444  
FXCA20 KWBC 251837  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
237 PM EDT WED OCT 25 2017  
 
TROPICAL DISCUSSION FROM OCT 25/12 UTC: A HIGH AMPLITUDE TROUGH  
WILL EXTEND ACROSS THE EASTERN USA TO WESTERN CUBA LATER TODAY.  
MID LEVEL AXIS IS TO THEN RAPIDLY DAMPEN AS IT LIFTS OVER A RIDGE  
TO THE EAST. ASSOCIATED FRONT MOVES ACROSS THE NORTHWEST  
BAHAMAS-CENTRAL/WESTERN CUBA TO BELIZE/CHIAPAS IN SOUTHERN MEXICO  
THIS EVENING. ON THURSDAY MORNING IT MOVES TO THE CENTRAL  
BAHAMAS...MEANDERING ACROSS CENTRAL CUBA/CAYMAN ISLES TO THE GULF  
OF HONDURAS. LATER ON THURSDAY THE FRONT WILL THEN MOVE TO THE  
SOUTHEAST BAHAMAS...WHILE TRAILING END OVER THE CARIBBEAN REMAINS  
OVER THE CAYMAN ISLES-GULF OF HONDURAS. EARLY ON FRIDAY THE FRONT  
STARTS TO RETROGRESS ACROSS THE BAHAMAS-CUBA AS IT LOSES ITS UPPER  
LEVEL SUPPORT...AND THROUGH SATURDAY MORNING THE FRONT IS TO  
FRONTOLIZE. THIS IS TO FAVOR MODERATE CONVECTION ACROSS SOUTHERN  
MEXICO-CENTRAL GUATEMALA WITH ACCUMULATION OF 10-15MM/DAY AND  
MAXIMA OF 20-30MM. HIGHER AMOUNTS ARE EXPECTED ACROSS SOUTHERN  
BELIZE-NORTHEAST GUATEMALA-NORTHERN HONDURAS...WHERE IT IS TO  
TRIGGER RAINFALL AMOUNTS OF 25-50MM/DAY AND MAXIMA OF 100-200MM.  
ON THURSDAY IT DECREASES TO 25-50MM/DAY AND MAXIMA OF 75-125MM  
WITH MOST INTENSE OVER NORTHERN HONDURAS. OVER THE NORTHWEST  
BAHAMAS THE FRONT IS TO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY  
AND MAXIMA OF 20-40MM...WHILE OVER THE CENTRAL-SOUTHEAST BAHAMAS  
EXPECT ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM ON  
THURSDAY. ACROSS CUBA THE FRONT WILL RESULT IN RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-20MM. OVER THE CAYMAN ISLANDS  
EXPECTING ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-40MM ON  
THURSDAY-FRIDAY.  
 
THE DEEPENING POLAR TROUGH OVER THE EASTERN USA/GULF OF MEXICO IS  
INTERACTING WITH A LOW/TROUGH OVER THE SOUTHERN CARIBBEAN. UNDER  
INFLUENCE OF THIS FEATURE THE LOW WILL LIFT ALONG THE COAST OF  
NICARAGUA/NORTHEAST HONDURAS ON THURSDAY...LIFTING TO THE  
NORTHWEST CARIBBEAN ON FRIDAY. MODELS THEN FORECAST A SECONDARY  
LOW TO FORM ALONG THE ITCZ TO THE SOUTH OF EL SALVADOR ON  
THURSDAY-FRIDAY. THE LOW ALSO FAVORS THE NORTHWARD MODULATION OF  
THE ITCZ ACROSS SOUTHERN NICARAGUA/COSTA RICA TO THE SOUTHERN  
CARIBBEAN...WHERE IT REMAINS DURING THE NEXT THREE DAYS. THIS IS  
ENHANCING LOW LEVEL MOISTURE CONVERGENCE TO FAVOR RAINFALL AMOUNTS  
OF 25-50MM/DAY AND MAXIMA OF 75-150MM DURING THE NEXT TWO DAYS. ON  
FRIDAY IT DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER  
EASTERN NICARAGUA AND NORTHEAST HONDURAS THE LOW IS TO FAVOR  
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 35-70MM/DAY THROUGH  
FRIDAY MORNING...WITH MOST INTENSE EXPECTED ON THURSDAY. THE  
EVOLVING PATTERN IS TO ALSO SUSTAIN A PLUME OF DEEP TROPICAL  
MOISTURE ACROSS THE CENTRAL CARIBBEAN...TO REACH JAMAICA AND THE  
CAYMAN ISLES LATER TODAY/EARLY THURSDAY MORNING. THE MOIST INFLOW  
WILL FEED CONVECTIVE DEVELOPMENT TO RESULT IN RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-40MM ON THURSDAY. ON FRIDAY...BEST  
MOISTURE CONVERGENCE IS EXPECTED OVER THE CAYMAN ISLES-WESTERN  
CUBA...WITH CONDITIONS APPEARING FAVORABLE FOR AN MCS TO DEVELOP.  
AS A RESULT EXPECTING ACCUMULATION OF 25-50MM/DAY AND MAXIMA OF  
75-125MM. OVER COLOMBIA-NORTHWEST VENEZUELA...AS THE ITCZ MEANDERS  
NORTH OF ITS CLIMATOLOGICAL POSITION...EXPECTING SCATTERED  
CONVECTION TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-30MM.  
 
NEXT POLAR TROUGH RACES ACROSS THE WESTERN USA TO TEXAS LATER ON  
FRIDAY. THE DEEP TROUGH WILL SUSTAIN A PROGRESSIVE FRONT ACROSS  
TEXAS TO COAHUILA MEXICO BY MIDDAY ON FRIDAY. EARLY ON SATURDAY  
MORNING IT MOVES TO THE SOUTHEAST USA...TRAILING ACROSS THE GULF  
TO VERACRUZ. THIS WILL BE ACCOMPANIED BY A NORTHERLY WIND  
SURGE...WITH WINDS ACROSS THE SOUTHERN GULF PEAKING A 25-35KT.  
MOST ACTIVE CONVECTION WITH THIS FEATURE IS EXPECTED OVER THE  
SOUTHERN STATES OF MEXICO LATER DURING THE WEEKEND.  
 
FARTHER EAST OVER THE CARIBBEAN...A TUTT LOW WEST OF THE WINDWARD  
ISLANDS EXTENDS A SHORT WAVE TROUGH TO EASTERN VENEZUELA. THIS IS  
TO REMAIN NEARLY STATIONARY DURING THE NEXT THREE TO FOUR DAYS. AS  
IT MEANDERS OVER THE EASTERN CARIBBEAN THE TROUGH WILL ENHANCE  
CONVECTION ACROSS THE WINDWARD ISLANDS-TRINIDAD/TOBAGO AND  
BARBADOS...TO RESULT IN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA  
OF 20-35MM. LOCALLY HIGHER AMOUNTS ARE HIGHLY PROBABLE. ON  
THURSDAY FOCUS OF THE HEAVY CONVECTION SHIFTS TO THE  
LEEWARD/FRENCH ISLES...WITH MAXIMA OF 20-30MM. OVER GUYANA AND  
NORTHEAST VENEZUELA THIS IS TO INITIALLY FAVOR MAXIMA OF 20-30MM.  
BUT THROUGH THURSDAY THIS DECREASES TO 15-20MM/DAY.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
55W 58W 61W 64W 66W 68W 70W 72W TW 12N  
59W 60W 61W 64W 66W 68W 70W 72W TUTT INDCD 18N  
66W 68W 70W 72W 74W 76W 78W 79W TW 20N  
 
TROPICAL WAVE ALONG 55W AND SOUTH OF 17N...MOVES ACROSS  
SURINAME-GUYANA ON WEDNESDAY...TO TRIGGER RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-35MM. OVER EASTERN/CENTRAL VENEZUELA  
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM ON  
THURSDAY....WHILE OVER NORTHWEST VENEZUELA THE MAXIMA ON FRIDAY  
PEAKS AT 15-20MM.  
 
THE DEEPENING TUTT OVER THE EASTERN CARIBBEAN IS INDUCING AN  
INVERTED TROUGH IN THE TRADES. THIS TROUGH IS FORECAST TO  
PROPAGATE IN PHASE WITH THE TROPICAL WAVE LOCATED AT 55W...TO  
ENHANCE PRECIPITATION IN THE NORTHERN CARIBBEAN. THE INDUCED  
PERTURBATION MOVES TO THE FRENCH/LEEWARD ISLES LATER ON THURSDAY  
MORNING...TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15MM. IT THEN MEANDERS ACROSS THE NORTHEAST CARIBBEAN THROUGH  
THURSDAY MORNING...MEANWHILE FAVORING RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-30MM. THE WAVE REACHES THE VIRGIN  
ISLES AND PUERTO RICO ON FRIDAY TO SUSTAIN RAINFALL AMOUNTS OF  
15-20MM/DAY AND MAXIMA OF 30-60MM.  
 
TROPICAL WAVE ALONG 66W AND SOUTH OF 20N...IS TO TRIGGER SCATTERED  
CONVECTION ACROSS EASTERN-CENTRAL VENEZUELA WITH ACCUMULATION OF  
10-15MM/DAY AND MAXIMA OF 20-35MM. OVER THE ABC ISLANDS-NORTH  
COAST OF VENEZUELA EXPECTING ACCUMULATION OF 05-10MM/DAY AND  
MAXIMA OF 15MM ON WEDNESDAY. THIS REACHES WESTERN  
VENEZUELA/EASTERN COLOMBIA EARLY ON THURSDAY MORNING...TO SUSTAIN  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH  
FRIDAY MORNING ACTIVITY SURGES...TO RESULT IN ACCUMULATION OF  
15-20MM/DAY AND MAXIMA OF 30-60MM.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  

 
 
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