Prognostic Meteorological Discussion
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FXCA20 KWBC 291809
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 PM EDT WED MAR 29 2017

TROPICAL DISCUSSION FROM MARCH 29/12 UTC: CONSISTENT WITH PREVIOUS
FORECASTS A MID/UPPER LEVEL TROUGH DOMINATES THE FLOW OVER THE
WESTERN USA-NORTHERN STATES OF MEXICO. THE TROUGH...WHILE PRESSING
AGAINST A RIDGE TO THE EAST...IS TO SLOWLY MOVE TO THE CENTRAL USA
LATER ON THURSDAY. IT IS TO THEN LIFT TO ACROSS THE EASTERN USA ON
FRIDAY AS ANOTHER TROUGH ENTERS THE WESTERN USA-BAJA PENINSULA. AT
LOW LEVELS...THE ASSOCIATED FRONTS ARE TO BOTTOM OUT ALONG THE
MEXICO-USA BORDER...WITH MOST ACTIVE CONVECTION EXPECTED OVER THE
USA. OVER MEXICO CONVECTION WILL LIMIT TO THE CENTRAL STATES OF
GUERRERO-PUEBLA-MEXICO-DF...WHERE DIURNAL CONVECTION IS TO RESULT
IN RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM THROUGH
THURSDAY MORNING...AND 05-10MM/DAY AND MAXIMA OF 15MM ON THURSDAY
TO FRIDAY. ON FRIDAY-SATURDAY ACTIVITY IS TO GRADUALLY BECOME
SPARSE AS MID LEVEL RIDGE BUILDS TO THE SOUTH.

A BROAD MID/UPPER LEVEL TROUGH EXTENDS OVER THE WESTERN
ATLANTIC...WHILE THE AFOREMENTIONED RIDGE LIES ACROSS THE EASTERN
USA. THROUGH THURSDAY EVENING THE TROUGH IS TO SLOWLY PULL WHILE
THE RIDGE MOVES TO THE WESTERN ATLANTIC/NORTHERN CARIBBEAN ISLES.
THE RIDGE WILL THEN HOLD THROUGH THE WEEKEND/EARLY NEXT WEEK. AS
THE RIDGE STRENGTHENS ITS FOOTHOLD OVER THE NORTHERN CARIBBEAN
ISLES...IT IS TO FAVOR A TRADE WINDS CAP. THIS IS TO THEN SUSTAIN
EROSION OF AVAILABLE MOISTURE THROUGH THURSDAY MORNING...WITH DRY
AND STABLE CONDITIONS TO GENERALLY DOMINATE THE NORTHERN CARIBBEAN
ISLES THROUGH SATURDAY MORNING. AT LOW LEVELS...THE MID LEVEL
TROUGH SUSTAINS AN OCCLUDING LOW OVER THE CENTRAL ATLANTIC WHILE A
WEAK FRONT SURGES ACROSS THE NORTHERN LEEWARD WHILE TRAILING
ACROSS THE GREATER ANTILLES/ NORTHERN CARIBBEAN. A BROAD RIDGE
OVER THE BAHAMAS/CUBA IS TO THEN FAVOR A NORTHERLY FLOW ACROSS THE
GREATER ANTILLES DURING THE NEXT COUPLE OF DAYS...DRIVING THE
FRONT SOUTH OF PUERTO RICO-HISPANIOLA INTO THE NORTHERN CARIBBEAN.
THE  PREVAILING EASTERLIES RETURN TO THE NORTHERN CARIBBEAN LATER
IN THE WEEK. THE NORTHERLIES WILL DRIVE SEA BREEZE CONVERGENCE TO
CENTRAL PORTIONS OF HISPANIOLA-PUERTO RICO DURING THE DAY
TODAY...TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND LOCALIZED
MAXIMA OF 10MM. ON THURSDAY-FRIDAY...AS A DRYER AIR MASS
ENTRENCHES ACROSS THE NORTHEAST CARIBBEAN ISLES... EXPECTING A
DECREASE IN ACTIVITY. ALTHOUGH ACTIVITY OVER THE NORTHERN
CARIBBEAN ISLES WANES...MOISTURE IS TO CONVERGE ALONG THE SURFACE
FRONT AS IT MEANDERS OVER THE FRENCH/LEEWARD ISLES. IN THIS AREA
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM OVER
THE NEXT COUPLE OF DAYS.

A WETTER PATTER IS POSSIBLE OVER THE NORTHEAST CARIBBEAN ISLES
LATER DURING THE WEEKEND...WHEN REMNANTS OF THE SURFACE FRONT ARE
TO RETROGRESS TO THE VIRGIN ISLES/PUERTO RICO. THIS WILL BE
ACCOMPANIED BY HIGHER MOISTURE CONTENT...WITH MODELS SHOWING
POTENTIAL FOR SCATTERED CONVECTION. THE GFS...IN CONTRAST TO THE
EUROPEAN MODELS...SHOWS DEEPER MOISTURE AND HIGHER RAINFALL
AMOUNTS. BUT AS THE MID LEVEL RIDGE IS TO HOLD THROUGHOUT THE
WEEKEND...CONDITIONS MIGHT NOT BE AS FAVORABLE AS THE GFS
SUGGESTS. AS A RESULT...DURING THAT TIME PERIOD WE ONLY FORESEE
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM TO AFFECT
PUERTO RICO-VIRGIN ISLES/NORTHERN LEEWARD ISLES.

AT 250 HPA...A HIGH NEAR 06N 45W EXTENDS A RIDGE ACROSS NORTHERN
SOUTH AMERICA TO CENTRAL AMERICA/EASTERN PACIFIC. MODELS CONTINUE
TO FORECAST A PERSISTENT SUBEQUATORIAL RIDGE PATTERN...WITH LITTLE
TO NO MODULATION EXPECTED OVER THE NEXT FEW DAYS. AS THE UPPER
LEVEL RIDGE HOLDS...IT IS TO VENT DIURNAL CONVECTION ACROSS
NORTHERN SOUTH AMERICA. ACROSS THE GUIANAS DIURNAL CONVECTION IS
TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM...WITH
GRADUAL INCREASE ON WEDNESDAY TO THURSDAY UNDER INFLUENCE OF A
TROPICAL WAVE (SEE BELOW). OVER SOUTHERN-CENTRAL VENEZUELA AND
AMAZONIA/PIEDEMONTE LLANERO OVER COLOMBIA EXPECTING RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM THROUGH THURSDAY
MORNING...WHILE ON FRIDAY-SATURDAY THE MAXIMA IS TO PEAK AT
25-50MM/DAY. ON THE ANDEAN REGION AND WESTERN PLAINS OF COLOMBIA
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM/DAY. ON THE SIERRA NEVADA TO THE NORTH AND NORTHWEST
VENEZUELA INITIALLY EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-40MM. THROUGH FRIDAY IT DECREASES TO 05-10MM/DAY AND
MAXIMA OF 15-25MM. THE RIDGE ALOFT IS TO ALSO VENT DIURNAL
CONVECTION ACROSS CENTRAL AMERICA. ACROSS COSTA RICA TO WESTERN
PANAMA EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM. OVER NORTHERN CENTRAL AMERICA CONVECTION IS TO CLUSTER
OVER SOUTHERN GUATEMALA-EL SALVADOR-SOUTHERN HONDURAS...WITH FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM/DAY. THROUGH
FRIDAY...HOWEVER...THE MAXIMA WILL INCREASE TO 15-20MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96       TYPE
46W      48W    50W    53W    56W    59W    62W    66W       TW

A TROPICAL WAVE IS INITIALIZED ALONG 46W AND SOUTH OF 10N. A TRADE
WIND SURGE TRAILS THIS PERTURBATION...AND THROUGH FRIDAY AFTERNOON
IT IS TO ENVELOP THE TROPICAL ATLANTIC/NORTHERN GUIANAS. AS IT
PULLS ACROSS FRENCH GUIANA/AMAPA IN BRASIL THIS IS TO FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM. ON THURSDAY
TO FRIDAY IT IS TO THEN FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM ACROSS SURINAME TO GUYANA...WHILE OVER RORAIMA
IN BRASIL/AMAZONIA IN VENEZUELA IT IS TO SUSTAIN RAINFALL AMOUNTS
OF 10-15MM/DAY AND MAXIMA OF 20-40MM ON SATURDAY.

JIMENEZ...IMN (COSTA RICA)
SUBRATH-ALI...TTMS (TRINIDAD AND TOBAGO)
DAVISON/GALVEZ...WPC (USA)
$$




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