[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 252336
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED APR 25 2012

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.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST OF GUINEA NEAR
10N14W TO 5N20W...WHERE THE ITCZ AXIS CONTINUES ALONG 2N32W TO
THE COAST OF BRAZIL NEAR 1S46W. ISOLATED WEAK TO MODERATE
CONVECTION IS WITHIN 50-85 NM ON EITHER SIDE OF THE ITCZ AXIS.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 1N8N E
OF 19W TO THE PRIME MERIDIAN.

...DISCUSSION...

GULF OF MEXICO...
AN ELONGATED UPPER LEVEL TROUGH AXIS EXTENDS ACROSS THE ERN
CONUS SEABOARD INTO THE FAR SW GULF OF MEXICO ON WATER VAPOR
IMAGERY. HOWEVER...VERY DRY AIR AND STRONG SUBSIDENCE ALOFT
ACCOMPANIES THE BASE OF THIS UPPER TROUGH...WHICH COVERS THE
ENTIRE GULF BASIN. THIS OVERALL STABLE ENVIRONMENT FILTERS DOWN
TO THE SURFACE AS A 1020 MB HIGH CENTERED OFF THE WESTERN COAST
OF THE FLORIDA PENINSULA NEAR 27N85W WITH CLEAR SKIES NOTED ON
VISIBLE SATELLITE IMAGERY. WITH THE RIDGE SLOWLY SHIFTING
EASTWARD OVER THE PAST 24 HOURS...E-SE WINDS IN THE RANGE OF 10
TO 15 KT INFLUENCE THE SOUTHEASTERN HALF OF THE BASIN WITH 10 TO
20 KT S-SW WINDS ESTABLISHING OVER THE NORTHWESTERN THIRD OF THE
BASIN. THURSDAY INTO FRIDAY THE RIDGE WILL CONTINUE TO SLIDE
INTO THE SW NORTH ATLC AS SOUTHERLY RETURN FLOW SPREADS EASTWARD
OVER MUCH OF THE GULF FOR THE WEEKEND.

CARIBBEAN SEA...
HAZARDOUS WEATHER CONTINUES TO FOCUS ON THE CENTRAL CARIBBEAN
BASIN AND INLAND PORTIONS OF HISPANIOLA THIS EVENING. A NEARLY
STATIONARY FRONT CROSSES THE ISLAND INTO THE CARIBBEAN WATERS
FROM 20N70W TO NEAR TO 15N77W. LAST VISIBLE SATELLITE PICTURES
OF THE DAY SHOWED SCATTERED NUMEROUS MODERATE TO HEAVY SHOWERS
AND THUNDERSTORMS WITHIN 120 NM ON EITHER SIDE OF A LINE
EXTENDING FROM 20N70W TO 12N78W TO 9N78W. GUSTY WINDS UP TO 30
KTS...FREQUENT DANGEROUS CLOUD TO GROUND LIGHTNING...AND
POSSIBLE WATER SPOUTS ARE LIKELY OVER WATER WITHIN THE
CONVECTIVE REGION...INCLUDING THE COASTAL WATERS OF HISPANIOLA.
THE NATIONAL WEATHER OFFICE IN DOMINICAN REPUBLIC HAS REPORTED
RAINFALL TOTAL ACCUMULATIONS RANGING FROM 4 TO 7 INCHES ACROSS
THEIR TERRITORY...ESPECIALLY OVER REGIONS WHERE THE HIGH
TOPOGRAPHY AND UPPER LEVEL DIFFLUENCE IS MAXIMIZED. TOTAL
PRECIPITABLE WATER IMAGERY HAS SHOWN CONSISTENT HIGH VALUES OF
LOW LEVEL MOISTURE AS WELL AS MIDDLE TO UPPER LEVEL MOISTURE
CONCENTRATED WITHIN THE CONVECTION REGION ON WATER VAPOR
IMAGERY. THIS SCENARIO IS SUPPORTING THE CONTINUOUS RAINFALL
THAT HAS PERSISTED OVER THE PAST FEW DAYS. THE FRONT IS EXPECTED
TO WEAKEN OVER THE NEXT 24 TO 36 HOURS AS SURFACE RIDGING BUILDS
TO THE NORTH AND EASTERLY TRADES INCREASE DUE TO A STRONGER
SURFACE PRESSURE GRADIENT. IT IS POSSIBLE THAT LOW-LEVEL
MOISTURE WILL LINGER ACROSS THE NORTH-CENTRAL CARIBBEAN FOR THE
NEXT DAY OR TWO AS THE FRONT BECOMES MORE DIFFUSE AND WILL
CONTINUE TO PROVIDE INCREASED PROBABILITY OF PRECIPITATION FOR
HISPANIOLA AND THE ADJACENT COASTAL WATERS THROUGH THE WEEKEND.
THE POTENTIAL FOR LOCALLY HEAVY RAINFALL AND FLOODING ACROSS
HAITI AND PORTIONS OF THE DOMINICAN REPUBLIC ARE EXPECTED OVER
THE NEXT FEW DAYS. NO SIGNIFICANT WEATHER IS OCCURRING ELSEWHERE
ACROSS THE DISCUSSION AREA THIS EVENING.

ATLANTIC OCEAN...
AN ELONGATED UPPER LEVEL TROUGH AXIS IS SLOWLY DRIFTING EASTWARD
OVER THE FAR WRN ATLC...CURRENTLY EXTENDING ALONG THE ERN CONUS
SEABOARD AND INTO THE GULF OF MEXICO. WATER VAPOR IMAGERY SHOWS
VERY DRY AIR AND STRONG SUBSIDENCE ALOFT E AND S OF THE UPPER
TROUGH AXIS. DESPITE THE DRY CONDITIONS ALOFT...THE CONVECTION
ASSOCIATED TO THIS SYSTEM IS FOCUSED WELL EAST OF THE UPPER
TROUGH...WITHIN 150-200 NM ON EITHER SIDE OF A NEARLY STATIONARY
FRONT EXTENDING INTO THE DISCUSSION AREA ALONG 30N61W TO 24N64W
THEN INTO THE N CENTRAL CARIBBEAN ACROSS HISPANIOLA NEAR 20N70W.
SCATTERED NUMEROUS MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS
ARE EVIDENT ON SATELLITE IMAGERY WITHIN THE CONVECTIVE REGION.
MAXIMUM LOW-LEVEL MOISTURE CONVERGENCE COUPLED WITH FAVORABLE
UPPER LEVEL DIFFLUENCE ON THE REAR RIGHT QUADRANT OF A STRONG
UPPER LEVEL JET STREAK CONTINUES TO SUPPORT THIS SYSTEM.
OTHERWISE...FAIR WEATHER CONDITIONS AREA ELSEWHERE ACROSS THE
DISCUSSION AREA...INFLUENCED BY A 1021 MB HIGH PRESSURE SYSTEM
OVER THE NW BAHAMAS AND A STRONG/BROAD SUBTROPICAL RIDGE AXIS
THAT EXTENDS IN TO THE REGION ANCHORED BY A 1036 MB HIGH
CENTERED WELL NORTH OF THE DISCUSSION AREA NEAR 50N40W. A SLIGHT
WEAKNESS REMAINS ON THE SOUTHERN PERIPHERY OF THE SUBTROPICAL
RIDGE DUE TO AN UPPER LEVEL LOW CENTERED NEAR 27N35W. THIS UPPER
LEVEL FEATURE IS ONLY PROVIDING FOR A REGION OF MIDDLE TO UPPER
LEVEL OVERCAST CLOUDINESS WITH A FEW POSSIBLE ISOLATED SHOWERS
FROM 16N-27N BETWEEN 24W-40W.

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

$$

GARCIA



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