[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON MAY 21 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1700 UTC.

...SPECIAL FEATURES...

TROPICAL STORM ALBERTO IS CENTERED NEAR 30.4N 78.8W AT 21/1500
UTC...OR ABOUT 150 NM E OF JACKSONVILLE FLORIDA AND 155 NM SSE
OF CHARLESTON SOUTH CAROLINA. ALBERTO IS MOVING EAST AT 4 KNOTS.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB WITH MAXIMUM
SUSTAINED WIND SPEEDS OF 35 KT WITH GUSTS TO 45 KT. THE SYSTEM
REMAINS SMALL WITH MODERATE CONVECTION EXTENDING UP TO 90NM FROM
THE CENTER. WATER VAPOR IMAGERY INDICATES THAT DRY AIR ALOFT
EXTENDS FROM THE GULF OF MEXICO INTO THE W ATLC AND IS
WRAPPING AROUND THE SYSTEM...WHICH WILL HELP DISSIPATE THE
SYSTEM OVER THE NEXT COUPLE OF DAYS. ALBERTO IS MOVING AWAY FROM
THE US COASTLINE...BUT DANGEROUS SURF IS STILL EXPECTED ALONG
THE COASTS OF NE FLORIDA...GEORGIA...AND S CAROLINA. PLEASE READ
THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/ WTNT21 KNHC...AND THE PUBLIC BULLETIN
MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE HAS MOVED OFF THE COAST OF AFRICA EXTENDING
ALONG 12N19W TO 5N19W MOVING W NEAR 15 KTS. UPPER AIR
TIME-SECTIONS FROM DAKAR SENEGAL INDICATE THAT THE WAVE PASSED
THE STATION AROUND 21/0600 UTC. THE WAVE COINCIDES WITH A SURGE
OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER
IMAGERY. CURRENTLY SCATTERED MODERATE CONVECTION IS FROM 4N-9N
BETWEEN 16W-24W.

A TROPICAL WAVE EXTENDS FROM 13N41W TO 6N41W MOVING W AT 15-20
KTS. THIS WAVE ALSO COINCIDES WITH A NWD SURGE IN DEEP LAYER
MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. HIGHER
MOISTURE VALUES LIE TO THE W ALONG THE ITCZ AND ALSO MATCH WHERE
THE AREAS OF CONVECTION ARE. SCATTERED MODERATE CONVECTION IS
FROM 5N-9N BETWEEN 43W-49W. MORE CONVECTION IS FARTHER W AND
WILL BE DISCUSSED IN THE ITCZ SECTION.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
SENEGAL AT 15N17W CONTINUING OVER WATER ALONG 8N23W 5N28W. THE
ITCZ CONTINUES FROM 5N28W ALONG 7N39W 6N54W. SCATTERED
MODERATE/STRONG CONVECTION IS FROM 6N-9N BETWEEN 49W-55W...AND
FROM 8N-10N BETWEEN 55W-63W.

...DISCUSSION...

THE GULF OF MEXICO...
DRY AIR ALOFT IN MAINLY ZONAL WLY FLOW COVERS MUCH OF THE GULF
OF MEXICO TODAY PROVIDING FAIR CONDITIONS ACROSS THE BASIN.
HOWEVER...A BROAD AREA OF LOW LEVEL CYCLONIC FLOW AROUND A
SURFACE TROUGH THAT EXTENDS FROM HONDURAS AT 15N88W TO THE SE
GULF AT 23N85W IS PROVIDING MOIST CONDITIONS ACROSS THE FAR SE
GULF. CURRENTLY ISOLATED SHOWERS/THUNDERSTORMS ARE S OF 24N E OF
88W. A FEW ISOLATED SHOWERS ARE ALSO IN THE SRN BAY OF CAMPECHE.
LIGHT ANTI-CYCLONIC FLOW SPREADS ACROSS THE BASIN AROUND WEAK
HIGH PRESSURE OVER THE GULF COAST STATES. EXPECT MOIST
CONDITIONS TO REMAIN OVER THE FAR SE GULF AS THE AREA OF
CYCLONIC FLOW IN THE NW CARIBBEAN GRADUALLY MOVES TOWARDS THE
NE.

THE CARIBBEAN SEA...
BROAD CYCLONIC SURFACE FLOW COVERS THE NW CARIBBEAN AROUND A
SURFACE TROUGH PARALLELING THE YUCATAN PENINSULA ALONG 23N85W TO
15N88W. SCATTERED SHOWERS/THUNDERSTORMS COVER THE AREA W OF 77W
WITH SOME OF THE STRONGEST ACTIVITY FROM 18N-21N BETWEEN 78W-83W
INCLUDING THE CAYMAN ISLANDS. THIS AREA OF MOISTURE IS EXPECTED
TO DRIFT TOWARDS THE NE...WHICH WILL CONTINUE TO BRING
SHOWERS/THUNDERSTORMS TO THE NW CARIBBEAN INCLUDING CUBA AND
JAMAICA. THE REMAINDER OF THE BASIN IS UNDER MOSTLY FAIR
CONDITIONS WITH CLEAR SKIES AND TRADEWIND FLOW OF 15-20 KTS.
ALOFT...AN UPPER LEVEL RIDGE EXTENDS FROM CENTRAL AMERICA TO
HISPANIOLA...WHILE AN UPPER LEVEL TROUGH EXTENDS FROM THE
CENTRAL ATLC TO VENEZUELA. DIFFLUENCE ALOFT AROUND THE E SIDE OF
THE UPPER TROUGH IS HELPING PRODUCING SHOWERS/THUNDERSTORMS SE
OF THE WINDWARD ISLANDS IN THE ITCZ REGION. MODEL GUIDANCE
INDICATES THAT THIS MOISTURE WILL ADVECT WWD AND MAY IMPACT THE
SRN MOST WINDWARD ISLANDS. A TROPICAL WAVE STILL WELL E OF THE
ISLANDS WILL APPROACH THE ERN CARIBBEAN NEAR THE END OF THE
WEEK.

THE ATLANTIC OCEAN...
TROPICAL STORM ALBERTO CONTINUES TO SPIN OFF THE US COASTLINE.
SEE SPECIAL FEATURES SECTION ABOVE. FARTHER E...A 1011 MB LOW IS
CENTERED NEAR 32N72W. A SURFACE TROUGH EXTENDS FROM THE LOW
CENTER TO NEAR 26N74W. THIS SYSTEM IS SUPPORTED BY AN UPPER
LEVEL TROUGH OVER THE W ATLC WITH AXIS ALONG 74W. DIFFLUENCE
ALOFT AROUND THE E SIDE OF THE TROUGH IS HELPING PRODUCE
SHOWERS/POSSIBLE THUNDERSTORMS N OF 25N BETWEEN 63W-70W. AN
UPPER LEVEL RIDGE EXTENDS FROM HISPANIOLA TO NEAR 37N56W. THE
RIDGE SUPPORTS A 1030 MB SURFACE HIGH NEAR 33N52W WHICH IS
PROVIDING FAIR CONDITIONS ACROSS THE CENTRAL ATLC. AN UPPER
LEVEL TROUGH EXTENDS FROM NEAR 34N40W TO 15N56W. THIS UPPER
TROUGH IS ENHANCING CONVECTION SE OF THE LESSER ANTILLES NEAR
THE ITCZ. AN UPPER LEVEL RIDGE COVERS MUCH OF THE ERN ATLC ALONG
33W SUPPORTING ANOTHER 1030 MB HIGH NEAR 32N34W...AND A 1026 MB
HIGH NEAR 35N18W. VISIBLE SATELLITE IMAGERY INDICATES AN AREA OF
AFRICAN DUST EXTENDS N OF THE TROPICAL WAVE NEAR THE AFRICAN
COASTLINE AND CONTINUES TO 35W.

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

$$
WALTON






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