000
AXNT20 KNHC 280541
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL  
205 AM EDT SAT MAY 28 2011

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0535 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS OFF THE COAST OF SURINAME FROM 11N54W TO 6N55W 
MOVING W AT 10-15 KT. CYCLONIC FLOW IS NOTED ALONG THE NORTHER 
AXIS IN THE LOW-LEVEL CLOUD PATTERN. HOWEVER...DRY NW FLOW IN 
THE MIDDLE TO UPPER LEVELS ABOVE THE LOW-LEVEL WAVE SIGNATURE IS 
INHIBITING ANY SIGNIFICANT CONVECTION WITH THE WAVE THIS EVENING.

TROPICAL WAVE IS INLAND OVER VENEZUELA FROM 10N63W TO 5N64W 
MOVING W AT ABOUT 10 KT. THIS WAVE IS EXPECTED TO REMAIN INLAND 
AND CONTINUE TO MOVE WEST WITH CONVECTION OVER THE NEXT 24 HOURS.

...ITCZ...

THE ITCZ AXIS IS ANALYZED FROM THE COAST OF SIERRA LEONE NEAR 
9N13W SW ALONG 6N20W 4N30W 3N40W EQ50W. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION IS WITHIN 120 NM ON EITHER SIDE OF 
THE AXIS E OF 44W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY COMBINED WITH UPPER LEVEL SATELLITE DERIVED 
WINDS INDICATE NW FLOW ALOFT MOVING A VERY DRY AIRMASS ACROSS 
THE GULF. AT SURFACE...WEAK SURFACE RIDGING COVERS THE AREA... 
CENTERED OVER THE NE CORNER OF THE BASIN BY A 1014 MB HIGH NEAR 
27N85W. THE OUTPUT OF THESE CONDITIONS BRING FAIR WEATHER ACROSS 
THE DISCUSSION AREA THIS EVENING. HOWEVER...HAZY SKIES ACROSS 
THE WESTERN HALF OF THE BASIN IS POSSIBLE DUE TO THE ADVECTION 
OF SMOKE FROM THE SOUTHERN MEXICO WILDFIRES. OTHERWISE...NO 
SIGNIFICANT CHANGES ARE EXPECTED OVER THE NEXT 24 HOURS.

CARIBBEAN SEA...
DRY WESTERLY ZONAL FLOW ALOFT IS NOTED ACROSS MUCH OF THE 
CARIBBEAN SEA THIS EVENING. THIS FEATURE IS KEEPING FAIR WEATHER 
CONDITIONS OVER MUCH OF THE CARIBBEAN...WITH A FEW ISOLATED 
SHOWERS LINGERING WITHIN 20 NM WEST AND SW OF THE GREATER 
ANTILLES. ON THE OTHER HAND...BROAD CYCLONIC TURNING IS NOTED ON 
THE S CENTRAL BASIN ACROSS THE COASTAL WATERS OF COLOMBIA. LOW 
LEVEL MOISTURE REMAINS QUITE HIGH IN THIS REGION...NOTICED ON 
TPW PRODUCT. SCATTERED SHOWERS AND TSTMS ARE S OF 12N AND W OF 
74W. THIS CONVECTION REMAINS ENHANCED OVER INTERIOR PORTIONS OF 
PANAMA AND COSTA RICA DUE TO THE CLOSE PROXIMITY OF THE EASTERN 
PACIFIC OCEAN ITCZ AXIS. MODEL GUIDANCE SUGGEST THE ACTIVITY IN 
THE SW BASIN WILL INCREASE OVER THE NEXT 24 HOURS...AS A WEAK 
LOW/TROUGH SYSTEM DEVELOPS IN THIS REGION. 

ATLANTIC OCEAN...
A SURFACE RIDGE COVERS THE WESTERN ATLC W OF 63W KEEPING 
CONDITIONS MOSTLY FAIR THIS EVENING. FARTHER EAST...A BROAD 
ELONGATED UPPER LEVEL LOW/TROUGH CONTINUES TO ROTATE AROUND 
31N52W. THIS UPPER LEVEL FEATURE IS SUPPORTING A SERIES OF 
SURFACE LOWS MOVING ACROSS THE S CENTRAL ATLC...ANALYZED AS A 
1015 MB LOW NEAR 27N54W...A 1014 MB LOW NEAR 30N57W...AND A 1014 
MB LOW NEAR 23N53W. A SURFACE TROUGH EXTENDS FROM THE 
EASTERNMOST LOW TO 19N57W. DESPITE THE LOCATION OF THESE SURFACE 
LOWS...SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS N OF 
18N BETWEEN 44W-51W...ASSOCIATED TO DIFFLUENCE FLOW ALOFT NOTED 
ON UPPER LEVEL SATELLITE DERIVED WINDS. WITHIN THIS AREA OF 
CONVECTION...A SHEAR LINE AXIS EXTENDS ALONG 32N47W TO 27N45W. 
THE PRESSURE GRADIENT IN THIS REGION REMAINS QUITE STRONG. AN 
EARLIER ASCAT PASS DEPICTED A CONTRAST OF 5 KT TO 25 KT FROM THE 
SW TO THE NE SIDE OF THE SHEAR AXIS. THE REMAINDER OF THE 
EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE KEEPING 
FAIR WEATHER CONDITIONS E OF 40W. FINALLY...AN ELONGATED UPPER 
LEVEL LOW IS CENTERED NE OF THE MADEIRA ISLANDS. SUPPORTS A 
SURFACE TROUGH EXTENDING FROM 33N13W TO 27N20W. 

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

$$

GARCIA