796  
FXCA20 KWBC 281814  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
214 PM EDT THU MAY 28 2020  
 
TROPICAL DISCUSSION FROM MAY 28/18 UTC: A SYSTEM OF CONCERN  
CONTINUES BEING THE CENTRAL AMERICAN GYRE...FORECAST TO FORM TO  
THE WEST-SOUTHWEST OF EL SALVADOR DURING THE WEEKEND. UNDER THE  
INFLUENCE OF AN UPPER DIVERGENT PULSE OF THE MADDEN JULIAN  
OSCILLATION AND A ROBUST KELVIN WAVE...EXPECTING THE DEVELOPMENT  
OF HEAVY RAINFALL TO AFFECT CENTRAL AND NORTHERN PORTIONS OF  
CENTRAL AMERICA DURING THE WEEKEND AND POSSIBLY INTO MID-NEXT  
WEEK. THE EXPECTED EVOLUTION OF THE GYRE...WILL FAVOR THE HEAVIEST  
PRECIPITATION TO DEVELOP FROM WESTERN NICARAGUA ACROSS SOUTHERN  
HONDURAS INTO EL SALVADOR AND SOUTHERN GUATEMALA. LARGEST  
ACCUMULATIONS ARE EXPECTED IN EL SALVADOR...ESPECIALLY FROM  
SATURDAY THROUGH MONDAY...WHEN THREE-DAY TOTALS COULD REACH  
200-300MM AND VERY ISOLATED MAXIMA OF 400-500MM IN REGIONS OF  
ENHANCED OROGRAPHIC FORCING. THE AMOUNTS OF RAIN WILL BE LARGELY  
DEPENDENT ON THE EVOLUTION OF THE GYRE AND THE ASSOCIATED ONSHORE  
SOUTHWEST FLOW INTO EL SALVADOR/SOUTHEAST GUATEMALA AND THE GULF  
OF FONSECA REGION FROM SATURDAY THROUGH MONDAY.  
 
NORTH IN THE DOMAIN...A LARGE UPPER TROUGH CENTERS OVER THE  
MISSISSIPPI VALLEY AND IS FORECAST TO BE RAPIDLY DRAWN  
NORTHEASTWARD BY A TROUGH IN THE WESTERLIES ON FRIDAY. AS THE  
TROUGH EXITS...IT WILL SUSTAIN THE BUILDING OF A POLAR RIDGE OVER  
THE PLAINS OF THE USA. THIS IS PUSHING A SURFACE COLD FRONT  
SOUTHWARD...BUT THE FRONT IS FORECAST TO LOOSE BAROCLINICITY AND  
FRONTOLIZE ACROSS EXTREME NORTHEAST MEXICO ON THURSDAY EVENING.  
REGARDLESS OF FRONTOLISIS...THE POLAR RIDGE IS ESTABLISH  
NORTHEASTERLY WINDS IN THE GULF OF MEXICO. THESE WILL STIMULATE  
MOISTURE CONVERGENCE ALONG THE SIERRA MADRE ORIENTAL AND GULF  
COAST OF MEXICO TO SUSTAIN HEAVIEST PRECIPITATION ON FRIDAY. IN  
THE MEANTIME...THE NORTHERLIES WILL START TO STIMULATE MOISTURE  
CONVERGENCE IN NORTHEAST MEXICO TO SUSTAIN 10-15MM/DAY AND MAXIMA  
OF 20-45MM WITH A RISK FOR SEVERITY ON THURSDAY. IN CENTRAL  
PORTIONS OF THE SIERRA MADRE ORIENTAL EXPECTING 05-10MM/DAY AND  
MAXIMA OF 15-30MM. THIS PEAKS ON FRIDAY TO SUSTAIN 15-30MM/DAY AND  
MAXIMA OF 40-80MM IN NORTHERN VERACRUZ...WHILE IN NORTHEAST MEXICO  
EXPECTING 05-10MM/DAY AND MAXIMA OF 15-30MM. IN SOUTHERN VERACRUZ  
EXPECING 15-20MM/DAY AND MAXIMA OF 25-50MM. REMNANT MOISTURE  
CONVERGENCE...AND THE REMNANTS OF A TROPICAL WAVE WILL SUSTAIN  
ENHANCED CONVECTION ON SATURDAY AS WELL WHEN EXPECTING 15-20MM/DAY  
AND MAXIMA OF 25-50MM FROM NORTHERN VERACRUZ INTO  
CHIAPAS/TABASCO/CAMPECHE.  
 
TO THE EAST IN CUBA AND THE BAHAMAS...EXPECTING GENERALLY FAIR  
WEATHER CONDITIONS AND ISOLATED CONVECTION INITIALLY. HOWEVER...A  
MOIST PLUME IS BUILDING IN THE CENTRAL NORTHERN CARIBBEAN IN  
ASSOCIATION WITH TUTT LOW TO THE NORTHEAST OF PUERTO RICO. THIS  
WILL SUSTAIN ENHANCED CONVECTION IN PUERTO RICO AND HISPANIOLA ON  
THURSDAY AND FRIDAY...BUT THE FOCUS SHIFTS TO CENTRAL CUBA  
AFTERWARDS. ON THURSDAY...EXPECTING 15-20MM/DAY AND ISOLATED  
MAXIMA OF 35-70MM IN PUERTO RICO AND HISPANIOLA...WHILE IN THE  
VIRGIN AND LEEWARD ISLANDS EXPECTING 05-10MM/DAY AND MAXIMA OF  
15-20MM. BY FRIDAY...EXPECTING STILL ACTIVE CONVECTION TO SUSTAIN  
15-20MM/DAY AND MAXIMA OF 30-60MM IN HISPANIOLA AND PUERTO RICO.  
IN THE VIRGIN ISLANDS EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM.  
CONVECTION WILL INCREASE IN SOUTHEAST CUBA ON FRIDAY TO SUSTAIN  
10-15MM/DAY AND MAXIMA OF 20-35MM...WHILE IN JAMAICA EXPECTING  
05-10MM/DAY AND MAXIMA OF 15-20MM. MOIST PLUME IN THE BAHAMAS AND  
TURKS AND CAICOS WILL ALSO SUSTAIN CONVECTION ON FRIDAY TO PRODUCE  
05-10MM/DAY AND MAXIMA OF 15MM. BY SATURDAY...LARGEST  
ACCUMULATIONS ARE EXPECTED IN CENTRAL AND SOUTHEAST CUBA...WHERE  
THE TROPICAL WAVE WILL SUSTAIN 10-15MM/DAY AND MAXIMA OF 20-35MM.  
TRAILING MOISTURE IN JAMAICA AND HISPANIOLA WILL SUSTAIN  
05-10MM/DAY AND MAXIMA OF 15-25MM. IN PUERTO RICO...A SHARP  
DECREASE IN MOISTURE WILL SUSTAIN MAXIMA OF 20-35MM. SIMILAR  
AMOUNTS ARE EXPECTED IN THE CENTRAL AND SOUTHEAST BAHAMAS...AS  
WELL AS IN THE CAYMAN ISLANDS AND WESTERN CUBA. ELSEWHERE IN THE  
EASTERN CARIBBEAN...UNDER THE INFLUENCE OF A STRONG MID-LEVEL  
RIDGE CENTERING IN THE WESTERN TROPICAL ATLANTIC...EXPECTING  
LITTLE ACCUMULATIONS IN TRADE WIND SHOWER CONVECTION...GENERALLY  
UNDER 10MM/DAY.  
 
IN CENTRAL AMERICA...MOIST WEATHER PATTERN CONTINUES UNRAVELING.  
MODELS HAVE BEEN RESOLVING THE CENTRAL AMERICAN GYRE FORMING OVER  
THE EASTERN PACIFIC...BUT CONFIDENCE HAS BEEN LOW. AS THE MODELS  
START TO BECOME IN BETTER AGREEMENT ON THE EVOLUTION THROUGH THE  
WEEKEND...IT IS BECOMING MORE EVIDENT THAT THE AREA EXPECTING THE  
LARGEST PRECIPITATION AMOUNTS EXTENDS FROM WESTERN  
NICARAGUA/EXTREME NORTHWEST COSTA RICA INTO SOUTHERN  
GUATEMALA...SOUTHERN HONDURAS AND EL SALVADOR...DURING SATURDAY  
THROUGH MONDAY. IN THE MEAN TIME...ACTIVITY WILL ME MODULATED BY  
TROPICAL WAVES AND INTERACTIONS WITH THE ITCZ. SEE BELOW FOR  
PRECIPITATION AMOUNTS IN ASSOCIATION WITH THE WAVES.  
 
IN NORTHERN SOUTH AMERICA...ACTIVITY WILL BE ORGANIZED MOSTLY WITH  
WAVES IN THE TRADES. SEE BELOW.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 00UTC ON MAY 28:  
========================================  
TYPE OF WAVE AND FORECAST LONGITUDE  
========================================  
TYPE - F12 F24 F36 F48 F60 F72 F84  
TW - 40W 44W 48W 52W 56W 60W 63W  
TW - 65W 68W 71W 75W 78W 82W 85W  
TW - 81W 84W 87W 90W LOW  
TW - 94W 96W 98W 100W 102W 104W 107W  
========================================  
 
A TROPICAL WAVE IS INITIALISED AT 40W AND TO THE SOUTH OF 10N.  
THIS WAVE CROSSES FRENCH GUIANA AND SURINAME ON FRIDAY...WHERE IT  
WILL ENHANCE CONVECTION TO SUSTAIN 10-15MM/DAY AND MAXIMA OF  
20-40MM IN NORTHERN SURINAME AND NORTHERN GUYANA...WHILE IN FRENCH  
GUIANA AND SOUTHERN SURINAME IT WILL SUSTAIN 05-10MM/DAY AND  
MAXIMA OF 15-30MM. ON SATURDAY...THE WAVE CROSSES GUYANA AND  
EASTERN VENEZUELA. IT WILL SUSTAIN 15-20MM/DAY AND MAXIMA OF  
25-50MM IN NORTHERN GUYANA AND THE RINICI DELTA...WHILE TRAILING  
MOISTURE WILL SUSTAIN 05-10MM/DAY AND MAXIMA OF 15-20MM IN  
NORTHERN SURINAME AND NORTHERN FRENCH GUIANA. ALSO...IT WILL  
SUSTAIN SIMILAR ACCUMULATIONS IN THE CANAIMA REGION IN SOUTHEAST  
VENEZUELA.  
 
A TROPICAL WAVE IS INITIALIZED AT 65W AND TO THE SOUTH OF 14N.  
THIS WAVE WILL SUSTAIN SCATTERED CONVECTION IN SOUTHERN VENEZUELA  
AND EASTERN COLOMBIA ON THURSDAY TO SUSTAIN 15-20MM/DAY AND MAXIMA  
OF 25-50MM. IN CENTRAL VENEZUELA IT WILL SUSTAIN 05-10MM/DAY AND  
MAXIMA OF 15-20MM. ON FRIDAY...THE WAVE WILL CROSS COLOMBIA WHERE  
IT WILL SUSTAIN 10-15MM/DAY AND MAXIMA OF 20-40MM EAST OF THE  
ANDES ACROSS THE ORINOQUIA AND AMAZON...AND 15-20MM/DAY AND MAXIMA  
OF 25-50MM IN NORTHERN...CENTRA.L AND NORTHWEST COLOMBIA INTO THE  
DARIEN. IN SOUTHWEST COLOMBIA IT WILL SUSTAIN 05-10MM/DAY AND  
MAXIMA OF 15-20MM. BY SUNDAY...THE WAVE WILL PROPAGATE ACROSS THE  
CAYMAN ISLANDS...CENTRAL CUBA AND PANAMA. LARGEST ACUMULATIONS ARE  
EXPECTED IN SOUTHERN PANAMA WHERE ENHANCED CONVECTION WILL SUSTAIN  
15-20MM/DAY AND MAXIMA OF 35-70MM. IN CENTRAL CUBA...EXPECTING  
10-15MM/DAY AND MAXIMA OF 20-35MM. IN THE CAYMAN ISLANDS EXPECTING  
MAXIMA OF 15MM. TRAILING MOISTURE IN JAMAICA WILL SUSTAIN  
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM. IN SAN  
ANDRES/PROVIDENCIA AND NORTHEAST NICARAGUA THE WAVE WILL SUSTAIN  
05-10MM/DAY AND MAXIMA OF 15-25MM.  
 
A TROPICAL WAVE IS INITIALIZED AT 81W AND TO THE SOUTH OF 15N.  
THIS WAVE WILL INTERACT WITH THE ITCZ TO SUSTAIN HEAVY RAINFALL IN  
COSTA RICA AND EASTERN NICARAGUA ON THURSDAY...WHERE EXPECTING  
15-20MM/DAY AND MAXIMA OF 40-80MM. IN PANAMA...TRAILING MOISTURE  
WILL SUSTAIN 05-10MM/DAY AND MAXIMA OF 15-25MM. BY FRIDAY...THE  
WAVE WILL PROPAGATE ACROSS WESTERN NICARAGUA...EL  
SALVADOR...HONDURAS AND GUATEMALA. IN INTERACTION WITH THE ITCZ  
AND THE FORMING CENTRAL AMERICAN GYRE...IT WILL SUSTAIN HEAVY  
RAINFALL FROM NORTHWEST COSTA RICA INTO EL SALVADOR AND SOUTHERN  
HONDURAS TO SUSTAIN 25-50MM/DAY AND MAXIMA OF 75-125MM. IT WILL  
THEN BECOME ABSORBED BY THE CENTRAL AMERICAN GYRE LOW IN THE  
EASTERN PACIFIC. HOWEVER...REMNANT MOISTURE WILL PROPAGATE INTO  
NORTHERN CENTRAL AMERICA AND SOUTHERN MEXICO. HERE...IT WILL  
SUSTAIN 15-20MM/DAY AND MAXIMA OF 25-50MM IN  
VERACRUZ/TABASCO/CAMPECHE AND NORTHERN CHIAPAS...WHILE IN  
BELIZE...GUATEMALA...WESTERN HONDURAS AND SOUTHERN CHIAPAS  
EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM.  
 
A TROPICAL WAVE IS INITIALIZED AT 94W AND TO THE SOUTH OF 18N. THE  
WAVE WILL ENHANCE CONVECTION IN VERACRUZ/CHIAPAS/OAXACA WHERE IT  
WILL SUSTAIN 05-10MM/DAY AND MAXIMA OF 15-30MM. IT WILL THEN EXERT  
LIMITED EFFECTS IN CONTINENTAL AREAS.  
 
GALVEZ/DAVISON...WPC (USA)  

 
 
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