THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


CARIBBEAN FORECAST DISCUSSION




TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EDT MON APR 20 2015

DISCUSSION FROM APRIL 20/12 UTC: BROAD MID/UPPER LEVEL RIDGE LIES
OVER SOUTHERN MEXICO/THE GULF-WESTERN CARIBBEAN-CENTRAL AMERICA
AND OVER CUBA. A 500 HPA HIGH OVER QUINTANA ROO IN THE YUCATAN
ANCHORS THIS RIDGE. THROUGH TUESDAY EVENING THE RIDGE IS TO BUILD
EAST ACROSS THE DOMINICAN REPUBLIC TO PUERTO RICO/VIRGIN ISLANDS.
AS IT BUILDS EAST...THIS IS TO STRENGTHEN THE TRADE WINDS CAP
ACROSS THE NORTHERN CARIBBEAN ISLANDS WHILE SUSTAINING GRADUAL
EROSION OF AVAILABLE MOISTURE. OVER NORTHERN CENTRAL AMERICA TO
SOUTHERN STATES OF MEXICO THIS IS TO GENERALLY FAVOR A DRY AND
STABLE PATTERN...EXCEPT FOR THE HIGHER ELEVATIONS OVER SOUTHERN
GUATEMALA-HONDURAS/EL SALVADOR...WHERE TOPOGRAPHICAL FORCING WILL
BE STRONG ENOUGH TO OVERCOME NEGATIVE INFLUENCE OF THE CAP
INVERSION. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15MM IN ISOLATED TO SCATTERED CONVECTION. THROUGH
TUESDAY THIS DECREASES TO 00-05MM/DAY AND MAXIMA OF 10MM.

MID/UPPER LEVEL SHORT WAVE PERTURBATIONS ON THE SOUTHERN STREAM
FLOW ARE TO PROPAGATE ACROSS THE SOUTHERN USA/NORTHERN STATES OF
MEXICO WHILE REVOLVING AROUND THE MEANDERING RIDGE TO THE SOUTH.
EARLY IN THE CYCLE THIS WILL ENHANCE DIURNAL CONVECTION ACROSS
NORTHEAST STATES OF MEXICO...WHERE WE EXPECT RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-30MM/DAY THROUGH TUESDAY
MORNING...WITH LESSER AMOUNTS IN THE AFTERNOON TO PEAK AT
05-10MM/DAY AND MAXIMA OF 15MM. BUT AS THE RIDGE BUILDS EAST AND
NORTH...FOCUS OF ENERGY SHIFTS AWAY...WITH MODELS SHOWING A
DECREASE IN CONVECTION ACROSS MEXICO.

BROAD MID/UPPER LEVEL POLAR TROUGH EXTENDS ACROSS THE EASTERN USA
TO THE WESTERN ATLANTIC...WITH AXIS FORECAST TO PRESS AGAINST
MEANDERING RIDGE TO THE SOUTH. BROAD TROUGH PATTERN IS TO PERSIST
OVER THE NEXT FEW DAYS. AT LOW LEVELS THIS IS TO SUSTAIN AN
ELONGATED FRONT OVER THE WESTERN NORTH ATLANTIC THAT IS TO MEANDER
INTO THE FLORIDA PENINSULA JUST NORTH OF THE BAHAMAS. ALTHOUGH
FRONT STALLS TO THE NORTH OF THE BAHAMAS LATER ON TUESDAY...A WEAK
PREFRONTAL SHEAR LINE IS TO FORM OVER THE NORTHWEST BAHAMAS BY
MIDDAY ON WEDNESDAY. EARLY IN THE CYCLE...PREFRONTAL CONVECTION
OVER THE NORTHWEST BAHAMAS WILL SUSTAIN RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM THROUGH TUESDAY MORNING...AND
MAXIMA OF 15-30MM ON TUESDAY-WEDNESDAY. THE EUROPEAN MODELS THEN
SHOW POTENTIAL FOR ORGANIZED HEAVY CONVECTION ACROSS GREAT
ABACO-GRAND BAHAMA ON WEDNESDAY...WITH RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 30-60MM IN RISK OF ECHO TRAINING. NOTE
THAT THIS IS HIGHER THAN WHAT THE GFS IS SUGGESTING FOR THE AREA.

BROAD DISORGANIZED TROUGH FLANKS THE EASTERN FRINGES OF THE
SUBTROPICAL RIDGE...WITH MID LEVEL TROUGH EXTENDING ACROSS THE
CENTRAL-EASTERN CARIBBEAN. BUILDING MID LEVEL RIDGE TO THE WEST
WILL CONFINE THIS TROUGH TO THE EASTERN CARIBBEAN ISLES-NORTHERN
SOUTH AMERICA LATER ON TUESDAY TO WEDNESDAY. EARLY IN THE CYCLE
THIS WILL ENHANCE CONVECTION ACROSS CENTRAL HISPANIOLA AND WESTERN
INTERIOR PORTIONS OF PUERTO RICO...TO FAVOR RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM. BUT AS THE RIDGE BUILDS AND THE
TROUGH PULLS AWAY THIS DECREASES TO 00-05MM/DAY AND MAXIMA OF 10MM
ON TUESDAY...WITH LESSER AMOUNTS EXPECTED ON WEDNESDAY-THURSDAY.
AS IT MEANDERS OVER THE SOUTHERN CARIBBEAN/NORTHERN SOUTH
AMERICA...THIS IS TO ENHANCE DIURNAL CONVECTION ACROSS
NORTHWEST-NORTHERN COLOMBIA AND THE MARACAIBO REGION IN VENEZUELA.
OVER NORTHWEST-NORTHERN COLOMBIA EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM THROUGH TUESDAY...AND
10-15MM/DAY WITH MAXIMA OF 20-30MM THEREAFTER. ACROSS NORTHWEST
VENEZUELA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM. THROUGH WEDNESDAY THIS DECREASES TO 05-10MM/DAY AND
MAXIMA OF 15MM.

THE SUBEQUATORIAL RIDGE IS THE DOMINANT FEATURE TO THE EAST AND
SOUTH...WITH AXIS AT 250 HPA TO EXTEND WEST ACROSS THE TROPICAL
ATLANTIC TO NORTHERN SOUTH AMERICA ALONG 05N. THE SUBTROPICAL
RIDGE LIES TO THE SOUTH... ENVELOPING MID/NORTHERN PORTIONS OF
SOUTH AMERICA. AN AREA OF DIFFLUENCE ALOFT SEPARATES THESE
RIDGES...AND THIS IS TO VENT DEEP CONVECTION ACROSS THE SOUTHERN
GUIANAS TO AMAZONIA IN SOUTHERN VENEZUELA AND COLOMBIA. IN THIS
AREA SCATTERED DEEP CONVECTION IS TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. ACROSS THE NORTHERN GUIANAS TO
NORTHEAST VENEZUELA...MEANWHILE...EXPECTING RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM. THROUGH WEDNESDAY...AS A MOIST
PLUME ADVECTS ACROSS THE TROPICAL ATLANTIC CONVECTION IS TO
INTENSIFY...WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM ACROSS GUYANA TO NORTHWEST SURINAME. OVER NORTHEAST
SURINAME TO FRENCH GUIANA EXPECTING HIGHER AMOUNTS WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-40MM.

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

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




Last Updated: 223 PM EDT MON APR 20 2015