942
FXCA20 KWBC 181703
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1203 PM EST WED NOV 18 2009
DISCUSSION FROM NOV 18/0000 UTC. THE GLOBAL AND REGIONAL MODELS
CONTINUE TO SHOW A TROUGH ENTERING THE WESTERN USA THROUGH 30-36
HRS...AND SLOWLY MOVE ACROSS 95W/100W TO NORTHERN MEXICO THROUGH
72 HRS. AS IT PUSHES INLAND...A TROUGH TO THE EAST IS TO GRADUALLY
PULL NORTH OVER A BLOCKING RIDGE...WITH THE LATTER TO GRADUALLY
DAMPEN THROUGH 60-72 HRS AS IT MOVES TO THE WESTERN ATLANTIC. THE
TROUGH SUPPORTS A SURFACE FRONT WITH AXIS EXTENDING ACROSS
SOUTHERN GEORGIA-THE GULF TO NORTHERN VERACRUZ BY 24 HRS. BY 36
HRS THE TRAILING END WILL RETROGRESSES TO THE NORTHWEST
GULF/SOUTHERN TEXAS...WHERE IT WILL MEANDER THROUGH 48-60 HRS. A
WAVE/LOW IS TO FORM ALONG THIS BOUNDARY BY 60-66 HRS. AS THE LOW
DEVELOPS/DEEPEN...THE FRONT IS TO THEN SURGE ACROSS TAMAULIPAS TO
NORTHERN VERACRUZ BY 84-96 HRS. A WIND SURGE OF 20-30KT IS
EXPECTED OVER THE NORTHWEST GULF IN ASSOCIATION WITH THIS BOUNDARY
LATER IN THE PERIOD. A TEHUANTEPECER WIND OVER SOUTHERN MEXICO IS
FORECAST TO WEAKEN THROUGH 24-36 HRS. AS THE FRONT RETROGRESSES
AND THE WINDS WANE...RAINFALL AMOUNTS OVER SOUTHERN MEXICO WILL
DECREASE TO 10-15MM/DAY AND MAXIMA OF 25-50MM BY 36 HRS. AS THE
WAVE/LOW FORMS ALONG THE FRONT LATER IN THE PERIOD...CONVECTION
ALONG THE RIO BRAVO WILL INCREASE...WITH ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15MM/DAY LATE ON DAY 02...AND
05-10MM/DAY AND MAXIMA OF 20-35MM/DAY ON DAY 03. ALONG THE NORTH
COAST OF HONDURAS BETWEEN ROATAN/LA CEIBA AND SAN PEDRO SULA INTO
PUERTO BARRIOS GUATEMALA/SOUTHERN BELIZE WE EXPECT ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15-25MM/DAY THROUGH 36 HRS. BY 36-84
HRS...AS AN EASTERLY FLOW ESTABLISHES ACROSS THE WESTERN
CARIBBEAN...THE FOCUS OF THE CONVECTION WILL SHIFT NORTH INTO
BELIZE/NORTHERN GUATEMALA...WITH ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15-25MM. LOCALLY HIGHER AMOUNTS ARE QUITE POSSIBLE.
A 500 HPA HIGH NEAR THE CAYMAN ISLANDS ANCHORS A RIDGE OVER THE
WESTERN/CENTRAL CARIBBEAN-WESTERN ATLANTIC. THROUGH 48-60 HRS THE
HIGH WILL MIGRATE SOUTH TO PUERTO LEMPIRA/CABO GRACIAS A DIOS.
THROUGH 60-72 HRS THE RIDGE WILL FLATTEN OVER THE WESTERN
ATLANTIC...WHILE A NARROW RIDGE REMAINS OVER THE WESTERN
CARIBBEAN/NORTHERN CENTRAL AMERICA-CUBA/THE BAHAMAS. THIS SUSTAINS
A STRONG SUBSIDENCE CAP AROUND 650/700 HPA ACROSS THE
BAHAMAS-CUBA-JAMAICA TO THE NORTHWEST CARIBBEAN/NORTHERN CENTRAL
AMERICA. IN A DIURNAL PATTERN...WIDELY ISOLATED SHALLOW CONVECTION
IS TO FAVOR LIGHT/TRACE RAINFALL AMOUNTS OF 00-05MM/DAY TO
CONCENTRATE ACROSS THE BAHAMAS AND NORTHERN PORTIONS OF CUBA.
AS THE SUBSIDENCE CAP PERSISTS INTO PORTIONS OF CENTRAL
AMERICA...ITCZ RELATED CONVECTION IS LIMITING TO COSTA RICA/PANAMA
AND WESTERN COLOMBIA. CONVECTION ACROSS WESTERN PANAMA AND THE
CARIBBEAN PLAINS OF COSTA RICA ARE FORECAST TO GRADUALLY
WANE/WEAKEN AS THE CYCLE PROGRESSES. INITIALLY EXPECT ACCUMULATION
OF 10-15MM/DAY AND MAXIMA OF 25-50MM. THEREAFTER EXPECT
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY. OVER
WESTERN COLOMBIA...TO AFFECT ANDEAN REGION AND PACIFIC COASTAL
PLAINS...EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
20-35MM/DAY. HIGHER AMOUNTS ON THE CAUCA VALLEY ARE TO PEAK AT
20-45MM/DAY. OVER SANTANDERES/SIERRA NEVADA DE SANTA MARTA IN
NORTHERN COLOMBIA AND NORTHWEST VENEZUELA EXPECT ISOLATED TO
SCATTERED CONVECTION TO RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15-25MM/DAY...WITH A DRYING TREND THROUGH DAY 02.
OTHER MAXIMA TO THE SOUTH WILL CONCENTRATE OVER AMAZONIA IN
SOUTHERN COLOMBIA AND VENEZUELA...WITH ACCUMULATION OF 05-10MM/DAY
AND MAXIMA OF 15-25MM/DAY.
OVER THE NORTHEAST CARIBBEAN...MEANWHILE...PATTERN IS STARTING TO
CHANGE AS A TUTT STARTS TO MIGRATE TO THE EAST. AS THE TUTT
PULLS...A RIDGE IS TO GRADUALLY ESTABLISH OVER THE EASTERN
CARIBBEAN BY THE END OF THE CYCLE...WITH GENERAL TENDENCY TO
FAVOR/SUSTAIN A GRADUAL DRYING TREND OVER THE NORTHEAST CARIBBEAN
ISLAND THROUGH DAY 04/05. AT MID/LOW LEVELS...A SHORT WAVE TROUGH
IS TO MEANDER NORTH OF THE ISLANDS THROUGH 36-42 HRS...AND THEN
PULLS WEST INTO HISPANIOLA BY 48-60 HRS...WHERE IT IS EXPECTED TO
REMAIN. UNFAVORABLE JET DYNAMICS ALOFT...AS THE CONVERGENT/RIGHT
EXIT REGION REMAINS TO THE NORTH OF THE ISLANDS...IS LIKELY TO
INHIBIT ORGANIZED HEAVY RAINFALL AMOUNTS ACROSS PUERTO
RICO-DOMINICAN REPUBLIC AND THE VIRGIN ISLANDS. WE NOW PROJECT
RAINFALL AMOUNTS OF 00-05MM/DAY AND ISOLATED MAXIMA OF 10-15MM
DURING THE NEXT THREE DAYS. MOST ACTIVE CONVECTION IS EXPECTED
ACROSS THE ISLAND CHAIN...WITH ACTIVITY TO PEAK THROUGH 48-72 HRS
WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. MOST
INTENSE IS EXPECTED TO THE SOUTH OVER THE WINDWARD ISLANDS/ORINOCO
DELTA REGION...WHERE THE MAXIMA IS TO PEAK AT 20-35MM/DAY LATER IN
THE CYCLE.
CANALES...SMN (HONDURAS)
DAVISON...NCEP (USA)
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