Prognostic Meteorological Discussion
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FXCA20 KWBC 181119
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
618 AM EST WED JAN 18 2017

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JAN 18/06
UTC: IN A HIGHLY AMPLIFIED SINUSOIDAL LONG WAVE PATTERN...A
MID/UPPER LEVEL RIDGE EXTENDS FROM CENTRAL AMERICA TO THE EASTERN
USA. THIS...IN-TURN...SUSTAINS THE SOUTHWARD AMPLIFICATION OF A
TROUGH ACROSS THE EASTERN CARIBBEAN ISLES TO NORTHERN VENEZUELA.
PUERTO RICO AND THE USVI LIE ON THE CONVERGENT SIDE OF THE
AMPLIFYING TROUGH. THIS IS STRENGTHENING THE CAP INVERSION WHILE
SUSTAINING THE RAPID EROSION OF AVAILABLE MOISTURE. AT LOW
LEVELS...A HIGH TO THE WEST-SOUTHWEST OF BERMUDA FAVORS A BRISK
NORTHEASTERLY FLOW ACROSS THE WESTERN ATLANTIC TO THE EASTERN
CARIBBEAN. SHALLOW MOISTURE IS CLUSTERING ALONG TWO MOIST
TONGUES...WITH ONE EXTENDING OVER THE NORTHEAST CARIBBEAN WHILE
THE OTHER MEANDERS JUST NORTH OF 22N. A DRY SLOT SEPARATES THE
MOIST TONGUES...AND IT IS EXPECTED TO SETTLE OVER THE FORECAST
AREA EARLY THIS AFTERNOON...TO GENERALLY FAVOR FAIR WEATHER
CONDITIONS OVER THE NEXT COUPLE OF DAYS.

MID/UPPER LEVEL RIDGE PATTERN IS TO GENERALLY PREVAIL TO THE WEST
OVER THE NEXT FEW DAYS. AS IT HOLDS...THE RIDGE WILL STEER SHORT
WAVE PERTURBATIONS TOWARDS THE FORECAST AREA. ONE IS EXPECTED BY
MIDDAY ON FRIDAY...WHILE THE NEXT IS TO ARRIVE ON SATURDAY. THE
INFLOW OF SHORT WAVE ENERGY WILL LEAD TO EROSION OF CAP INVERSION
LATER DURING THE WEEKEND...FAVORING AN INCREASE IN PWAT CONTENT.
AT LOW LEVELS... RIDGE TO THE NORTH WEAKENS EARLY IN THE CYCLE
UNDER PRESSURE FROM POLAR FRONTS EXITING THE EASTERN USA. THROUGH
THIS AFTERNOON THE TRADES ARE TO WEAKEN WHILE VEERING TO THE EAST.
AS THE RIDGE WILL BE REPLACED BY A BROAD POLAR TROUGH LATER ON
THURSDAY/FRIDAY MORNING. THE LOW LEVEL WINDS ARE TO BACK TO THE
NORTH-NORTHWEST ON SATURDAY MORNING AS WANING FRONT APPROACHES THE
FORECAST AREA. THIS WILL BE ACCOMPANIED BY ISOLATED TO SCATTERED
SHOWERS THAT ARE TO PRIMARILY AFFECT THE NORTHERN VI/NORTH COAST
OF PUERTO RICO ON SATURDAY TO SUNDAY.


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

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