Prognostic Meteorological Discussion
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FXCA20 KWBC 201938
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 PM EST TUE FEB 20 2018

TROPICAL DISCUSSION FROM FEB 20/12 UTC: LONG WAVE PATTERN IS
ESTABLISHED AT UPPER LEVELS. THE PATTERN CONSISTS OF A RIDGE THAT
EXTENDS FROM NORTHERN CENTRAL AMERICA/SOUTHERN MEXICO INTO
CUBA/THE BAHAMAS...AND A TROUGH PATTERN OVER THE ATLANTIC/EASTERN
CARIBBEAN. AT MID-LEVELS....THIS REFLECTS ON A ROBUST RIDGE THAT
CENTERS ON A HIGH AT 28N 76W...AND SPREADS ITS INFLUENCE OVER THE
GULF OF MEXICO...NORTHERN CARIBBEAN INTO CUBA AND THE BAHAMAS. TO
THE EAST OF THE RIDGE...A TROUGH EXTENDS IN THE TROPICAL ATLANTIC
ACROSS 12N 45W...GUYANA INTO SOUTHERN VENEZUELA. A SECOND TROUGH
IS MEANDERING SOUTHWARD WHILE EXTENDING ZONALLY ALONG 26-29N. AT
LOW-LEVELS...A SURFACE COLD FRONT EXTENDS ALONG 23-25N WEST INTO
70W. THIS COLD FRONT HAS VERY LITTLE BAROCLINICITY ASSOCIATED WITH
IT...YET IT HAS A WELL DEFINED SIGNATURE IN MOISTURE CONVERGENCE.
THE FRONT WILL MEANDER SOUTHWARD THROUGH WEDNESDAY EVENING WHILE
GRADUALLY LOSING DEFINITION. BY TUESDAY EVENING IT WILL EXTEND
ALONG 20-21N WEST TO 28N 72W. BY WEDNESDAY EVENING IT WILL EXTEND
ALONG 18N...ACROSS PUERTO RICO...NORTHERN HISPANIOLA INTO SOUTH
ANDROS ISLAND. BY THURSDAY EVENING THE ILL-DEFINED BOUNDARY WILL
EXTEND ACROSS THE FRENCH ANTILLES...TO THE DOMINICAN REPUBLIC AND
ENDING IN THE SOUTHEAST BAHAMAS. THROUGH EARLY WEDNESDAY...TRADE
WIND CONVERGENCE WILL LEAD TO 05-10MM/DAY AND ISOLATED MAXIMA OF
15-25MM IN PUERTO RICO...AND 10-15MM/DAY AND MAXIMA OF 20-30MM/DAY
IN HISPANIOLA. AS THE FRONT ARRIVES AND MOISTURE CONVERGENCE
PEAKS...RAINFALL ACCUMULATIONS WILL PEAK DURING WEDNESDAY-EARLY
FRIDAY TO PRODUCE 15-20MM/DAY AND ISOLATED MAXIMA OF 25-50MM IN
PUERTO RICO AND HISPANIOLA BY WEDNESDAY-THURSDAY. AMOUNTS WILL
DECREASE AFTER.

WHILE THE RIDGE PATTERN IS FORECAST TO HOLD...THE MID-LEVEL TROUGH
PATTERN IS FORECAST TO PERSIST AND INTENSIFY ACROSS THE EASTERN
CARIBBEAN. THE TROUGH MEANDERING SOUTHWARD IS FORECAST TO EXTEND
ALONG 20N-22N BY TUESDAY EVENING...AND ALONG 15N-18N BY WEDNESDAY
EVENING. THIS WILL DESTABILIZE THE BOUNDARY LAYER OF THE LESSER
ANTILLES SUFFICIENTLY TO WEAKEN THE TRADE WIND CAP AND LIFT IT TO
500 HPA BY THURSDAY. ACCORDINGLY...THIS WILL LEAD TO A GRADUAL
INCREASE IN ACCUMULATIONS IN THE LESSER ANTILLES AS THE CYCLE
PROGRESSES. THROUGH EARLY WEDNESDAY...EXPECTING MAXIMA OF 15MM IN
THE LESSER ANTILLES. THIS WILL INCREASE TO 10-15MM/DAY AND MAXIMA
OF 20-30MM ON WEDNESDAY-THURSDAY. A FURTHER INCREASE WILL LEAD TO
15-20MM/DAY AND MAXIMA OF 25-50MM BY THURSDAY-FRIDAY.

ALSO IN THE CARIBBEAN...TRADE WIND CONVERGENCE WILL STIMULATE
ACTIVITY IN PARTS OF EASTERN CENTRAL AMERICA. IN COSTA
RICA/WESTERN PANAMA...EXPECTING AN INCREASE IN ACCUMULATIONS FROM
05-10MM/DAY AND MAXIMA OF 15-20MM ON TUESDAY-WEDNESDAY...TO
10-15MM/DAY AND MAXIMA OF 20-30MM BY WEDNESDAY/THURSDAY. THIS WILL
DECREASE IN NORTHERN COSTA RICA BY THURSDAY-FRIDAY...WHILE
PERSISTING IN WESTERN PANAMA. SCATTERED TRADE WIND SHOWERS WILL
ALSO PERSIST IN THE GULF OF HONDURAS. THIS WILL LEAD TO AMOUNTS IN
THE 05-10MM/DAY AND MAXIMA OF 15MM RANGE...FOCUSING IN QUINTANA
ROO ON TUESDAY...AND SOUTHERN BELIZE/CENTRAL GUATEMALA ON
WEDNESDAY THROUGH FRIDAY.

AS THE DIVERGENT PULSE OF THE MADDEN-JULIAN OSCILLATION EXITS THE
AMERICAS TOWARDS AFRICA...ENHANCED UPPER DIVERGENCE CONTINUES
STIMULATING CONVECTION IN THE TROPICAL ATLANTIC. FURTHERMORE...THE
ATLANTIC ITCZ IS INTERACTING WITH THE BASE OF A NORTHERN
HEMISPHERE TROUGH IN EASTERN FRENCH GUIANA/AMAPA IN BRASIL. THIS
WILL SUSTAIN HEAVY RAINFALL THROUGH THURSDAY TO PRODUCE
ACCUMULATIONS OF 25-50MM/DAY AND MAXIMA OF 75-150MM WITH THE RISK
OF MCS FORMATION. ACCUMULATIONS WILL DECREASE AFTER. ALSO IN SOUTH
AMERICA...DIURNAL CONVECTION WILL PERSIST IN ECUADOR AND
ANDEAN/WESTERN COLOMBIA THROUGH THE CYCLE. EXPECTING ACCUMULATIONS
IN THE 10-15MM/DAY AND 20-30MM/DAY MAXIMA.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL    24   36   48   60   72   84   96    TYPE  SOF
NONE

GORDON...NMS (BELIZE)
NIXON...BDM (THE BAHAMAS)
DAVISON/GALVEZ...WPC (USA)

$$





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