Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXCA20 KWBC 251050
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
649 AM EDT MON SEP 25 2017

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM SEP
25/06UTC: AT UPPER LEVELS...A TUTT CENTERS AT 23N 54W...WHILE A
RIDGE CENTERS JUST TO THE SOUTH OF JAMAICA AND EXTENDS AN AXIS
ACROSS HISPANIOLA INTO 24N 64W. THE INTERACTION OF THIS SYSTEMS IS
LEADING TO NORTHERLY FLOW OVER PUERTO RICO AND THE USVI. THIS IS
VENTILATING DEEP CONVECTION TO THE EAST OF THE VIRGIN
ISLANDS...SOME OF WHICH IS OCCURRING IN THE VICINITY OF ST. CROIX.
THIS CONVECTION ALSO ASSOCIATED WITH A WEAK TROPICAL WAVE THAT
EXTENDS ALONG 63W. ACTIVITY OVER THE ISLANDS SHOULD DECREASE
DURING THE DAY...AS SOLAR RADIATION WARMS UP THE ATMOSPHERE AND
STABILITY INCREASES.

MODELS SHOW THE TROPICAL WAVE CROSSING PUERTO RICO DURING MONDAY
AFTERNOON-EVENING. THIS IS ASSOCIATED WITH A PEAK IN MOISTURE
CONTENT AND CONVECTIVE INSTABILITY. UNDER THE INFLUENCE OF
SOUTHEASTERLY TRADES...EXPECTING A MAXIMA IN SHOWERS IN
SOUTHEASTERN PUERTO RICO DURING MORNING HOURS...AND MAXIMA IN
NORTHWESTERN PUERTO RICO DURING THE AFTERNOON/EVENING. YET...UNDER
THE INFLUENCE OF MID-TO-HIGH CLOUD COVER...EXPECTING LIMITED
INSTABILITY AND RESULTING RAINFALL TOTALS IN AFTERNOON CONVECTION.
THE GLOBAL MODELS ARE ALL SHOWING LIGHT ACCUMULATIONS...AS WELL AS
THE HIGH-RESOLUTION WRF MODELS. ON MONDAY...WE EXPECT THE LARGEST
ACCUMULATIONS IN SOUTHEASTERN PUERTO RICO...WHERE NUMEROUS MORNING
SHOWERS SHOULD LEAD TO MAXIMA OF 15-20MM. TO THE
NORTHWEST...ISOLATED THUNDERSTORMS SHOULD LEAD TO LOCALIZED MAXIMA
UNDER 15MM.

A DRYING TREND FOLLOWS...AS A DRY AIR MASS IN THE LOW-TO-MID
TROPOSPHERE ARRIVES INTO THE REGION DURING EARLY TUESDAY. MODELS
ARE SHOWING A SUBSIDENCE CAP ACCOMPANIED BY DRY MID LEVELS
ESTABLISHING NEAR 900-850 HPA AND PERSISTING THROUGH THURSDAY.
DURING THURSDAY AND INTO FRIDAY...THE ARRIVAL OF THE
AFOREMENTIONED TUTT...ACCOMPANIED BY A TUTT-INDUCED WAVE...ARE
FORECAST TO LEAD TO AN INCREASE IN PRECIPITATION. MODELS ARE ALL
SHOWING THIS TREND. ALTHOUGH IT IS TOO EARLY TO SPEAK ABOUT
RAINFALL TOTALS...MODELS ARE SUGGESTING MAXIMA UNDER 2 INCHES
DURING FRIDAY.

GUY...NMS (BELIZE)
RIVAS...SENAMHI (PERU)
DAVISON/GALVEZ...WPC (USA)

$$




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