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Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
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623 FXCA20 KWBC 181848 PMDCA TROPICAL DISCUSSION - INTERNATIONAL DESKS NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 247 PM EDT TUE JUN 18 2024 FORECAST BULLETIN 18 JUN 2024 AT 1845 UTC: THE NATIONAL HURRICANE CENTER IS NOW ISSUING ADVISORIES ON WHAT IS KNOWS AS POTENTIAL TROPICAL CYCLONE (PTC) ONE. THIS AREA OF LOW PRESSURE KNOWN AS PTC ONE IS FORECAST...BY THE NATIONAL HURRICANE CENTER...TO STRENGTHEN INTO A TROPICAL STORM ON WEDNESDAY...AND MAKE LANDFALL IN SOUTHERN TAMAULIPAS BY WEDNESDAY EVENING AS A TROPICAL STORM. THIS PTC ONE IS ASSOCIATED WITH A BROADER CIRCULATION THAT IS CAUSING AND WILL CONTINUE TO CAUSE SIGNIFICANT AMOUNTS OF RAIN ACROSS CENTRAL AMERICA AND MEXICO FOR AT LEAST THE REST OF THE WORKWEEK. THEREFORE...REGARDLESS OF THE DEVELOPMENT OF PTC ONE...PORTIONS OF CENTRAL AMERICA AND MEXICO WILL RECEIVE EXCESSIVE AND VERY HAZARDOUS AMOUNTS FOR THE REST OF THIS WEEK. ANOTHER FEATURE OF SIGNIFICANCE IS THE TUTT LOCATED OVER THE WESTERN TROPICAL ATLANTIC...NEAR THE TURKS AND CAICOS...WHICH IS DRIFTING WEST AND EXPECTED TO BE OVER THE NORTHWESTERN CARIBBEAN TO THE SOUTHEASTERN GULF OF MEXICO BY LATE WEDNESDAY INTO THURSDAY...THEN OVER THE NORTHWEST YUCATAN PENINSULA BY LATE THURSDAY INTO FRIDAY. THIS TUTT WILL PROVIDE INSTABILITY ACROSS THE CARIBBEAN ISLANDS AND THE BAHAMAS...CAUSING A MARGINAL TO SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE GREATER ANTILLES INTO THE BAHAMAS LATER TODAY INTO LATE WEDNESDAY NIGHT. EXCESSIVE AMOUNTS OF RAIN ARE EXPECTED ACROSS PORTIONS OF CENTRAL AMERICA FOR THE REST OF THIS WEEK...EVEN BEYOND OUR 3-DAY PERIOD. THE LATEST MODEL GUIDANCE SUGGESTED THAT THE 72-HR RAINFALL TOTAL WILL RANGE BETWEEN 10 AND 16 INCHES (250-400MM)...WITH ISOLATED HIGHER AMOUNTS ON THE PACIFIC SIDE OF CENTRAL AMERICA FROM THE GOLFO DE FONSECA TO CHIAPAS OF MEXICO. ADDING TO THAT...SOME OF THE MODEL GUIDANCE AVAILABLE SUGGESTED OVER 16 INCHES (400MM) ACROSS ISOLATED SECTORS OF EL SALVADOR INTO HONDURAS AND EXTREME SOUTHWEST NICARAGUA. OTHER SIGNIFICANT AMOUNTS OF RAIN ARE FORECAST OVER CHIAPAS...CAMPECHE...AND INTO THE NORTHEAST YUCATAN PENINSULA...AS WELL AS NORTHEASTERN MEXICO IN AND AROUND TAMAULIPAS...WHERE 72-HR MAX TOTALS OF 8 TO 12 INCHES (200-300MM) ARE SUGGESTED BY THE MODEL GUIDANCE. THE PERSISTENT ONSHORE FLOW INTO THE PACIFIC CENTRAL AMERICAN COAST...WITH THE ABOVE NORMAL MOISTURE...WILL PROVIDE A PERSISTENT PATTERN FOR SHOWER DEVELOPMENT FOR THE AFOREMENTIONED AREAS. THE CARIBBEAN REGION WILL BE UP AND DOWN DURING THE MIDWEEK AS THERE IS SOME SAHARAN DUST OVER THE LESSER ANTILLES THAT WILL CONTINUE TO MOVE WEST. THE SAHARAN DUST IS EXPECTED TO GET TO HISPANIOLA BY LATE WEDNESDAY INTO THURSDAY. FOR THAT REASON...THE UPPER TROUGH WILL HELP DEVELOP THUNDERSTORMS TODAY ACROSS THE EASTERN GREATER ANTILLES TODAY INTO EARLY WEDNESDAY. AS THE UPPER TROUGH MOVES WEST...IT WILL PROVIDE INSTABILITY FOR STRONG THUNDERSTORM DEVELOPMENT OVER PORTIONS HAITI INTO CUBA ON WEDNESDAY INTO THURSDAY...WHILE THE DENSER SAHARAN DUST CONCENTRATION LAGS BEHIND...BEING OVER PUERTO RICO AND EASTERN HISPANIOLA WEDNESDAY INTO THURSDAY. THE OVERALL EXPECTED RAINFALL OVER THE CARIBBEAN IS UNDER 50MM FOR THE 3-DAY PERIOD...BUT ISOLATED SECTIONS COULD OBSERVE HIGHER AMOUNTS...SUCH AS THE POSSIBLE STRONG THUNDERSTORMS THAT DO DEVELOP OVER HISPANIOLA...WHICH CAUSE ISOLATED AMOUNTS TO 50MM ACROSS PORTIONS OF HAITI TODAY AND WEDNESDAY. CUBA AND THE BAHAMAS MAY ALSO OBSERVE STRONG THUNDERSTORMS BUT THE TIMING FOR THE STRONGEST STORMS WOULD BE LATE WEDNESDAY INTO THURSDAY. THERE HAS BEEN VERY LITTLE TO NO CHANGE IN THE FORECAST FOR NORTHERN SOUTH AMERICA. THE REGION WILL HAVE A SERIES OF SFC TROUGHS IN THE AREA OVER THE NEXT FEW DAYS. THE 72-HR RAINFALL ACCUMULATION COULD HAVE ISOLATED MAX VALUES OF 50-100MM ACROSS PORTIONS OF COLOMBIA AND ECUADOR...WHILE VENEZUELA...NORTHWESTERN BRAZIL AND THE GUIANAS WOULD HAVE 72-HR MAX TOTALS OF UP TO AROUND 50-75MM. BUT OVERALL...MOST OF THE RAINFALL EXPECTED OVER NORTHERN SOUTH AMERICA WILL BE CONVECTIVE...AS THE DIURNAL HEATING INTERACTS WITH THE AVAILABLE MOISTURE...AND MAY BE ENHANCED BY THE TROUGHS IN THE AREA. EACH DAY WILL HAVE MAX TOTALS OF 25-45MM IN DIFFERENT SECTIONS. IN SUMMARY...THE LATEST GUIDANCE CONTINUES TO SUGGEST THAT THE POSITIONING OF THE MONSOON TROUGH IN THE PACIFIC...COMBINED WITH THE BROAD CAG CIRCULATION WILL CONTINUE TO PROMOTE A VERY MOIST ONSHORE FLOW INTO CENTRAL AMERICA FOR THE NEXT SEVERAL DAYS. THIS WILL CONTINUE THE VERY HAZARDOUS MULTI-DAY WET SPELL FOR PORTIONS OF CENTRAL AMERICA INTO MEXICO. THE CARIBBEAN WILL HAVE SOME MOMENTS WITH STRONG THUNDERSTORMS...PARTICULARLY LATE TODAY AND WEDNESDAY...BUT SAHARAN DUST MAY LIMIT THE CONVECTION ACROSS THE NORTHEASTERN CARIBBEAN AS IT MOVES IN. NORTHERN SOUTH AMERICA WILL ALSO HAVE MOMENTS OF SHOWERS AND LOCALLY INDUCED THUNDERSTORMS AS THE AVAILABLE MOISTURE COMBINES WITH THE DIURNAL HEATING. ALAMO (WPC) CLARKE (CINWS) FERNANDER (BDM) $$