Prognostic Meteorological Discussion
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FXCA20 KWBC 171849
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 PM EST FRI NOV 17 2017

TROPICAL DISCUSSION FROM NOV 17/12 UTC: MID/UPPER LEVEL RIDGE
ACROSS WESTERN PORTIONS OF THE DOMAIN DOMINATES THE FLOW ACROSS
NORTHERN/CENTRAL MEXICO AND THE SOUTHERN USA WHILE CENTERING ON A
CLOSED HIGH OVER MEXICO NEAR 22N 101W. CONSISTENT WITH PREVIOUS
FORECAST THE BROAD UPPER RIDGE PATTERN IS TO PERSIST THROUGH
SATURDAY MORNING. LATER IN THE DAY...IT WILL START TO CRUMBLE
UNDER PRESSURE FROM AMPLIFYING POLAR TROUGH OVER THE USA. AS THE
RIDGE COLLAPSES...ASSOCIATED CAP INVERSION ACROSS MEXICO IS TO
GRADUALLY WEAKEN. BROAD POLAR TROUGH IS TO THEN DOMINATE THE FLOW
ACROSS THE USA-GULF OF MEXICO LATER DURING THE WEEKEND. AT LOW
LEVELS THE TROUGH ALOFT IS TO SUSTAIN A PROGRESSIVE FRONT THAT
MOVES TO NORTHERN FLORIDA/NORTHERN GULF OF MEXICO-TAMAULIPAS EARLY
ON SUNDAY MORNING. THE FRONT SLIDES ACROSS THE FLORIDA PENINSULA
TO THE NORTHWEST BAHAMAS EARLY ON MONDAY MORNING...WHILE TRAILING
END MEANDERS OVER THE GULF TO NORTHEAST STATES OF MEXICO. OVER
SOUTHERN TAMAULIPAS/NORTHERN VERACRUZ THIS WILL SUSTAIN RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM....WHILE ACROSS
SOUTHERN VERACRUZ-CHIAPAS THE FRONTAL NORTHERLIES WILL FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.

THE FRONT IS TO ALSO FAVOR A PREFRONTAL SHEAR LINE THAT MOVES OVER
THE CENTRAL BAHAMAS-CENTRAL CUBA-CAYMAN ISLES LATER ON SUNDAY. ON
MONDAY MORNING IT MOVES TO THE SOUTHEAST BAHAMAS-TURKS AND
CAICOS/JAMAICA WHILE TRAILING TO NORTHEAST NICARAGUA. ACROSS THE
CENTRAL BAHAMAS-CENTRAL CUBA THIS WILL TRIGGER RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM. OVER THE CAYMAN ISLES ALSO
EXPECTING ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM. ON
MONDAY...IT IS TO THEN TRIGGER SCATTERED CONVECTION ACROSS THE
SOUTHEAST BAHAMAS-TURKS AND CAICOS...WITH ACCUMULATION OF
00-05MM/DAY AND MAXIMA OF 10MM. ACROSS JAMAICA EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM...WHILE OVER NORTHEAST
HONDURAS/ NICARAGUA EXPECTING ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15-20MM.

A LONG WAVE TROUGH TO THE EAST FLANKS THE EASTERN FRINGES OF THE
CONTINENTAL RIDGE...WITH MID/UPPER LEVEL AXIS EXTENDING FROM THE
WESTERN ATLANTIC...ACROSS CUBA TO THE WESTERN CARIBBEAN/NORTHERN
CENTRAL AMERICA. BUT AS THE RIDGE TO THE WEST COLLAPSES...THE
TROUGH WILL THEN BEGIN TO PULL TO THE EAST-NORTHEAST. OVER THE
CENTRAL/WESTERN CARIBBEAN THIS WILL THEN WEAKEN TO A SHEAR AXIS
LATER DURING THE WEEKEND...WHILE TO THE NORTH IT GRADUALLY PULLS
AWAY. AS THE TROUGH OVER THE CARIBBEAN WEAKENS IT WILL MAKE WAY
FOR A CELL OF THE SUBEQUATORIAL RIDGE TO BUILD ACROSS THE ISLAND
CHAIN TO THE EASTERN CARIBBEAN LATER ON SUNDAY/MONDAY. THE
BUILDING RIDGE IS TO THEN FAVOR A TRADE WINDS CAP. ON
SUNDAY-MONDAY THE INVERSION IS TO LINGER AROUND 500/600
HPA...WHILE LATER ON MONDAY-TUESDAY IT DROPS TO AROUND 700 HPA.

AT LOW LEVELS...WANING FRONT EXTENDS ACROSS THE CENTRAL/SOUTHEAST
BAHAMAS AS ANOTHER BOUNDARY SURGES ACROSS FLORIDA TO THE ISLANDS.
EARLY ON SATURDAY MORNING THIS MOVES TO THE CENTRAL
BAHAMAS-CENTRAL CUBA. LATER ON SATURDAY IT IS TO MEANDER NORTH TO
THE NORTHWEST BAHAMAS...TO DISSIPATE EARLY ON SUNDAY MORNING. AS
IT ENTERS THE BAHAMAS THIS SUSTAINS A PREFRONTAL SHEAR LINE OVER
THE ISLANDS TO CUBA. LATER TODAY THIS MOVES ACROSS THE TURKS TO
NORTHERN HISPANIOLA...WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. ON SATURDAY THIS BOUNDARY
BECOMES ILL DEFINED.

SOUTH OVER THE BASIN...THE UPPER LEVEL TROUGH CONTINUES TO
INTERACT WITH LOW LEVEL TROUGH MEANDERING OVER THE CENTRAL
CARIBBEAN. THIS TROUGH SUSTAINS A MOIST SOUTHWESTERLY FLOW ACROSS
THE CENTRAL CARIBBEAN...WITH DEEP TROPICAL MOISTURE CONVERGING
ACROSS HISPANIOLA-PUERTO RICO/VIRGIN ISLES. THIS PATTERN HOLDS
THROUGH MIDDAY ON SATURDAY...WITH WINDS BACKING TO THE
SOUTH-SOUTHEAST LATER IN THE DAY. ON MONDAY TO TUESDAY PREVAILING
EASTERLY TRADES RETURN TO THE EASTERN CARIBBEAN. AS THE WINDS BACK
TO THE SOUTHEAST...IT WILL CUTOFF THE SUPPLY OF DEEP TROPICAL
MOISTURE...WITH GLOBAL MODEL GUIDANCE AGREEING ON GRADUAL EROSION
OF AVAILABLE WATER EARLY NEXT WEEK AS MID LEVEL RIDGE STRENGTHENS.
THE GFS GDI FORECAST RESPONDS IN KIND...SHOWING A CONVECTIVELY
UNSTABLE AIR MASS ENVELOPING PUERTO RICO AND THE USVI THROUGH
MIDAFTERNOON ON SUNDAY...AND HAITI/DOMINICAN REPUBLIC THROUGH
TUESDAY. OVER THE NEXT FEW DAYS THIS WILL LIKELY FAVOR SCATTERED
DEEP CONVECTION...WITH MCS ACTIVITY LIKELY TO DEVELOP ON THE
CARIBBEAN COASTAL WATERS OF HISPANIOLA/MONA PASSAGE. IN THIS AREA
EXPECTING RAINFALL AMOUNTS OF 20-40MM/DAY AND MAXIMA OF 50-100MM
THROUGH SATURDAY MORNING. ON SATURDAY-SUNDAY IT DECREASES TO
15-20MM/DAY AND MAXIMA OF 30-60MM...WHILE ON SUNDAY EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. ACROSS
PUERTO RICO THIS IS TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM/DAY. ON SATURDAY IT INCREASES TO 15-20MM/DAY AND
MAXIMA OF 30-60MM. ON SUNDAY...AS THE TRADE WINDS CAP STARTS TO
STRENGTHEN...IT WILL DECREASE TO 05-10MM/DAY AND MAXIMA OF 15-20MM
IN SHALLOW CONVECTION.

SOUTH OVER THE BASIN...FOCUS OF THE HEAVY CONVECTION SHIFTS TO
NORTHERN COLOMBIA EARLY IN THE CYCLE...TO SUSTAIN RAINFALL AMOUNTS
OF 15-20MM/DAY AND MAXIMA OF 30-60MM. ON SATURDAY IT DECREASES TO
10-15MM/DAY AND MAXIMA OF 20-40MM...WHILE BUILDING EAST ACROSS
NORTHWEST VENEZUELA. ON SUNDAY...CONVERGENCE ALONG THE NEAR
EQUATORIAL TROUGH IS TO THEN SUSTAIN RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM. ON THE ANDEAN REGION/WESTERN
COLOMBIA...MEANWHILE...EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-30MM. OVER COSTA RICA-PANAMA EXPECT RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. ACROSS VENEZUELA MOST
ACTIVE IS EXPECTED OVER AMAZONIA TO THE SOUTH...WITH ACCUMULATION
OF 05-10MM/DAY AND MAXIMA OF 15-20MM...INCREASING TO 10-15MM/DAY
AND MAXIMA OF 20-35MM ON SUNDAY.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24    36    48    60    72    84    96    TYPE        SOF
42W      44W   46W   49W   52W   54W   56W   57W    EW          12N
67W      68W   69W   70W   71W   72W   73W   74W    EW          15N

AN EASTERLY WAVE IS INITIALIZED ALONG 42W TO 12N. THIS REACHES
FRENCH GUIANA LATER ON SATURDAY/EARLY SUNDAY MORNING WHERE IT IS
TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY. ACROSS SURINAME IT IS TO
FAVOR SIMILAR RAINFALL AMOUNTS. MOST ACTIVE IS EXPECTED TO THE
NORTH ALONG THE ITCZ.

AN EASTERLY WAVE ALONG 67W AND SOUTH OF 16N IS TO SUSTAIN
SCATTERED CONVECTION ACROSS WESTERN VENEZUELA TO EASTERN COLOMBIA
WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15MM. ACROSS
NORTHWEST VENEZUELA TO NORTHERN COLOMBIA THIS IS TO THEN FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM ON SATURDAY
TO SUNDAY...DECREASING TO 00-05MM/DAY AND MAXIMA OF 10MM ON SUNDAY.

GUY...NMS (BELIZE)
PECK...MS (JAMAICA)
RIVAS...SENAMHI (PERU)
DAVISON...WPC (USA)

$$





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