Atlantic Basin Tropical Discussion Atlantic | Pacific

000
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