[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 312354
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED JUL 31 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 16N83W TO 24N82W MOVING W AT 10 KT.
THE WAVE IS BEGINNING TO BECOME MORE DIFFICULT TO DISCERN ON
SATELLITE IMAGERY...HOWEVER GLOBAL MODEL GUIDANCE INDICATES THE
LARGE AREA OF DISORGANIZED POTENTIAL VORTICITY IS MOVING ACROSS
THE WESTERN CARIBBEAN. MOST LIKELY THESE LOW TO MIDDLE LEVEL
DYNAIMCS ARE GENERATING THE SCATTERED SHOWERS AND TSTMS THIS
EVENING N OF 19N BETWEEN 79W-86W OVER THE NW CARIBBEAN SEA
WATERS AND PORTIONS OF WESTERN CUBA. THE WAVE IS EXPECTED TO
CROSS THE YUCATAN PENINSULA TOMORROW AND SOUTHERN MEXICO ON
FRIDAY.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR
22N17W TO 18N20W TO 10N29W TO 07N40W. THE INTERTROPICAL
CONVERGENCE ZONE AXIS EXTENDS FROM 07N40W TO 05N52W. SCATTERED
MODERATE CONVECTION IS FROM 12N-15N BETWEEN 12W-19W. ISOLATED
MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF A LINE FROM
09N18W TO 05N30W TO 06N38W.

...DISCUSSION...

GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED
OVER TEXAS NEAR 32N101W AND IS PROVIDING MUCH OF THE GULF WITH
NORTH TO NORTHEASTERLY TO EASTERLY UPPER LEVEL FLOW THIS
EVENING. AS WITH MOST RIDGES ALOFT...A FAIRLY STABLE ATMOSPHERE
IS PREVAILING OVER THE GULF BASIN W OF 90W AS A 1020 MB HIGH IS
CENTERED NEAR 27N95W. ACROSS THE EASTERN GULF HOWEVER...THE
INFLUENCE OF THE UPPER LEVEL RIDGING LESSENS AS A MID-LEVEL
SHORTWAVE TROUGH IS NOTED ON WATER VAPOR IMAGERY OVER EASTERN
GEORGIA PROGRESSING EASTWARD INTO THE SW NORTH ATLC WATERS. THE
SHORTWAVE TROUGH SUPPORTS A STATIONARY BOUNDARY ANALYZED ACROSS
SOUTH CAROLINA AND CENTRAL GEORGIA INTO NE ALABAMA. A MOIST AND
UNSTABLE AIRMASS LIES SOUTH OF THIS BOUNDARY AND WITH PEAK
AFTERNOON HEATING SCATTERED SHOWERS AND TSTMS ARE OCCURRING
PRIMARILY N OF 29N E OF 88W...INCLUDING PORTIONS OF THE NORTHERN
HALF OF FLORIDA. FURTHERMORE...A SURFACE TROUGH EXTENDS FROM THE
SW NORTH ATLC TO JACKSONVILLE FLORIDA AND INTO THE NE GULF
WATERS NEAR 30N83W TO 26N86W. THIS BOUNDARY IS PROVIDING FOCUS
FOR WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS FROM 23N-29N
BETWEEN 81W-90W. LOOKING AHEAD...SURFACE RIDGING IS FORECAST TO
PERSIST ACROSS THE GULF THROUGH THE WEEKEND WITH AXIS EXTENDING
FROM THE SW NORTH ATLC ALONG 27N/28N THROUGH SUNDAY.

CARIBBEAN SEA...
NORTHEASTERLY WINDS DOMINATE ACROSS THE NW CARIBBEAN THIS
EVENING WHILE AT THE SURFACE A TROPICAL WAVE CONTINUES TO SLOWLY
PROGRESS WESTWARD. THE WAVE ALONG 83W IS BECOMING MORE DIFFICULT
TO TRACK...HOWEVER GLOBAL MODEL GUIDANCE INDICATES AN AREA OF
UNORGANIZED MID-LEVEL VORTICITY WILL CONTINUE TO MOVE ACROSS THE
NW CARIBBEAN OVER THE NEXT 24 TO 36 HOURS. THE TROPICAL WAVE
ALONG WITH PEAK DAYTIME HEATING AND INSTABILITY ACROSS THE
ISLAND OF CUBA IS GENERATING WIDELY SCATTERED SHOWERS AND TSTMS
FROM 18N-23N BETWEEN 75W-86W. FARTHER WEST...SCATTERED SHOWERS
AND TSTMS ARE ONGOING ACROSS INLAND PORTIONS OF THE YUCATAN
PENINSULA...BELIZE...AND NORTHERN GUATEMALA. TO THE SOUTH...AN
UPPER LEVEL DIFFLUENT ATMOSPHERE IS NOTED ACROSS THE SW
CARIBBEAN. THE UPPER LEVEL DIFFLUENCE ALONG WITH THE CLOSE
PROXIMITY OF THE MONSOON TROUGH AXIS ALONG 09N/10N IS GENERATING
SCATTERED SHOWERS AND TSTMS S OF 14N BETWEEN 77W-86W...INCLUDING
PANAMA...COSTA RICA...AND NICARAGUA. OTHERWISE...A MAJORITY OF
THE CENTRAL AND EASTERN CARIBBEAN IS UNDER A RELATIVELY DRY AND
STABLE AIRMASS AS NOTED ON WATER VAPOR IMAGERY WITH CLEAR SKIES
THIS EVENING. IN THE VICINITY OF HISPANIOLA...PUERTO RICO...AND
THE LESSER ANTILLES...A VERY WEAK UPPER LEVEL LOW IS CENTERED
NEAR 18N65W WHICH IS GENERATING ISOLATED SHOWERS AND TSTMS FROM
14N-20N BETWEEN 60W-64W...AND FROM 17N-21N BETWEEN 64W-72W.

HISPANIOLA...
CURRENTLY ISOLATED SHOWERS AND TSTMS ARE OCCURRING ACROSS
HISPANIOLA AS A MIDDLE TO UPPER LEVEL REMAINS TO THE NORTH-
NORTHWEST CENTERED NEAR 24N75W. THIS CONVECTION IS EXPECTED TO
DIMINISH OVER THE NEXT FEW HOURS WITH THE LOSS OF DAYTIME
HEATING. AS THE UPPER LEVEL LOW DRIFTS NORTHWEST OVER THE NEXT
FEW DAYS...OVERALL SYNOPTIC CONDITIONS ARE EXPECTED TO
IMPROVE...HOWEVER WEAK TROUGHING IS CURRENTLY MOVING ACROSS THE
LESSER ANTILLES AND THIS AREA OF ISOLATED SHOWERS AND TSTMS IS
EXPECTED TO MOVE WESTWARD OVER THE NEXT 48 HOURS. ALONG WITH
PEAK DAYTIME HEATING AND INSTABILITY...THIS MARGINAL AREA OF
LIFT IS EXPECTED TO AID IN AFTERNOON AND EVENING CONVECTION THE
NEXT COUPLE OF DAYS.

ATLANTIC OCEAN...
NORTH-NORTHEASTERLY UPPER LEVEL FLOW LIES ACROSS THE SW NORTH
ATLC BETWEEN A BROAD UPPER LEVEL ANTICYCLONE CENTERED OVER THE
SOUTHERN U.S. PLAINS AND AN UPPER LEVEL LOW CENTERED NEAR
24N74W. WITH A MID-LEVEL SHORTWAVE PROGRESSING OFF THE GEORGIA
COAST...A STATIONARY FRONT IS ANALYZED ALONG 33N WITH A SURFACE
TROUGH EXTENDING FROM 32N77W TO THE FLORIDA PENINSULA NEAR
JACKSONVILLE. ISOLATED SHOWERS AND TSTMS ARE OCCURRING N OF 29N
BETWEEN 67W-80W...AND N OF 29N W OF 80W. FARTHER SOUTH...THE
UPPER LEVEL LOW IS GENERATING AN AREA OF MAXIMUM MIDDLE TO UPPER
LEVEL DIFFLUENCE EAST OF THE LOW FOCUSED ALONG A SURFACE TROUGH
ANALYZED FROM EASTERN CUBA NEAR 20N74W TO 26N72W. THE LOW-LEVEL
MOISTURE CONVERGENCE ALONG WITH THE DIFFLUENCE IS GENERATING AN
AREA OF SCATTERED SHOWERS AND TSTMS FROM 20N-27N BETWEEN 69W-
78W. ANOTHER AREA OF ISOLATED SHOWERS IS OCCURRING IN ASSOCIATED
WITH A WEAK SURFACE TROUGH ANALYZED FROM 27N63W TO 33N61W. A
WEAKNESS WITHIN THE SURFACE RIDGING ACROSS THE CENTRAL AND
WESTERN ATLC...ISOLATED SHOWERS ARE POSSIBLE WITHIN 120 NM
EITHER SIDE OF THE BOUNDARY. OTHERWISE...THE REMAINDER OF THE
CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE
RIDGE ANCHORED ON A 1024 MB HIGH CENTERED NEAR 30N43W. A LARGE
REASON THE EASTERN AND CENTRAL ATLC IS UNDER MOSTLY STABLE
CONDITIONS THIS EVENING IS THE PRESENCE OF THE SAHARAN AIR
LAYER. THIS PARTICULAR WESTWARD SURGE OF SAHARAN DUST IS
APPARENT ON SATELLITE IMAGERY PRIMARILY N OF 08N E OF 50W.

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

$$
HUFFMAN


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