920  
FXCA20 KWBC 261540  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1139 AM EDT FRI MAY 26 2017  
 
LAST NO AMENDS...NEXT BULLETIN MAY 30.  
 
TROPICAL DISCUSSION FROM MAY 26/12 UTC: POLAR TROUGH EXITED THE  
EASTERN USA EARLY IN THE CYCLE...AND THROUGH SATURDAY MORNING IT  
IS EXPECTED TO RAPIDLY PULL TO THE NORTHEAST WHILE LIFTING OVER A  
BROAD RIDGE TO THE EAST. AT LOW LEVELS ASSOCIATED SURFACE FRONT IS  
LOSING UPPER LEVEL SUPPORT...AND IT IS FORECAST TO FRONTOLIZE  
LATER TODAY AS IT MEANDERS JUST NORTH OF THE NORTHWEST BAHAMAS.  
MEANWHILE...UNDER INFLUENCE OF THE MID/UPPER LEVEL TROUGH...SOME  
RESIDUAL CONVECTION IS EXPECTED OVER THE NORTHWEST BAHAMAS AND  
WESTERN CUBA DURING THE DAY TODAY...TO FAVOR RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15MM.  
 
NEXT POLAR TROUGH MOVES ACROSS THE CENTRAL USA ON SUNDAY TO  
MONDAY. THE ASSOCIATED FRONT MOVES ACROSS THE CENTRAL USA TO TEXAS  
EARLY ON MONDAY MORNING...INTO THE NORTHEAST STATES OF MEXICO  
LATER IN THE DAY. AS IT MOVES ACROSS TEXAS THIS WILL SUSTAIN A  
PREFRONTAL TROUGH ACROSS NORTHEAST MEXICO... WHERE IT WILL ENHANCE  
LOW LEVEL MOISTURE CONVERGENCE. ON SUNDAY THIS WILL RESULT IN  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH  
MONDAY ACTIVITY INTENSIFIES ACROSS TAMAULIPAS/VERACRUZ...WITH  
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 40-80MM.  
 
SIMULTANEOUSLY...THE MODELS FORECAST A MID LEVEL RIDGE TO  
GRADUALLY BUILD ACROSS THE NORTHERN STATES OF MEXICO/THE GULF TO  
THE SOUTHEAST USA...TO ANCHOR AT 500 HPA ON A CLOSED HIGH JUST  
SOUTH OF LOUISIANA/MISSISSIPPI LATER ON SATURDAY-SUNDAY. AS THE  
RIDGE CONFINES TO THE NORTHERN GULF/NORTHERN STATES OF MEXICO...A  
WEAKNESS IN THE HEIGHT FIELD IS TO PERSIST OVER THE SOUTHERN  
STATES OF MEXICO/NORTHERN CENTRAL AMERICA... WITH MODELS SHOWING  
AN INVERTED TROUGH EXTENDING NORTH FROM THE EASTERN TROPICAL  
PACIFIC TO GUATEMALA/SOUTHERN MEXICO DURING THE NEXT 72-84 HRS.  
THIS IS TO THEN FAVOR A CONVECTIVELY UNSTABLE AIR MASS DURING THE  
NEXT FEW DAYS. THIS...IN COMBINATION WITH TROPICAL WAVES STREAMING  
ACROSS THE EASTERN PACIFIC...IS TO SUSTAIN A SURGE IN CONVECTION.  
ON THE SOUTHERN STATES OF MEXICO EXPECTING RAINFALL AMOUNTS OF  
20-30MM/DAY AND MAXIMA OF 40-80MM EARLY IN THE CYCLE...GRADUALLY  
INCREASING TO 35-50MM/DAY AND MAXIMA OF 75-150MM ON SUNDAY TO  
MONDAY WHILE GRADUALLY SHIFTING TO GUERRERO/OAXACA AND THE SIERRA  
MADRE DEL SUR. ON MONDAY MAXIMA IN THIS AREA WILL PEAK AT  
125-250MM. OVER SOUTHERN GUATEMALA-SOUTHERN HONDURAS/EL  
SALVADOR-GULF OF FONSECA CONVECTION GRADUALLY BECOMES MORE  
ACTIVE/BETTER ORGANIZED...WITH RAINFALL AMOUNTS OF 20-30MM/DAY AND  
MAXIMA OF 40-80MM ON FRIDAY TO SATURDAY MORNING. ON SATURDAY  
EXPECTING ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF  
30-60MM...DECREASING TO 05-10MM/DAY AND MAXIMA OF 15-25MM ON  
SUNDAY TO MONDAY. OVER NICARAGUA/NORTHEAST HONDURAS INITIALLY  
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM.  
THROUGH SUNDAY THIS DECREASES AS A DRYER AIR MASS ENTRAINS FROM  
THE EAST. ACROSS COSTA RICA-PANAMA EXPECT RAINFALL AMOUNTS OF  
15-20MM/DAY AND MAXIMA OF 30-60MM DURING THE NEXT FOUR DAYS AS  
ENHANCED BY THE ITCZ.  
 
ALSO AT 500 HPA...A SHORT WAVE RIDGE OVER THE WESTERN CARIBBEAN  
FAVORS THE SOUTHWARD AMPLIFICATION OF A TUTT ACROSS THE EASTERN  
CARIBBEAN ISLES. THE TUTT ANCHORS ON A CLOSED LOW TO THE  
EAST-NORTHEAST OF THE NORTHERN LEEWARD ISLANDS. THE TUTT PATTERN  
WILL HOLD NEARLY UNCHANGED THROUGH MIDDAY ON SATURDAY...THEN  
GRADUALLY FILLS TO AN OPEN TROUGH EARLY ON SUNDAY. REMNANTS OF THE  
TUTT WILL THEN LIFT TO THE NORTHEAST AS A SHORT WAVE TROUGH  
AMPLIFIES ACROSS THE WESTERN ATLANTIC TO THE NORTHERN CARIBBEAN  
ISLES DURING THE WEEKEND. AT LOW LEVELS THE TUTT ALOFT FAVORS THE  
GENERATION OF PERTURBATIONS IN THE EASTERLY TRADES...WITH MODEL  
ANALYSIS/FORECAST SHOWING A COUPLE OF WAVES STREAMING ACROSS THE  
NORTHEAST CARIBBEAN OVER THE NEXT COUPLE OF DAYS. AS THEY MEANDER  
WEST THESE ARE TO ENHANCE LOW LEVEL MOISTURE CONVERGENCE. AS A  
RESULT...PWAT CONTENT WILL GRADUALLY INCREASE TO AROUND 30-35MM  
OVER THE NEXT DAY OR SO. ACROSS THE LEEWARD/VIRGIN ISLES THIS IS  
TO FAVOR MOSTLY LIGHT CONVECTION WITH ACCUMULATION OF 00-05MM/DAY  
AND MAXIMA OF 10MM. ACROSS PUERTO RICO TO HISPANIOLA THIS WILL  
RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15MM...WITH LOCALIZED MAXIMA OF 75-125MM POSSIBLE AS TUTT ALOFT  
ENHANCES EFFECTS OF SEA BREEZE CONVERGENCE OVER WESTERN PUERTO  
RICO AND CENTRAL HISPANIOLA.  
 
FARTHER SOUTH...ITCZ RELATED CONVERGENCE OVER THE NORTHERN GUIANAS  
WILL SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-25MM...WITH LOCALLY HIGHER AMOUNTS LIKELY AS TROPICAL WAVES  
PROPAGATE ALONG THE ITCZ TO THE NORTH (SEE BELOW). OVER VENEZUELA  
AND EASTERN COLOMBIA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND  
MAXIMA OF 20-30MM. THROUGH SUNDAY THE MAXIMA INCREASES TO 20-45MM.  
HIGHER AMOUNTS ARE FORECAST ACROSS THE EJE CAFETERO IN  
NORTHWESTERN COLOMBIA...WHERE UNDER INFLUENCE OF THE PANAMANIAN  
LOW EXPECTING RAINFALL ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF  
30-60MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE  
35W 37W 40W 43W 47W 50W 53W 56W TW  
49W 52W 56W 58W 61W 64W 68W 70W TW  
55W 58W 62W DISSIPATES EW  
67W 69W 71W 74W 77W 79W 81W 83W TW  
81W 83W 86W 89W 92W 95W 97W 99W EW  
90W 93W 95W 98W 101W DISSIPATES EW  
 
TROPICAL WAVE IS INITIALIZED ALONG 35W AND TO THE SOUTH OF 10N.  
THE WAVE REACHES EASTERN FRENCH GUIANA/AMAPA IN BRASIL LATER ON  
SUNDAY...WHERE IN INTERACTION WITH THE ITCZ IT IS TO TRIGGER  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. AS IT MOVES  
ACROSS SURINAME TO GUIANA ON MONDAY IT INCREASES TO 10-15MM/DAY  
AND MAXIMA OF 20-30MM.  
 
A TROPICAL WAVE IS INITIALIZED ALONG 49W AND TO THE SOUTH OF 17N.  
IT MOVES ACROSS FRENCH GUIANA TO SURINAME LATER TODAY/EARLY  
SATURDAY MORNING...TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-25MM. ACTIVITY THEN SPREADS INTO EASTERN  
VENEZUELA/SOUTHERN WINDWARD ISLES ON SATURDAY-SUNDAY MORNING.  
ACROSS VENEZUELA IT WILL SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY  
AND MAXIMA OF 20-30MM...WHILE OVER TRINIDAD AND THE WINDWARD ISLES  
EXPECTING ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15MM. THIS IS  
TO THEN INTERACT WITH DEEPENING TROUGH OVER THE NORTHEAST  
CARIBBEAN TO SUSTAIN A PLUME OF TROPICAL MOISTURE ACROSS THE  
ISLAND CHAIN ON SUNDAY-MONDAY...WHERE IT WILL RESULT IN RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. THROUGH MONDAY THIS  
INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-45MM...WITH MOST INTENSE  
OVER THE FRENCH AND LEEWARD ISLANDS.  
 
AN EASTERLY WAVE ALONG 55W AND SOUTH OF 14N MOVES ACROSS SURINAME  
TO GUYANA EARLY IN THE CYCLE...TO TRIGGER RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-35MM. AS IT ENTERS EASTERN VENEZUELA  
ON SATURDAY THE WAVE IS FORECAST TO DISSIPATE.  
 
A TROPICAL WAVE ALONG 67W AND TO THE SOUTH OF 07N CONTINUES TO  
INTERACT WITH THE NEAR EQUATORIAL TROUGH OVER VENEZUELA-COLOMBIA.  
THIS IS TO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-35MM. ON SUNDAY IT IS TO THEN INTERACT WITH THE PANAMANIAN LOW  
TO ENHANCE CONVECTION ACROSS NORTHWEST COLOMBIA/THE DARIEN IN  
EASTERN PANAMA TO FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA  
OF 30-60MM.  
 
AN EASTERLY WAVE ALONG 81W IS TO ENHANCE ITCZ RELATED CONVECTION  
ACROSS PANAMA-COSTA RICA DURING THE NEXT 24-36 HRS...TO FAVOR  
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM. OVER EL  
SALVADOR/SOUTHERN HONDURAS IT IS TO ALSO TRIGGER RAINFALL AMOUNTS  
OF 15-20MM/DAY AND MAXIMA OF 30-60MM ON SATURDAY TO SUNDAY...WHILE  
ACROSS CHIAPAS IT WILL SUSTAIN ACCUMULATION OF 25-50MM/DAY AND  
MAXIMA OF 75-150MM. OVER GUERRERO OAXACA THIS INCREASES TO  
50-75MM/DAY AND MAXIMA OF 125-250MM.  
 
EASTERLY WAVE ALONG 90W AND TO THE SOUTH OF 14N WILL SUSTAIN  
ORGANIZED CONVECTION ACROSS SOUTHERN MEXICO...TO TRIGGER RAINFALL  
AMOUNTS OF 20-30MM/DAY AND MAXIMA OF 40-80MM. OVER GUERRERO/OAXACA  
IT IS TO THEN SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA  
OF 20-45MM ON SATURDAY TO SUNDAY...WITH WAVE TO DISSIPATE LATER ON  
SUNDAY.  
 
GAJADHAR...SLMS (SAINT LUCIA)  
SUBRATH-ALI...TTMS (TRINIDAD AND TOBAGO)  
DAVISON/GALVEZ...WPC (USA)  

 
 
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