Prognostic Meteorological Discussion
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FXCA20 KWBC 251826
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EDT TUE APR 25 2017

TROPICAL DISCUSSION FROM APRIL 25/12 UTC: WEST OVER THE DOMAIN...A
500 HPA HIGH SOUTH OF COLIMA/NAYARIT IN SOUTHWEST MEXICO ANCHORS A
RIDGE OVER THE EASTERN PACIFIC. CONSISTENT WITH PREVIOUS FORECASTS
THE RIDGE IS TO BUILD EAST ACROSS CENTRAL AMERICA TO THE CENTRAL
CARIBBEAN LATER ON WEDNESDAY...WHERE IT IS TO THEN HOLD THROUGH
THURSDAY. AS IT BUILDS ACROSS CENTRAL AMERICA-THE CARIBBEAN TO
NORTHERN SOUTH AMERICA THE RIDGE WILL SUSTAIN A WEAK MID LEVEL CAP
THAT IS TO FAVOR EROSION OF AVAILABLE MOISTURE AND A DRYING TREND.
OVER SOUTHERN MEXICO...INITIALLY EXPECTING RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM. THROUGH THURSDAY ACTIVITY BECOMES
WIDELY ISOLATED. OVER CENTRAL AMERICA...DIURNAL CONVECTION IS TO
CLUSTER ACROSS SOUTHERN HONDURAS-NORTHERN EL SALVADOR...WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-30MM THROUGH
WEDNESDAY MORNING. ON WEDNESDAY TO THURSDAY...AS THE MID LEVEL
RIDGE STRENGTHENS...IT DECREASES TO 00-05MM/DAY AND MAXIMA OF
10MM. OVER SOUTHERN CENTRAL AMERICA...MEANWHILE...EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. HIGHER AMOUNTS
ARE EXPECTED OVER NORTHERN SOUTH AMERICA. OVER WESTERN COLOMBIA
THE PANAMANIAN LOW/TROUGH IS TO INTENSIFY EARLY THIS
AFTERNOON...TO SUSTAIN A MOIST ONSHORE FLOW ACROSS THE WESTERN
PLAINS TO THE ANDEAN REGION. THIS WILL FEED ORGANIZED CONVECTION
THIS AFTERNOON...WITH ACCUMULATION OF 15-30MM/DAY AND MAXIMA OF
40-80MM/DAY TO CLUSTER ON THE CAUCA/CAUCA VALLEY TO THE SOUTHWEST.
ON WEDNESDAY TO THURSDAY THIS DECREASES TO 10-15MM/DAY AND MAXIMA
OF 20-40MM....WHILE ON THURSDAY AND FRIDAY THE MAXIMA PEAKS AT
15-20MM. OVER NORTHERN COLOMBIA/NORTHWEST VENEZUELA INITIALLY
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM.
THROUGH THURSDAY/FRIDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA
OF 15-20MM. OVER AMAZONIA IN SOUTHERN VENEZUELA-SOUTHEAST COLOMBIA
EXPECT RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. NOTE
THAT ON FRIDAY EXPECTING A SURGE IN ACTIVITY AS A SOUTHERN
HEMISPHERE WIND SURGE SPREADS ACROSS NORTHWEST BRASIL-PERU TO
SOUTHERN COLOMBIA. THIS WILL LIKELY FAVOR AN MCS WITH ACCUMULATION
OF 20-35MM/DAY AND MAXIMA OF 50-100MM. OVER THE NORTHERN GUIANAS
PASSING SHOWERS ARE TO TRIGGER LIGHT CONVECTION ALONG THE COAST.
ORGANIZED CONVECTION WILL CONFINE TO THE NEAR EQUATORIAL TROUGH TO
THE SOUTH...WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF
15-20MM/DAY THROUGH WEDNESDAY...INCREASING TO 10-15MM/DAY AND
MAXIMA OF 20-35MM/DAY ON THURSDAY-FRIDAY.

NORTH OF THE MID LEVEL RIDGE...A POLAR TROUGH IS PULLING ACROSS
THE SOUTHWEST USA. THE TROUGH IS FORECAST TO BOTTOM OUT ALONG THE
MEXICO/USA BORDER EARLY ON WEDNESDAY MORNING...WITH AXIS TO THEN
PULL AS IT MOVES ACROSS THE CENTRAL USA LATER IN THE DAY. AT LOW
LEVELS THE TROUGH WILL SUSTAIN A SURFACE FRONT THAT MOVES TO SOUTH
TEXAS/RIO BRAVO BASIN LATER ON WEDNESDAY. HOWEVER...LACKING UPPER
LEVEL SUPPORT...THIS IS TO HAVE LITTLE TO NO IMPACT ACROSS MEXICO.

FARTHER EAST...AT 500 HPA...A POLAR TROUGH EXTENDS OVER THE
EASTERN USA/WESTERN ATLANTIC...WHILE A RIDGE LIES TO THE EAST. AS
IT LIFTS OVER THE RIDGE TO THE EAST THE TROUGH IS BECOMING
NEGATIVELY TILTED...WITH AXIS TO MOVE ACROSS THE DOMINICAN
REPUBLIC TO PUERTO RICO LATER THIS AFTERNOON. ON WEDNESDAY
AFTERNOON IT IS TO THEN MOVE TO THE EAST-NORTHEAST OF THE ISLAND
CHAIN. AT 250 HPA A SUBTROPICAL JET LIES TO THE SOUTH. AS IT
ROUNDS THE BASE OF THE UPPER LEVEL TROUGH IT IS TO THEN EXIT JUST
SOUTH OF PUERTO RICO EARLY THIS AFTERNOON. THIS IS TO THEN FAVOR
AN UPPER DIVERGENT PATTERN ACROSS PUERTO RICO-VIRGIN
ISLES-NORTHERN LEEWARD ISLES THAT IS TO VENT DEEP CONVECTION. AT
LOW LEVELS THIS SUSTAINS A POLAR TROUGH OVER THE WESTERN ATLANTIC
WITH ASSOCIATED FRONT TRAILING ACROSS THE BAHAMAS-CUBA TO THE GULF
OF MEXICO. BOUNDARY IS TO REMAIN NEARLY STATIONARY WHILE GRADUALLY
WEAKENING ON WEDNESDAY. A RIDGE LIES TO THE EAST OF THIS
TROUGH...SUSTAINING A MOIST SOUTHEASTERLY FLOW ACROSS THE LESSER
ANTILLES-PUERTO RICO/EASTERN HISPANIOLA. OVER THE NORTHEAST
CARIBBEAN ISLES THIS FAVORS A HIGH MOISTURE CONTENT...WITH PWAT OF
NEARLY 50MM. LATER ON WEDNESDAY...AS THE FRONT/POLAR TROUGH
WEAKENS TO THE WEST...THE RIDGE WILL BUILD ACROSS THE GREATER
ANTILLES/NORTHERN CARIBBEAN TO THE GULF. THE LOW LEVEL WINDS WILL
THEN BACK TO THE EAST ACROSS THE ENTIRE BASIN...AND THIS IS TO
PERSIST THROUGH THE END OF THE WEEK. OVER THE CENTRAL/NORTHWEST
BAHAMAS THE WANING FRONT WILL SUSTAIN LIGHT RAINFALL AMOUNTS IN
WIDELY ISOLATED CONVECTION. OVER EASTERN CUBA-JAMAICA AND HAITI
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.
AS THE UPPER LEVEL TROUGH PULLS ACROSS THE DOMINICAN REPUBLIC TO
WESTERN PUERTO RICO IT WILL SUSTAIN RAINFALL AMOUNTS OF
20-35MM/DAY AND MAXIMA OF 50-100MM. ON WEDNESDAY-THURSDAY IT
DECEASES TO 05-10MM/DAY AND MAXIMA OF 15-25MM. OVER EASTERN PUERTO
RICO-NORTHERN LEEWARDS EXPECTING ACCUMULATION OF 10-15MM/DAY AND
MAXIMA OF 20-30MM THROUGH TUESDAY MORNING...AND TRACE AMOUNTS
THEREAFTER. FARTHER SOUTH...THE MOIST INFLOW ACROSS THE NORTHERN
FRENCH/SOUTHERN LEEWARD ISLES IS TO FAVOR SCATTERED CONVECTION
THROUGH WEDNESDAY MORNING WITH ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15MM. ON WEDNESDAY-THURSDAY IT DECREASES TO 00-05MM/DAY
AND MAXIMA OF 10MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96       TYPE
12W      14W    16W    18W    20W    23W    DISSIPATES       TW
45W      48W    51W    54W    56W    60W    64W    68W       TW
59W      61W    64W    67W    70W    73W    76W    79W       TW

A NEW TROPICAL WAVE IS INITIALIZED ALONG 12W AND SOUTH OF 09N.
THIS...HOWEVER...IS FORECAST TO DISSIPATE LATER ON THURSDAY.

A TROPICAL WAVE IS INITIALIZED ALONG 45W AND SOUTH OF 05N. THE
WAVE ENTERS AMAPA IN BRASIL/EASTERN FRENCH GUIANA EARLY ON
WEDNESDAY MORNING...TO THEN MOVE ACROSS SOUTHERN FRENCH GUIANA
LATER IN THE DAY...WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM. THIS SPREADS ACROSS SURINAME TO
GUYANA ON WEDNESDAY-THURSDAY...WHERE IT IS TO FAVOR SIMILAR
RAINFALL AMOUNTS. ON THURSDAY THIS INCREASES TO 10-15MM/DAY AND
MAXIMA OF 20-35MM WHILE SPREADING ACROSS SOUTHERN VENEZUELA.

A TROPICAL WAVE IS INITIALIZED ALONG 59W AND SOUTH OF 05N. IT
MOVES TO SOUTHERN VENEZUELA EARLY ON WEDNESDAY WHERE IT IS TO
TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM.
ACROSS SOUTHEAST COLOMBIA IT IS TO THEN TRIGGER RAINFALL AMOUNTS
OF 10-15MM/DAY AND MAXIMA OF 20-35MM ON THURSDAY.

GAJADHAR...SLMS (SAINT LUCIA)
SUBRATH-ALI...TTMS (TRINIDAD AND TOBAGO)
DAVISON/GALVEZ...WPC (USA)
$$




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