THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


CARIBBEAN FORECAST DISCUSSION




TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
707 AM EDT FRI APR 18 2014

LAST NO AMENDS...NEXT BULLETIN ON MONDAY APRIL 21.

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. FORECAST AREA
REMAINS ON THE CONVERGENT SIDE OF A RIDGE-TUTT PAIR DOMINATING THE
EASTERN CARIBBEAN-TROPICAL ATLANTIC. THE RIDGE EXTENDS NORTH FROM
THE EASTERN CARIBBEAN TO THE ISLAND OF BERMUDA...WHILE THE TROUGH
EXTENDS BETWEEN 60W-50W TO THE NORTHERN GUIANAS. THE COLD CORE
TROUGH IS ENHANCING CONVECTIVE INSTABILITY ACROSS THE CENTRAL
ATLANTIC...FAVORING GENERATION OF CLOUD CLUSTERS IN THE LOW LEVEL
EASTERLIES. AT LOW LEVELS...BROAD CELL OF THE SUBTROPICAL RIDGE
DOMINATES THE ATLANTIC...SUSTAINING AN EASTERLY FLOW ACROSS THE
ISLAND CHAIN INTO THE CARIBBEAN. EMBEDDED IN THIS
FLOW...PERTURBATION IN THE LOW LEVEL EASTERLIES MOVED ACROSS THE
FORECAST AREA DURING THE EARLY MORNING HOURS. THIS SUSTAINED LOW
LEVEL MOISTURE CONVERGENCE WHILE TRIGGERING SCATTERED SHOWERS. A
LULL IN ACTIVITY SEPARATES THE FORMER FROM ANOTHER PERTURBATION TO
THE EAST THAT EXTENDS ALONG 56W/57W TO 20N. THIS APPEARS
CONSIDERABLY WEAKER THAN THE PREVIOUS ONE...WITH SATELLITE DERIVED
PWAT ANALYSIS SHOWING MOISTURE CONTENT OF LESS THAN 30MM WITH THE
LATTER.

CONSISTENT WITH PREVIOUS FORECASTS...EXPECTING THE GRADUAL EROSION
OF THE SUBTROPICAL RIDGE PATTERN ACROSS THE EASTERN
CARIBBEAN/WESTERN ATLANTIC DURING THE WEEKEND. AS THE RIDGE
WEAKENS...THE TUTT TO THE EAST IS TO PULL AWAY...QUICKLY LOSING
THE DYNAMICAL SUPPORT AND GENERATION OF SHALLOW CONVECTIVE
INSTABILITY. PATTERN IS TO THEN EVOLVE TROUGH THE MIDDLE OF NEXT
WEEK WHEN A TROUGH IS TO DEEPEN ACROSS THE WESTERN ATLANTIC. THIS
IS TO HAVE A STRONG LOW LEVEL REFLECTION...SUSTAINING A BROAD
SURFACE TROUGH ACROSS THE BAHAMAS-CUBA/HISPANIOLA. UNDER PRESSURE
FROM THIS FEATURE...THE SUBTROPICAL RIDGE IS TO RECEDE. AS THE
RIDGE MOVES AWAY...LOW LEVEL WINDS ARE TO VEER TO THE
SOUTH-SOUTHEAST. THIS IS TO THEN ENHANCE MOISTURE
TRANSPORT/CONVERGENCE ACROSS THE FORECAST AREA. THROUGH THE DAY ON
TUESDAY MODEL GUIDANCE SHOWING PWAT INCREASING AS THE INVERSION
HEIGHT RISES TO THE MID LEVELS OF THE ATMOSPHERE. BEST DYNAMICAL
SUPPORT...HOWEVER...IS EXPECTED TO THE WEST OVER THE DOMINICAN
REPUBLIC. SO PUERTO RICO-USVI WILL BE MORE DEPENDENT ON DIURNAL
EFFECTS-SEA/LAND BREEZE CONVERGENCE FOR THE GENERATION OF
CONVECTION. IN A SOUTHERLY FLOW...MOST ACTIVE IS TO CLUSTER ALONG
THE NORTH COAST OF PUERTO RICO...WITH GDI SHOWING POTENTIAL FOR
ISOLATED DEEP CONVECTION BY THE MIDDLE OF THE WEEK. INDEX SUGGESTS
HIGHER POTENTIAL FOR DEEP CONVECTION LATER DURING THE WEEK.

DISCUSSION FROM APRIL 18/00UTC:

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

GALVEZ...WPC (USA)
GARCIA...SMN (MEXICO)
FIGUEROA...MARN (EL SALVADOR)




Last Updated: 707 AM EDT FRI APR 18 2014