Prognostic Meteorological Discussion
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FXCA20 KWBC 201839
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 PM EDT WED SEP 20 2017

AT 18 UTC HURRICANE MARIA CENTERED NEAR 18.5N 66.9W..WITH MAXIMUM
SUSTAINED WINDS OF 100KT AND CENTRAL PRESSURE OF 961 HPA. THE
HURRICANE IS MOVING TO THE NORTHWEST AT 10KT.

TROPICAL DISCUSSION FROM SEP 20/12 UTC: A 200 HPA HIGH NEAR 20N
100W EXTENDS A RIDGE ACROSS MEXICO TO THE GULF. THROUGH FRIDAY
AFTERNOON THE RIDGE IS FORECAST TO BUILD NORTH ACROSS NORTHERN
MEXICO TO THE WESTERN USA. AS THE RIDGE BUILDS...THIS WILL THEN
INDUCE THE SOUTHWARD AMPLIFICATION OF A TROUGH ACROSS THE GULF OF
MEXICO TO THE YUCATAN/CAMPECHE SOUND LATER ON FRIDAY. UNDER
INFLUENCE OF THE RIDGE ALOFT...SCATTERED CONVECTION WILL BUILD
ALONG THE SIERRA MADRE BETWEEN SONORA-SINALOA IN WESTERN
MEXICO...WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM. THROUGH THURSDAY/FRIDAY THIS DECREASES TO 00-05MM/DAY AND
MAXIMA OF 10MM. OVER CENTRAL-SOUTHERN MEXICO EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. HIGHER AMOUNTS ARE
POSSIBLE ALONG THE COAST BETWEEN OAXACA AND JALISCO AS A NASCENT
TROPICAL DISTURBANCE PROPAGATES TO THE SOUTH...TO FAVOR COASTAL
CONVECTION WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-30MM.
ON FRIDAY THIS INCREASES TO 15-20MM/DAY AND MAXIMA OF 25-50MM.
ACROSS THE YUCATAN-NORTHERN GUATEMALA AND BELIZE EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. ON THURSDAY IT
DECREASES TO 00-05MM/DAY AND MAXIMA OF 10MM. ON FRIDAY...UNDER THE
INFLUENCE OF THE MID/UPPER LEVEL TROUGH...THE MOST ACTIVE IS
EXPECTED ACROSS CHIAPAS IN SOUTHERN MEXICO-GUATEMALA WITH
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

AN ELONGATED TROUGH TO THE EAST STRETCHES FROM THE
BAHAMAS...ACROSS CENTRAL/WESTERN CUBA TO HONDURAS/EL SALVADOR. THE
TROUGH IS TO CUT OFF FROM THE FLOW EARLY IN THE CYCLE...AND AS
SUCH IT IS TO GRADUALLY WEAKEN/FILL LATER ON FRIDAY. EARLY IN THE
CYCLE THE TROUGH ALOFT WILL VENT CONVECTION ACROSS NORTHERN
HONDURAS...TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM/DAY. ON THURSDAY IT DECREASES TO 00-05MM/DAY AND MAXIMA OF
10MM. ON FRIDAY...DIURNAL CONVECTION WILL INCREASES TO 05-10MM/DAY
AND MAXIMA OF 15-25MM. OVER SOUTHERN HONDURAS-EL SALVADOR/WESTERN
NICARAGUA EXPECT RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM. OVER COSTA RICA-PANAMA...UNDER INFLUENCE OF THE
ITCZ...EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM. ON THURSDAY-FRIDAY THIS INCREASES TO 10-15MM/DAY AND
MAXIMA OF 20-35MM. OVER CUBA THE MEANDERING UPPER LEVEL TROUGH
WILL FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM...WITH MOST ACTIVE ON EASTERN HALF OF THE ISLAND. ACROSS
THE CAYMAN ISLES-JAMAICA EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY
AND MAXIMA OF 10MM EARLY IN THE CYCLE. OVER THE BAHAMAS EXPECT
RAINFALL ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15MM. THROUGH
FRIDAY CONVECTION IS TO INTENSIFY UNDER INFLUENCE OF HURRICANE
MARIA.

A CELL OF THE SUBTROPICAL RIDGE LIES OVER THE WESTERN ATLANTIC
NORTH OF THE GREATER ANTILLES. THE RIDGE ALOFT IS TO STEER
HURRICANE MARIA TO THE NORTH-NORTHEAST OF THE DOMINICAN REPUBLIC
LATER TODAY. AS THE AFOREMENTIONED TROUGH DEEPENS ACROSS THE
SOUTHEAST USA LATER IN THE WEEK...THE NHC THEN FORECASTS THE
HURRICANE TO LIFT TO THE NORTH WHILE MOVING AWAY FROM THE BAHAMAS.
THE HURRICANE WILL MODULATE THE ATLANTIC ITCZ NORTH ACROSS THE
WINDWARD ISLES...TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-40MM. ACROSS THE LEEWARD ISLANDS EXPECTING ADDITIONAL
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM THROUGH
THURSDAY MORNING. THROUGH FRIDAY THIS DECREASES TO 05-10MM/DAY AND
MAXIMA OF 15-25MM. OVER THE VIRGIN ISLES-NORTHERN LEEWARD
EXPECTING RAINFALL AMOUNTS OF 100-200MM/DAY AND MAXIMA OF
300-375MM THROUGH THURSDAY MORNING. OVER PUERTO RICO THIS IS TO
TRIGGER RAINFALL AMOUNTS OF 250-375MM AND MAXIMA OF 500-625MM. ON
THURSDAY... FEEDER BAND CONVERGENCE IS TO THEN TRIGGER ADDITIONAL
RAINFALL AMOUNTS OF 25-50MM/DAY AND MAXIMA OF
75-150MM...DECREASING TO 15-20MM/DAY AND MAXIMA OF 35-70MM ON
FRIDAY. OVER THE DOMINICAN REPUBLIC THIS IS TO TRIGGER RAINFALL
AMOUNTS OF 25-50MM/DAY AND MAXIMA OF 75-125MM THROUGH THURSDAY
MORNING. ON THURSDAY TO FRIDAY THIS INCREASES TO 75-150MM/DAY AND
MAXIMA OF 250MM. OVER NORTHERN HAITI EXPECTING RAINFALL AMOUNTS OF
25-50MM/DAY AND MAXIMA OF 75-150MM ON THURSDAY...WHILE ACROSS THE
HAITIAN PENINSULA EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY AND
MAXIMA OF 25-50MM. OVER THE TURKS/SOUTHEAST BAHAMAS IT IS TO
SUSTAIN RAINFALL AMOUNTS OF 75-150MM/DAY AND MAXIMA OF 250MM ON
THURSDAY TO FRIDAY...WHILE ON FRIDAY TO SATURDAY EXPECT RAINFALL
AMOUNTS OF 50-75MM/DAY AND MAXIMA OF 100-200MM. ACROSS THE CENTRAL
BAHAMAS THIS IS TO TRIGGER RAINFALL AMOUNTS OF 25-50MM/DAY AND
MAXIMA OF 75-125MM.

AS MARIA MEANDERS NORTH OF THE GREATER ANTILLES...IT IS TO INDUCE
AN INVERTED TROUGH ACROSS NORTHERN COLOMBIA/NORTHWEST VENEZUELA.
THIS IS TO GRADUALLY DRAW THE ITCZ NORTH ACROSS PANAMA-COSTA RICA
TO THE SOUTHERN CARIBBEAN...AND THE NEAR EQUATORIAL TROUGH ACROSS
NORTHERN COLOMBIA/NORTHWEST VENEZUELA TO THE SOUTHERN CARIBBEAN.
MEANWHILE...ON THE WESTERN PLAINS OF COLOMBIA EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. THROUGH FRIDAY THE
DAILY MAXIMA INCREASES TO 20-40MM. OVER NORTHERN
COLOMBIA/NORTHWEST VENEZUELA EXPECT RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-30MM. ON THURSDAY-FRIDAY THIS
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER THE ABC ISLE
THE ITCZ IS TO THEN FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15MM ON THURSDAY-FRIDAY...WHILE ACROSS CENTRAL/EASTERN
VENEZUELA TO GUYANA EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24    36    48    60    72    84    96   TYPE  SOF
29W      33W   37W   41W   44W   48W   51W   55W   TW    24N
44W      47W   49W   51W   DISSIPATES              TW    23N
96W      97W   98W  100W  102W  103W  104W  105W   TW    20N

TROPICAL WAVE ALONG 29W AND SOUTH OF 24N IS TO CONFINE TO THE
ATLANTIC ITCZ DURING THE NEXT THREE DAYS. A TRADE WINDS SURGE AND
A DUSTY SAHARAN AIR LAYER ACCOMPANIES THIS PERTURBATION. ON
SATURDAY IT MOVES NORTH OF THE GUIANAS WHERE IT IS TO FAVOR
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.

A TROPICAL WAVE ALONG 44W ORIGINATED FROM THE REMNANTS OF TROPICAL
DEPRESSION LEE. AS IT INTERACTS WITH A TUTT OVER THE TROPICAL
ATLANTIC THE WAVE IS FORECAST TO DISSIPATE LATER ON THURSDAY.

TROPICAL WAVE ALONG 96W AND SOUTH OF 20N IS TO SLOWLY PROPAGATE
ALONG THE EASTERN PACIFIC ITCZ/SOUTHERN-CENTRAL STATES OF MEXICO.
NOTE THAT THE NHC IS MONITORING THIS FEATURE FOR POSSIBILITY OF A
TROPICAL CYCLONE FORMING LATER THIS WEEKEND. MEANWHILE...ON THE
SOUTHERN-SOUTHEAST STATES OF MEXICO THIS IS TO SUSTAIN RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. ACROSS SOUTHWEST
MEXICO...AS THIS FEATURE BECOMES BETTER ORGANIZED...IT IS TO THEN
TRIGGER RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM ON
FRIDAY.

GUY...NMS (BELIZE)
RIVAS...SENAMHI (PERU)
DAVISON/GALVEZ...WPC (USA)

$$





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