000
AXNT20 KNHC 172336
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE APR 17 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.

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

THE MONSOON TROUGH EXTENDS INLAND ACROSS WEST AFRICA INTO THE E 
TROPICAL ATLC ACROSS THE COAST OF GUINEA-BISSAU NEAR 12N16W TO 
5N22W...WHERE THE ITCZ AXIS CONTINUES ALONG 2N32W CROSSING THE 
EQUATOR ALONG 40W TO THE COAST OF BRAZIL NEAR 2S44W. CLUSTERS OF 
SCATTERED MODERATE TO STRONG CONVECTION ARE FROM 4N TO 5S 
BETWEEN 27W-42W. SIMILAR CONVECTION IS S OF 6N BETWEEN THE PRIME 
MERIDIAN AND 17W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH AXIS DIPS S FROM THE CENTRAL PLAIN STATES 
TO ERN TEXAS WITH A SHORTWAVE EMBEDDED AT THE BASE OF THE UPPER 
TROUGH MOVING ACROSS THE NW GULF BASIN SUPPORTING LOW PRESSURE 
SYSTEM OVER S-WRN MISSISSIPPI AND ASSOCIATED COLD FRONT THAT 
EXTENDS SW ACROSS THE AREA FROM THE COAST OF MISSISSIPPI NEAR 
30N89W TO THE COAST OF MEXICO JUST S OF TAMPICO NEAR 21N97W. 
DOPPLER RADAR IMAGERY DEPICTS SCATTERED MODERATE TO HEAVY 
SHOWERS AND THUNDERSTORMS WITHIN 60 NM ON EITHER SIDE OF THE 
FRONT N OF 26N...WITH ISOLATED SHOWERS AND POSSIBLE 
THUNDERSTORMS IN THE VICINITY OF THE FRONTAL BOUNDARY S OF 26N. 
STRONGER CONVECTION IS OVER THE ERN BAY OF CAMPECHE AND THE NRN 
COASTAL WATERS OF THE YUCATAN PENINSULA S OF 23N BETWEEN 
87W-94W. COMPUTER MODELS SUGGEST THE FRONT WILL LOOSE MOMENTUM 
DURING THE EVENING HOURS AND DISSIPATE OVER NE GULF WATERS BY 
WEDNESDAY. 

CARIBBEAN SEA...
DRY AIR AND SUBSIDENCE ALOFT COVERS A GREAT PORTION OF THE 
CARIBBEAN BASIN THIS EVENING...ASSOCIATED TO AN UPPER LEVEL 
RIDGE OF HIGH PRESSURE CENTERED OVER COSTA RICA. A MODERATE TO 
STRONG PRESSURE GRADIENT COVERS THE CARIBBEAN...SUPPORTING A 
TRADEWIND FLOW IN THE RANGE OF 15-25 KT DEPICTED ON A RECENT 
ASCAT SCATTEROMETER PASS. THIS FLOW IS PUSHING LOW LEVEL 
MOISTURE AGAINST THE COAST OF NICARAGUA GENERATING SCATTERED 
SHOWERS AND THUNDERSTORMS WITHIN 100 NM OFF THE COAST. A 
DISSIPATING SHEAR AXIS REMAINS OVER THE SE BASIN EXTENDING FROM 
13N63W TO 13N72W. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS 
ARE WITHIN 70-120 NM N OF THE SHEAR AXIS. OTHERWISE...SMALL 
CLUSTERS OF WEAK CONVECTION ARE ELSEWHERE ACROSS THE DISCUSSION 
AREA. THE PRESSURE GRADIENT IS EXPECTED TO REMAIN CONSTRICTED 
THROUGH WEDNESDAY.

ATLANTIC OCEAN...
A SURFACE RIDGE ANCHORED BY A 1024 MB HIGH NEAR 30N76W DOMINATES 
THE WRN ATLC WATERS W OF 65W. A DEEP OCCLUDED 1002 MB LOW IS 
CENTERED NEAR 33N60W. A FORMING COLD FRONT EXPANDS S OF THE LOW 
CENTER ANALYZED FROM 32N54W TO 27N59W TO 30N65W. SCATTERED WEAK 
TO ISOLATED MODERATE CONVECTION IS WITHIN 50-100 NM E AND S OF 
THE FRONTAL BOUNDARY. A SECONDARY FRONTAL BOUNDARY EXTENDS INTO 
THE AREA AS STATIONARY ALONG 32N44W TO 20N48W...WHERE IT 
DISSIPATES TO 15N58W. SCATTERED WEAK CONVECTION IS WITHIN 70 NM 
ON EITHER SIDE OF THE BOUNDARY. ISOLATED WEAK CONVECTION IS 
POSSIBLE WITHIN 30 NM EITHER SIDE OF THE REMAINDER OF THE FRONT. 
THIS LOW PRESSURE SYSTEM IS EXPECTED TO SHIFT SSW TONIGHT AND 
ENTER THE DISCUSSION AREA BY WEDNESDAY MORNING. A BROAD SURFACE 
RIDGE OVERTAKES THE REMAINDER OF THE ATLC WITH FAIR WEATHER 
CONDITIONS E OF 42W.

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

$$

GARCIA