Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
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672 FXCA20 KWBC 041900 PMDCA TROPICAL DISCUSSION - INTERNATIONAL DESKS NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 259 PM EDT FRI OCT 04 2024 FORECAST BULLETIN 04 OCT 2024 AT 1900 UTC: THE NATIONAL HURRICANE CENTER (NHC) CONTINUES TO ISSUE ADVISORIES ON HURRICANE KIRK AND TROPICAL STORM LESLIE IN THE ATLANTIC WATERS. THERE ARE ALSO TWO AREAS OF POSSIBLE TROPICAL CYCLONE DEVELOPMENT OVER THE NEXT 7 DAYS...ONE OF THEM IS IN THE GULF OF MEXICO AND THE OTHER IS IN THE EAST PACIFIC...OFF THE COAST OF SOUTHWESTERN MEXICO. ACCORDING TO THE LATEST NHC OUTLOOK...BOTH OF THOSE AREAS HAVE A LOW CHANCE OF TROPICAL CYCLONE FORMATION THROUGH 48 HOURS...AND A MEDIUM PERCENT CHANCE OF FORMATION THROUGH 7 DAYS. PLEASE SEE THE LATEST ADVISORIES AND OUTLOOKS ISSUED BY THE NHC AT WWW.HURRICANES.GOV. ACROSS THE TROPICAL REGION...OTHER THAN THE TROPICAL CYCLONES KIRK AND LESLIE...THERE IS AN EXTRA-TROPICAL LOW PRESSURE NEAR 33N/60W THAT IS CAUSING NORTHERLY WINDS AND BRINGING DRIER AIR INTO THE BAHAMAS TODAY. THIS LOW PRESSURE IS FORECAST TO MEANDER OVER THE AREA THROUGH THE NEXT FEW DAYS AS IT WEAKENS. THERE IS ALSO A TROUGH OF LOW PRESSURE ACROSS THE WESTERN GULF OF MEXICO...WHICH HAS THE POTENTIAL OF DEVELOPING A BROAD CIRCULATION OVER THE NEXT FEW DAYS AS IT SLOWLY MOVES INTO THE CENTRAL GULF OF MEXICO. THERE IS ALSO AN AREA OF LOW PRESSURE JUST SOUTH OF SOUTHWESTERN MEXICO...WHICH IS FORECAST TO DEEPEN AND MOVE WEST NORTHWEST OFFSHORE OF SOUTHWESTERN MEXICO OVER THE NEXT SEVERAL DAYS. THESE LOW PRESSURES WILL CAUSE SHOWERS AND THUNDERSTORMS TO AFFECT PORTIONS OF THE GULF COAST OF MEXICO FROM VERACRUZ TO THE YUCATAN PENINSULA...AS WELL AS THE PACIFIC COAST OF MEXICO...FROM GUERRERO TO JALISCO. THERE ARE A FEW FEATURES OF INTEREST IN THE MID LEVELS ACROSS THE TROPICAL REGION. A MID LEVEL LOW ASSOCIATED WITH THE EXTRA TROPICAL LOW EXTENDS SOME TROGHINESS TO THE SOUTHWEST INTO THE TURKS AND CAICOS. THIS MID LEVEL TROUGH OVER THE AREA WILL LIFT BY LATE SUNDAY AS THE MID LEVEL LOW MOVES EAST. THERE IS A BROAD MID LEVEL HIGH ACROSS THE WESTERN CARIBBEAN...ENCOMPASSING A LARGE AREA OF THE CARIBBEAN AND INTO CENTRAL AMERICA...PROVIDING SUBSIDENCE. HOWEVER...THERE IS A MID LEVEL LOW DEVELOPING WITH LOCALLY HIGHER VORTICITY ACROSS THE WESTERN TO SOUTHWESTERN GULF OF MEXICO...ASSOCIATED WITH THE DEVELOPING LOW OVER THE AREA...AND THERE IS ALSO A MID LEVEL LOW OVER NORTHERN MEXICO...WHICH COULD PROVIDE INSTABILITY AND PROMOTE CONVECTION OVER PORTIONS OF WESTERN AND SOUTHERN MEXICO...AS IT COMBINES WITH THE DEEPER MOISTURE AND THE LOW LEVEL FEATURES IN THE GULF AND EASTERN PACIFIC. IN THE UPPER LEVELS...THERE IS A TROUGH THAT ALSO EXTENDS FROM THE WEST CENTRAL ATLANTIC INTO THE TURKS AND CAICOS...WITH AN INVERTED TROUGH AXIS OVER HISPANIOLA AND INTO THE SOUTHERN CARIBBEAN. THIS UPPER TROUGH IS EXPECTED TO MOVE EAST THROUGH THE WEEKEND AS IT WEAKENS. AN UPPER LEVEL HIGH PRESSURE IS DOMINATING THE GULF OF MEXICO INTO THE WESTERN CARIBBEAN...AND IS EXPECTED TO ELONGATE NORTHEAST INTO THE BAHAMAS...BUT PREVAIL THROUGH THE WEEKEND. AN UPPER RIDGE IS ALSO FORECAST ACROSS THE EASTERN CARIBBEAN. HOWEVER...A WEAK UPPER TROUGH IS FORECAST TO HAVE ITS AXIS OVER NORTH CENTRAL MEXICO THIS WEEKEND...WHICH WILL HELP PROMOTE INSTABILITY OVER PORTIONS OF THE SOUTHERN HALF OF MEXICO...ESPECIALLY AFTER CONSIDERING THE MID LEVEL TROUGH AND LOW LEVEL FEATURES IN THE AREA. OVERALL...THE GENERAL SYNOPTIC PATTERN IS CONDUCIVE FOR SOME ENHANCED CONVECTION OVER PORTIONS OF SOUTHERN MEXICO INTO NORTHERN CENTRAL AMERICA...WHILE THE CARIBBEAN...THE BAHAMAS...AND THE SOUTHERN HALF OF CENTRAL AMERICA COULD EXPECT RELATIVELY MODEST AMOUNTS OF RAIN THROUGH THE WEEKEND. THE SYNOPTIC SITUATION OVER NORTHERN SOUTH AMERICA IS UNIMPRESSIVE...BUT LARGE AREAS WITH SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED EACH DAY...HOWEVER. THERE ARE A FEW SFC TROUGHS MOVING THROUGH THE AREA...BUT THE MID AND UPPER LEVEL WINDS AND HEIGHTS ARE NOT VERY CONDUCIVE FOR PROLONGED AND ENHANCED CONVECTION. THIS IS BECAUSE THERE IS A BROAD MID LEVEL HIGH PRESSURE OVER CENTRAL SOUTH AMERICA...CAUSING RELATIVELY LIGHT EASTERLY WINDS OVER NORTHERN SOUTH AMERICA. THE UPPER LEVELS WILL ALSO PROVIDE PREVAILING EASTERLY WINDS...NOT VERY CONDUCIVE TO ENHANCED CONVECTION...WITH THE EXCEPTION OF SOME DIVERGENCE. THAT BEING SAID...THE AVAILABLE MOISTURE AND DIURNAL HEATING...COMBINED WITH THE SFC TROUGHS MOVING THROUGH WILL BE ENOUGH TO CAUSE DIURNAL CONVECTION OVER THE AREA. THE EGDI ALGORITHM ALSO SUGGESTS LARGE AREAS WITH THUNDERSTORM POTENTIAL...ESPECIALLY OVER NORTHWESTERN BRAZIL TO THE NORTHWEST OF THE CONTINENT. ONE THING TO NOTE...IS THAT A PERSISTENT AND LONG FETCH LOW LEVEL WIND FLOW INTO WESTERN COLOMBIA IS EXPECTED THROUGH THE WEEKEND. THIS ONSHORE FLOW WILL CAUSE THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS ACROSS WESTERN COLOMBIA AS THE MOISTURE INTERACTS WITH THE OROGRAPHIC LIFTING. IN TERMS OF RAINFALL OVER THE REGION THROUGH THE WEEKEND...THE AREAS WITH THE HIGHEST RAINFALL POTENTIAL ARE PORTIONS OF THE SOUTHERN HALF OF MEXICO INTO GUATEMALA...AND NORTHWESTERN SOUTH AMERICA...FROM NORTHWEST BRAZIL TO WESTERN COLOMBIA...GIVEN THE AFOREMENTIONED SYNOPTIC PATTERNS. THE AMOUNTS OF RAIN IN THE FORECAST OVER MEXICO HAVE A HIGHER UNCERTAINTY THEN NORMAL...CONSIDERING THAT THE MODEL GUIDANCE IS IN SOME DISAGREEMENT...AND THAT SOME OF THE RAINFALL WILL DEPEND ON THE EVENTUAL DEVELOPMENT OF THE LOW PRESSURES IN THE GULF OF MEXICO AS WELL AS THE EASTERN PACIFIC ALONG THE SOUTHWESTERN MEXICAN COAST. IN THE CARIBBEAN...THE LESSER ANTILLES ARE FORECAST LITTLE TO NO RAINFALL ACCUMULATIONS THROUGH THE WEEKEND...WHILE THE GREATER ANTILLES ARE FORECAST MINOR ACCUMULATIONS THROUGH MOST OF THE DAY...BUT AFTERNOON CONVECTION MAY CAUSE LOCALIZED PRECIPITATION THAT COULD REACH 25 TO 35MM. WESTERN CUBA DOES HAVE A HIGHER CHANCE OF RAIN...UP TO 50MM TODAY INTO SATURDAY MORNING AS A TROUGH WITH THUNDERSTORM ACTIVITY MOVES OVER THE AREA...THEN SATURDAY AND SUNDAY WILL HAVE LOCALIZED CONVECTION. CENTRAL AMERICA...GENERALLY FROM HONDURAS SOUTHWARD TO PANAMA WILL HAVE MODELS AMOUNTS OF RAIN EACH DAY THROUGH THE WEEKEND. THE FORECAST IS FOR MAX DAILY RAIN OF UP TO 35MM...THOUGH MOST OF THE AREA IS FORECAST MAX DAILY RAINFALL OF 25MM OR LESS. ALAMO...(WPC) $$