Prognostic Meteorological Discussion
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
705 AM EDT MON OCT 23 2017

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM OCT 23/06
UTC: TUTT LOW NEAR 24N 65W EXTENDS A TROUGH TO THE SOUTH ACROSS
THE EASTERN CARIBBEAN TO NORTHERN VENEZUELA. THE DEEP MID/UPPER
LEVEL TROUGH PATTERN SUSTAINS AN INVERTED TROUGH IN THE EASTERLY
WINDS...WITH AXIS NORTH ALONG 57W/58W TO 24N. THE LOW LEVEL
PERTURBATION IS ENHANCING CONVECTION ALONG THE ITCZ AND TO THE
EAST OF THE ISLAND CHAIN...WHILE THE TROUGH ALOFT IS ENHANCING
CONVECTION TO THE NORTH OF THE ISLANDS.

MODELS FORESEE GRADUAL DECOUPLING OF THE MID/UPPER LEVEL TROUGH
AXIS AS A RIDGE BUILDS FROM THE WEST. THE 250 HPA AXIS IS TO
SLOWLY RELOCATE ACROSS THE ISLAND CHAIN...WHILE WANING MID LEVEL
CIRCULATION IS TO MEANDER OVER THE NORTHEAST CARIBBEAN ISLES
THROUGH WEDNESDAY AFTERNOON. UNDER INFLUENCE OF THE MID/UPPER
LEVEL FEATURE...BEST CONVECTIVE INSTABILITY IS EXPECTED DURING THE
NEXT TWO DAYS. AT LOW LEVELS...THE INDUCED TROUGH MOVES ACROSS 60W
EARLY THIS EVENING...NEARING 64W/65W EARLY ON WEDNESDAY MORNING.
IT THEN RAPIDLY BECOMES ILL DEFINED AS IT LOSES ITS UPPER LEVEL
SUPPORT. AHEAD OF THIS PERTURBATION...EASTERLY TRADES ARE TO
DOMINATE THE ATMOSPHERE BELOW 700 HPA DURING THE NEXT TWO DAYS. ON
WEDNESDAY THE WINDS ARE TO VEER TO THE SOUTHEAST. THE PREVAILING
EASTERLY TRADES ARE TO RETURN LATER ON THURSDAY.

OVER THE NEXT TWO DAYS THE DEEP LAYER EASTERLY TRADES AHEAD OF THE
TUTT INDUCED TROUGH ARE TO ENHANCE CONVERGENCE ACROSS WESTERN
INTERIOR PORTIONS OF PUERTO RICO. UNDER INFLUENCE OF AN UPPER JET
MAXIMA REVOLVING AROUND THE UPPER LEVEL TROUGH...THE ENVIRONMENTAL
CONDITIONS ON TUESDAY BECOME SOMEWHAT MORE FAVORABLE FOR DEEPER
CONVECTION TO DEVELOP THAN TODAY. SO EXPECTING AN INCREASE ACROSS
THE GUAJATACA BASIN. ON WEDNESDAY...AS THE STEERING FLOW SHIFTS TO
THE SOUTHEAST...MOST ACTIVE CONVECTION IS TO CLUSTER ACROSS
NORTHWEST PUERTO RICO...MAINLY TO THE WEST OF MANATI/BARCELONETA.
BUT AS THE EASTERLY TRADES RETURN LATER IN THE WEEK... CONVECTION
IS TO ONCE AGAIN CLUSTER ALONG THE GUAJATACA BASIN/WESTERN
INTERIOR PORTIONS OF PUERTO RICO.

GUY...NMS (BELIZE)
PECK...MS (JAMAICA)
DAVISON...WPC (USA)
$$





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