Prognostic Meteorological Discussion
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FXCA20 KWBC 231923
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EST TUE JAN 23 2018

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JAN 23/06
UTC: A MID LEVEL HIGH OVER THE DOMINICAN REPUBLIC ANCHORS A RIDGE
OVER THE WESTERN ATLANTIC-NORTHEAST CARIBBEAN ISLES. THIS FAVORS A
CONVERGENT/SUBSIDENT PATTERN ACROSS THE FORECAST AREA. ALTHOUGH
THE HIGH RELOCATES TO THE BAHAMAS AS THE WEEK WEARS ON...THE RIDGE
IS TO PERSIST AND THE ASSOCIATED TRADE WINDS CAP IS TO HOLD WITH
AN ELEVATED CAP INVERSION IS TO PREVAIL THROUGH THE END OF THE
WEEK.

AT LOW LEVELS...A HIGH OVER BERMUDA ANCHORS A RIDGE OVER THE
WESTERN ATLANTIC/ NORTHERN CARIBBEAN ISLANDS. A WANING FRONT
BOUNDS THE SOUTHERN FRINGES OF THIS RIDGE...WITH BOUNDARY
EXTENDING JUST NORTH OF THE GREATER ANTILLES. LACKING UPPER LEVEL
SUPPORT...THE FRONT IS TO DISSIPATE DURING THE NEXT DAY OR SO.
FURTHERMORE...UNDER PRESSURE FROM POLAR FRONT/TROUGH EXITING THE
USA...THE LOW LEVEL RIDGE IS TO WEAKEN AS IT RELOCATES TO THE
CENTRAL ATLANTIC EARLY IN THE CYCLE. AS THE PRESSURE GRADIENT
SLACKENS...LIGHTER EASTERLY TRADES ARE TO PREVAIL THROUGH
MIDMORNING ON FRIDAY. THE LIGHTER WINDS WILL ALLOW SHALLOW
MOISTURE TO POOL ACROSS THE NORTHEAST CARIBBEAN...WITH PWAT
CONTENT FORECAST TO PEAK AROUND 1.50 INCHES ON TUESDAY AFTERNOON
THROUGH EARLY THURSDAY MORNING. THIS WILL FEED DIURNAL CONVECTION
OVER THE FORECAST AREA ON TUESDAY AND WEDNESDAY. DURING THIS
PERIOD THE NAM AND REGIONAL HRWRF SHOW POTENTIAL FOR MODERATE
RAINFALL AMOUNTS ACROSS WESTERN PUERTO RICO. A DRYER AIR MASS IS
TO THEN ENTRAIN FROM THE EAST ON THURSDAY...WITH LIGHT AFTERNOON
CONVECTION TO LIMIT TO THE CORDILLERA/INTERIOR PORTIONS OF PUERTO
RICO.

LATER IN THE WEEK...POLAR FRONT EXITING THE EASTERN USA MOVES JUST
NORTH OF THE FORECAST AREA ON FRIDAY...WITH THE BOUNDARY STALLING
ALONG 22N/23N. AS THE FRONT MOVES ACROSS THE WESTERN ATLANTIC THIS
WILL BE PRECEDED BY A PREFRONTAL SHEAR LINE. NOTE THAT IN THIS
CYCLE THE GFS FAVORS A MORE DYNAMIC FEATURE...WITH THE SHEAR LINE
MOVING OVER PUERTO RICO ON FRIDAY AND OVER THE LEEWARD ISLES LATER
IN THE DAY/EARLY SATURDAY MORNING. MODELS CONTINUE TO FORECAST A
FAIRLY STRONG TRADE WINDS SURGE TO ACCOMPANY THE SHEAR LINE AS IT
ENTERS THE FORECAST AREA...WITH 850 HPA WINDS PEAKING AT 30-35KT.
THIS WILL FAVOR A COLD ADVECTIVE PATTERN THAT IS TO ENHANCE
CONVECTIVE DEVELOPMENT ON FRIDAY TO SATURDAY. SCATTERED SHOWERS
ARE EXPECTED DURING THE DAY...WITH MOST ACTIVE CONVECTION
AFFECTING THE NORTHERN VI AND THE SAN JUAN METRO AREA/NORTHERN
HALF OF PUERTO RICO.


TROPICAL DISCUSSION FROM JAN 23/12 UTC: IN MEXICO...AT UPPER
LEVELS...A TROUGH EXTENDS AN AXIS OVER THE PACIFIC ALONG 112W.
THIS IS INTERACTING WITH A MOIST TROPICAL PLUME AND ENHANCING DEEP
CONVECTION JUST TO THE EAST OF ISLA SOCORRO IN THE PACIFIC...WHICH
IS RESULTING IN PLENTY OF HIGH CLOUDS IN CENTRAL AND NORTHERN
MEXICO. IN THE GULF OF MEXICO...A FRONT EXTENDS FROM THE FLORIDA
PENINSULA INTO CENTRAL VERACRUZ. THIS IS LEADING TO SCATTERED
CONVECTION MOSTLY IN THE GULF...BUT AFFECTING PARTS OF VERACRUZ
AND TABASCO. THIS FRONT IS ASSOCIATED WITH AN UPPER TROUGH
PROPAGATING TOWARDS THE EAST COAST OF THE UNITED STATES. THE FRONT
WILL BE THE FEATURE OF INTEREST IN MEXICO AND NORTHERN CENTRAL
AMERICA...AS IT WILL ENHANCE PRECIPITATION THROUGH THE FORECAST
CYCLE. BY TUESDAY EVENING...THE FRONT WILL EXTEND FROM CENTRAL
FLORIDA INTO THE SOUTHERN GULF OF CAMPECHE NEAR COATZACOALCOS. BY
WEDNESDAY EVENING THE FRONT WILL EXTEND FROM SOUTHERN FLORIDA...
JUST TO THE NORTH OF THE YUCATAN PENINSULA...INTO CENTRAL
VERACRUZ. BY THURSDAY EVENING THE BOUNDARY WILL MEANDER ACROSS THE
NORTHERN BAHAMAS...NORTHERN CUBA... WHILE THE TAIL OF THE FRONT
STARTS LOSING DEFINITION OVER THE GULF. THIS WILL ALSO CONTINUE
LEADING TO A TEHUANTEPECER JET. THE JET IS FORECAST TO REACH PEAK
INTENSITY BETWEEN TUESDAY NIGHT AND EARLY THURSDAY MORNING...WHEN
IT IS FORECAST TO REACH 50-55KT. A SHEAR LINE IS ALSO ORGANIZING.
BY TUESDAY EVENING IT WILL EXTEND ACROSS EXTREME WESTERN CUBA INTO
QUINTANA ROO-NORTHERN GUATEMALA. BY WEDNESDAY EVENING IT WILL
EXTEND ACROSS THE NORTHERN BAHAMAS...CENTRAL-NORTHERN
CUBA...BELIZE. BY THURSDAY EVENING THE SHEAR LINE WILL EXTEND
ACROSS EASTERN HISPANIOLA INTO NORTHEASTERN NICARAGUA.

THE BULK OF PRECIPITATION WITH THE FRONT/SHEAR LINE SYSTEM WILL
OCCUR ALONG THE GULF OF CAMPECHE AND EASTERN SLOPES OF SOUTHERN
MEXICO...GUATEMALA...TO EXTEND INTO SOUTHERN BELIZE. BY
TUESDAY-EARLY WEDNESDAY...EXPECTING THE DEVELOPMENT OF
THUNDERSTORMS IN SOUTHEASTERN VERACRUZ/TABASCO/NORTHERN CHIAPAS TO
PRODUCE 10-15MM/DAY AND MAXIMA OF 20-45MM. THIS WILL INCREASE TO
15-20MM/DAY AND MAXIMA OF 35-70MM ON
WEDNESDAY-THURSDAY...DECREASING TO 15-20MM/DAY AND MAXIMA OF
25-50MM ON THURSDAY-FRIDAY. OTHER REGION OF CONTINUED MODERATE
RAINFALL WILL BE SOUTHERN BELIZE/CENTRAL GUATEMALA. ON
TUESDAY-WEDNESDAY EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM.
THIS WILL INCREASE TO 15-20MM/DAY AND MAXIMA OF 25-50MM ON
WEDNESDAY-THURSDAY EXPANDING INTO MOST OF BELIZE...IN ASSOCIATION
WITH THE SHEAR LINE. BY THURSDAY-FRIDAY EXPECTING SCATTERED
CONVECTION FROM NORTHERN HONDURAS INTO BELIZE/CENTRAL GUATEMALA
WITH ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. INLAND IN
THE YUCATAN PENINSULA...DIURNAL ACCUMULATIONS WILL GRADUALLY
INCREASE FROM 00-05MM/DAY AND MAXIMA OF 10MM ON
TUESDAY-WEDNESDAY...TO 05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM
BY THURSDAY-FRIDAY. AS THE FRONT APPROACHES CUBA AND THE
BAHAMAS...CONVECTION WILL BE SUPPORTED BY THE UPPER LEVELS. THIS
WILL LEAD TO ACCUMULATIONS OF 05-10MM/DAY AND ISOLATED MAXIMA OF
15-20MM IN THUNDERSTORMS ON WEDNESDAY THROUGH FRIDAY.

IN THE CENTRAL AND EASTERN CARIBBEAN...SEASONALLY DRY CONDITIONS
CONTINUE ESTABLISHING. A MID-LEVEL RIDGE WILL BE PRESENT THROUGH
THE FORECAST CYCLE TO CONTINUE SUSTAINING THE SUBSIDENCE CAP. THE
RIDGE IS FORECAST TO MEANDER FROM CENTRAL/EASTERN CUBA EAST TO 55W
ACROSS THE GREATER ANTILLES...AND INTO THE SOUTHEASTERN
CARIBBEAN/WINDWARD ISLANDS/NORTHEASTERN VENEZUELA. ACTIVITY WILL
CONCENTRATE IN POCKETS OF ENHANCED TRADE WIND SHOWERS...TO PRODUCE
LIGHT ACCUMULATIONS. AT LOW-LEVELS...THE REMNANTS OF A SURFACE
FRONT LIE IN THE TROPICAL ATLANTIC TO THE NORTH OF PUERTO RICO AND
THE LEEWARD ISLANDS. THE REMNANTS ARE RETROGRESSING WESTWARD IN
THE FORM OF WEAK WAVES IN THE TRADES. SINCE PRECIPITABLE WATER
WILL REMAIN LIMITED TO BELOW 40MM AND THE SUBSIDENCE CAP WILL BE
IN PLACE...EXPECTING LIGHT ACCUMULATIONS. ISOLATED HIGHER AMOUNTS
ARE EXPECTED IN NORTHEASTERN HISPANIOLA FROM WEDNESDAY THROUGH
FRIDAY...WHERE A PREFRONTAL THROUGH AND THEN THE SHEAR LINE WILL
LEAD TO 05-10MM/DAY AND MAXIMA OF 15-20MM.

AS THE MID-LEVEL RIDGE PATTERN DOMINATES THE CARIBBEAN...A
MID-LEVEL TROUGH IS FORECAST TO PERSIST ACROSS CENTRAL AND
SOUTHERN CENTRAL AMERICA. THIS WILL CONTINUE STIMULATING THE
DEVELOPMENT OF CONVECTION ALONG THE CARIBBEAN BASIN OF CENTRAL
AMERICA. LARGEST ACCUMULATIONS ARE EXPECTED IN COSTA
RICA/SOUTHEASTERN NICARAGUA/EXTREME WESTERN PANAMA...WHERE
OROGRAPHIC UPLIFT IN THE SOUTHERN TIER OF THE CARIBBEAN LOW-LEVEL
JET WILL STIMULATE DEVELOPMENT. THIS WILL SUSTAIN 15-20MM/DAY AND
MAXIMA OF 25-50MM THROUGH THURSDAY...DECREASING AFTER. IN NORTHERN
NICARAGUA/EASTERN HONDURAS...EXPECTING A GRADUAL INCREASE TO
10-15MM/DAY AND MAXIMA OF 20-45MM BY THURSDAY-FRIDAY.

IN NORTHERN SOUTH AMERICA...LARGEST ACCUMULATIONS WILL CLUSTER IN
COLOMBIA WHILE THE PACIFIC ITCZ REMAINS TO THE NORTH OF ITS
CLIMATOLOGICAL POSITION. THIS WILL LEAD TO 05-10MM/DAY AND MAXIMA
OF 15-20MM THROUGH THE CYCLE IN WESTERN COLOMBIA.
OTHERWISE...EXPECTING DIURNAL CONVECTION TO CONSTRAIN TO THE
SOUTHERN AMAZON...AND ISOLATED AND LIGHT DIURNAL SHOWERS IN PARTS
OF THE ANDES. WHILE THE ATLANTIC ITCZ REMAINS IN NORTHERN
BRAZIL...EXPECTING LIGHT ACCUMULATIONS IN THE GUIANAS THROUGH THE
CYCLE.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL  24    36    48    60    72    84    96           TYPE
SOF
51W     56W   61W   65W   69W   73W   77W   82W        TUTT INDCD
18N
67W     72W   76W   80W   84W   88W   92W   DISSIPATED    EW24N

A TUTT-INDUCED WAVE IS INITIALIZED AT 51W. THIS WAVE WILL ENHANCE
ACTIVITY IN THE LESSER ANTILLES ON WEDNESDAY MORNING...TO PRODUCE
05-10MM/DAY AND MAXIMA OF 15MM. ELSEWHERE...THE EFFECTS OF THIS
WAVE WILL BE LIMITED UNDER THE PRESENCE OF DRY MID-LEVELS.

AN EASTERLY WAVE IS ANALYZED OVER AT 67W. THIS WAVE WILL LEAD TO A
MINOR ENHANCEMENT IN ACCUMULATIONS IN THE NORTHEASTERN DOMINICAN
REPUBLIC ON TUESDAY-WEDNESDAY...CAYMAN ISLANDS ON
WEDNESDAY-THURSDAY...AND THE EASTERN YUCATAN PENINSULA ON FRIDAY.

GORDON...NMS (BELIZE)
PECK...MS (JAMAICA)
DAVISON/GALVEZ...WPC (USA)

$$




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