Prognostic Meteorological Discussion
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FXCA20 KWBC 212032
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
431 PM EDT THU MAY 21 2015

DISCUSSION FROM MAY 21/12 UTC: MID-UPPER LEVEL RIDGE OVER MEXICO
EXTENDS ACROSS THE GULF INTO THE SOUTHERN US STATES. CUT OFF LOW
FORMS OVER THE PACIFIC AS THE NORTHERN PART OF LONGWAVE TROUGH
BECOMES OUT OF PHASE WITH SOUTHERN END. RIDGE CURRENTLY OVER
NORTHERN SOUTH AMERICA CONTINUES TO BUILD NORTHWARD/NORTHWESTWARD
EXTENDING INTO THE SOUTHERN BAHAMAS.

OVER MEXICO DIURNAL PATTERN WOULD BE ENHANCED BY THE VENTILATION
IN THE PERIPHERY OF THE RIDGE ALOFT. IN NORTHEASTERN
MEXICO...INITIALLY...EXPECTING MAXIMA OF 40-80MM WITH THE RISK OF
MCS THROUGH FRIDAY...AS SYSTEM CURRENTLY AFFECTING SOUTH TEXAS
PROPAGATES INTO THE AREA. MAXIMA DECREASES TO 15-25MM/DAY
AFTERWARDS AS RIDGE IS DISPLACED SOUTH WITH THE ENTRANCE OF AN
UPPER LOW INTO CALIFORNIA. ASSOCIATED JET DYNAMICS IS EXPECTED TO
ENHANCE CONVECTION ONCE AGAIN ON SUNDAY WITH ACCUMULATIONS UP TO
20-40MM/DAY. OVER CENTRAL MEXICO DIURNAL PATTERN IS EXPECTED TO BE
ENHANCED AS AFOREMENTIONED LOW DISPLACES RIDGE SOUTHWARD.
EXPECTING AND INCREASE IN MAXIMA FROM 15-20MM/DAY THROUGH FRIDAY
MORNING TO 20-35MM/DAY ON SUNDAY MORNING. THE DISPLACED
RIDGE...COMBINED WITH THE DIGGING TROUGH INTO THE PACIFIC...ALSO
ENHANCES DIURNAL PATTERN OVER SOUTHERN MEXICO-NORTHERN CENTRAL
AMERICA WHERE WE EXPECT MAXIMA INCREASING FROM 15-25MM/DAY ON
THURSDAY INTO FRIDAY TO 20-35 THROUGH SUNDAY MORNING.

TO THE EAST...PROPAGATING UPPER LEVEL TROUGH IS FAVORABLE FOR
ENHANCED CONVECTION OVER THE GREATER ANTILLES. OVER EASTERN
CUBA-JAMAICA-HISPANIOLA EXPECTING MAXIMA OF 20-35MM/DAY THROUGH
FRIDAY MORNING. AS UPPER SHORT WAVE TROUGH DEPARTS AREA EXPECTING
A DECREASE IN MAXIMA TO 15-20MM/DAY OVER EASTERN CUBA...ISOLATED
MAXIMA OF 10MM/DAY OVER JAMAICA AND...ISOLATED MAXIMA OF 15MM/DAY
OVER HISPANIOLA THROUGH SUNDAY MORNING. UNDER THE INFLUENCE OF A
SHORT-LIVED AND ILL-DEFINED SHEAR LINE FORMING IN THE AREA
EXPECTING AN INCREASE TO 15-25MM/DAY OVER EASTERN CUBA AND JAMAICA
BY SUNDAY. OVER PUERTO RICO...DIURNAL PATTERN IS INHIBITED BY
MID-UPPER LEVEL CLOUDS BEING ADVECTED OVER THE AREA. EXPECTING
MAXIMA OF 15-20MM/DAY THROUGH FRIDAY MORNING...DECREASING TO
ISOLATED MAXIMA OF 15MM/DAY THROUGH SUNDAY...WITH STRONGEST
CONVECTION CONSTRAINED TO NORTHWESTERN PUERTO RICO AND THE
SOUTHEASTERN COAST.

OVER THE LESSER ANTILLES...CONVECTION WOULD BE SUPPRESSED BY THE
SAHARAN AIR LAYER (SAL) ENTERING DURING THURSDAY AND REMAINING IN
PLACE DURING THE WEEKEND. TO THE SOUTH...EASTERLY WAVES WILL AID
SOME CONVECTIVE DEVELOPMENT ESPECIALLY FROM GRENADA/ST VINCENT TO
THE SOUTH. WITH THE ARRIVAL OF THE MOISTURE SURGE WITH PROPAGATING
EW...EXPECTING AN INCREASE TO ISOLATED MAXIMA OF 10MM/DAY OVER THE
REGION.

TO THE SOUTH OVER THE GUIANAS...INTERACTIONS BETWEEN THE
ITCZ...STRONG BUT WANING UPPER LEVEL DIFFLUENCE...AND SUCCESSIVE
EASTERLY WAVES WILL CONTINUE LEADING MODERATE...BUT GRADUALLY
DECREASING ACCUMULATIONS AS STRONGEST DIFFLUENCE MOVES AWAY INTO
WESTERN LOCATIONS. EXPECTING MAXIMA OF 15-25MM/DAY THROUGHOUT THE
PERIOD...ON FRIDAY TO SATURDAY TEMPORARILY INCREASING TO
15-30MM/DAY... AS AN EASTERLY WAVE IS EXPECTED TO PASS THE AREA.
AS EASTERLY WAVES AND UPPER DIFFLUENCE PROPAGATE
WESTWARD...INCREASED ACTIVITY IS EXPECTED TO CONTINUE ACROSS THE
AMAZON REGION IN VENEZUELA-COLOMBIA. EXPECTING MAXIMA OF
25-50MM/DAY OVER EASTERN-CENTRAL VENEZUELA THROUGH THE CYCLE. OVER
ANDEAN AND WESTERN COLOMBIA...EXPECTING A SLIGHT INCREASING TREND
FROM MAXIMA OF 25-50MM/DAY TO 30-60MM/DAY AS THE SEVERAL
AFOREMENTIONED EASTERLY WAVES CROSS THE REGION.

FURTHER WEST OVER SOUTHERN-CENTRAL AMERICA...ACTIVE CONVECTION
WILL DOMINATE THE REGION AS WELL UNDER THE INFLUENCE OF WIDESPREAD
CONVECTIVELY UNSTABLE AIR MASS...FAVORABLE VENTILATION AS UPPER
RIDGE BUILDS INTO THE AREA...AND EVENTUALLY THE ARRIVAL OF
EASTERLY WAVES. ALSO EXPECTING AN INCREASE FROM MAXIMA OF
25-50MM/DAY TO 30-60MM/DAY DURING THE WEEKEND...WITH ISOLATED
HIGHER AMOUNTS IN INTERACTION WITH OROGRAPHY.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE
SEE CHARTS

CRAIG...TTMS (TRINIDAD AND TOBAGO)
SAMUEL...MDS (SURINAME)
GALVEZ...WPC (USA)
$$




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