000 FXCA20 KWBC 211822 PMDCA TROPICAL DISCUSSION - INTERNATIONAL DESKS NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 222 PM EDT TUE OCT 21 2008 DISCUSSION FROM 21/0000 UTC... AT 250 HPA.. THE GFS MAINTAINS A STRONG ANTICYCLONE OVER THE CARIBBEAN THROUGH 72 HRS. THE RIDGE AXIS IS FORECAST TO EXTEND WESTWARD ACROSS NICARAGUA AND HONDURAS INTO THE EASTERN PACIFIC. TO THE EAST THE RIDGE IS FORECAST TO EXTENDED ACROSS THE WINDWARD/LEEWARD ISLES THROUGH 48 HRS. AFTER 48 HRS.. A NORTH CENTRAL ATLANTIC TROUGH IS FORECAST TO BUILD SOUTHWARD ACROSS THE LEEWARD/WINDWARD ISLES AT 60-72 HRS. BROAD WEST TO SOUTHWEST FLOW IS EXPECTED ALONG THE NORTHERN PERIPHERY OF THE ANTICYCLONE OVER MUCH OF MEXICO.. THE GULF OF MEXICO AND FLORIDA THROUGH THE FORECAST PERIOD. AT 500 HPA.. SIMILAR TO 250 HPA.. AN ANTICYCLONE IS FORECAST TO REMAIN POSITIONED OVER EASTERN CUBA AND THE NORTHERN CARIBBEAN THROUGH THE FORECAST PERIOD. A TROUGH IS FORECAST TO CARVE OUT OVER THE U.S. CENTRAL PLAINS AND EXTEND SOUTHWARD INTO THE NORTHERN HALF OF MEXICO FROM 48-72 HRS. BROAD CYCLONIC FLOW IS FORECAST TO EXTEND ACROSS THE GULF OF MEXICO WITH THIS FEATURE. A VORTICITY MAXIMA IS FORECAST TO TRACK ACROSS NORTHERN MEXICO IN THE CYCLONIC FLOW THEREBY INITIATING THE THREAT FOR SHOWERY CONVECTION OVER CHIHUAHUA ON DAY 1. 00-05MM OR RAINFALL IS POSSIBLE. DIURNAL CONVECTION IS ALSO POSSIBLE ON DAYS 2-3 OVER SECTIONS OF TAMAULIPAS AND VERACRUZ. 05-10MM/DAY ARE POSSIBLE WITH LOCAL MAXIMA OF 15-25MM. EASTERLY FLOW IS FORECAST TO PERSIST ACROSS THE LOWER CARIBBEAN ALONG THE SOUTHERN PERIPHERY OF THE ANTICYCLONE KEEPING A STEADY PROGRESSION OF MOVEMENT OF EASTERLY WAVES (SEE BELOW). AT 850 HPA.. A CLOSED CYCLONIC CIRCULATION IS FORECAST ALONG THE SOUTHERN COAST OF COSTA RICA AT 24 HRS AND IS THEN FORECAST TO DRIFT SOUTHWESTWARD INTO THE ATLANTIC AT 36-72 HRS AND MOVE TOWARDS THE EQUATOR BY 72 HRS. THROUGH 48 HRS.. AN INVERTED TROUGH IS FORECAST TO EXTEND NORTHWARD ACROSS NICARAGUA AND HONDURAS.. OVER THE CARIBBEAN THEN ACROSS YUCATAN. SATELLITE IR IMAGERY SHOWS MOST OF THE CONVECTION OCCURRING OFFSHORE ALONG THE CARIBBEAN COAST OF HONDURAS.. NICARAGUA.. BELIZE AND YUCATAN MEXICO. THE SNM MM5 MODEL HAS PERFORMED REASONABLY WELL WITH POSITIONING OF THIS CONVECTION THE PAST 24 HRS SO WILL STAY CLOSE TO THIS MODEL OUTPUT FOR THE CURRENT FORECAST. RAINFALL AMOUNTS OF 15-30MM/DAY ARE POSSIBLE EACH DAY OF THE FORECAST CYCLE ON THE IMMEDIATE COAST OF THE AFOREMENTIONED REGIONS. LOCAL RAINFALL MAXIMA OF 50-100MM/DAY ARE POSSIBLE ON DAYS 1-2. LOCAL MAXIMA COULD EXCEED 100MM ON DAY 2. BY DAY 3.. THE HEAVY RAINFALL THREAT IS EXPECTED TO END OVER CENTRAL AMERICA BUT CONTINUE OVER PORTIONS OF YUCATAN. ONCE AGAIN.. 15-30MM ARE POSSIBLE WITH LOCAL MAXIMA OF 75-150MM. RAINFALL AMOUNTS OF 05-15MM/DAY WITH LOCAL MAXIMA OF 30-60MM ARE POSSIBLE ALONG THE WESTERN SIDE OF THE CYCLONIC FLOW OVER CHIAPAS ON DAYS 2-3. OVER MEXICO A CLOSED CYCLONIC CIRCULATION IS FORECAST TO PERSIST OVER JALISCO THROUGH MUCH OF THE FORECAST PERIOD. THE FLOW AROUND THIS CIRCULATION IS EXPECTED TO ADVECT MOISTURE INTO GUERRERO.. MICHOACAN AND COLIMA. THE SNM MM5 MODEL SUGGESTS DAILY RAINFALL AMOUNTS OF O5-15MM/DAY EACH DAY OF THE FORECAST CYCLE. BETWEEN 48-72 HRS.. A CYCLONIC CIRCULATION IS FORECAST TO DEVELOP BETWEEN CUBA AND THE BAHAMAS. OVER HISPANIOLA.. CUBA.. JAMAICA AND THE LOWER BAHAMAS.. 05-10MM OF RAINFALL IS POSSIBLE ON DAY 1 FROM MAINLY SHALLOW CONVECTION. LOCAL MAXIMA MAY EXCEED 15MM. ON DAYS 2-3.. THE ENVIRONMENT IS EXPECTED TO BECOME MORE FAVORABLE FOR DEEP CONVECTION. RAINFALL AMOUNTS OF 10-30MM/DAY ARE POSSIBLE WITH LOCAL MAXIMA AS HIGH AS 40-60MM. TROPICAL WAVES INIT F24 F36 F48 F60 F72 F84 47W 54W 56W 57W 59W 62W 65W 73W 75W 77W 80W 81W 82W 84W THE WAVE INITIALIZING ALONG 47W IS FORECAST TO INITIATE AREAS OF DEEP CONVECTION OVER THE EASTERN CARIBBEAN THROUGH THE FORECAST PERIOD. OVER THE LEEWARD/WINDWARD ISLES AND GUYANA.. CONVECTIVE RAINFALL AMOUNTS OF 05-15MM/DAY WITH LOCAL MAXIMA OF 20-35MM/DAY ARE POSSIBLE ON DAYS 1-2. BY DAY 3.. THESE AREAS ARE EXPECTED TO BE ON THE EAST SIDE OF THE WESTWARD MOVING WAVE THEREBY LESS RAINFALL IS ANTICIPATED. 05-10MM ARE POSSIBLE WITH A FEW 15MM AMOUNTS LOCALLY. THE WAVE INITIALIZING AT 73W IS FORECAST TO MOVE ACROSS NORTHWEST COLOMBIA AND CENTRAL AMERICA DAYS 1-3. THE AFOREMENTIONED 850 HPA CIRCULATION WILL BRING COPIOUS AMOUNTS OF ITCZ MOISTURE INTO THE REGION SETTING THE STAGE FOR POTENTIAL LOCALLY HEAVY RAINFALL. MODEL FORECAST SOUNDINGS SHOW MODERATE TO STRONG INSTABILITY OVER THE REGION. OVER NORTHWEST COLOMBIA AND PANAMA.. RAINFALL ACCUMULATIONS OF 05-15MM/DAY WITH LOCAL MAXIMA OF 25-45MM ARE POSSIBLE EACH DAY OF THE FORECAST CYCLE. FURTHER TO THE NORTH OVER COSTA RICA AND NICARAGUA.. 15-25MM/DAY AMOUNTS ARE EXPECTED ON DAYS 1-2 WITH LOCAL MAXIMA OF 30-60MM. BY DAY 3.. A BIT MORE SUBSIDENCE IS EXPECTED AS THE WAVE BEGINS TO PULL WESTWARD. 05-10MM/DAY ARE POSSIBLE WITH LOCAL MAXIMA OF 20-35MM. GREENE...DM (BAHAMAS) ARANDA...ETESA (PANAMA) BODNER...NCEP (USA) $$