[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 090545
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI AUG 09 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0522 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS WITH AXIS
EXTENDING FROM 22N31W TO 10N31W MOVING W NEAR 10 KT. METEOSAT
SATELLITE IMAGERY SHOW SAHARAN DRY AIR SPREADING OVER
THE WAVE ENVIRONMENT WHICH IS HINDERING CONVECTION.

A TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN WITH AXIS
EXTENDING FROM 23N79W TO 09N79W MOVING W NEAR 5 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 23N79W WHICH EXTENDS A TROUGH ACROSS THE WESTERN CARIBBEAN
SUPPORTS LOW VALUES OF DEEP LAYER ENVIRONMENTAL WIND
SHEAR...THUS ENHANCING SCATTERED MODERATE CONVECTION AND TSTMS
OVER CUBA AND ADJACENT WATERS N OF 17N W OF 77W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM THE WEST AFRICAN COAST NEAR
14N17W TO 09N30W 07N40W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
STARTS NEAR 07N40W AND CONTINUES ALONG 07N47W TO 08N55W...THEN
RESUMES W OF A SURFACE TROUGH NEAR 08N58W TO 07N61W. A CLUSTER
OF MODERATE CONVECTION IS FROM 06N-12N E OF 18W. SCATTERED
MODERATE CONVECTION IS FROM 05N-09N BETWEEN 23W-35W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0300 UTC...SURFACE TROUGHINESS AND ABUNDANT MOISTURE
DOMINATES ACROSS THE BASIN ASSOCIATED WITH A SURFACE TROUGH WITH
AXIS EXTENDING FROM 28N88W TO 17N90W. STRONG NORTHEASTERLY FLOW
AROUND AN UPPER LEVEL RIDGE CENTERED OVER THE SE CONUS AND
EXTENDING INTO THE GULF IS LIMITING CONVECTIVE ACTIVITY
ASSOCIATED WITH THE TROUGH TO ISOLATED RAINSHOWERS WITHIN 30 NM
EITHER SIDE OF ITS AXIS. OTHERWISE...FAIR WEATHER IS W OF 94W
AND E OF 88W FAVORED BY DRY AIR SUBSIDENCE AND HIGH VALUES OF
DEEP LAYER ENVIRONMENTAL WIND SHEAR...RESPECTIVELY.

THE SURFACE TROUGH WILL CONTINUE TO DRIFT W-NW AND ENTER
SOUTHERN TEXAS AND NE MEXICO SATURDAY MORNING. RAINSHOWERS ARE
LIKELY OVER THE WESTERN GULF DURING THIS PERIOD.

CARIBBEAN SEA...
A TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN WITH AXIS
EXTENDING FROM 23N79W TO 09N79W. AN UPPER LEVEL LOW CENTERED
NEAR 23N79W WHICH EXTENDS A TROUGH ACROSS THE WESTERN CARIBBEAN
SUPPORTS LOW VALUES OF DEEP LAYER ENVIRONMENTAL WIND
SHEAR...THUS ENHANCING SCATTERED MODERATE CONVECTION AND TSTMS
OVER CUBA AND ADJACENT WATERS N OF 17N W OF 77W. SCATTERED
MODERATE CONVECTION IS ACROSS THE WINDWARD PASSAGE AND HAITI
BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE FROM THE UPPER LOW
CENTERED N OF CUBA AND A RIDGE WITH A CENTER OVER SOUTHERN-
CENTRAL CARIBBEAN. SIMILAR CONVECTION IS IN THE SOUTHERN BASIN S
OF 11N...HOWEVER ASSOCIATED WITH THE MONSOON TROUGH AXIS WHICH
MOVES ACROSS COSTA RICA AND PANAMA TO A LOW CENTER OVER NORTHERN
COLOMBIA. A SURFACE TROUGH AXIS EXTENDS FROM 16N68W TO 11N68W
WITH NO CONVECTION ASSOCIATED WITH IT.

THE WAVE WILL CONTINUE TO MOVE WESTWARD AND IS EXPECTED TO BE
ALONG HONDURAS AND NICARAGUA BY SATURDAY MORNING. THE TRAILING
SURFACE TROUGH IS EXPECTED TO DISSIPATE FRIDAY
AFTERNOON...HOWEVER ANOTHER SURFACE TROUGH IS EXPECTED TO MOVE
ACROSS THE LESSER ANTILLES FRIDAY MORNING INCREASING THE CHANCES
OF PRECIPITATION FOR THIS PART OF THE BASIN.

HISPANIOLA...
SCATTERED MODERATE CONVECTION IS ACROSS THE WINDWARD PASSAGE AND
HAITI BEING SUPPORTED BY UPPER LEVEL DIFFLUENCE FROM AN UPPER
LOW CENTERED N OF CUBA AND A RIDGE WITH A CENTER OVER SOUTHERN-
CENTRAL CARIBBEAN. RAINSHOWERS ARE EXPECTED TO CONTINUE TO
AFFECT AT LEAST HAITI THROUGH FRIDAY MORNING...HOWEVER MORE
CONVECTION WILL BUILD IN THE AFTERNOON/EARLY EVENING HOURS
ASSOCIATED WITH DAYTIME HEATING. WEATHER CONDITIONS ARE EXPECTED
TO IMPROVE EARLY ON SATURDAY DUE TO THE WESTWARD TRANSIT OF A
DRY AIRMASS.

ATLANTIC OCEAN...
AN UPPER LEVEL LOW CENTERED NEAR 23N79W WHICH EXTENDS A TROUGH
ACROSS THE WESTERN CARIBBEAN SUPPORTS LOW VALUES OF DEEP LAYER
ENVIRONMENTAL WIND SHEAR...THUS ENHANCING SCATTERED MODERATE
CONVECTION AND TSTMS OVER CUBA...THE STRAITS OF FLORIDA AND THE
BAHAMAS S OF 26N W OF 74W. SIMILAR CONVECTION IS FROM 29N-30N
BETWEEN 60W-63W ASSOCIATED WITH A SURFACE TROUGH N OF 30N.
MIDDLE LEVEL TROUGHINESS IS SUPPORTING ISOLATED SHOWERS ACROSS
THE VIRGIN AND LEEWARD ISLANDS. ANOTHER SURFACE TROUGH EXTENDS
FROM 14N56W TO 09N56W WITH SCATTERED RAINSHOWERS WITHIN 30 NM E
OF ITS AXIS FROM 10N-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
HTTP://WWW.HURRICANES.GOV/MARINE

$$
RAMOS


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