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000
FXCA20 KWBC 291832
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
232 PM EDT THU SEP 29 2016

AT 15 UTC TROPICAL STORM MATTHEW CENTERED NEAR 14.2N 66.3W...WITH
MAXIMUM SUSTAINED WINDS OF 60KT AND MINIMAL CENTRAL PRESSURE OF
996 HPA. THE STORM IS MOVING WEST AT 13KT...SEE NHC DISCUSSION FOR
DETAILS AND OFFICIAL FORECAST.

TROPICAL DISCUSSION FROM SEPTEMBER 29/12UTC: AT 500/250 HPA...WEST
OVER THE DOMAIN...BROAD CELL OF THE SUBTROPICAL RIDGE DOMINATES
THE FLOW ACROSS MEXICO/CENTRAL USA-THE GULF TO NORTHERN CENTRAL
AMERICA. RIDGE ALOFT IS TO HOLD NEARLY UNCHANGED THROUGH THURSDAY
EVENING. MEANWHILE...THE RIDGE IS TO ANCHOR AT 250 HPA 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. ON FRIDAY IT WILL
INCREASE TO 15-20MM/DAY AND MAXIMA OF 25-50MM AS SHORT WAVE TROUGH
STREAMS ACROSS NORTHERN MEXICO. OVER SINALOA-COLIMA/NAYARIT TO
GUERRERO EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-35MM. THROUGH FRIDAY THIS IS TO ALSO INCREASE TO 15-20MM/DAY
AND MAXIMA OF 20-35MM. ON THE SOUTHERN STATES OF MEXICO EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM....INCREASING
TO 05-10MM/DAY AND MAXIMA OF 15-20MM LATER ON FRIDAY.

ALSO AT 250 HPA...A SHORT WAVE TROUGH EXTENDS TO THE
NORTH-NORTHEAST ACROSS THE EASTERN TROPICAL PACIFIC TO NORTHERN
CENTRAL AMERICA. THIS IS TO GRADUALLY SHEAR WEST UNDER THE
SUBTROPICAL RIDGE TO THE NORTH. MEANWHILE...THIS IS TO ENHANCE
CONVECTION ACROSS SOUTHERN GUATEMALA-EL SALVADOR AND SOUTHERN
HONDURAS...WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-30MM. ON SATURDAY...AS THE UPPER TROUGH MOVES
AWAY...EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM.

IN A SINUSOIDAL LONG WAVE PATTERN...THE RIDGE OVER THE WESTERN USA
IS INDUCING THE SOUTHWARD AMPLIFICATION OF A LONG WAVE TROUGH
ACROSS THE EASTERN USA TO THE EASTERN GULF/NORTHWEST CARIBBEAN.
THROUGH FRIDAY EVENING THE TROUGH WILL REACH MAXIMUM
AMPLITUDE...AND THIS IS TO THEN HOLD THROUGH SATURDAY. THE HIGH
AMPLITUDE TROUGH WILL FOCUS SHORT WAVE ENERGY ACROSS WESTERN CUBA
INTO 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 THROUGH FRIDAY...DECREASING
TO 05-10MM/DAY AND MAXIMA OF 15MM ON SATURDAY. 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. OVER NORTHERN HONDURAS TO CENTRAL
GUATEMALA EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM ON FRIDAY. ON SATURDAY THIS WILL INCREASE TO 10-15MM/DAY
AND MAXIMA OF 20-35MM.

THE DEEPENING TROUGH OVER THE CONTINENT IS TO ALSO FAVOR A SURFACE
FRONT THAT SURGES ACROSS THE USA TO THE NORTHERN GULF/NORTHEAST
MEXICO EARLY ON FRIDAY MORNING. AS IT ENTERS NORTHEAST MEXICO THIS
WILL TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM
EARLY ON FRIDAY MORNING. 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.
THROUGH SATURDAY THIS WILL DECREASE TO 05-10MM/DAY AND MAXIMA OF
15MM.

BROAD CELL OF THE SUBEQUATORIAL RIDGE DOMINATES THE FLOW ACROSS
THE CARIBBEAN BASIN AND NORTHERN SOUTH AMERICA/SOUTHERN CENTRAL
AMERICA. THE RIDGE ALOFT IS VENTING CONVECTION IN ASSOCIATION WITH
TROPICAL STORM MATTHEW. MID LEVEL RIDGE TO THE NORTH OF THE
ISLANDS IS TO STEER THIS SYSTEM IN A WESTERLY DIRECTION...WITH THE
NHC FORECASTING GRADUAL INTENSIFICATION TO A HURRICANE ON FRIDAY
MORNING. THROUGH SATURDAY IT IS TO MEANDER WEST ACROSS THE
SOUTHERN CARIBBEAN WHILE REMAINING NORTH OF LA GUAJIRA PENINSULA.
THE STORM IS MODULATING THE ATLANTIC ITCZ ACROSS THE WINDWARD
ISLES. CONVECTIVE CELLS ARE CURRENTLY TRAINING ACROSS TRINIDAD
INTO THE GRENADINES/SOUTHERN WINDWARD ISLANDS...AND THIS WILL
RESULT IN ADDITIONAL RAINFALL AMOUNTS OF 25-50MM WITH MAXIMA OF
100-125MM. ACROSS THE NORTHERN WINDWARDS AND FRENCH ISLES OUTER
BAND CONVECTION WOULD LIKELY FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-40MM...WITH LOCALLY HIGHER AMOUNTS HIGHLY LIKELY.
OUTER BAND CONVECTION IS TO ALSO AFFECT THE ABC ISLES...LA GUAJIRA
PENINSULA IN NORTHERN COLOMBIA AND PORTIONS OF FALCON IN NORTHWEST
VENEZUELA...TO RESULT IN RAINFALL AMOUNTS OF 15-20MM/DAY AND
MAXIMA OF 35-70MM. OVER THE NORTHEAST CARIBBEAN ISLES...THE STORM
TO THE SOUTH IS TO SUSTAIN STRONG BOUNDARY LAYER WINDS THROUGH
FRIDAY MORNING. THE STRONG WINDS ACROSS THE NORTHERN
LEEWARD/VIRGIN ISLES WILL FAVOR GENERATION OF STREAMERS THAT ARE
TO AFFECT PUERTO RICO AND EASTERN HISPANIOLA FROM
TIME-TO-TIME...TRIGGERING LIGHT RAINFALL AMOUNTS WITH ACCUMULATION
OF 00-05MM/DAY AND ISOLATED MAXIMA OF 10MM.

THE SUBEQUATORIAL RIDGE...AS IT MEANDERS OVER NORTHERN SOUTH
AMERICA...IS TO VENT DIURNAL CONVECTION. ACROSS COLOMBIA INITIALLY
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-30MM.
AS TROPICAL STORM MATTHEW MOVES NORTH OF LA GUAJIRA LATER ON
FRIDAY THIS IS TO STRENGTHEN THE PANAMANIAN TROUGH...ENHANCING THE
ONSHORE FLOW ACROSS WESTERN COLOMBIA TO THE ANDEAN REGION. IN THIS
AREA RAINFALL AMOUNTS WILL INCREASE TO 15-20MM/DAY AND MAXIMA OF
25-50MM THROUGH SUNDAY MORNING. ON SUNDAY TO MONDAY...AS THE STORM
LIFTS NORTH...THIS WILL DECREASE TO 10-15MM/DAY AND MAXIMA OF
20-30MM. OVER EASTERN COLOMBIA TO CENTRAL VENEZUELA EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ON
SATURDAY...ACTIVITY ACROSS EASTERN COLOMBIA TO APURES-BARINAS AND
ZULIA IN NORTHWEST VENEZUELA WILL INCREASE TO 15-30MM/DAY AND
MAXIMA OF 40-80MM. THIS IS LIKELY TO PERSIST THROUGH MONDAY
MORNING.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:

INITIAL  24      36      48      60      72      84      96
TYPE
43W      46W     49W    52W     55W     58W     61W     64W
TUTT INDUCED
84W      88W     92W    95W     98W    101W    104W    107W
EW
102W    105W    108W   111W    114W   DISSIPATES
EW

BROAD TUTT OVER THE CENTRAL ATLANTIC SUSTAINS AN INDUCED/INVERTED
TROUGH IN THE EASTERLY TRADES...WITH AXIS NORTH ALONG 43W. THIS
REACHES THE ISLAND CHAIN EARLY ON SUNDAY MORNING. AS IT ENTERS THE
ISLANDS THIS WILL INTERACT WITH THE ATLANTIC ITCZ TO TRIGGER LIGHT
TO MODERATE CONVECTION ACROSS THE NORTHERN WINDWARD AND FRENCH
ISLES...WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND
MAXIMA OF 10MM LATER ON SUNDAY.

EASTERLY WAVE ALONG 84W IS MOVING AT A SLOWER PACE THAN PREVIOUSLY
ANTICIPATED. IT IS NOW FORECAST TO MOVE ACROSS HONDURAS TO
GUATEMALA EARLY ON FRIDAY MORNING. MEANWHILE...IN INTERACTION WITH
THE ITCZ IT IS TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-30MM. LATER ON FRIDAY TO EARLY SATURDAY MORNING IT
MOVES ACROSS THE SOUTHERN MEXICO STATES...TRIGGERING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. LATER ON SATURDAY IT
WILL FAVOR SCATTERED CONVECTION ACROSS CENTRAL STATES OF MEXICO
WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM.

AN EASTERLY WAVE ALONG 102W WILL MOVE ACROSS SOUTHWEST MEXICO
THROUGH FRIDAY MORNING...MEANWHILE FAVORING RAINFALL AMOUNTS OF
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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