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Tropical Discussion
 
(Latest Discussion - Issued 1043Z Apr 25, 2019)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
643 AM EDT THU APR 25 2019

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR 25/06
UTC: IN A SINUSOIDAL PATTERN...A MID/UPPER LEVEL RIDGE EXTENDS TO
THE NORTH-NORTHEAST FROM THE YUCATAN/SOUTHERN STATES OF MEXICO TO
THE EASTERN USA. EAST OF THIS AXIS...A TROUGH EXTENDS TO THE SOUTH
SOUTHEAST FROM THE CENTRAL ATLANTIC TO THE EASTERN CARIBBEAN. AT
250 HPA A JET MAXIMA ROUNDING THE BASE OF THE TROUGH NOW EXTENDS
OVER THE EASTERN CARIBBEAN AND ACROSS THE FRENCH ISLES. FORECAST
AREA LIES ON THE CONVERGENT/SUBSIDENT SIDE OF THE UPPER LEVEL JET
MAXIMA. AT LOW LEVELS...UNDER INFLUENCE OF A WANING TROUGH NORTH
OF THE ISLANDS...LIGHT MEANDERING WINDS PREVAIL...WITH SEA/LAND
BREEZES DOMINATING THE LOW LEVEL FLOW PATTERN.

MID/UPPER LEVEL RIDGE WILL ROLL ACROSS THE EASTERN USA TO THE
WESTERN ATLANTIC/NORTHERN CARIBBEAN WHILE YIELDING TO A
PROGRESSIVE TROUGH STREAMING ACROSS THE USA. AS THE RIDGE MOVES
OVER THE FORECAST AREA IT IS TO STRENGTHEN THE TRADE WINDS
INVERSION...CAPPING MOISTURE TO THE LOWER LEVELS OF THE
ATMOSPHERE. THIS WILL CONTINUE INHIBITING ORGANIZED DEEP
CONVECTION...WITH SHALLOW DEVELOPMENT LIMITING TO INTERIOR
PORTIONS OF PUERTO RICO IN A DIURNAL PATTERN. AT LOW LEVELS...AS A
HIGH/RIDGE ROLLS ACROSS THE WESTERN TO THE CENTRAL
ATLANTIC...WINDS ARE FORECAST TO GRADUALLY VEER TO THE EAST DURING
THE DAY TODAY TO THE EAST-SOUTHEAST ON FRIDAY. MOIST PLUME TO THE
SOUTH IS TO THEN START A SLOW NORTHWARD MIGRATION ACROSS THE
EASTERN CARIBBEAN. THIS IS TO INITIALLY AFFECT THE VIRGIN
ISLES-SOUTHEAST PUERTO RICO...THEN BUILD FARTHER NORTH AND WEST
DURING THE WEEKEND.

ALTHOUGH INITIALLY STRONG...MID LEVEL RIDGE IS TO GRADUALLY
COLLAPSE UNDER PRESSURE FROM POLAR TROUGH STREAMING ACROSS THE
EASTERN CARIBBEAN TO THE WESTERN ATLANTIC ON FRIDAY. ON ITS
WAKE...SUCCESSIVE SHORT WAVE PERTURBATIONS ON THE SOUTHERN STREAM
ARE TO THEN RACE ACROSS THE GULF OF MEXICO-THE BAHAMAS-NORTHERN
CARIBBEAN ISLES DURING THE WEEKEND. THIS WILL SUSTAIN THE FURTHER
EROSION OF MID LEVEL RIDGE PATTERN AND ASSOCIATED TRADE WINDS CAP
DURING THE WEEKEND. ON SUNDAY...THE RIDGE WILL WEAKEN ENOUGH TO
ALLOW FOR A DEEPER POOL OF MOISTURE TO ADVECT NORTH ACROSS THE
FORECAST AREA. INFLOW OF MID LEVEL VORTICES WILL COINCIDE WITH
UPPER LEVEL JET MAXIMA STREAMING JUST NORTH OF THE GREATER
ANTILLES. AS THE TRADE WINDS CAP RELAXES ITS FOOTHOLD...AND JET
PULLS TO THE NORTH...DEEPER CONVECTION IS THEN EXPECTED ON
SUNDAY-MONDAY. AS A RESULT...TRENDING IN FAVOR OF HIGHER RAINFALL
AMOUNTS ACROSS THE ENTIRE FORECAST AREA...WITH MOST ACTIVE TO
AFFECT SOUTHERN PORTIONS OF THE SAN JUAN METRO AREA/DOWNSTREAM
FROM EL YUNQUE AS WELL AS ACROSS WESTERN PORTIONS OF THE ISLAND.

GALVEZ/DAVISON...WPC (USA)