HPC Caribbean Forecast Discussion

Hydrometeorological Prediction Center

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
227 PM EDT MON MAY 21 2012

DISCUSSION FROM MAY 21/00 UTC: WIDE MID/UPPER TROUGH PATTERN
EXTENDS OVER THE USA...WHILE RIDGE PATTERN DOMINATES TO THE
SOUTHEAST OVER MOST OF CARIBBEAN. SHORT WAVE TROUGHS EXTEND TO THE
SOUTH OF MAIN TROUGHS. ONE SHORT WAVE TROUGH EXTENDS INTO EASTERN
MEXICO/EXTREME NORTHWEST CENTRAL AMERICA AND IS FORECAST TO
MEANDER OVER THE REGION WHILE TROUGHS PUSH OVER THE
CENTRAL/EASTERN USA...AND RIDGE PERSISTS TO THE SOUTHEAST.
MID/UPPER TROUGH HAS BEEN ENHANCING CONVECTION OVER EXTREME
SOUTHEASTERN MEXICO AND NORTHWEST CENTRAL AMERICA INCLUDING THE
GULF OF HONDURAS AND WEST INTO THE CAYMAN ISLANDS. A SHORT WAVE
PULSE IS PROGRESSING TO THE NORTHEAST AND IS FORECAST TO INTENSIFY
AS IT CROSSES INTO CUBA BY 24-48 HRS AND INTO THE BAHAMAS LATER IN
THE CYCLE. AT LOW LEVELS...A DEEP MOISTURE POOL PERSISTS OVER THE
REGION WITH PWAT EXCEEDING 60MM OVER WESTERN CARIBBEAN. OVER THE
GULF OF HONDURAS...AN INDUCED TROUGH ENHANCING LOW-LEVEL
CONVERGENCE AND PRODUCING WIDESPREAD DEEP CONVECTION...WITH
STRONGEST AFFECTING THE CAYMAN ISLANDS. AS SHORTWAVE PULSE
PROGRESSES NORTHEASTWARD OVER A VERY FAVORABLE LOW-LEVEL
ENVIRONMENT...EXPECT STRONG CONVECTION TO CONTINUE AND INTENSIFY
AS IT MOVES OVER CUBA AND INTO THE BAHAMAS. ACCORDINGLY...EXPECT
ACCUMULATIONS TO INCREASE TO 15-20MM/DAY WITH MAXIMA OF
35-70MM/DAY THROUGH 36 HRS...AND THEN TO 25-50MM/DAY WITH MAXIMA
OF 75-100 MM/DAY BY 36-60 HRS. ONCE SURFACE LOW/UPPER SHORT WAVE
MOVE NORTHEASTWARD...PRECIPITATIONS WILL DECREASE TO 15-30MM/DAY
WITH MAXIMA OF 40-80MM/DAY BY 60-84 HRS. OVER THE BAHAMAS...EXPECT
HEAVIEST PRECIPITATION TO DEVELOP BY 60-84 HRS...WHERE EXPECTING
ACCUMULATIONS DE 15-30MM/DAY WITH MAXIMA OF 40-80MM/DAY.

OVER SOUTHERN MEXICO...EXPECT BOUNDARY-LAYER MOISTURE TO GRADUALLY
INCREASE DURING THE CYCLE...WHILE CYCLONES CONTINUE DEVELOPING TO
THE SOUTHEAST OVER THE EASTERN PACIFIC. FURTHERMORE...MID/UPPER
TROUGH PATTERN WILL FURTHER ENHANCE CONVECTION TO PRODUCE
ACCUMULATIONS INCREASING TO 05-10MM/DAY WITH MAXIMA OF 15-20MM/DAY
BY 60-84 HRS OVER SOUTHERN MOUNTAINS OF GUERRERO AND OAXACA.
SCATTERED CONVECTION WILL ALSO BE PRESENT OVER YUCATAN AND THE
SOUTHERN GULF COAST UNDER INFLUENCE OF MID/UPPER TROUGH AND WHILE
LARGE MOISTURE POOL PERSISTS. EXPECT ACCUMULATIONS GRADUALLY
DECREASING FROM 10-15MM/DAY WITH MAXIMA OF 20-35MM/DAY THROUGH 36
HRS...TO 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY BY 36-60 HRS.

OVER NORTHERN CENTRAL AMERICA...MID/UPPER TROUGH CONTINUES
INDUCING LOW-LEVEL TROUGH OVER HONDURAS AND NORTH INTO GULF OF
HONDURAS/WESTERN CUBA/SOUTHEASTERN FLORIDA. FURTHERMORE...EASTERLY
WAVE OVER WESTERN CARIBBEAN WILL SOON BE ABSORBED TO FURTHER
ENHANCE LOW-LEVEL CONVERGENCE OVER THE REGION. EXPECT ACTIVE
PATTERN TO CONTINUE TO PRODUCE LOCALLY HEAVY RAINS OVER THE
MOUNTAINS OF GUATEMALA/EL SALVADOR AND HONDURAS...AND PARTS OF
BELIZE...WHERE ACCUMULATIONS OF 15-20MM/DAY AND MAXIMA OF
35-70MM/DAY THROUGH 36 HRS INCREASING TO 15-30MM/DAY AND MAXIMA OF
40-80MM/DAY BY 36-60 HRS...GRADUALLY DECREASING AFTERWARDS. ACTIVE
PATTERN IS ALSO EXPECTED TO PERSIST OVER NICARAGUA WITH
ACCUMULATIONS IN THE ORDER OF 10-15MM/DAY WITH MAXIMA OF
20-35MM/DAY THROUGH THE CYCLE.

FURTHER SOUTH...EASTERN PACIFIC ITCZ REMAINS WELL TO THE NORTH OF
ITS CLIMATOLOGICAL POSITION AND WILL CONTINUE STIMULATING AN
ACTIVE CONVECTIVE PATTERN OVER COSTA RICA AND PANAMA. MID-LEVEL
RIDGE IS FORECAST TO REMAIN IN PLACE OVER CARIBBEAN AND EXTEND TO
THE SOUTHWEST INTO SOUTHERN CENTRAL AMERICA. A WEAK EASTERLY WAVE
WILL ENHANCE CONVECTIVE ACTIVITY LATE IN THE CYCLE.
INITIALLY...EXPECT ACCUMULATIONS OF 10-15MM/DAY WITH MAXIMA OF
20-40MM/DAY GRADUALLY INCREASING TO 15-20MM/DAY WITH MAXIMA OF
35-70MM/DAY BY 60-84 HRS.

TO THE EAST OVER THE NORTHEASTERN ISLES...SUBSIDENCE INVERSION IS
FORECAST TO CONTINUE STRENGTHENING WHILE MID-LEVEL RIDGE CONTINUES
BUILDING OVER THE REGION. FRESH SOUTHEASTERLY WINDS OF 15-20KT ARE
FORECAST TO CONTINUE THROUGH THE CYCLE. MODELS ARE ALSO SHOWING A
DECREASE IN BOUNDARY-LAYER MOISTURE AS DRIER AIR MASS IS ADVECTED
FROM THE EAST/SOUTHEAST WHILE INVERSION STRENGTHENS. EXPECT
GENERALLY FAIR WEATHER WITH A FEW ISOLATED MODERATE
SHOWERS...WHILE STRONG LOW-LEVEL WINDS INTERACT WITH
OROGRAPHY...MODULATING PATTERN OF SHALLOW CONVECTION. EXPECT
HEAVIEST PRECIPITATION EARLY IN THE CYCLE WITH ACCUMULATIONS OF
05-10MM/DAY AND ISOLATED MAXIMA OF 15MM/DAY...DECREASING THROUGH
THE CYCLE.

OVER NORTHERN SOUTH AMERICA...EXPECT MOST ACTIVE CONVECTION TO
PERSIST OVER COLOMBIA...WHILE DRIER PATTERN CONTINUES OVER
VENEZUELA. OVER THE GUYANAS/EASTERN VENEZUELA...PRECIPITATION WILL
BE MODULATED BY ARRIVING TROPICAL WAVE...WITH POSITION DESCRIBED
IN THE FOLLOWING. OVER COLOMBIA...EXPECT ACCUMULATIONS OF
10-15MM/DAY WITH ISOLATED MAXIMA OF 20-35MM/DAY TO PERSIST THROUGH
THE CYCLE. OVER SOUTHERN VENEZUELA...EXPECTING LIGHTER
ACCUMULATIONS WITH MAXIMA OF 15-20MM/DAY THROUGH THE CYCLE. OVER
THE GUIANAS...EXPECT ACCUMULATIONS TO INCREASE TO 05-10MM/DAY AND
MAXIMA OF 15-25MM/DAY BY LATE CYCLE...AS TROPICAL WAVE ARRIVES
FROM THE ATLANTIC.

PERTURBATIONS IN THE EASTERLIES...INITIALIZED AT 12UTC

INITIAL    24    36    48    60    72    84    TYPE
85W        DISSIPATES                          TW
75W        76W   77W   78W   80W   81W   82W   EW
47W        48W   51W   55W   59W   63W   66W   TW

MARINERO...DGOA/MARN (EL SALVADOR)
SOLORZANO...SMN (HONDURAS)
GALVEZ...HPC (USA)