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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1044Z Mar 31, 2015)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
644 AM EDT TUE MAR 31 2015

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI (FROM MARCH
31/06UTC). SUCCESSIVE MID/UPPER LEVEL PERTURBATIONS ARE TO STREAM
ACROSS THE WESTERN ATLANTIC OVER THE NEXT FEW DAYS. THESE ARE TO
PRESS AGAINST WANING CELL OF THE SUBTROPICAL RIDGE OVER THE
EASTERN CARIBBEAN...WITH ASSOCIATED MID LEVEL CAP INVERSION TO
LIFT AS THE RIDGE CRUMBLES THROUGH THE SHORT RANGE PERIOD. THIS
WILL ALLOW FOR DEEPER MOISTURE TO POOL ACROSS THE FORECAST
AREA...WITH PWAT EXPECTED TO PEAK AT 35-40MM. A STRONG SHORT WAVE
PERTURBATION IS TO STREAM ACROSS THE FORECAST AREA ON
THURSDAY...WITH MODELS PROJECTING STRONG UPWARD VERTICAL MOTIONS
AS A LOW LEVEL CONVERGENT PATTERN ESTABLISHES ACROSS THE NORTHEAST
CARIBBEAN ISLANDS. IN RESPONSE...BOTH THE GFS AND UKMET SHOW AN
INCREASE IN CONVECTION ACROSS THE FORECAST AREA...WITH UKMET
SHOWING MOST ACTIVE CLUSTERING OVER WESTERN/SOUTHWESTERN PORTIONS
OF PUERTO RICO. IN THIS AREA THE UKMET IS SHOWING 24HRS RAINFALL
AMOUNTS TO EXCEED 25MM. DEPENDING ON THE TIMING OF THE UPPER
TROUGH AND ITS INTERACTION WITH SEA BREEZE CONVERGENCE...MUCH
HIGHER AMOUNTS ARE LIKELY TO DEVELOP.

THIS IS TO SET THE STAGE FOR A DEEPER TROUGH TO AMPLIFY ACROSS THE
FORECAST AREA DURING THE WEEKEND...WITH AXIS TO GRADUALLY DEEPEN
AS A RIDGE BUILDS ACROSS WESTERN PORTIONS OF THE DOMAIN. DEEPENING
TROUGH IS TO ALSO STEER A SUBTROPICAL JET MAXIMA ACROSS THE
FORECAST AREA...WITH CONVERGENCE ON ITS RIGHT EXIT REGION EXPECTED
TO FAVOR A LULL IN CONVECTION DURING THE DAY ON FRIDAY. BUT AS THE
TROUGH MOVES EAST AND THE JET BEGINS TO ROUND THE BASE OF THE
TROUGH...ENVIRONMENTAL CONDITIONS ARE TO BECOME MORE FAVORABLE FOR
DEEP CONVECTION DURING THE DAY ON SATURDAY. ALTHOUGH DYNAMICS
APPEAR TO BE FALLING INTO PLACE...EVOLVING MJO PATTERN IS GOING TO
MAKE THE DIFFERENCE. IF WE REMAIN NEUTRAL TO SLIGHTLY DIVERGENT
HEAVY RAINFALL AMOUNTS ARE POSSIBLE. BUT IF AN UPPER CONVERGENT
PATTERN DEVELOPS AS SOME OF THE CLIMO MODELS SUGGEST...ACTIVITY
COULD BECOME MORE LOCALIZED AND NOT AS INTENSE. SO THE UNCERTAINTY
IS HIGH DURING THE WEEKEND.

CRAIG...TTMS (TRINIDAD AND TOBAGO)
NANDA...MDS (SURINAME)
DAVISON...WPC (USA)