN NORTHEASTWARD IN THE
SOUTHWESTERLY FLOW AHEAD OF AN APPROACHING MID- TO UPPER-LEVEL
TROUGH. SINCE THE HWRF AND GFDN APPEAR TO BE NORTHERN OUTLIERS AND
THE NOGAPS DOES NOT EVEN PULL TOMAS OUT OF THE CARIBBEAN...THE
OFFICIAL FORECAST IS BASED ON A CONSENSUS OF THE GFS...ECMWF...
GFDL...AND UKMET. THE GUIDANCE ENVELOPE HAS SHIFTED A BIT TO THE
WEST ON THIS CYCLE...MAINLY IN THE DAY 2 AND 3 TIME FRAME...AND THE
NEW OFFICIAL FORECAST FOLLOWS THAT TREND.
Vortex Data Message
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000
URNT12 KNHC 020707
VORTEX DATA MESSAGE AL212010
A. 02/06:47:10Z
B. 13 deg 29 min N
071 deg 34 min W
C. 925 mb 718 m
D. 29 kt
E. 126 deg 22 nm
F. 194 deg 21 kt
G. 130 deg 40 nm
H. EXTRAP 1003 mb
I. 22 C / 796 m
J. 24 C / 792 m
K. 22 C / NA
L. NA
M. NA
N. 12345 / 09
O. 0.02 / 0.5 nm
P. AF300 0721A TOMAS OB 07
MAX OUTBOUND AND MAX FL WIND 42 KT NW QUAD 06:57:30Z
SLP EXTRAP FROM 925 MB
SFMR AND EXTRAP SLP INDICATE SFC CNTR NW AT 3 NM FM FL CNTR.
SOME BANDING ON E SIDE.