000 FXCA20 KWBC 201747 PMDCA TROPICAL DISCUSSION - INTERNATIONAL DESKS NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 146 PM EDT THU MAY 20 2004 DISCUSSION VALID FROM MAY 20/0000 UTC... A WELL DEFINED BROAD MID/UPPER LEVEL TROUGH WITH AXIS ORIENTATED NORTHEAST-SOUTHWEST ACROSS THE SOUTHERN CARIBBEAN SEA-SOUTHERN NICARAGUA AND THE EASTERN PACIFIC AT 24-30HRS WILL DRIFT SLOWLY NORTHWARD TO REACH JUST SOUTH OF HISPANIOLA-JAMAICA BY 72HRS. AT 850 HPA... HUGGING THE AXIS OF THE TROUGH ARE TWO CYCLONIC CENTERS... LOCATED NEAR 10N 88W AND 15N 70W RESPECTIVELY. NOTE... THIS IS A LITTLE SLOWER THAN PREVIOUSLY FORECAST. THE CYCLONIC TURNING ASSOCIATED WITH BOTH CENTERS AS WELL AS THE WELL DEFINED AXIS OF THE TROUGH IS QUITE EVIDENT ON SATELLITE IMAGERY. THE MODELS REMAIN IN AGREEMENT WITH THE NORTHWARD MOTION OF THE TROUGH AXIS THROUGH 72-84HRS. THE AXIS OF THE TROUGH AT 500 HPA FOLLOWS A VERY SIMILAR PATTERN AS DOES THE POSITIONING OF THE CYCLONIC CENTERS. AN ELONGATED MID/UPPER LEVEL TROUGH WILL REMAIN STATIONARY ACROSS THE SOUTHWEST ATLANTIC-NORTHERN BAHAMAS-SOUTHERN FLORIDA WITH THE BASE TRAILING ACROSS THE EASTERN GULF OF MEXICO-YUCATAN TO SOUTHERN GUATEMALA THROUGH 48-54HRS. AT 500 HPA THE ELONGATED TROUGH AXIS IS SUPPORTED BY A CYCLONIC CENTER NEAR 23N 90W THROUGH 24-36HRS... HEREAFTER TO DRIFT EAST TO 23N 81W BY 60-72HRS. PROPAGATING TO THE RIGHT OF THIS TROUGH AXIS... OVER THE CENTRAL/SE BAHAMAS AND NORTH OF THE LEEWARD ISLES IS A SUBTROPICAL JET WITH WINDS IN EXCESS OF 60-90KTS. A BROAD AREA OF CYCLONIC FLOW DOMINATES MOST OF THE CARIBBEAN-CENTRAL AMERICA THROUGH 60-72HRS WHICH WILL HELP TO PROVIDE GOOD OUTFLOW OVER THE LOW-MID LEVEL TROUGH... THE ETA MODEL IS ALSO SHOWING A FAIRLY GOOD AREA OF UPPER LEVEL DIVERGENCE OVER NICARAGUA/HONDURAS DURING THE NEXT 30-48HRS. THEREFORE... THE CARIBBEAN PLAINS OF NICARAGUA-COSTA RICA AND EASTERN HONDURAS CAN EXPECT RAINFALL ACCUMULATION OF 35-50MM/DAY AND MAXIMA OF 75-125MM. OVER BELIZE-EL SALVADOR AND YUCATAN EXPECT RAINFALL AMOUNTS OF 05-15MM/DAY WHILE OVER GUATEMALA EXPECT RAINFALL ACCUMULATION OF 15-30MM/DAY AND MAXIMA OF 50-75MM. WITH MOST OF THE ENERGY LIFTING SLOWLY NORTHWARD WITH THE TROUGH... PANAMA- WESTERN/NORTHERN COLOMBIA CAN EXPECT RAINFALL ACCUMULATION OF 10-25MM/DAY AND MAXIMA OF 30-60MM TO CONCENTRATE OVER NORTHWESTERN COLOMBIA. UPSTREAM OF THE AFOREMENTIONED ELONGATED TROUGH... A MID/UPPER LEVEL RIDGE CONTINUES TO BUILD OVER THE CENTRAL US AND INTO SOUTHWEST MEXICO. THIS RIDGE IS BEING SUPPORTED BY A NEARLY STACKED STATIONARY HIGH LOCATED ALONG 25N 104W THROUGH 72HRS. THE RIDGE WILL HELP TO PRODUCE A MORE SUBSIDENT(DRYING) PATTERN OVER CENTRAL-EASTERN MEXICO THROUGH 72HRS... TO RESULT IN SHALLOW CONVECTION OVER SOUTHERN MEXICO/MEXICO CITY-DF WITH RAINFALL ACCUMULATION OF 10-20MM/DAY AND MAXIMA OF 35MM MAINLY OVER CHIAPAS AND OAXACA TO PEAK IN A DIURNAL PATTERN. AT 850 HPA A BROAD ANTICYCLONIC CENTER DOMINATES THE SOUTHEAST US-WESTERN ATLANTIC AND CARIBBEAN BASIN THROUGH THE ENTIRE CYCLE. THE CENTER WHICH IS LOCATED NEAR 32 86W THROUGH 24-30 HRS WILL DRIFT TO 30N 70W BY 60-72HRS. THIS WILL RESULT IN A LIGHT TO MODERATE EASTERLY FLOW OVER THE AFOREMENTIONED REGION THROUGH THE CYCLE. HOWEVER... AS THE BEFORE MENTIONED LOW/MID LEVEL TROUGH DRIFTS NORTHWARD... THE EASTERLY FLOW OVER CENTRAL AMERICA-WESTERN CARIBBEAN WILL BECOME MORE NORTHEAST THROUGH 48-72HRS... WHILE BECOMING MORE SOUTHEAST OVER THE WINDWARD ISLES. THIS NORTHEAST FLOW ACROSS THE CARIBBEAN PLAINS OF CENTRAL AMERICA WILL HELP TO SUSTAINED SCATTERED CONVECTION THROUGH MOST OF THE CYCLE. OVER JAMAICA-HISPANIOLA-CAYMAN ISLES AND PUERTO RICO EXPECT ISOLATED TO SCATTERED CONVECTION THROUGH 48 HRS WITH RAINFALL ACCUMULATION OF 05-15MM/DAY AND ISOLATED MAXIMA OF 25MM. HOWEVER... AS THE TROUGH MOVES FURTHER NORTH... THIS WILL RESULT IN DEEP/ SCATTERED CONVECTION LATER THIS CYCLE. THE VIRGIN/LEEWARD ISLES WILL CONTINUE TO RECEIVE WIDELY SCATTERED CONVECTION THROUGH 54- 60HRS AS THE SUBTROPICAL JET MEANDERS NORTH OF THE ISLANDS. THIS WILL RESULT IN RAINFALL ACCUMULATION OF 15-30MM/DAY OVER THE LEEWARD/VIRGIN ISLES WITH MAXIMA OF 50MM MAINLY OVER THE FRENCH ISLES. THE SUB-EQUATORIAL RIDGE IS TO CONTINUE MEANDERING ALONG 11N AT 250 HPA THROUGH 72 HRS. SUPPORTED THIS RIDGE IS A SERIES OF ANTICYCLONIC CENTERS EAST OF THE SOUTHERN WINDWARD ISLES NEAR 11N 47W AND 11N 25W RESPECTIVELY. AS THE CENTER ALONG 47W NORTH OF 10N STRENGTHENS AND DRIFTS WEST THROUGH 48-54 HRS... IT WILL BUILD A RIDGE NORTH ALONG 67W/68W THROUGH 72HRS. THIS BUILDING RIDGE WILL SPLIT THE AFOREMENTIONED ELONGATED TROUGH LOCATED NORTH OF THE ISLANDS. THIS WILL FORCE THE AXIS OF THE LOW/MID LEVEL TROUGH IN THE CENTRAL/SOUTHERN CARIBBEAN SEA TO BECOME MORE SOUTHEAST TO NORTHEAST ORIENTATED. THE MAIN AXIS OF THE SUB-EQUATORIAL RIDGE WILL CONTINUE TO EXTEND WESTWARD ACROSS NORTHERN SOUTH AMERICA TO THE EASTERN PACIFIC THROUGH 60-72HRS. AT 500 HPA. .. THE RIDGE EXTENDS E-W ACROSS THE SOUTHERN ATLANTIC- NORTHERN SOUTH AMERICA THROUGH 72HRS. THE BROAD AXIS OF THIS RIDGE WILL CONTINUE TO SUPPORT UPPER LEVEL DIFFLUENCE OVER NORTHERN VENEZUELA-SOUTHERN WINDWARD THROUGH 72HRS. EARLY THIS CYCLE AS THE LOW-MID LEVEL TROUGH REMAINS NEARLY STATIONARY NORTH OF THE NETHERLANDS ANTILLES(ABC ISLES)/LAKE MARACAIBO... ALONG WITH THE UPPER LEVEL DIFFLUENCE OVER NORTHERN VENEZUELA... THIS WILL RESULT IN RAINFALL ACCUMULATION OF 10-20MM/DAY OVER ABC/NORTHERN VENEZUELA AND MAXIMA OF 40MM TO CONCENTRATE OVER LAKE MARACAIBO. OVER SOUTHERN VENEZUELA/COLOMBIA EXPECT RAINFALL AMOUNTS OF 15- 30MM/DAY AND MAXIMA OF 50-75MM OVER SOUTHERN COLOMBIA. WITH MOST OF THE MOISTURE MOVING NORTH EARLY THIS CYCLE... THIS WILL RESULT IN ISOLATED TO SCATTERED CONVECTION OVER THE GUIANAS... TO RESULT IN RAINFALL ACCUMULATION OF 10-25MM/DAY WITH MAXIMA OF 45MM OVER GUYANA. THE SOUTHERN WINDWARD ISLES CAN EXPECT RAINFALL AMOUNTS OF 10-20MM/DAY. GUERRERO.......ONAMET (REPUBLICA DOMINICANA) MOXEY-BONAMY...NWS (THE BAHAMAS) CARR...........NCEP (HPC) $$