790  
FXCA20 KWBC 261926  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
325 PM EDT THU SEP 26 2024  
 
FORECAST BULLETIN 26 SEP 2024 AT 1830 UTC:  
 
THE NATIONAL HURRICANE CENTER IS MONITORING TROPICAL CYCLONE  
HELENE LOCATED NEAR 25.5N AND 85.5W ON THURSDAY.THE UPPER-LEVEL  
TROUGH OVER THE NORTHERN GULF OF MEXICO...ALONG WITH THE RIDGE TO  
THE NORTHEAST EXTENDING OVER THE BAHAMAS AND INTO THE NORTHERN  
ATLANTIC...WILL SUPPORT A NORTHWARD MOVEMENT OF THE SYSTEM. IN THE  
LOWER LEVELS...FEEDER BAND STRUCTURES ARE EXPECTED TO PERSIST  
ACROSS PORTIONS OF THE NORTHERN CARIBBEAN ON THURSDAY. AS  
HURRICANE HELENE CONTINUES MOVING NORTHWARD...THE FEEDER BAND  
CONVECTION ASSOCIATED TO THIS SYSTEM WILL FAVOR A MAXIMA OF  
20-35MM OVER WESTERN CUBA AND 15-25MM OVER YUCATAN PENINSULA ON  
THURSDAY AND FRIDAY. THE IMPACT OF THIS SYSTEM WILL DIMINISH AS  
HELENE CONTINUES TO MOVE FURTHER NORTH INTO THE UNITED STATES.  
 
THE NATIONAL HURRICANE CENTER IS ALSO MONITORING THE TROPICAL  
STORM JOHN...LOCATED NEAR 17.5N AND 102.7W AT 15 UTC ON THURSDAY.  
THE TROPICAL STORM IS EXPECTED TO CONTINUE MOVING ALONG THE  
WESTERN COAST OF MEXICO. FORECASTS INDICATE THAT HIGH LEVELS OF  
MOISTURE WILL PERSIST...DUE TO ONSHORE FLOW LEADING TO SIGNIFICANT  
PRECIPITATION FROM THURSDAY INTO FRIDAY. BY SATURDAY A DECREASE IN  
PRECIPITATION IS EXPECTED. ON THURSDAY..RAINFALL MAXIMA ARE  
EXPECTED TO REACH A MAXIMA OF 75-125MM IN COLIMA..GUERRERO AND  
MICHOACAN. IN PORTIONS OF WESTERN OAXACA A MAXIMA OF 20-35MM. IN  
JALISCO...ALONG THE EJE VOLCĂNICO TRANSVERSAL...EXTENDING INTO  
VERACRUZ...A MAXIMA OF 15-25MM IS EXPECTED.  
 
LOOKING AHEAD TO FRIDAY...AS THE SYSTEM BEGINS TO  
DISSIPATE...COLIMA...GUERRERO...MICHOACAN WILL EXPERIENCE MAXIMA  
OF 75-125MM. IN JALISCO AND CENTRAL MEXICO A MAXIMA OF 20-40MM IS  
EXPECTED. OVER THE EJE VOLCANICO TRANSVERSAL AND SOUTH  
VERACRUZ...WESTERN CHIAPAS AND EAST OAXACA...EXPECT A RAINFALL  
MAXIMA OF 15-25MM. BY SATURDAY FROM JALISCO TO NORTHERN GUERRERO  
MAXIMA OF 15-25MM AND FROM SOUTHERN GUERRERO TO OAXACA MAXIMA OF  
20-45MM...IN NAYARIT MAXIMA OF 20-35MM...OVER PUEBLA AND VERACRUZ  
THEY MAY EXPERIENCE MAXIMA OF 25-50MM.  
 
PLEASE REVIEW THE MOST RECENT FORECAST FOR THE ACTIVE TROPICAL  
CYCLONE ISSUED BY THE NATIONAL HURRICANE CENTER ON THEIR WEBSITE:  
WWW.HURRICANES.GOV  
 
IN THE UPPER LEVELS THE PRESENCE OF A RIDGE OVER THE EASTERN  
PACIFIC EXTENDING INTO PORTIONS OF CENTRAL PERU AND BOLIVIA IS  
ENHANCING VENTILATION FOR DEEP CONVECTION OVER SOUTHERN  
COLOMBIA...AMAZONAS BRAZIL AND SOUTHERN VENEZUELA WILL PERSIST IN  
THE NEXT FORECAST CYCLE.  
IN ADDITION...BY FRIDAY...THE UPPER-LEVEL TROUGH OVER THE  
CARIBBEAN SEA IS EXPECTED TO RETROGRADE TO THE WESTERN  
CARIBBEAN..EXTENDING OVER COSTA RICA AND PANAMA..WHERE IT WILL  
INTERACT WITH THE RIDGE TO THE SOUTH..RESULTING IN INCREASED  
DIFFLUENCE AND ENHANCED DIVERGENCE OVER NORTHWEST SOUTH AMERICA.  
IN ADDITION THE INCREASE ON THE MOISTURE LEVELS DUE TO THE ONSHORE  
FLOW FAVORED BY THE LOW-LEVEL JET...WILL FAVOR THE CHANCE OF HEAVY  
PRECIPITATION. THIS LEADS TO A MAXIMA OF 20-35MM ON THURSDAY OVER  
COLOMBIA ON THURSDAY. AN INCREASE WILL BE OBSERVED IN THE NEXT FEW  
DAYS.. WITH MAXIMA OF 25-50MM IN WESTERN COLOMBIA AND 20-35MM FROM  
CENTRAL COLOMBIA INTO ECUADOR ON FRIDAY. BY SATURDAY MAXIMA OF  
40-80MM IN WESTERN COLOMBIA AND 25-50MM IN NORTHERN COLOMBIA AND  
WESTERN VENEZUELA IS EXPECTED. ADDITIONAL MAXIMA OF 20-35MM FROM  
CENTRAL COLOMBIA INTO ECUADOR WILL PERSIST ON SATURDAY.  
 
EASTERLY/TROPICAL WAVES INITIALIZED AT 12 UTC  
TYPE SOF INIT 27/00 27/12 28/00 28/12 29/00 29/12 30/00 30/12  
TW 18N 61W 63W 66W 69W 72W 75W 78W 81W 84W  
 
AN INCREASE IN MOISTURE IS EXPECTED FROM THURSDAY INTO SATURDAY AS  
A TROPICAL WAVE ENHANCED BY AN UPPER-LEVEL TROUGH IN THE CARIBBEAN  
BASIN MOVES OVER THE LESSER ANTILLES AND EXTREME NORTHEASTERN  
VENEZUELA. BY THURSDAY...RAINFALL MAXIMA OF 25-50MM ARE EXPECTED  
IN THE LESSER ANTILLES...TRINIDAD...IN VENEZUELA AND NORTHERN  
BRASIL EXPECT MAXIMA OF 20-40MM. ANOTHER MAXIMA OF 20-35MM IN  
PUERTO RICO AND EAST OF DOMINICAN REPUBLIC ON THURSDAY. ON FRIDAY  
IN THE LESSER ANTILLES...IN VENEZUELA AND NORTHERN BRASIL WILL  
OBSERVED A DECREASE WITH MAXIMA OF 15-25MM. HOWEVER...PUERTO RICO  
AND DOMINICAN REPUBLIC WILL EXPERIENCE AN INCREASE WITH MAXIMA OF  
20-35MM. AS THE TROPICAL WAVE CONTINUES PROPAGATING OVER THE  
WESTERN CARIBBEAN...BY SATURDAY RAINFALL MAXIMA OF 15-25MM OVER  
PUERTO RICO...DOMINICAN REPUBLIC AND EAST OF CUBA IS  
EXPECTED...AND JAMAICA CAN EXPECT A MAXIMA OF 20-35MM.  
 
ACOSTA...(WPC)  
LEDESMA...(WPC)  
 
 
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