000
AXNT20 KNHC 202348
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL  
805 PM EDT FRI MAY 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 66W/67W S OF 13N TO INLAND OVER SOUTH 
AMERICA MOVING W 10-15 KT. WAVE REMAINS EMBEDDED WITHIN AN AREA 
OF DEEP LAYERED MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE 
WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
INLAND OVER VENEZUELA. 

...THE ITCZ...

ITCZ AXIS IS ANALYZED ALONG 10N14W 5N21W 3N33W 1N40W S OF THE 
EQUATOR NEAR 46W TO INLAND OVER SOUTH AMERICA. CLUSTERS OF 
SCATTERED/NUMEROUS STRONG CONVECTION ARE FROM 1N-10N BETWEEN 
11W-18W INCLUDING THE INLAND OVER SIERRA LEONE. CLUSTERS OF 
SCATTERED MODERATE/STRONG CONVECTION ARE WITHIN 90/120 NM EITHER 
SIDE OF THE ITCZ BETWEEN 19W-26W. CLUSTERS OF SCATTRED MODERATE/ 
ISOLATED STRONG CONVECTION ARE FROM THE EQUATOR TO 5N BETWEEN 
27W-37W. 
 
...DISCUSSION...

GULF OF MEXICO...
A BROAD LOW AMPLITUDE UPPER RIDGE COVERS MOST OF THE GULF WITH 
THE AXIS EXTENDING FROM THE E PACIFIC REGION ACROSS THE BAY OF 
CAMPECHE TO OVER THE N GULF COAST NEAR THE MISSISSIPPI DELTA OF 
LOUISIANA AND COUPLED WITH THE BROAD UPPER TROUGH OVER NEW 
ENGLAND AND THE W ATLC IS GIVING THE GULF WATERS NW FLOW ALOFT. 
SOMEWHAT DRY STABLE AIR ALOFT COVERS MUCH OF THE GULF LIMITING 
SHOWER ACTIVITY. DENSE SMOKE REMAINS OVER THE W GULF W OF 90W 
FROM FIRES REPORTED OVER S MEXICO AND THE YUCATAN PENINSULA ON 
NOAA SSD FIRE PRODUCTS. A WEAK SURFACE RIDGE REMAINS OVER THE NE 
GULF GIVING THE GULF E TO SE SURFACE FLOW AND LEAVING THE THE 
GULF UNDER MOSTLY CLEAR SKIES THIS EVENING. WEAK SURFACE RIDGE 
WILL REMAIN NEARLY STATIONARY IN THE NE GULF THROUGH TUE. FRESH 
RETURN FLOW WILL CONTINUE OVER THE W GULF THROUGH TUE. THEN 
DIMINISH WED AS A COLD FRONT APPROACHES THE TEXAS GULF COAST.

CARIBBEAN SEA...
A BROAD SHORTWAVE UPPER TROUGH EXTENDS ACROSS E CUBA NEAR 20N78W 
TO THE SW CARIBBEAN NEAR THE PANAMA/COSTA RICA BORDER A SURFACE 
TROUGH EXTENDS ALONG THE E SIDE OF THE UPPER TROUGH FROM 17N71W 
TO INLAND OVER SOUTH AMERICA NEAR 12N72W WITH ISOLATED SHOWERS 
WITHIN 60 NM EITHER SIDE OF THE TROUGH AXIS. A BROAD UPPER RIDGE 
COVERS THE E CARIBBEAN E OF 70W WITH THE AXIS E OF THE LESSER 
ANTILLES. DEEP LAYERED MOISTURE REMAINS OVER THE E CARIBBEAN 
AND COUPLED WITH THE DIFFLUENT FLOW ALOFT IS GENERATING 
SCATTERED SHOWERS OVER THE E CARIBBEAN WITHIN 180 NM OF LINE 
FROM 14N69W ACROSS PUERTO RICO AND VIRGIN ISLANDS NEAR 18N65W. 
DRY STABLE AIR ALOFT REMAINS OVER THE W CARIBBEAN LEAVING THE 
AREA W OF 73W UNDER MOSTLY CLEAR SKIES THIS EVENING. SMOKE IS 
OBSERVED ON THE LAST VISIBLE SATELLITE IMAGES OVER THE GULF OF 
HONDURAS W OF LINE FROM THE HONDURAS COAST NEAR 16N85W TO THE 
YUCATAN PENINSULA N OF BELIZE NEAR 19N87W. SURFACE TROUGH WILL 
REMAIN NEARLY STATIONARY THROUGH SAT BEFORE DISSIPATING. 

ATLANTIC OCEAN...
AN UPPER TROUGH COVERS THE W ATLC N OF 20N BETWEEN 65W-80W 
SUPPORTING A COLD FRONT THAT IS N OF THE REGION. THE SEABREEZE 
OVER THE FLORIDA PENINSULA IS GENERATING SCATTERED SHOWERS/ 
ISOLATED THUNDERSTORMS S 29N. A SURFACE TROUGH IS OVER THE 
W/CENTRAL ATLC EXTENDING ALONG 59W/60W FROM 24N-30N. A BROAD 
UPPER RIDGE EXTENDS FROM THE TROPICS E OF THE LESSER ANTILLES 
ALONG 55W TO BEYOND 32N SUPPLYING DIFFLUENT FLOW ALOFT AND 
ENHANCING SCATTERED SHOWERS WITHIN 200 NM OF LINE FROM THE 
VIRGIN ISLANDS NEAR 18N65W TO 28N55W. A WEAKENING UPPER TROUGH 
IS IN THE N/CENTRAL ATLC IS N OF 29N BETWEEN 30W-45W SUPPORTING 
A WEAK SURFACE TROUGH EXTENDING ALONG 29N50W TO BEYOND 32N49W. 
THESE SURFACE TROUGHS ARE EMBEDDED WITHIN A BROAD SURFACE RIDGE 
THAT COVERS THE ATLC N OF 20N FROM SW AFRICA TO FLORIDA AND INTO 
THE NE GULF OF MEXICO. SURFACE RIDGE ALONG 30N IN THE W ATLC 
WILL MOVE TO ALONG 28N SAT THEN WILL DRIFT BACK N TO ALONG 30N 
MON THROUGH WED. 

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

$$
PAW