THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


CARIBBEAN FORECAST DISCUSSION




TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
650 AM EDT TUE SEP 30 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. ALOFT...THE
SUBTROPICAL RIDGE CONTINUES TO SLOWLY BUILD ACROSS THE FLORIDA
PENINSULA/BAHAMAS TO THE WESTERN ATLANTIC...WITH A TUTT TO THE
SOUTH EXTENDING ACROSS THE EASTERN-CENTRAL CARIBBEAN. AT MID
LEVELS...CLOSED HIGH OVER PUERTO RICO ANCHORS A SHORT WAVE RIDGE
ACROSS THE EASTERN CARIBBEAN. THIS SUSTAINS A TRADE WINDS CAP AND
A PWAT MINIMA ACROSS THE FORECAST AREA. AT LOW LEVELS...A TROPICAL
WAVE EXTENDS ALONG 52W/53W EARLY THIS MORNING. A SAL/DUST CLOUD TO
THE EAST OF 45W IS TRAILING THIS WAVE.

AT 250 HPA...SUBTROPICAL RIDGE IS TO GENERALLY REMAIN TO THE NORTH
OF THE GREATER ANTILLES...WHILE TUTT TO THE SOUTH IS TO INITIALLY
MEANDER ALONG 15N/16N. LATER IN THE WEEK THE TUTT IS TO MEANDER
NORTH OVER THE NORTHEAST CARIBBEAN ISLES AS A CELL OF THE
SUBEQUATORIAL RIDGE BUILDS TO THE SOUTH. THE MID LEVEL
RIDGE...MEANWHILE...LIFTS ACROSS THE NORTHERN CARIBBEAN ISLES
THROUGH WEDNESDAY MORNING...THEN ALIGNS EAST-TO-WEST ALONG
23N/24N... STACKING WELL WITH THE SUBTROPICAL RIDGE ALOFT. AS THE
MID LEVEL HIGH/RIDGE MOVES NORTH...CAP INVERSION IS TO SLOWLY
LIFT. EARLY IN THE CYCLE IT IS TO MEANDER AROUND 750-800 HPA...AND
THROUGH THURSDAY EVENING IT RISES TO 600 HPA. PWAT IS THEN
EXPECTED TO GRADUALLY INCREASE TO 40-45MM...PEAKING ON THURSDAY AS
THE TROPICAL WAVE TAKES A BEELINE ACROSS THE FORECAST AREA. BUT
THIS WILL BE SHORT LIVED...WITH MODELS SHOWING A SHARP DECREASE IN
AVAILABLE WATER AS THE SAL ENTERS THE FORECAST AREA DURING THE
WEEKEND.

IN THIS PATTERN INITIALLY EXPECTING FAIR WEATHER CONDITIONS ACROSS
THE FORECAST AREA...WITH DIURNAL CONVECTION LIMITING TO
NORTHWESTERN PORTIONS OF PUERTO RICO. ON THURSDAY-FRIDAY...AS
INVERSION LIFTS AND SOMEWHAT DEEPER MOISTURE ENVELOPS THE FORECAST
AREA...MODELS SHOWING AN INCREASE IN ACTIVITY ACROSS THE VIRGIN
ISLES-PUERTO RICO. BUT THEY ARE SHOWING RAINFALL AMOUNTS PEAKING
AT LESS THAN HALF AN INCH. THAT SEEMS REASONABLE CONSIDERING LACK
OF SYNOPTIC FORCING. BUT IN A PREVAILING SOUTHEASTERLY LOW LEVEL
FLOW...WE WILL PROBABLY SEE HIGHER THAN THAT ACROSS WESTERN
INTERIOR PORTIONS OF PUERTO RICO DURING THE AFTERNOON HOURS.

VALVERDE...IMN (COSTA RICA)
MEDINA...ONAMET (REPUBLICA DOMINICANA)
DAVISON...WPC (USA)




Last Updated: 650 AM EDT TUE SEP 30 2014