772  
FXCA20 KWBC 181834  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
234 PM EDT WED OCT 18 2017  
 
TROPICAL DISCUSSION FROM OCT 18/12 UTC: STRONG POLAR OFF THE EAST  
COAST OF THE UNITED STATES SUSTAINS A SURFACE FRONT THAT WILL  
EXTEND INTO THE NORTHEASTERN GULF OF MEXICO BY WEDNESDAY  
EVENING...TO THEN START MEANDERING SOUTH AND EXTEND CLOSE TO GRAND  
BAHAMA BY THURSDAY EVENING. BY FRIDAY EVENING THE FRONT WILL  
EXTEND OVER GRAND BAHAMA WHILE BECOMING STATIONARY. TO THE SOUTH  
OF THE FRONT...A POOL OF MOISTURE WITH PRECIPITABLE WATER VALUES  
EXCEEDING 50MM IS FAVORING SCATTERED CONVECTION. THIS ACTIVITY  
WILL AFFECT THE BAHAMAS DURING THE NEXT THREE DAYS...TO PRODUCE  
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM IN THE NORTHERN  
BAHAMAS ON WEDNESDAY. SIMILAR AMOUNTS ARE EXPECTED ON THURSDAY AND  
FRIDAY ACROSS THE CENTRAL BAHAMAS.  
 
TO THE WEST...WANING NORTHERLY WIND SURGE IN THE GULF OF  
MEXICO/GULF OF HONDURAS WILL CONTINUE SUSTAINING MODERATE RAINFALL  
AMOUNTS IN THE REGION. THIS WILL CONTINUE WHILE NORTHEASTERLY  
TRADES CONTINUE ENHANCING LOW-LEVEL MOISTURE CONVERGENCE ALONG  
NORTHERN SLOPES OF NORTHERN CENTRAL AMERICA. THROUGH EARLY  
FRIDAY...THIS WILL LEAD TO 10-15MM/DAY AND MAXIMA OF 20-40MM FROM  
SOUTHERN VERACRUZ/TABASCO SOUTHEAST INTO GUATEMALA AND SOUTHERN  
BELIZE. IN THE YUCATAN PENINSULA EXPECTING 10-15MM/DAY AND MAXIMA  
OF 20-30MM THROUGH THURSDAY...DECREASING TO 05-10MM/DAY AND MAXIMA  
OF 15-20MM ON FRIDAY. BY FRIDAY-SATURDAY...EXPECTING 15-20MM/DAY  
AND MAXIMA OF 30-60MM IN SOUTHERN BELIZE AND NORTHERN  
HONDURAS/NORTHEASTERN NICARAGUA. IN THE YUCATAN PENINSULA AND INTO  
OAXACA/VERACRUZ IN MEXICO...EXPECTING 05-10MM/DAY AND MAXIMA OF  
15-20MM.  
 
IN THE CARIBBEAN...A TRADE WIND SURGE IS ENTERING THE BASIN FROM  
THE TROPICAL ATLANTIC AND IS FORECAST TO EXTEND ACROSS THE VIRGIN  
ISLANDS BY WEDNESDAY EVENING...THE EASTERN DOMINICAN REPUBLIC BY  
THURSDAY EVENING...AND TURKS AND CAICOS/HAITI BY FRIDAY EVENING.  
THE SURGE IS ACCOMPANIED BY 25-35KT TRADES...AND BY A STRONG  
SUBSIDENCE CAP AND DRY MID-LEVELS. THIS WILL LEAD TO A SIGNIFICANT  
DECREASE IN ACCUMULATIONS ONCE THE LEADING EDGE OF THE SURGE  
CROSSES A GIVEN LOCATION. IN THE MEAN TIME...A MOIST PLUME LIES  
AHEAD OF THE SURGE...AS WELL AS A TROPICAL WAVE (SEE BELOW). THESE  
TWO SYSTEMS WILL LEAD TO LOCALLY HEAVY PRECIPITATION AS THEY  
PROPAGATE WESTWARD ACROSS THE CARIBBEAN. THROUGH EARLY  
THURSDAY...LARGEST ACCUMULATIONS ARE EXPECTED IN PUERTO RICO AND  
THE VIRGIN ISLANDS WHERE ENHANCED MOISTURE CONVERGENCE WILL FAVOR  
15-20MM/DAY AND MAXIMA OF 25-50MM. IN SOUTHERN HISPANIOLA  
EXPECTING ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF 20-45MM. BY  
THURSDAY-FRIDAY EXPECTING LARGEST ACCUMULATIONS IN SOUTHERN  
HISPANIOLA AND SOUTHEASTERN JAMAICA...WHERE EXPECTING 10-15MM/DAY  
AND MAXIMA OF 20-35MM. BY FRIDAY-SATURDAY...EXPECTING LARGEST  
ACCUMULATIONS TO OCCUR IN JAMAICA WHERE AMOUNTS ARE TO REACH  
10-15MM/DAY AND MAXIMA OF 20-35MM.  
 
ALSO IN THE CARIBBEAN...AS THE TRADE WIND SURGE PROPAGATES ACROSS  
THE NORTHERN TIER...THE ITCZ IS TO CONFINE TO THE SOUTHERN  
CARIBBEAN...ENTERING THE BASIN THROUGH TRINIDAD AND TOBAGO. THIS  
WILL SUSTAIN CURRENT UNRAVELING WET SPELL IN TRINIDAD AND  
TOBAGO/NORTHEASTERN VENEZUELA THROUGH THE WEEKEND. IN THESE  
LOCATIONS...EXPECTING AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM  
ON WEDNESDAY...15-20MM/DAY AND MAXIMA OF 25-50MM ON THURSDAY...AND  
10-15MM/DAY AND MAXIMA OF 20-40MM ON FRIDAY. CONVECTION WILL  
EXTEND INTO THE ABC ISLANDS DURING THE CYCLE...WHERE EXPECTING  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM...SPREADING WEST ON  
THURSDAY AND ON.  
 
IN NORTHWESTERN SOUTH AMERICA AND SOUTHERN CENTRAL AMERICA...THE  
PANAMANIAN LOW HAS ORGANIZED SLIGHTLY. THE ITCZ IS  
DISORGANIZED...AND IS FORECAST TO MEANDER SLIGHTLY TO THE NORTH OF  
PANAMA THROUGH THE CYCLE. CURRENTLY...A MOISTURE POOL AND A  
TROPICAL WAVE CROSSING INTO THE PACIFIC BASIN OF COSTA  
RICA/NICARAGUA WILL CONTINUE SUSTAINING MODERATE RAINFALL  
ACCUMULATIONS. THROUGH EARLY THURSDAY EXPECTING 15-20MM/DAY AND  
MAXIMA OF 25-50MM IN EASTERN NICARAGUA/EASTERN COSTA RICA. IN  
PANAMA EXPECTING 05-10MM/DAY AND MAXIMA OF 15-25MM.  
THURSDAY-FRIDAY...EXPECTING 10-15MM/DAY AND MAXIMA 20-35MM ACROSS  
PANAMA/COSTA RICA AND NICARAGUA. ON FRIDAY-SATURDAY...EXPECTING  
10-15MM/DAY AND MAXIMA OF 20-40MM IN COSTA RICA...WHILE LIGHTER  
AMOUNTS ARE EXPECTED IN PANAMA. IN COLOMBIA AND WESTERN  
VENEZUELA...DIURNAL CONVECTION WILL LEAD TO AMOUNTS OF 10-15MM/DAY  
AND MAXIMA OF 20-35MM THROUGH THE CYCLE. AS LOW-LEVEL WESTERLIES  
INCREASE ON FRIDAY...EXPECTING AN INCREASE IN ACCUMULATIONS IN  
SOUTHWESTERN COLOMBIA TO 15-20MM/DAY AND MAXIMA OF 25-50MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
29W 32W 35W 38W 41W 44W 46W 48W TW 15N  
67W 69W 72W 76W 78W 80W 82W 84W TW 19N  
85W 87W 90W 92W 94W 96W DISSIPATES TW 19N  
 
A TROPICAL WAVE IS INITIALIZED AT 29W. THIS WAVE IS INTERACTING  
WITH A TUTT TO THE NORTHWEST AND AMPLIFYING. MODELS HAVE THIS WAVE  
MEANDERING IN THE ATLANTIC THROUGH THE NEXT THREE DAYS...WITHOUT  
AFFECTING DIRECTLY THE FORECAST REGION.  
 
TROPICAL WAVE INITIALIZED AT 67W WILL CONTINUE STIMULATING  
CONVECTION AS IT PROPAGATES WEST ACROSS THE CARIBBEAN BASIN. ON  
WEDNESDAY...IT WILL STIMULATE CONVECTION IN HISPANIOLA TO PRODUCE  
MAXIMA OF 20-45MM. IN COLOMBIA/WESTER VENEZUELA...IT WILL CONTINUE  
SUSTAINING MAXIMA OF 20-35MM. BY THURSDAY-EARLY FRIDAY...IT WILL  
ENHANCE ACTIVITY IN SOUTHERN HISPANIOLA AND JAMAICA WHERE IT WILL  
SUSTAIN MAXIMA OF 20-34MM. SIMILAR AMOUNTS ARE EXPECTED IN  
NORTHERN COLOMBIA. BY FRIDAY-SATURDAY...THIS WILL STIMULATE  
PRECIPITATION IN COSTA RICA TO SUSTAIN AMOUNTS OF 10-15MM/DAY AND  
MAXIMA OF 20-40MM...WHILE IN NORTHEASTERN NICARAGUA AND NORTHERN  
HONDURAS EXPECTING 15-20MM/DAY AND MAXIMA OF 30-60MM.  
 
A TROPICAL WAVE INITIALIZED AT 81W CONTINUES TO BE ILL-DEFINED IN  
TERMS OF ROTATION...YET ASSOCIATED MOISTURE POOL IS ENHANCING  
CONVECTION IN CENTRAL AMERICA ON WEDNESDAY. ON THURSDAY...THE WAVE  
WILL ENHANCE ACTIVITY IN GUATEMALA...TO THEN EXIT INTO OPEN WATERS  
OF THE PACIFIC OCEAN.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
GALVEZ...WPC (USA)  

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page