Prognostic Meteorological Discussion
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
219 PM EDT MON AUG 29 2016

AT 15 UTC TD NINE CENTERED NEAR 23.6N 84.3W...WITH MAXIMUM
SUSTAINED WINDS OF 30KT AND MINIMAL CENTRAL PRESSURE OF 1007 HPA.
THE TD IS MOVING WEST AT 06KT. SEE NHC BULLETIN FOR OFFICIAL
FORECAST.

TROPICAL DISCUSSION FROM AUG 29/12UTC: AT 250 HPA THE SUBTROPICAL
RIDGE EXTENDS FROM MEXICO TO THE WESTERN CARIBBEAN...WITH AXIS
ANCHORING ON TWO CLOSED HIGHS. THE WESTERNMOST CENTERS OVER MEXICO
NEAR 20N 100W WHILE THE ONE TO THE OTHER MEANDERS OVER WESTERN
CUBA/STRAITS OF FLORIDA. THIS PATTERN IS EXPECTED TO HOLD DURING
THE NEXT FEW DAYS. A TROUGH FLANKS THE WESTERN FRINGES OF THIS
RIDGE...AS IT EXTENDS ACROSS THE WESTERN USA TO NORTHWEST
MEXICO/BAJA PENINSULA. THROUGH TUESDAY EVENING THE BASE OF THE
TROUGH IS EXPECTED TO PULL. MEANWHILE...THE UPPER LEVEL TROUGH
WILL ENHANCE DIURNAL CONVECTION ACROSS SONORA-SINALOA-CHIHUAHUA IN
NORTHWEST MEXICO...TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM. ON TUESDAY...AS THE UPPER SUPPORT WANES...THIS
WILL DECREASE TO 05-10MM/DAY AND MAXIMA OF 15-25MM. AN INCREASE IN
ACTIVITY...HOWEVER...IS EXPECTED ON WEDNESDAY AS ENHANCED BY A
SHORT WAVE TROUGH LIFTING ACROSS NORTHWEST MEXICO. THIS IS TO
FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THE
RIDGE ALOFT...AS IT MEANDERS OVER MEXICO...IT WILL VENT DIURNAL
CONVECTION ALONG THE SIERRA MADRE DEL SUR IN SOUTHWEST MEXICO. IN
THIS AREA EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM THROUGH TUESDAY MORNING. THEREAFTER THE MAXIMA IS EXPECTED
TO PEAK AROUND 15MM.

THE RIDGE ALOFT IS TO ALSO VENT CONVECTION IN ASSOCIATION WITH TD
NINE. THE NHC IS FORECASTING THIS DEPRESSION TO STRENGTHEN TO A
TROPICAL STORM LATER THIS AFTERNOON. MEANWHILE...THIS WILL ENHANCE
MOISTURE CONVERGENCE ACROSS THE CAYMAN ISLES-CUBA TO FAVOR
RAINFALL AMOUNTS OF 35-70MM/DAY AND MAXIMA OF 150-200MM. LOCALLY
HIGHER AMOUNTS ARE HIGHLY LIKELY. THROUGH TUESDAY...AS THE CYCLONE
MEANDERS TO THE WEST-NORTHWEST...THIS WILL DECREASE TO 10-15MM/DAY
AND MAXIMA OF 20-30MM. IN A MOIST ADVECTIVE PATTERN...THE
DEPRESSION IS TO ALSO FAVOR CONVECTION ACROSS THE NORTHWEST
BAHAMAS...WITH RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
35-70MM. THROUGH TUESDAY THIS WILL DECREASE TO 10-15MM/DAY AND
MAXIMA OF 20-45MM...WHILE ON WEDNESDAY THE MAXIMA WILL PEAK AT
15MM. OTHER CONVECTION IS TO BUILD TO THE SOUTH ACROSS
BELIZE-QUINTANA ROO/YUCATAN TO NORTHERN GUATEMALA. IN THIS AREA
INITIALLY EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM. AS THE STORM MEANDERS INTO THE GULF OF MEXICO...AND AN
INDUCED TROUGH TO THE SOUTH MEANDERS INLAND ACROSS BELIZE...THIS
WILL INCREASE TO 10-15MM/DAY AND MAXIMA OF 20-45MM. ON WEDNESDAY
EXPECT LESSER AMOUNTS...WITH ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15-25MM.

A TUTT LOW OVER THE NORTHWEST GULF EXTENDS A SHORT WAVE TROUGH
ALONG THE GULF COAST OF MEXICO. TUTT AXIS IS CUT OFF FROM THE
FLOW...AND GENERAL TENDENCY IS FOR IT TO GRADUALLY WEAKEN.
MEANWHILE...IT IS TO ALSO ENHANCE DIURNAL CONVECTION BETWEEN
COAHUILA-TAMAULIPAS IN NORTHEAST MEXICO...WHERE WE EXPECT RAINFALL
AMOUNTS OF 05-10MM/DAY AND ISOLATED MAXIMA OF 15MM IN ISOLATED TO
SCATTERED CONVECTION.

ANOTHER TUTT LOW TO THE EAST LIES TO THE NORTH-NORTHWEST OF PUERTO
RICO...WITH UPPER CIRCULATION EXTENDING A SHORT WAVE TROUGH TO THE
EASTERN CARIBBEAN. THIS IS INTERACTING WITH THE ITCZ TO THE
SOUTH...PROVIDING THE VENTILATION ALOFT. SIMULTANEOUSLY...A 500
HPA HIGH NEAR 23N 55W IS TO BUILD A RIDGE WEST INTO THE EASTERN
CARIBBEAN. UNDER INFLUENCE OF THIS RIDGE THE UPPER LEVEL TROUGH
WILL MEANDER WEST TO 70W LATER ON TUESDAY...WHILE THE ASSOCIATED
MID LEVEL CIRCULATION IS TO LIFT TO THE NORTH AS IT DECOUPLES FROM
THE UPPER LEVEL CIRCULATION. AS THE TROUGH PATTERN UNRAVELS AND
THE RIDGE BUILDS INTO THE NORTHEAST CARIBBEAN THE GLOBAL MODEL
GUIDANCE SHOW RAPID INTENSIFICATION OF TRADE WINDS CAP INVERSION
ACROSS THE EASTERN CARIBBEAN. THIS IS TO FAVOR A RAPID DRYING
TREND ACROSS THE ISLAND CHAIN. THIS PATTERN IS FORECAST TO HOLD
THROUGH AT LEAST THURSDAY MORNING. AT LOW LEVELS...SOUTHEASTERLY
TRADES DOMINATE THE EASTERN CARIBBEAN. BUT AS THE RIDGE BUILDS
WEST NORTH OF THE ISLANDS THE WINDS WILL BACK TO THE EAST DURING
THE DAY ON TUESDAY. IN A TIGHT GRADIENT BRISK EASTERLY TRADES ARE
TO THEN PREVAIL. OVER THE NORTHEAST CARIBBEAN THE 850 HPA WINDS
WILL PEAK AT 20-25KT...WHILE ACROSS THE SOUTHEAST-CENTRAL
CARIBBEAN WINDS WILL PEAK AT 30-35KT. BRISK EASTERLY TRADES WILL
FAVOR GENERATION OF STREAMERS/SHALLOW CONVECTION ACROSS THE ISLAND
CHAIN...MOST ACTIVE IN THE MORNING HOURS. BUT THESE ARE TO ONLY
TRIGGER LIGHT RAINFALL AMOUNTS IN BRIEF SHOWERS. MOST ACTIVE
CONVECTION IS EXPECTED TO THE SOUTH AS THE TROUGH ALOFT INTERACTS
WITH THE ITCZ OVER THE SOUTHERN WINDWARD ISLES/NORTHEAST
VENEZUELA. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-35MM THROUGH THIS EVENING...DECREASING TO
05-10MM/DAY AND MAXIMA OF 15-20MM/DAY ON TUESDAY AND WEDNESDAY.

ITCZ CONVERGENCE ACROSS SOUTHERN CENTRAL AMERICA IS TO FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. SIMILAR
AMOUNTS ARE EXPECTED ALONG THE NEAR EQUATORIAL TROUGH OVER CENTRAL
VENEZUELA AND AMAZONIA IN EASTERN COLOMBIA THROUGH TUESDAY
MORNING. LATER IN THE DAY...POLAR FRONT SURGING ACROSS BRASIL WILL
FAVOR AN INCREASE IN CONVECTION ACROSS AMAZONIA IN
VENEZUELA-COLOMBIA AND THE PIEDEMONTE LLANERO...WITH RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM. BUT AS THE FRONT
WANES ON WEDNESDAY THIS WILL DECREASE TO 10-15MM/DAY AND MAXIMA OF
20-35MM. OTHER CONVECTION IS TO CLUSTER ACROSS THE WESTERN
PLAIN/ANDEAN REGION OF COLOMBIA...WHERE LOW LEVEL WESTERLY WINDS
ARE TO FAVOR TOPOGRAPHICALLY INDUCED CONVECTION. IN THIS AREA
EXPECTING MODERATE RAINFALL AMOUNTS WITH ACCUMULATION OF
10-15MM/DAY AND MAXIMA OF 20-40MM. THROUGH WEDNESDAY THIS WILL
DECREASE TO 05-10MM/DAY AND MAXIMA OF 15-25MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC

INITIAL    24      36      48      60      72      84      96
TYPE
40W       44W     48W     52W     54W     56W     60W      63W
TW
87W       88W     90W     91W     93W     94W     95W      96W
EW
98W      100W    101W    103W    105W    107W    109W     111W
EW

A TROPICAL WAVE IS INITIALIZED ALONG 40W. CONVECTION WITH THIS
FEATURE IS TO CONFINE TO THE ATLANTIC ITCZ THROUGH THURSDAY
MORNING. AS IT ENTERS THE ISLAND CHAIN LATER IN THE DAY IT IS TO
SUSTAIN SCATTERED CONVECTION WITH ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15MM.

AN EASTERLY WAVE ALONG 87W IS TO SLOWLY MOVE ACROSS EL
SALVADOR-GUATEMALA TO SOUTHERN CHIAPAS. MEANWHILE...THIS WILL
FAVOR SCATTERED CONVECTION WITH ACCUMULATION OF 10-15MM/DAY AND
MAXIMA OF 20-35MM/DAY. IN A WESTERLY LOW LEVEL FLOW ACROSS THE
EASTERN PACIFIC...MOST ACTIVE CONVECTION IS TO CLUSTER ALONG THE
CONTINENTAL DIVIDE BETWEEN NORTHERN NICARAGUA-SOUTHERN GUATEMALA.
DUE TO TOPOGRAPHICAL FORCING LOCALLY HIGHER AMOUNTS ARE HIGHLY
PROBABLE.

AN EASTERLY WAVE ALONG 98W IS TO ENHANCE CONVECTION ACROSS
COLIMA-NAYARIT-GUERRERO IN SOUTHWEST MEXICO...WHERE IT IS TO FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH
TUESDAY THIS WILL DECREASE TO 05-10MM/DAY AND MAXIMA OF 15MM.

CONTRERAS...IMN (COSTA RICA)
GALVEZ/DAVISON...WPC (USA)
$$





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