Prognostic Meteorological Discussion
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FXCA20 KWBC 281831
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 PM EDT WED SEP 28 2016

AT 15 UTC TROPICAL STORM MATTHEW CENTERED NEAR 13.4N 60.7W...WITH
MAXIMUM SUSTAINED WINDS OF 50KT AND MINIMAL CENTRAL PRESSURE OF
1008 HPA. THE STORM IS MOVING WEST AT 18KT...SEE NHC DISCUSSION
FOR DETAILS AND OFFICIAL FORECAST.

TROPICAL DISCUSSION FROM SEPTEMBER 28/12UTC: WEST OVER THE
DOMAIN...BROAD CELL OF THE SUBTROPICAL RIDGE DOMINATES THE FLOW
ACROSS MEXICO-THE GULF TO NORTHERN CENTRAL AMERICA. RIDGE ALOFT IS
TO HOLD NEARLY UNCHANGED THROUGH THURSDAY EVENING... MEANWHILE
ANCHORING ON A CLOSED HIGH OVER CENTRAL MEXICO. LATER ON
FRIDAY...AS A SHORT WAVE TROUGH LIFTS ACROSS THE WESTERN USA...THE
RIDGE IS FORECAST TO FLATTEN TO THE NORTH WHILE PERSISTING OVER
MEXICO-NORTHERN CENTRAL AMERICA. THE RIDGE ALOFT IS TO VENT
DIURNAL CONVECTION ACROSS MEXICO AND NORTHERN CENTRAL AMERICA.
ACROSS WESTERN MEXICO EXPECTING ACTIVITY TO CLUSTER ALONG THE
SIERRA MADRE. OVER SONORA EXPECTING RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM THROUGH THURSDAY. ON FRIDAY...AS
THE SHORT WAVE TROUGH AMPLIFIES...ACTIVITY WILL BECOME BETTER
ORGANIZED AND WILL INCREASE TO 10-15MM/DAY AND MAXIMA OF 20-40MM.
OVER SINALOA-COLIMA/NAYARIT TO GUERRERO EXPECTING RAINFALL AMOUNTS
OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON THURSDAY THIS DECREASES
TO 10-15MM/DAY AND MAXIMA OF 20-35MM. ON THE SOUTHERN STATES OF
MEXICO EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF
10MM....INCREASING TO 05-10MM/DAY AND MAXIMA OF 15-20MM LATER ON
FRIDAY.

A 250 HPA SHORT WAVE TROUGH TO THE EAST EXTENDS NORTH ACROSS
CENTRAL AMERICA TO THE WESTERN CARIBBEAN. UNDER INFLUENCE OF THE
RIDGE TO THE WEST THE TROUGH ALOFT IS TO MEANDER WEST ACROSS
NORTHERN CENTRAL AMERICA...CROSSING 90W LATER ON THURSDAY. AS IT
MEANDERS WEST THE TROUGH WILL PROVIDE ENHANCEMENT TO THE DIURNAL
CONVECTION.
ACROSS BELIZE-NORTHERN GUATEMALA EXPECT RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM. OVER SOUTHERN GUATEMALA-EL
SALVADOR/HONDURAS EXPECT RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-30MM ON THURSDAY THROUGH FRIDAY. OVER NICARAGUA-COSTA
RICA-PANAMA THE TROUGH ALOFT WILL ENHANCE ACTIVITY EARLY IN THE
CYCLE...TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM.

ALSO...EAST OF THE RIDGE...A DEEPENING MID/UPPER LEVEL TROUGH IS
TO DOMINATE THE FLOW ACROSS THE CENTRAL-EASTERN USA DURING THE
NEXT FEW DAYS...WITH AXIS TO AMPLIFY ACROSS FLORIDA TO THE GULF OF
MEXICO EARLY IN THE CYCLE. AS IT DEEPENS...THE TROUGH WILL FOCUS
SHORT WAVE ENERGY ACROSS THE CENTRAL/NORTHWEST BAHAMAS. THIS WILL
ENHANCE CONVECTIVE DEVELOPMENT OVER THE NEXT FEW DAYS...TO RESULT
IN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-30MM. SOME
ENHANCEMENT IS ALSO POSSIBLE AS THE BASE OF THE UPPER TROUGH
EXTENDS INTO THE NORTHWEST CARIBBEAN LATER ON THURSDAY/EARLY ON
FRIDAY. ACROSS THE CAYMAN ISLES AND JAMAICA THIS WILL RESULT IN
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.

THE DEEPENING TROUGH WILL ALSO SUSTAIN A SURFACE FRONT THAT SURGES
ACROSS THE USA TO THE NORTHERN GULF/NORTHEAST MEXICO LATER ON
THURSDAY. AS IT ENTERS NORTHEAST MEXICO THIS WILL TRIGGER RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM ON THURSDAY TO FRIDAY
MORNING...WHILE ON FRIDAY TO SATURDAY FOCUS OF THE ACTIVITY WILL
BE BETWEEN TAMAULIPAS AND VERACRUZ WHERE IT WILL FAVOR RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM.

A MID LEVEL RIDGE DOMINATES THE FLOW ACROSS THE CENTRAL-WESTERN
ATLANTIC WHILE ANCHORING ON A CLOSED HIGH NEAR 30N 58W. THIS RIDGE
IS TO GENERALLY HOLD OVER THE NEXT FEW DAYS...WITH AXIS ENVELOPING
THE NORTHEAST CARIBBEAN ISLES. AS IT HOLDS...THE RIDGE ALOFT WILL
PROVIDE THE STEERING FLOW TO TROPICAL STORM MATTHEW. THROUGH
FRIDAY MORNING THE NHC IS FORECASTING THE STORM TO INTENSIFY TO A
HURRICANE AS ENVIRONMENTAL CONDITIONS BECOME MORE FAVORABLE FOR
INTENSIFICATION. ACROSS THE WINDWARD-FRENCH ISLES THIS IS TO FAVOR
RAINFALL AMOUNTS OF 50-100MM/DAY AND MAXIMA OF 150-200MM THROUGH
THURSDAY MORNING...WHILE OVER THE NORTHERN LEEWARD/VIRGIN ISLES
AND EASTERN PUERTO RICO EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY
AND MAXIMA OF 25-50MM. ON THURSDAY TO FRIDAY...MOST ACTIVE
CONVECTION IS EXPECTED OVER WATER...WHILE ON THE SOUTHERN FRINGES
OUTER BAND CONVECTION IS TO AFFECT THE ABC ISLES/NORTHWEST COAST
OF VENEZUELA AND THE GUAJIRA PENINSULA...WITH RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 35-70MM. ON FRIDAY...AS IT MEANDERS WEST
OFF THE COAST OF COLOMBIA...THE STORM WILL ENHANCE THE ONSHORE
FLOW ACROSS WESTERN COLOMBIA...TO RESULT IN RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM...WHILE OVER NORTHWEST VENEZUELA
THIS WILL FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:

INITIAL  24      36      48      60      72      84      96
TYPE
41W      45W     49W    53W     57W     61W     65W     68W
TW
81W      84W     89W    91W     94W     97W    100W    103W
EW
95W      98W    102W   105W    109W    112W    114W  DISSIPATES
EW

TROPICAL WAVE ALONG 41W REACHES THE LESSER ANTILLES LATER ON
FRIDAY...WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND
MAXIMA OF 10MM. ON THE SOUTHERN WINDWARD ISLES THIS IS TO FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM IN
INTERACTION WITH THE ATLANTIC ITCZ.

TROPICAL WAVE ALONG 81W WILL MOVE ACROSS COSTA RICA TO NICARAGUA
LATER TODAY. MEANWHILE...IN INTERACTION WITH THE ITCZ IT IS TO
SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ON
THURSDAY IT MOVES ACROSS EL SALVADOR TO GUATEMALA...WITH RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. SIMILAR AMOUNTS ARE
EXPECTED ACROSS GUATEMALA-BELIZE TO SOUTHERN MEXICO EARLY ON
FRIDAY. LATER IN THE DAY...THIS WILL FAVOR SCATTERED CONVECTION
ACROSS CENTRAL STATES OF MEXICO WITH ACCUMULATION OF 10-15MM/DAY
AND MAXIMA OF 20-35MM.

AN EASTERLY WAVE ALONG 95W WILL MOVE ACROSS CENTRAL TO SOUTHWEST
MEXICO THROUGH THURSDAY MORNING...MEANWHILE FAVORING RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. THROUGH THURSDAY
EVENING THIS WILL DECREASE TO 10-15MM/DAY AND MAXIMA OF 20-35MM.

AGRAMONTE...ONAMET (DOMINICAN REPUBLIC)
CASTILLO...UCR (COSTA RICA)
CONTRERAS...IMN (COSTA RICA)
DAVISON/GALVEZ...WPC (USA)
$$





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