Prognostic Meteorological Discussion
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FXCA20 KWBC 301823
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EDT MON MAR 30 2015

DISCUSSION FROM MARCH 30/00 UTC: MID/UPPER LEVEL POLAR
PERTURBATIONS EXITING THE EASTERN USA AND ENTERING THE WESTERN
ATLANTIC CONTINUE TO PRESS AGAINST THE SUBTROPICAL RIDGE TO THE
SOUTH. UNDER PRESSURE FROM THESE PERTURBATIONS THE RIDGE DIVIDED
IN TWO CELLS...WITH ONE OVER CENTRAL/SOUTHERN MEXICO AND THE OTHER
OVER THE EASTERN CARIBBEAN. AT 500 HPA THE WESTERNMOST IS TO
ANCHOR ON A CLOSED HIGH THAT IS TO MEANDER OVER SOUTHWEST STATES
OF MEXICO. ASSOCIATED RIDGE AXIS IS TO SLOWLY BUILD EAST ACROSS
THE YUCATAN/NORTHERN CENTRAL AMERICA TO THE WESTERN
ATLANTIC...WITH MID LEVEL RIDGE PATTERN EXPECTED TO STRENGTHEN ITS
FOOTHOLD THROUGH THURSDAY EVENING. THIS IS TO SUSTAIN A GRADUAL
EROSION OF AVAILABLE MOISTURE AND DECREASE IN CONVECTION AS THE
WEEK WEARS ON. CELL OVER THE EASTERN CARIBBEAN...MEANWHILE...IS TO
SLOWLY MOVE EAST ACROSS THE ISLAND CHAIN INTO THE TROPICAL
ATLANTIC/NORTHERN GUIANAS. AS IT PULLS AWAY...CAP INVERSION ACROSS
PUERTO RICO-ISLAND CHAIN IS FORECAST TO WEAKEN. THIS WILL ALLOW
FOR DEEPER MOISTURE TO POOL ACROSS THE NORTHEAST CARIBBEAN ISLES.
ACROSS THE GUIANAS THE OPPOSITE IS TRUE...WITH RELOCATING MID
LEVEL RIDGE TO STRENGTHEN THE CAP INVERSION AND FAVOR GRADUAL
EROSION OF AVAILABLE MOISTURE. EARLY IN THE CYCLE EXPECTING
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM ACROSS
SURINAME-GUYANA...WITH A RAPID DRYING TREND THROUGH WEDNESDAY
MORNING. OVER FRENCH GUIANA HIGHER AMOUNTS ARE EXPECTED EARLY IN
THE PERIOD...WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF
20-35MM.

POLAR TROUGH OVER THE WESTERN NORTH ATLANTIC IS TO LIFT TO THE
NORTHEAST EARLY IN THE CYCLE...WITH ANOTHER PERTURBATION TO
CLOSELY FOLLOW. THE LATTER BOTTOMS OUT JUST NORTH OF 20N EARLY ON
TUESDAY...THEN PULLS AS IT LIFTS OVER THE SUBTROPICAL RIDGE TO THE
EAST. A THIRD AND DEEPER PERTURBATION IS THEN EXPECTED OVER THE
WESTERN ATLANTIC LATER ON WEDNESDAY. AT LOW LEVELS THE POLAR
TROUGH SUSTAINS A MEANDERING FRONT ACROSS THE SOUTHEAST
BAHAMAS/TURKS AND CAICOS-EASTERN CUBA-NORTHWEST CARIBBEAN. FRONTAL
BOUNDARY LOSES UPPER LEVEL SUPPORT THROUGH TUESDAY EVENING...AND
IT IS TO THEN FRONTOLIZE AS IT MEANDERS ACROSS THE
SOUTHEAST/CENTRAL BAHAMAS. MEANWHILE...THIS IS TO SUSTAIN
SCATTERED CONVECTION ACROSS THE SOUTHEAST
BAHAMAS/TURKS-EASTERN/CENTRAL PORTIONS OF CUBA-HISPANIOLA AND
JAMAICA WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-30MM.

INFLOW OF SHORT WAVE ENERGY IS TO THEN SUSTAIN A NEW FRONTAL
BOUNDARY LATER ON WEDNESDAY/EARLY THURSDAY MORNING...BUT THIS
BOTTOMS OUT TO THE NORTH OF 25N EARLY ON THURSDAY.
HOWEVER...BUILDING POLAR RIDGE WILL THEN DRIVE A PREFRONTAL SHEAR
LINE ACROSS THE NORTHEAST CARIBBEAN ISLES LATER ON
WEDNESDAY...INTO THE LEEWARD ISLES EARLY ON THURSDAY. ARRIVAL OF
THE SHEAR LINE WILL COINCIDE WITH WEAKENING OF THE TRADE WINDS CAP
ACROSS THE NORTHEAST CARIBBEAN ISLANDS. MOST ACTIVE IS EXPECTED
OVER PUERTO RICO AND THE VIRGIN ISLES...WITH RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15MM. ACROSS PUERTO RICO THE MAXIMA
INCREASES TO 15-30MM ON FRIDAY-SATURDAY. ACROSS THE LEEWARD/FRENCH
ISLANDS THE SHEAR LINE IS TO THEN FAVOR RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15MM.

A SHORT WAVE TROUGH ON THE SOUTHERN STREAM IS INITIALIZED OVER THE
WESTERN CARIBBEAN/CENTRAL AMERICA. BUILDING MID LEVEL RIDGE TO THE
WEST DISPLACES THIS TROUGH EAST...WITH AXIS TO RELOCATE TO THE
CENTRAL CARIBBEAN/SOUTHERN CENTRAL AMERICA LATER ON TUESDAY.
THROUGH WEDNESDAY MORNING THE TROUGH RELOCATES ACROSS THE BASIN TO
THE EASTERN CARIBBEAN. EARLY IN THE CYCLE THIS IS TO ENHANCE
CONVECTIVE DEVELOPMENT ACROSS THE WESTERN CARIBBEAN/CENTRAL
AMERICA. BUT AS THE RIDGE BUILDS AND THE CAP INVERSION STRENGTHENS
EXPECTING AN EROSION OF AVAILABLE WATER. EARLY IN THE CYCLE THE
SHORT WAVE TROUGH IS TO ENHANCE CONVECTION ACROSS
BELIZE-GUATEMALA-QUINTANA ROO IN THE YUCATAN TO NORTHERN HONDURAS
TO RESULT IN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM.. THROUGH TUESDAY EVENING THIS DECREASES TO 05-10MM/DAY
AND MAXIMA OF 15MM...WITH LESSER AMOUNTS ON WEDNESDAY TO THURSDAY
MORNING. ACROSS PANAMA-COSTA RICA THIS WILL SUSTAIN AN INCREASE IN
CONVECTION DURING THE DAY ON TUESDAY...TO FAVOR RAINFALL AMOUNTS
OF 05-10MM/DAY AND MAXIMA OF 15MM. AS IT MEANDERS OVER THE CENTRAL
CARIBBEAN...THE TROUGH IS TO THEN ENHANCE CONVECTION ACROSS
COLOMBIA...WITH MOST ACTIVE EXPECTED TO AFFECT FROM AMAZONIA TO
THE ANDEAN REGION. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-25MM THROUGH TUESDAY. ON WEDNESDAY
THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-45MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE
NONE

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





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