[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081041
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU AUG 08 2013

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1022 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS NEAR THE CAPE VERDE ISLANDS WITH AXIS
EXTENDING FROM 21N26W TO 07N27W MOVING W NEAR 5 KT. THE SOUTHERN
PART OF THE WAVE IS EMBEDDED WITHIN THE MONSOON TROUGH WHERE
TOTAL PRECIPITABLE WATER IMAGERY SHOW A MODERATE TO HIGH MOIST
ENVIRONMENT AND WHERE SCATTERED MODERATE CONVECTION IS OBSERVED
FROM 06N-10N BETWEEN 25W-32W. NORTH OF THE MONSOON TROUGH
AXIS...SAHARAN DRY AIR SPREADS OVER THE WAVE ENVIRONMENT HINDERING
CONVECTION.

A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS
EXTENDING FROM 21N73W TO 09N74W MOVING W NEAR 10 KT. THE WAVE IS
EMBEDDED IN A LIGHT TO MODERATE MOIST ENVIRONMENT AS DEPICTED ON
TOTAL PRECIPITABLE WATER IMAGERY. AN UPPER LEVEL LOW CENTERED
NEAR 23N74W WHICH EXTENDS A TROUGH ACROSS THE CENTRAL-SOUTHERN
CARIBBEAN SUPPORTS LOW VALUES OF DEEP LAYER ENVIRONMENTAL WIND
SHEAR...THUS ENHANCING SCATTERED MODERATE CONVECTION AND TSTMS
OVER NORTHERN HAITI...THE WINDWARD PASSAGE AND EASTERN CUBA. S
OF 18N...THERE IS NO CONVECTION ASSOCIATED WITH THIS WAVE
UNFAVORED BY DRY AIR SUBSIDENCE AND HIGH VALUES OF DEEP LAYER
ENVIRONMENTAL WIND SHEAR.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM THE WEST AFRICAN COAST NEAR
16N16W TO 10N27W 07N38W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
STARTS NEAR 07N38W AND CONTINUES ALONG 06N47W TO 06N56W. BESIDES
THE CONVECTION ASSOCIATED WITH THE WAVE NEAR THE CAPE VERDE
ISLANDS ALREADY DISCUSSED...SCATTERED MODERATE CONVECTION IS
FROM 06N-16N E OF 25W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0900 UTC...WIND IN THE RANGE OF 5-15 KT SPREADS ACROSS THE
BASIN. ANTICYCLONIC FLOW IS OVER THE NW GULF ANCHORED BY A 1013
MB HIGH CENTERED NEAR 27N92W. SURFACE TROUGHINESS IS E OF 90 W
WHERE A TROUGH AXIS EXTENDS FROM 29N87W TO 19N86W IN THE W
CARIBBEAN. THERE IS A MODERATE TO HIGH MOIST ENVIRONMENT AND LOW
VALUES OF DEEP LAYER ENVIRONMENTAL WIND SHEAR IN THIS REGION OF
THE GULF WHICH IS SUPPORTING SCATTERED RAINSHOWERS/TSTMS E OF
THE AXIS AS WELL AS WITHIN 120 NM W OF THE TROUGH AXIS S OF
26N.  OTHERWISE...DRY AIR SUBSIDENCE IS SUPPORTING FAIR WEATHER
OVER THE WESTERN GULF.

THE CENTER OF HIGH PRESSURE IS EXPECTED TO DISSIPATE LATER THIS
MORNING. THE SURFACE TROUGH WILL CONTINUE TO MOVE WESTWARD
PROVIDING TROUGHINESS ACROSS THE WESTERN GULF UNTIL FRIDAY
NIGHT. RAINSHOWERS ASSOCIATED WITH THE TROUGH ARE EXPECTED TO
CONTINUE IN THE CENTRAL GULF AND BUILD OVER THE WESTERN GULF
LATER TODAY.

CARIBBEAN SEA...
TOTAL PRECIPITABLE WATER IMAGERY SHOW A MODERATE TO HIGH MOIST
ENVIRONMENT OVER THE WESTERN CARIBBEAN WHERE UPPER LEVEL
DIFFLUENCE FROM A BROAD HIGH CENTERED OVER LOUISIANA AND A LOW
ACROSS THE CENTRAL-SOUTHERN CARIBBEAN IS ENHANCING ISOLATED
MODERATE CONVECTION/ISOLATED TSTMS. IN THE SOUTHERN BASIN...A
1008 MB LOW CENTER OVER NORTHERN COLOMBIA IS SUPPORTING A
CLUSTER OF MODERATE CONVECTION WITH EMBEDDED TSTMS THAT EXTENDS
WITHIN 80 NM OFF THE COAST. A TROPICAL WAVE IS MOVING ACROSS THE
CENTRAL CARIBBEAN WITH THE NORTHERN PART OF ITS AXIS CURRENTLY
OVER THE WINDWARD PASSAGE WHERE UPPER LEVEL DIFFLUENCE IS
ENHANCING SCATTERED MODERATE CONVECTION AND TSTMS WHICH EXTENDS
TO HAITI AND EASTERN CUBA. S OF 18N...THERE IS NO CONVECTION
ASSOCIATED WITH THIS WAVE UNFAVORED BY DRY AIR AND HIGH VALUES
OF DEEP LAYER ENVIRONMENTAL WIND SHEAR. A SURFACE TROUGH
ASSOCIATED WITH A 1009 MB LOW EXTENDS FROM 17N66W TO 11N64W. A
CLUSTER OF SCATTERED MODERATE CONVECTION AND TSTMS IS FROM
11N-14N BETWEEN 65W-67W. IN ADDITION...RAINSHOWERS HAS BEEN
REPORTED WITHIN THE LAST COUPLE OF HOURS BY MANY OF THE LESSER
ANTILLES.

BOTH THE WAVE AND THE TROUGH ARE EXPECTED TO CONTINUE MOVING
WESTWARD WITHIN THE NEXT 48 HOURS GENERATING RAINSHOWERS OVER
THE CENTRAL AND SOUTHERN CARIBBEAN. ANOTHER SURFACE TROUGH IS
EXPECTED TO MOVE ACROSS THE LESSER ANTILLES FRIDAY NIGHT
INCREASING THE CHANCES OF PRECIPITATION.

HISPANIOLA...
A TROPICAL WAVE IS MOVING ACROSS THE CENTRAL CARIBBEAN WITH THE
NORTHERN PART OF ITS AXIS CURRENTLY OVER THE WINDWARD PASSAGE
WHERE UPPER LEVEL DIFFLUENCE IS SUPPORTING SCATTERED MODERATE
CONVECTION AND TSTMS THAT EXTENDS TO HAITI. RAINSHOWERS ARE
EXPECTED TO CONTINUE TO AFFECT THE ISLAND THROUGH LATE
THURSDAY...HOWEVER WEATHER CONDITIONS IMPROVE ON EARLY FRIDAY
WHEN A DRY AIRMASS IS EXPECTED TO MOVE ACROSS THE ISLAND.

ATLANTIC OCEAN...
A BROAD UPPER LEVEL TROUGH N OF 30N AND THE ELONGATED LOW
CENTERED OVER THE BAHAMAS SUPPORT A SURFACE TROUGH THAT AS OF
0900 UTC EXTENDS FROM 30N56W TO 29N66W 27N72W 23N75W. SCATTERED
MODERATE CONVECTION AND TSTMS ARE FROM 28N-31N BETWEEN 53W-61W
AS WELL AS WITHIN 50 NM EITHER SIDE OF THE TROUGH AXIS BETWEEN
67W-76W. ANOTHER SURFACE TROUGH EXTENDS FROM 13N54W TO 08N54W
WITH ISOLATED MODERATE CONVECTION WITHIN 220 NM EITHER SIDE OF
ITS AXIS FROM 08N-11N. OTHERWISE...BESIDES THE TROPICAL WAVE
ALREADY DISCUSSED...SURFACE RIDGING AND FAIR WEATHER SUPPORTED
BY LOWER-MIDDLE LEVELS DRY AIR DOMINATE THE REMAINDER BASIN.

FOR ADDITIONAL INFORMATION PLEASE VISIT
WWW.HURRICANES.GOV/MARINE

$$
RAMOS




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