459  
FXCA20 KWBC 231825  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
224 PM EDT TUE OCT 23 2018  
 
AT 15 UTC HURRICANE WILLA CENTERED NEAR 21.4N 106.9W..WITH MAXIMUM  
SUSTAINED WINDS OF 110KT AND MINIMAL CENTRAL PRESSURE OF 966KT.  
THE HURRICANE IS MOVING NORTH-NORTHEAST AT 5KT. SEE NHC DISCUSSION  
FOR OFFICIAL FORECAST.  
 
TROPICAL DISCUSSION FROM OCT 23/12 UTC: CONSISTENT WITH PREVIOUS  
ANALYSIS AND FORECAST...A 500 HPA HIGH OVER THE NORTHERN YUCATAN  
ANCHORS A RIDGE THAT EXTENDS FROM EASTERN MEXICO/THE GULF...TO THE  
GREATER ANTILLES/NORTHERN CARIBBEAN. THE MID LEVEL RIDGE PATTERN  
IS EXPECTED TO PERSIST DURING THE NEXT THREE DAYS. AS IT HOLDS  
OVER THE GREATER ANTILLES-NORTHERN CENTRAL AMERICA...THE MID LEVEL  
RIDGE PATTERN IS TO SUSTAIN A TRADE WINDS CAP. THE CAP INVERSION  
IS TO INHIBIT ORGANIZED DEEP CONVECTION. ACROSS PUERTO RICO AND  
JAMAICA...SHALLOW CONVECTION IS TO INITIALLY TRIGGER RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. THIS DECREASES TO  
00-05MM/DAY AND ISOLATED MAXIMA OF 10MM ON WEDNESDAY AND ONWARD.  
 
THE MID LEVEL RIDGE...AS IT HOLDS...IS STEERING HURRICANE WILLA TO  
THE NORTHEAST...WITH THE NHC FORECASTING THE HURRICANE TO LANDFALL  
BETWEEN SOUTHERN SINALOA AND NAYARIT LATER TODAY. THIS IS TO THEN  
WEAKEN AS IT LIFTS ACROSS DURANGO TO COAHUILA/TAMAULIPAS ON  
WEDNESDAY. MEANWHILE...EXPECTING HEAVY RAINFALL AMOUNTS TO AFFECT  
SOUTHERN SINALOA-NAYARIT-SOUTHWEST DURANGO...WITH ACCUMULATION  
RANGING BETWEEN 150-350MM. DUE TO STRONG TOPOGRAPHICAL  
FORCING...EXPECTING LOCALIZED MAXIMA OF AROUND 500MM. ACROSS  
EASTERN DURANGO-SOUTHERN COAHUILA-NORTHERN ZACATECAS THIS IS TO  
TRIGGER SCATTERED CONVECTION WITH RAINFALL AMOUNTS OF 10-15MM/DAY  
AND MAXIMA OF 20-35MM EARLY ON WEDNESDAY.  
 
LATER ON WEDNESDAY...AS THE REMNANTS OF THE CYCLONE LIFT ACROSS  
NORTHEAST MEXICO...IT IS TO COMBINE WITH AN AMPLIFYING MID/UPPER  
LEVEL TROUGH STREAMING ACROSS TEXAS. MODELS THEN SHOW FORMATION OF  
AN EXTRATROPICAL CYCLONE/FRONTAL LOW OVER SOUTH TEXAS/NORTHWEST  
GULF OF MEXICO. THE LOW IS TO RAPIDLY INTENSIFY AS IT MIGRATES  
ACROSS THE NORTHERN GULF TO THE SOUTHEASTERN USA...DRIVING A FRONT  
SOUTH ACROSS NORTHEAST MEXICO TO VERACRUZ/CENTRAL MEXICO LATER ON  
THURSDAY. AS IT RACES ACROSS NORTHEAST MEXICO...THIS IS TO SUSTAIN  
SCATTERED CONVECTION ACROSS TAMAULIPAS WITH RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15MM ON WEDNESDAY...INCREASING TO  
10-15MM/DAY AND MAXIMA OF 20-40MM ACROSS VERACRUZ ON THURSDAY.  
 
NORTH OF THE MID LEVEL RIDGE...OVER THE WESTERN ATLANTIC...POLAR  
TROUGH LIES NORTH OF THE ISLANDS. THE TROUGH IS EXPECTED TO  
GRADUALLY LIFT TO THE NORTH-NORTHEAST EARLY IN THE CYCLE. AS IT  
PULLS AWAY...ASSOCIATED SURFACE FRONT WILL LOSE ITS UPPER LEVEL  
SUPPORT...WITH BOUNDARY TO WEAKEN TO A TROUGH AS IT MEANDERS  
ACROSS THE NORTHWEST BAHAMAS. THE TROUGH IS TO THEN ENHANCE LOW  
LEVEL MOISTURE CONVERGENCE...WITH PWAT CONTENT PEAKING AROUND 50MM  
ON WEDNESDAY. OVER THE NORTHWEST BAHAMAS INITIALLY EXPECTING  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ON  
WEDNESDAY THIS WILL INCREASE TO 10-15MM/DAY AND MAXIMA OF  
20-35MM...WHILE ON THURSDAY EXPECTING ADDITIONAL RAINFALL AMOUNTS  
OF 05-10MM/DAY AND MAXIMA OF 15MM.  
 
FARTHER TO THE EAST OF THIS FEATURE...A TUTT EXTENDS OVER THE  
CENTRAL ATLANTIC...WITH AXIS SOUTH ALONG 60W TO THE ISLAND  
CHAIN/NORTHEAST VENEZUELA. THIS TROUGH IS FORECAST TO LIFT TO THE  
EAST-NORTHEAST ON WEDNESDAY AS AHEAD OF A DEEPENING MID/UPPER  
LEVEL TROUGH TO THE WEST. MEANWHILE...AS IT MEANDERS ACROSS THE  
ISLAND CHAIN...THIS IS TO INTERACT WITH THE NEAR EQUATORIAL TROUGH  
OVER VENEZUELA-COLOMBIA. IN THIS AREA EXPECTING RAINFALL AMOUNTS  
OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON WEDNESDAY...AS THE TROUGH  
PULLS...THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF  
15-20MM...WHILE ON THURSDAY THE MAXIMA PEAKS AT 20-30MM.  
 
OVER WESTERN COLOMBIA...UNDER THE INFLUENCE OF THE PANAMANIAN  
LOW...MOISTURE IS TO CONVERGE ALONG THE WEST COAST TO THE EJE  
CAFETERO. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY  
AND MAXIMA OF 20-40MM/DAY...WITH PEAK IN ACTIVITY ON WEDNESDAY.  
OVER COSTA RICA/SOUTHERN NICARAGUA-PANAMA...ITCZ RELATED  
CONVERGENCE WILL SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-25MM/DAY.  
 
TROPICAL/EASTERLY WAVES/TRADE WIND SURGES FROM 00 UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
91W 94W 97W 99W 103W 105W 107W 110W EW 19N  
 
AN EASTERLY WAVE ALONG 91W AND SOUTH OF 19N IS TO TRIGGER ISOLATES  
TO SCATTERED CONVECTION AS IT STREAMS ACROSS SOUTHERN TO CENTRAL  
MEXICO EARLY IN THE CYCLE...FAVORING RAINFALL AMOUNTS OF  
00-05MM/DAY AND MAXIMA OF 10MM. OVER SOUTHWEST MEXICO THIS  
INCREASES TO 05-10MM/DAY AND MAXIMA OF 15MM ON WEDNESDAY.  
 
SERNA...IDEAM (COLOMBIA)  
TEJADA...AAC (PANAMA)  
DAVISON...WPC (USA)  

 
 
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