301  
FXCA20 KWBC 271832  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
232 PM EDT THU JUL 27 2017  
 
TROPICAL DISCUSSION FROM JUL 27/12 UTC: A 250 HPA HIGH OVER  
NORTHERN TEXAS/ OKLAHOMA EXTENDS A RIDGE EAST ACROSS THE SOUTHERN  
USA. AS THE UPPER RIDGE HOLDS TO THE NORTH...IT IS TO PROVIDE THE  
STEERING FLOW TO A TUTT MOVING ACROSS NORTHERN MEXICO. LATER TODAY  
THE TUTT IS TO MIGRATE ACROSS SONORA/NORTHERN SINALOA TO THE BAJA  
PENINSULA. THE TUTT IS TO THEN WEAKEN LATER DURING THE WEEKEND. A  
SECONDARY TUTT IS TO THEN RETROGRESS ACROSS THE NORTHERN  
GULF...REACHING NORTHEAST MEXICO LATER ON FRIDAY/EARLY SATURDAY  
MORNING. AS THE UPPER TROUGH MEANDERS ACROSS NORTHERN MEXICO EARLY  
IN THE CYCLE...IT IS TO ENHANCE DIURNAL CONVECTION ALONG THE  
SIERRA MADRE OCCIDENTAL. ACROSS SONORA-SINALOA-COLIMA AND NAYARIT  
THIS IS TO INITIALLY FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND  
MAXIMA OF 20-45MM. ON FRIDAY-SATURDAY THIS WILL SET AT 10-15MM/DAY  
AND MAXIMA OF 20-30MM/DAY. ON THE CENTRAL-SOUTHWEST STATES OF  
MEXICO...INITIALLY EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15MM. THROUGH SATURDAY EVENING THIS WILL INCREASE TO  
10-15MM/DAY AND MAXIMA OF 20-30MM. OVER THE YUCATAN-SOUTHERN  
MEXICO DIURNAL CONVECTION IS TO TRIGGER RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-20MM.  
 
FARTHER EAST...AT 500 HPA...A HIGH TO THE NORTH-NORTHEAST OF THE  
DOMINICAN REPUBLIC IS TO ANCHOR A SHORT WAVE RIDGE NORTH OF THE  
ISLANDS. MID LEVEL RIDGE PATTERN IS TO REMAIN ILL ORGANIZED UNDER  
PRESSURE FROM BROAD POLAR TROUGH TO THE NORTH OF 30N...AND DURING  
THE WEEKEND IT IS TO NEARLY COLLAPSE OVER THE BAHAMAS/CUBA AS A  
DEEPER TROUGH SETTLES ACROSS THE EASTERN USA/WESTERN ATLANTIC. AT  
250 HPA... A TUTT/TUTT LOW OVERLAYS THE WANING MID LEVEL RIDGE  
AXIS...WITH TROUGH EXTENDING OVER THE BAHAMAS-CUBA TO THE WESTERN  
CARIBBEAN. THE TROUGH ALOFT IS TO PERSIST DURING THE NEXT 72-96  
HRS. MEANWHILE...AS IT MEANDERS OVER CUBA...THE TROUGH WILL  
ENHANCE DIURNAL CONVECTION...WITH RAINFALL AMOUNTS OF 05-10MM/DAY  
AND MAXIMA OF 15-25MM/DAY. ON FRIDAY-SATURDAY THIS IS TO GRADUALLY  
INCREASE TO 10-15MM/DAY AND MAXIMA OF 20-30MM/DAY. OVER THE  
NORTHWEST BAHAMAS EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM/DAY. THROUGH SATURDAY THIS INCREASES TO  
10-15MM/DAY AND MAXIMA OF 20-30MM. THE TROUGH ALOFT TO ALSO  
ENHANCE CONVECTION ACROSS JAMAICA...TO FAVOR RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-20MM. ON FRIDAY THIS INCREASES TO  
10-15MM/DAY AND MAXIMA OF 20-30MM.  
 
ALTHOUGH WEAKENING...THE MID LEVEL CELL OF THE SUBTROPICAL RIDGE  
NORTH OF THE GREATER ANTILLES REMAINS STRONG ENOUGH TO BLOCK A  
TUTT/TUTT LOW TO THE NORTH-NORTHEAST OF THE ISLAND CHAIN. THE TUTT  
LOW IS FORECAST TO SLOWLY WEAKEN WHILE DRIFTING TO THE  
NORTH-NORTHEAST DURING THE NEXT FEW DAYS. AS THE TUTT WEAKENS AND  
CONVECTIVE INSTABILITY WANES EXPECTING CONVECTION OVER THE EASTERN  
CARIBBEAN ISLES TO ALSO WEAKEN EARLY IN THE CYCLE. INITIALLY  
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF  
10MM...WITH FAIR WEATHER CONDITIONS TO THEN PREVAIL ON  
FRIDAY-SATURDAY MORNING. THIS SETS THE STAGE FOR A SECONDARY TUTT  
TO RETROGRESS ACROSS THE ISLAND CHAIN LATER ON FRIDAY/EARLY  
SATURDAY MORNING. AS IT ENTERS THE NORTHEAST CARIBBEAN ISLES THIS  
WILL ENHANCE CONVECTIVE INSTABILITY TO ONCE AGAIN FAVOR  
ENVIRONMENTAL CONDITIONS FAVORABLE FOR SCATTERED CONVECTION TO  
DEVELOP...TO SUSTAIN AN INCREASE IN CONVECTION ON SATURDAY-SUNDAY.  
FURTHERMORE...PER THE CLIMATE FORECAST SYSTEM (CFS) AN ATMOSPHERIC  
KELVIN WAVE IS TO PROPAGATE ACROSS THE CARIBBEAN DURING THE  
WEEKEND. IN RESPONSE TO IMPROVING CONDITIONS THE GFS AND ECMWF  
BOTH SHOW MODERATE TO HEAVY RAINFALL AMOUNTS TO AFFECT THE  
NORTHEAST CARIBBEAN ISLES EARLY NEXT WEEK.  
 
SOUTH OVER THE BASIN...AT 250 HPA...AN EAST-TO-WEST RIDGE EXTENDS  
ALONG THE COAST OF VENEZUELA-NORTHERN COLOMBIA TO CENTRAL AMERICA.  
AFOREMENTIONED TUTT...AS IT RETROGRESSES ACROSS THE ISLAND CHAIN  
ON SATURDAY WILL THEN SUSTAIN EROSION OF SHORT WAVE RIDGE PATTERN  
OVER THE EASTERN CARIBBEAN. IN RESPONSE...CONVECTION ACROSS  
CENTRAL-EASTERN VENEZUELA TO NORTHERN GUYANA WILL INCREASE FROM  
10-15MM/DAY AND MAXIMA OF 20-35MM EARLY IN THE CYCLE TO  
10-15MM/DAY AND MAXIMA OF 20-45MM ON FRIDAY-SATURDAY. ACROSS  
SURINAME-FRENCH GUIANA EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY  
AND MAXIMA OF 15MM. OVER NORTHERN COLOMBIA-NORTHWEST VENEZUELA AND  
ACROSS PANAMA...CONVECTION ALONG THE NEAR EQUATORIAL TROUGH/ITCZ  
WILL RANGE BETWEEN 10-15MM/DAY AND MAXIMA OF 20-30MM/DAY...WITH  
HIGHER AMOUNTS ON THE CHOCO/EJE CAFETERO OF WESTERN COLOMBIA WHERE  
THE DAILY MAXIMA IS TO PEAK AT 25-50MM AS ENHANCED BY THE  
PANAMANIAN LOW. OVER COSTA RICA-SOUTHERN NICARAGUA EXPECTING  
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. THROUGH  
SATURDAY THE DAILY MAXIMA WILL DECREASE TO 20-40MM. OVER EL  
SALVADOR-HONDURAS AND NORTHERN NICARAGUA EXPECTING RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. THROUGH FRIDAY  
AFTERNOON THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-40MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE  
38W 41W 44W 48W 51W 55W 58W 62W TUTT INDCD  
61W 64W 67W 70W 73W 76W 79W 82W TUTT INDCD  
67W 70W 74W 77W DISSIPATES TUTT INDCD  
77W 81W 84W 86W 88W DISSIPATES TUTT INDCD  
94W 97W 99W 103W 106W 109W 111W 113W TW  
 
TUTT OVER THE TROPICAL ATLANTIC SUSTAINS AN INDUCED PERTURBATION  
IN THE EASTERLY TRADES WITH AXIS ALONG 38W TO 28N. THIS MOVES TO  
THE EASTERN CARIBBEAN ISLES EARLY ON SUNDAY MORNING...WHERE IT IS  
TO TRIGGER RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. ON  
SUNDAY-MONDAY THE CONVECTION IS TO INTENSIFY WHILE BUILDING WEST  
ACROSS THE VIRGIN ISLES TO PUERTO RICO.  
 
THE TUTT NORTH OF THE LESSER ANTILLES SUSTAINS IN INDUCED TROUGH  
IN THE EASTERLY TRADES WITH AXIS ALONG 61W TO 26N. OVER THE  
LEEWARD-VIRGIN ISLES TO EASTERN PUERTO RICO THIS WILL SUSTAIN  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. ACROSS PUERTO  
RICO THIS IS TO THEN TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM ON FRIDAY...WHILE ACROSS HISPANIOLA IT IS TO  
SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM.  
OVER EASTERN CUBA-SOUTHEAST BAHAMAS IT IS TO THEN TRIGGER RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM ON SATURDAY.  
 
A TUTT INDUCED TROUGH EXTENDS ALONG 67W TO 23N. AS IT DECOUPLES  
FROM THE TUTT ALOFT THE WAVE IS TO WEAKEN/DISSIPATE EARLY ON  
SATURDAY MORNING. MEANWHILE...ACROSS HISPANIOLA THIS IS TO SUSTAIN  
RAINFALL AMOUNTS OF 05-10MMD/AY AND MAXIMA OF 15-20MM. OVER  
EASTERN CUBA-JAMAICA IT IS TO FAVOR RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-30MM ON FRIDAY.  
 
ANOTHER WANING TUTT INDUCED TROUGH EXTENDS ALONG 77W TO 26N. THIS  
WAVE TENDS TO WEAKEN AS IT MOVES ACROSS THE YUCATAN PENINSULA  
EARLY ON SATURDAY. MEANWHILE...OVER WESTERN CUBA AND THE NORTHWEST  
BAHAMAS THIS IS TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM. ON FRIDAY TO SATURDAY THIS INCREASES TO  
10-15MM/DAY AND MAXIMA OF 20-30MM. OVER THE YUCATAN THIS IS TO  
THEN TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM  
ON SATURDAY.  
 
A TROPICAL WAVE ALONG 94W AND SOUTH OF 19N IS TO SUSTAIN SCATTERED  
CONVECTION ACROSS SOUTHWEST-CENTRAL MEXICO WITH ACCUMULATION OF  
05-10MM/DAY AND MAXIMA OF 15-20MM THROUGH FRIDAY EVENING.  
THEREAFTER...ASSOCIATED CONVECTION IS TO LIMIT TO THE EASTERN  
PACIFIC ITCZ.  
 
GAJADHAR...SLMS (SAINT LUCIA)  
DAVISON...WPC (USA)  

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page