Prognostic Meteorological Discussion
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FXCA20 KWBC 221958
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 PM EST THU FEB 22 2018

TROPICAL DISCUSSION FROM FEB 22/12 UTC: A LONG-WAVE UPPER TROUGH
PATTERN WILL CONTINUE PERSISTING IN THE WESTERN UNITED STATES.
THIS EXTENDS INTO EXTREME NORTHWESTERN MEXICO. A SIGNIFICANT
LIMITATION FOR PRECIPITATION IS MOISTURE CONTENT. THIS WILL LIMIT
THE DEVELOPMENT OF MOIST CONVECTION THROUGH THE CYCLE. ANY
PRECIPITATION WILL BE LIMITED TO THE EASTERN SLOPES OF THE SIERRA
MADRE ORIENTAL/GULF OF MEXICO COAST. HERE...INTERACTIONS BETWEEN
THE SOUTHERLY LOW-LEVEL JET AND THE COAST/TERRAIN WILL SUSTAIN
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM THROUGH THE CYCLE.
FURTHERMORE...A WEAK ONSHORE COMPONENT NEAR 1000 HPA WILL FAVOR A
FEW SHOWERS AND STRAY THUNDERSTORMS DEVELOPING INTO COAHUILA/NUEVO
LEON.

TO THE SOUTHEAST...A MID-LEVEL RIDGE WILL CONTINUE EXTENDING FROM
CENTRAL/SOUTHERN MEXICO INTO FLORIDA AND THE NORTHERN BAHAMAS
THROUGH THE CYCLE. THE RIDGE WILL CONTINUE ANCHORING ON A HIGH
THAT WILL MEANDER SOUTHWESTWARD DURING THE WEEKEND...FROM THE
NORTHWESTERN BAHAMAS INTO THE GULF OF MEXICO. THIS WILL CONTINUE
SUSTAINING GENERALLY FAIR WEATHER CONDITIONS ACROSS THE
BAHAMAS...CUBA...CAYMAN ISLANDS...GULF OF HONDURAS REGION...AND
THE GULF OF MEXICO REGION. ANY PRECIPITATION WILL PRODUCE MAXIMA
UNDER 10MM/DAY. NOTE THAT VERY ISOLATED THUNDERSTORMS ARE POSSIBLE.

A ROBUST MID-UPPER TROUGH HAS DEVELOPED IN THE NORTHEASTERN
CARIBBEAN. GIVEN THE TIGHT GRADIENT IN THE UPPER LEVELS...THIS HAS
DEVELOPED AN UPPER JET THAT EXTENDS ACROSS THE CENTRAL LESSER
ANTILLES. SUCH A ROBUST TROUGH HAS A WELL DEFINED SIGNATURE IN THE
MID-LEVELS...AND SOUNDING DATA SHOWS THAT THE TROUGH REFLECTS AS
LOW AS 650 HPA IN THE LESSER ANTILLES. THE TROUGH AND ASSOCIATED
UPPER JET ARE FORECAST TO PERSIST INTO EARLY NEXT WEEK WHILE
MEANDERING NORTHWESTWARD BETWEEN THE WINDWARD ISLANDS INTO PUERTO
RICO/HISPANIOLA. THIS WILL CONTINUE LEADING TO DESTABILIZATION OF
THE LOW AND MID-LEVELS AND CONSEQUENT INCREASE IN PRECIPITATION.
NOTE THAT AN IMPORTANT LIMITATION IS WATER VAPOR CONTENT. THIS
WILL LIMIT POTENTIAL RAINFALL ACCUMULATIONS...YET IT WILL LIKELY
ENHANCE THE DEVELOPMENT OF DOWNDRAFTS IN THE FEW CELLS THAT GROW
INTO THUNDERSTORMS. FURTHERMORE...AT LOW LEVELS...SOME ENHANCEMENT
WILL BE PROVIDED BY THE REMNANTS OF A SURFACE FRONT...WHICH ARE
FORECAST TO MEANDER ACROSS THE FRENCH ANTILLES ON THURSDAY...THE
WINDWARD ISLANDS ON FRIDAY...NORTHERN GUYANA/NORTHEASTERN
VENEZUELA ON SATURDAY. THROUGH EARLY FRIDAY...EXPECTING
10-15MM/DAY AND MAXIMA OF 20-35MM ACROSS THE CENTRAL LESSER
ANTILLES. ALSO ON FRIDAY...EXPECTING MAXIMA OF 15MM IN THE
DOMINICAN REPUBLIC AND JAMAICA. BY FRIDAY-SATURDAY...EXPECTING A
DECREASE IN THE LESSER ANTILLES TO 05-10MM/DAY AND MAXIMA OF
15-20MM...WHILE AMOUNTS INCREASE IN PUERTO RICO AND THE DOMINICAN
REPUBLIC TO 05-10MM/DAY AND MAXIMA OF 15-25MM. BY
SATURDAY-SUNDAY...EXPECTING ACTIVITY TO CONCENTRATE IN PUERTO RICO
AND THE DOMINICAN REPUBLIC WHERE AMOUNTS WILL INCREASE TO
10-15MM/DAY AND MAXIMA OF 20-30MM. IN NORTHERN GUYANA/NORTHEASTERN
VENEZUELA...EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM. ALSO...AS
THE NORTHERN CARIBBEAN DESTABILIZES...EXPECTING AN INCREASE IN
ACCUMULATIONS IN JAMAICA TO 05-10MM/DAY AND MAXIMA OF 15MM. IN
FRENCH GUIANA...RAINFALL VARIABILITY WILL BE DIFFERENT. EXPECTING
SCATTERED THUNDERSTORMS ON A DAILY BASIS TO PRODUCE AMOUNTS OF
10-15MM/DAY AND MAXIMA IN THE ORDER OF 20-40MM ON A DAILY BASIS.

MODELS AGREE ON A CLOSED LOW FORMING IN THE BASE OF THE
AFOREMENTIONED TROUGH. THE MID-LEVEL LOW IS FORECAST TO MEANDER
FROM NORTHWESTERN COLOMBIA WEST INTO COSTA RICA/PANAMA THROUGH THE
WEEKEND. THIS WILL SUSTAIN A WEAKENING OF THE TRADE WIND CAP
ACROSS THE SOUTHERN CARIBBEAN INTO EARLY NEXT WEEK. ALSO IN
CENTRAL AMERICA...A MOIST PLUME IN THE TRADES IS FORECAST TO
ARRIVE INTO NORTHERN NICARAGUA/HONDURAS BY FRIDAY-SATURDAY...TO
ALSO PRODUCE A TRANSIENT INCREASE IN ACCUMULATIONS. IN SOUTHERN
NICARAGUA/NORTHERN COSTA RICA...AMOUNTS WILL GRADUALLY INCREASE
FROM 05-10MM/DAY AND MAXIMA OF 15-20MM ON THURSDAY...TO
10-15MM/DAY AND MAXIMA OF 20-30MM BY SATURDAY-SUNDAY. IN NORTHERN
NICARAGUA/NORTHEASTERN HONDURAS EXPECTING ACTIVITY TO PEAK ON
FRIDAY WHEN ENHANCED SHOWERS AND A FEW EMBEDDED THUNDERSTORMS WILL
LEAD TO 05-10MM/DAY AND MAXIMA OF 15-25MM.

CONVECTION ALONG THE PACIFIC ITCZ HAS DECREASED IN COVERAGE AND IN
VERTICAL DEVELOPMENT. MODELS ARE SHOWING THAT THE LOW-LEVEL WINDS
OFF THE PACIFIC COAST OF COLOMBIA AND ECUADOR WILL BE UNFAVORABLE
FOR HEAVY RAINFALL THROUGH THE CYCLE. YET...SEA SURFACE
TEMPERATURES ALONG THE COAST REMAIN OVER 27C...AND UNDER WEAK
WINDS AT LOW-LEVELS...DIURNAL CIRCULATIONS WILL STILL LEAD TO
ISOLATED THUNDERSTORM DEVELOPMENT IN THE AFTERNOON/EVENINGS.
DIURNAL CONVECTION IS ALSO EXPECTED IN ANDEAN COLOMBIA AND ANDEAN
ECUADOR THROUGH THE CYCLE. IN TERMS OF ACCUMULATIONS...IN ECUADOR
EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM ON THURSDAY DECREASING
TO 05-10MM/DAY AND MAXIMA OF 15-20MM BY SATURDAY/SUNDAY. IN ANDEAN
COLOMBIA...EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM ON A DAILY
BASIS.

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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