Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4
000
FXCA20 KWBC 291037
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
636 AM EDT THU JUN 29 2017

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUNE
29/06 UTC: TROPICAL WAVE EXTENDS OVER THE EASTERN CARIBBEAN ALONG
65W/66W. THIS WAVE...IN INTERACTION WITH A TUTT NORTH OF THE
ISLANDS...FAVORS A MOIST ADVECTIVE PATTERN. IN RESPONSE...PWAT
CONTENT OF NEARLY TWO INCHES IS ADVECTING ACROSS THE SOUTHERN VI
TOWARDS EASTERN PUERTO RICO...TO ENVELOP THE ENTIRE FORECAST AREA
EARLY THIS AFTERNOON. INITIALLY THE MOST ACTIVE CONVECTION IS
EXPECTED ACROSS THE USVI-EASTERN PUERTO RICO. BUT AS THE WINDS
VEER TO THE SOUTHEAST LATER THIS MORNING EXPECTING A SECONDARY
SURGE ACROSS NORTHWEST PUERTO RICO DURING THE AFTERNOON HOURS.
CONSISTENT WITH PREVIOUS FORECASTS THE GLOBAL MODELS THEN SHOW
HIGH MOISTURE CONTENT TO PERSIST THROUGH FRIDAY EVENING/SATURDAY
MORNING. THIS WILL BE FOLLOWED BY RAPID EROSION OF AVAILABLE WATER
AS A TRAILING SAHARAN AIR LAYER ENTRAINS ACROSS THE NORTHEAST
CARIBBEAN. ACROSS THE VIRGIN ISLES TO EASTERN PUERTO RICO THIS IS
EXPECTED TO FAVOR RAINFALL AMOUNTS OF 2-3 INCHES DURING THE DAY
TODAY AS IT CONTINUES TO INTERACT WITH UPPER LEVEL TUTT
PATTERN...WHILE OVER WESTERN INTERIOR/NORTHWEST PUERTO RICO MAXIMA
WILL RANGE BETWEEN 2-4 INCHES AS ENHANCED BY SEA BREEZE
CONVERGENCE/DIURNAL HEATING. ON FRIDAY EXPECTING LESSER AMOUNTS
ACROSS THE VIRGIN ISLES...WHILE ACROSS PUERTO RICO THE THREAT OF
MODERATE TO HEAVY CONVECTION WILL PERSIST.

ON SATURDAY-MONDAY A STRONG TRADE WINDS CAP IS TO SET IN AS THE
SAHARAN AIR LAYER RAPIDLY ENTRAINS ACROSS THE FORECAST AREA.
SIMULTANEOUSLY...TRADE WIND EASTERLIES WILL THEN RETURN TO THE
EASTERN CARIBBEAN...WITH THE 850 HPA WINDS EXPECTED TO PEAK AT
15-20KT. THE CHANGE IN REGIME WILL ONCE AGAIN FAVOR GENERATION OF
STREAMERS WITH LIGHT CONVECTION TO AFFECT THE USVI-EASTERN PUERTO
RICO FROM TIME-TO-TIME IN PASSING SHOWERS. MEASURABLE AMOUNTS WILL
THEN LIMIT TO WESTERN PUERTO RICO IN LATE AFTERNOON CONVECTION.

GAJADHAR...SLMS (SAINT LUCIA)
GALVEZ/DAVISON...WPC (USA)
$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.