Prognostic Meteorological Discussion
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FXCA20 KWBC 191129
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
629 AM EST THU JAN 19 2017

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JAN 19/00
UTC: LONG WAVE RIDGE OVER THE WESTERN CARIBBEAN/EASTERN USA FAVORS
THE SOUTHWARD AMPLIFICATION OF A TROUGH OVER THE WESTERN ATLANTIC.
THE TROUGH ENVELOPS AREA BETWEEN 75W-60W AND TO THE NORTH OF 22N.
THIS...HOWEVER...IS NOT STRONG ENOUGH TO WEAKEN THE TRADE WINDS
CAP ENVELOPING THE FORECAST AREA. AT LOW LEVELS...IT SUSTAINS A
BROAD TROUGH OVER THE WESTERN ATLANTIC...WHILE LIGHT EASTERLY
TRADES DOMINATE THE FLOW ACROSS THE CARIBBEAN BASIN. THIS PATTERN
IS TO GENERALLY FAVOR FAIR WEATHER CONDITIONS OVER THE NEXT TWO
DAYS. CONVECTION...IF ANY...WILL CONFINE TO WESTERN INTERIOR
PORTIONS OF PUERTO RICO AS ENHANCED BY DIURNAL HEATING. BUT THESE
ARE TO RESULT IN MOSTLY LIGHT RAINFALL AMOUNTS IN ISOLATED
CONVECTION.

A SECONDARY MID LEVEL SHORT WAVE TROUGH WILL FOLLOW...TAKING A
BEELINE ACROSS THE BAHAMAS ON FRIDAY...AND REACHING PUERTO
RICO/USVI EARLY ON SATURDAY MORNING. ON ITS WAKE...MID LEVEL RIDGE
IS TO RELOCATE TO THE WESTERN ATLANTIC. AT LOW LEVELS...BROAD
TROUGH IS TO SLOWLY YIELD TO A MODIFYING POLAR RIDGE...WITH WINDS
FORECAST TO BACK TO THE NORTH LATER ON FRIDAY/EARLY ON SATURDAY
MORNING. THIS WILL DRIVE A WANING FRONT TO JUST NORTH OF THE
FORECAST AREA EARLY ON SATURDAY...WHERE BOUNDARY IS TO ENHANCE LOW
LEVEL MOISTURE CONVERGENCE WHILE GRADUALLY DISSIPATING. LACKING
STRONG UPPER LEVEL SUPPORT...THIS IS TO GENERALLY FAVOR LIGHT
COASTAL CONVECTION ACROSS PUERTO RICO AND THE NORTHERN VI. AS THE
FRONT WEAKENS AND RIDGE PATTERN MOVES IN...THE LOW LEVEL WINDS ARE
TO THEN GRADUALLY VEER TO THE EAST-SOUTHEAST ON SUNDAY. THIS IS TO
THEN FAVOR A WARM ADVECTIVE PATTERN ACROSS THE ENTIRE FORECAST
AREA.

JIMENEZ...IMN (COSTA RICA)
MIRANDA...INAMEH (VENEZUELA)
DAVISON...WPC (USA)

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