689  
FXCA20 KWBC 241822  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
221 PM EDT TUE APR 24 2018  
 
TROPICAL DISCUSSION FROM APR 24/12 UTC: CONSISTENT WITH PREVIOUS  
FORECASTS...A DEEP TROUGH MOVES TO THE EASTERN USA LATER  
TODAY...TO CONTINUE INTO THE WESTERN ATLANTIC ON WEDNESDAY. THIS  
IS TO THEN LIFT OVER A BUILDING RIDGE TO THE SOUTH AND EAST ON  
THURSDAY TO FRIDAY. A SECONDARY MID/UPPER LEVEL TROUGH ON THE  
SOUTHERN STREAM IS TO FOLLOW...FORECAST TO STREAM ACROSS TEXAS TO  
NORTHEAST MEXICO LATER ON WEDNESDAY. THIS IS TO THEN AMPLIFY  
ACROSS THE GULF OF MEXICO TO THE YUCATAN/SOUTHERN STATES OF MEXICO  
ON THURSDAY...FOCUSING CYCLONIC VORTICITY AND SHORT WAVE ENERGY  
ACROSS WESTERN CUBA AND THE NORTHWEST BAHAMAS ON FRIDAY. AT LOW  
LEVELS THE ASSOCIATED FRONT MOVES TO SOUTH FLORIDA WHILE TRAILING  
ACROSS THE GULF OF MEXICO TO NORTHEAST MEXICO/RIO BRAVO BASIN  
LATER TODAY. EARLY ON WEDNESDAY MORNING THE FRONT MEANDERS INTO  
THE NORTHWEST BAHAMAS...WITH BOUNDARY TO THEN REMAIN NEARLY  
STATIONARY WHILE GRADUALLY WEAKENING LATER ON THURSDAY. AS IT  
MEANDERS OVER NORTHEAST STATES OF MEXICO THIS WILL FAVOR SCATTERED  
CONVECTION WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM.  
AS THE SOUTHERN STREAM TROUGH INTERACTS WITH THIS BOUNDARY ON  
WEDNESDAY THIS INCREASES TO 15-20MM/DAY AND MAXIMA OF 30-60MM. ON  
THURSDAY THE FOCUS OF THE CONVECTION WILL SHIFT TO VERACRUZ WHERE  
IT IS TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-45MM. OVER CHIAPAS-TABASCO-NORTHERN YUCATAN THE UPPER LEVEL  
TROUGH IS TO ALSO TRIGGER MODERATE RAINFALL AMOUNTS ON THURSDAY  
WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-45MM. ON FRIDAY  
EXPECTING SIMILAR AMOUNTS ACROSS QUINTANA ROO AND BELIZE/NORTHERN  
GUATEMALA. THIS TROUGH IS TO ALSO ENHANCE DIURNAL CONVECTION ALONG  
THE CONTINENTAL DIVIDE OVER SOUTHERN CHIAPAS TO SOUTHERN GUATEMALA  
ON THURSDAY...FAVORING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA  
OF 20-45MM. ACTIVITY BUILDS ACROSS EL SALVADOR/SOUTHERN HONDURAS  
ON THURSDAY-FRIDAY...WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA  
OF 20-30MM. AS THE FRONT MEANDERS OVER THE NORTHWEST  
BAHAMAS-WESTERN CUBA...THIS IS TO FAVOR SCATTERED CONVECTION WITH  
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY. THROUGH  
FRIDAY...AS A SUBTROPICAL JET MAXIMA ROUNDS THE BASE OF THE UPPER  
LEVEL TROUGH...FAVORING AN UPPER DIVERGENT PATTERN...CONVECTION  
ACROSS WESTERN CUBA AND THE NORTHWEST BAHAMAS INCREASES TO  
15-20MM/DAY AND MAXIMA OF 35-70MM. NOTE THAT THIS IS TO COINCIDE  
WITH FAVORABLE MJO ENVIRONMENTAL CONDITIONS...THUS LEADING TO A  
HIGHER RISK OF ORGANIZED DEEP CONVECTION.  
 
FARTHER EAST...A BROAD/LOW AMPLITUDE TROUGH IS TO EXTEND ACROSS  
THE CENTRAL ATLANTIC TO THE EASTERN CARIBBEAN/NORTHERN SOUTH  
AMERICA LATER TODAY. AS IT PRESSES AGAINST A CELL OF THE  
SUBEQUATORIAL RIDGE TO THE EAST...THIS IS TO SUSTAIN A SUBTROPICAL  
JET MAXIMA OF 70-90KT ACROSS THE EASTERN CARIBBEAN-FRENCH ISLES  
EARLY IN THE CYCLE. THIS JET IS FORECAST TO MEANDER TO THE  
EAST-NORTHEAST LATER IN THE WEEK. THE TROUGH IS TO THEN GRADUALLY  
PULL WHILE GRADUALLY YIELDING TO A BUILDING RIDGE OVER THE EASTERN  
CARIBBEAN. THROUGH THURSDAY THE SHORT WAVE RIDGE IS TO THEN BECOME  
THE DOMINANT FEATURE...STRENGTHENING THE TRADE WINDS INVERSION  
WHILE CAPPING MOISTURE TO LOWER LEVELS OF THE ATMOSPHERE.  
MEANWHILE...ACROSS HISPANIOLA EXPECTING RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-30MM/DAY. OVER PUERTO RICO INITIALLY  
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM...  
DECREASING TO 00-05MM/DAY AND MAXIMA OF 10MM ON THURSDAY-FRIDAY.  
OVER THE WINDWARD AND FRENCH ISLES THE UPPER LEVEL TROUGH IS TO  
INTERACT WITH AN EASTERLY WAVE TO SUSTAIN RAINFALL AMOUNTS OF  
00-05MM/DAY AND MAXIMA OF 10MM LATER TODAY...WHILE ON WEDNESDAY  
THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF 15MM AS A DEEPER PLUME  
OF MOISTURE LIFTS ACROSS THE LESSER ANTILLES TO THE EASTERN  
CARIBBEAN.  
 
THE SUBEQUATORIAL RIDGE TO THE SOUTH IS TO EXTEND WEST ACROSS THE  
TROPICAL ATLANTIC TO NORTHERN SOUTH AMERICA/SOUTHERN CENTRAL  
AMERICA. THIS PATTERN IS TO HOLD DURING THE NEXT FEW DAYS. OVER  
THE GUIANAS TO AMAZONIA IN SOUTHERN VENEZUELA THIS IS TO VENT  
ITCZ/NEAR EQUATORIAL TROUGH RELATED CONVERGENCE TO FAVOR RAINFALL  
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON WEDNESDAY AND  
ONWARD THIS DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-45MM/DAY.  
OVER AMAZONIA/EASTERN COLOMBIA EXPECTING ACCUMULATION OF  
15-20MM/DAY AND MAXIMA OF 25-50MM/DAY. THROUGH THURSDAY THIS  
INCREASES TO 15-20MM/DAY AND MAXIMA OF 30-60MM. ON THE ANDEAN  
REGION OF COLOMBIA EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM. ON WEDNESDAY TO THURSDAY THIS INCREASES TO  
10-15MM/DAY AND MAXIMA OF 20-35MM/DAY. OVER PANAMA-COSTA  
RICA...THE RIDGE ALOFT IS TO VENT ITCZ RELATED CONVECTION...TO  
FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM/DAY. ON  
WEDNESDAY-THURSDAY THIS IS TO ALSO INCREASE TO 10-15MM/DAY AND  
MAXIMA OF 20-35MM/DAY.  
 
TROPICAL/EASTERLY WAVES/TRADE WIND SURGES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
32W 35W 38W 40W 42W 44W 46W 48W TW 12N  
61W 63W 66W 68W 70W 72W 74W 76W EW 15N  
81W 83W 85W 87W 88W DISSIPATES EW 15N  
 
A TROPICAL WAVE ALONG 32W AND SOUTH OF 12N IS TO CONFINE TO THE  
ATLANTIC ITCZ DURING THE NEXT FOUR DAYS.  
 
AN EASTERLY WAVE ALONG 61W AND SOUTH OF 15N IS TO ENHANCE NET  
RELATED CONVERGENCE ACROSS SOUTHERN VENEZUELA TO FAVOR RAINFALL  
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. OVER THE  
FRENCH/WINDWARD ISLES THIS IS TO SUSTAIN RAINFALL AMOUNTS OF  
00-05MM/DAY AND MAXIMA OF 10MM EARLY IN THE CYCLE...INCREASING TO  
05-10MM/DAY AND MAXIMA OF 15MM ON WEDNESDAY. ON WEDNESDAY-THURSDAY  
THIS IS TO THEN TRIGGER SCATTERED CONVECTION ACROSS EASTERN  
COLOMBIA TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-45MM...INCREASING TO 15-20MM/DAY AND MAXIMA OF 30-60MM ON  
THURSDAY. AS IT MOVES INTO WESTERN COLOMBIA ON FRIDAY EXPECTING  
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM...WITH MOST  
ACTIVE ALONG THE ANDES.  
 
AN EASTERLY WAVE ALONG 81W AND SOUTH OF 15N IS TO ENHANCE ITCZ  
RELATED CONVECTION ACROSS PANAMA-COSTA RICA EARLY IN THE  
CYCLE...TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15MM. ON WEDNESDAY THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF  
20-30MM. AS IT MOVES ACROSS HONDURAS/EL SALVADOR ON WEDNESDAY THIS  
IS TO THEN SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-25MM.  
 
HUDSON...MS (JAMAICA)  
NIXON...BDM (THE BAHAMAS)  
DAVISON...WPC (USA)  
 

 
 
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