000 AXNT20 KNHC 212343 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI MAY 21 2010 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC... ...SPECIAL FEATURES... AS OF 21/2100 UTC...A BROAD 1011 MB LOW IS CENTERED E OF THE BAHAMAS NEAR 25N73W. A SURFACE TROUGH EXTENDS N-NE FROM THE LOW TO 31N70W WHILE ANOTHER SURFACE TROUGH EXTENDS FROM THE LOW TO EASTERN CUBA NEAR 21N75W. THIS AREA OF LOW PRESSURE IS SUPPORTED ALOFT BY AN UPPER LEVEL TROUGH AXIS THAT EXTENDS FROM 31N71W TO 24N73W WITH A BROAD AREA OF UPPER LEVEL DIFFLUENCE LOCATED EAST OF THE UPPER LEVEL TROUGH AXIS OVER THE W ATLC...GENERATING NUMEROUS SHOWERS FROM 21N-32N BETWEEN 60W-71W. GLOBAL MODEL GUIDANCE INDICATES A COMPLEX LOW IS FORECAST TO REMAIN OVER THE W ATLC WATERS AND WITH CLOSE PROXIMITY TO THE SUB-TROPICAL RIDGE TO THE NORTH AND EAST...CREATING AN INCREASED PRESSURE GRADIENT THROUGH THE WEEKEND. WINDS ARE FORECAST TO REACH GALE FORCE OVER THE NE QUADRANT OF THE LOW BY EARLY SUNDAY AS A RESULT. THESE FORECAST GALES ARE UNSEASONABLE IN NATURE AS THE REGION TRANSITIONS TO A CLIMATOLOGICAL SUMMER PATTERN. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 33W S OF 10N MOVING W AT 10-15 KT. THE WAVE CONTINUES TO SHOW SLIGHT LOW-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS S OF 7N AND COINCIDES WITH A RELATIVE MAXIMUM IN THE TOTAL PRECIPITABLE WATER IMAGERY BETWEEN 27W-34W. ISOLATED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 30W-37W. TROPICAL WAVE IS ALONG 57W S OF 11N MOVING W AT 10-15 KT. THIS WAVE ALSO COINCIDES WITH A MAXIMUM IN TOTAL PRECIPITABLE WATER AS IT MOVES OVER PORTIONS OF THE TROPICAL NORTH ATLC AND SECTIONS OF SURINAME AND GUYANA WITH SCATTERED MODERATE ISOLATED STRONG CONVECTION FROM THE EQUATOR TO 8N BETWEEN 49W-62W. TROPICAL WAVE IS ANALYZED FROM 12N76W TO EASTERN PANAMA NEAR 9N78W AND INTO THE E PACIFIC REGION MOVING W-NW AT 5-10 KT. SOUTHEASTERLY LOW TO MID-LEVEL FLOW WILL CONTINUE TO ADVECT MOISTURE ASSOCIATED WITH THE WAVE ACROSS PORTIONS OF THE SW CARIBBEAN AND EVENTUALLY INLAND PORTIONS OF CENTRAL AMERICA OVER THE NEXT 24 HOURS. WIDELY SCATTERED MODERATE CONVECTION REMAINS LARGELY SOUTH OF 12N BETWEEN 75W-82W AND CONTINUES TO BE ENHANCED BY A FAVORABLE UPPER LEVEL ENVIRONMENT. TROPICAL WAVE IS ANALYZED FROM 13N82W TO SOUTHERN NICARAGUA NEAR 11N85W AND INTO THE E PACIFIC REGION MOVING W-NW AT 5-10 KT. NORTHERN PORTIONS OF THE WAVE CONTINUE SUPPORTING SCATTERED MODERATE CONVECTION OVER THE SW CARIBBEAN AND PORTIONS OF CENTRAL AMERICA FROM 12N-16N BETWEEN 80W-87W. A FAVORABLE UPPER LEVEL ENVIRONMENT WILL ALSO CONTRIBUTE TO SUSTAINED CONVECTION OVER THE NEXT 24 HOURS OVER NICARAGUA AND HONDURAS AS ENERGY FROM THE WAVE FRACTURES AND MOVES NW. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 11N15W 4N33W 4N51W AND INLAND ACROSS SOUTH AMERICA ALONG 6N57W 9N77W THEN ALONG 9N TO COSTA RICA. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN 120 NM OF THE W AFRICA COAST BETWEEN 6W-15W. SCATTERED MODERATE CONVECTION IS WITHIN 200 NM SOUTH OF THE AXIS BETWEEN 15W AND 29W. A SURFACE TROUGH IS EMBEDDED WITHIN THE ITCZ ALONG 45W S OF 9N WITH WIDELY SCATTERED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF A LINE FROM 6N36W TO 8N47W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY THIS EVENING INDICATES VERY DRY AND STABLE CONDITIONS ALOFT OVER MUCH OF THE GULF AND FLORIDA PENINSULA WITH NEARLY ZONAL UPPER LEVEL WESTERLY FLOW FROM ACROSS EASTERN MEXICO TO 80W. THIS UPPER LEVEL REGIME IS CONTINUING TO SUPPORT A WEAK SURFACE RIDGE WITH AXIS FROM THE NE GULF TO EAST-CENTRAL MEXICO NEAR TUXPAN WITH GENERALLY E TO SE WINDS UP TO 15 KT. HOWEVER...LOW-LEVEL MOISTURE IS ADVECTING FROM THE NW CARIBBEAN SEA AND CUBA OVER THE SE GULF WATERS AND YUCATAN CHANNEL PROVIDING FOR ISOLATED SHOWERS S OF 23N E OF 87W. THIS ACTIVITY IS MOSTLY LOCATED EAST OF A SURFACE TROUGH ANALYZED FROM 23N87W TO A 1010 MB LOW CENTERED OVER THE YUCATAN PENINSULA NEAR 21N88W. GLOBAL MODEL GUIDANCE SUGGESTS THE LOW AND SURFACE TROUGH WILL DRIFT WESTWARD AND DISSIPATE ON THE SOUTHEASTERN PERIPHERY OF THE RIDGE AS IT MOVES OVER THE SW GULF THROUGH EARLY SUNDAY. CARIBBEAN SEA... A 1010 MB LOW IS CENTERED OVER THE YUCATAN PENINSULA NEAR 21N88W WITH A SURFACE TROUGH EXTENDING NE FROM THE LOW TO 23N87W AND S FROM THE LOW TO SOUTHERN BELIZE. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING EAST OF THE SURFACE TROUGH OVER THE NW CARIBBEAN FROM 17N-23N BETWEEN 74W-87W. THIS CONVECTIVE ACTIVITY CONTINUES TO BE ENHANCED BY UPPER LEVEL DIFFLUENT FLOW ACROSS PORTIONS OF THE NW CARIBBEAN AND CUBA...EXTENDING EASTWARD INTO THE SW NORTH ATLC E OF 76W. ISOLATED SHOWERS AND TSTMS SPREAD E OF 76W...REMAINING LARGELY N OF 18N ACROSS THE NORTHERN CARIBBEAN SEA AND GREATER ANTILLES THIS EVENING DUE TO A BROAD AREA OF CONVERGENT TRADE WINDS FOCUSED IN THE VICINITY OF HISPANIOLA AND THE WINDWARD PASSAGE. WITH THE UPPER LEVEL TROUGH SLOW TO MOVE EASTWARD OVER THE NEXT COUPLE OF DAYS...AND A DEVELOPING AREA OF LOW PRESSURE TO LOCATE OVER THE W ATLC ALONG 70W OVER THE NEXT 24-48 HOURS...CONTINUED PRECIPITATION IS FORECAST ACROSS PORTIONS OF HISPANIOLA AND CUBA THROUGH THE WEEKEND. ELSEWHERE...A PAIR OF TROPICAL WAVES ARE PROGRESSING WESTWARD ACROSS THE SW CARIBBEAN BRINGING SCATTERED SHOWERS AND ISOLATED TSTMS SW OF A LINE FROM 17N85W TO THE COAST OF NORTHERN COLOMBIA NEAR 11N75W...INCLUDING INLAND SECTIONS OF CENTRAL AMERICA TO 17N THIS EVENING. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH IS ACROSS THE W ATLC WITH AXIS ALONG 32N71W TO THE CENTRAL BAHAMAS NEAR 22N75W. THIS UPPER LEVEL TROUGHING IS SUPPORTING A 1011 MB LOW CENTERED NEAR 25N73W LISTED ABOVE AS THE SPECIAL FEATURE. ELSEWHERE...A BROAD SURFACE RIDGE ENGULFS THE REMAINDER OF THE ATLC E OF 60W ANCHORED BY A 1031 MB HIGH CENTERED NORTH OF THE DISCUSSION AREA NEAR 39N38W. HOWEVER...A SURFACE TROUGH IS ANALYZED OVER THE TROPICAL NORTH ATLC FROM 22N53W TO 16N55W WITH ISOLATED SHOWERS FROM 16N-22N BETWEEN 50W-56W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN