Prognostic Meteorological Discussion
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FXCA20 KWBC 171838
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 PM EDT THU AUG 17 2017

TROPICAL DISCUSSION FROM AUG 17/12 UTC: A TUTT LOW CENTERS OVER
NORTHEASTERN MEXICO AND IS SPLITTING THE SUBTROPICAL RIDGE IN TWO.
A CELL CENTERS OVER SONORA/CHIHUAHUA AND ANOTHER OVER THE
NORTHEASTERN GULF OF MEXICO. THE TUTT IS FORECAST TO RETROGRESS TO
THE SOUTH WEST...AND BY SATURDAY EVENING IT WILL CENTER OVER
ZACATECAS/NORTHERN JALISCO IN MEXICO. THIS WILL INTERACT WITH
SEASONALLY MOIST AND UNSTABLE AIR MASS IN WESTERN AND SOUTHWESTERN
MEXICO TO SUSTAIN DIURNAL CONVECTION THAT WILL PRODUCE MODERATE
RAINFALL AMOUNTS. THROUGH EARLY FRIDAY EXPECTING AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM ALONG THE SIERRA MADRE
OCCIDENTAL...AND 10-15MM/DAY WITH MAXIMA OF 20-30MM IN
SOUTHWESTERN MEXICO/EJE VOLCANICO. ALONG THE GULF COAST STATES OF
MEXICO EXPECTING 05-10MM/DAY AND ISOLATED MAXIMA OF 15-25MM IN
THUNDERSTORMS. BY FRIDAY-EARLY SATURDAY...EXPECTING LARGEST
ACCUMULATIONS ALONG SOUTHWESTERN AND WESTERN MEXICO WHERE DIURNAL
CONVECTION WILL PRODUCE 10-15MM/DAY AND MAXIMA OF 20-40MM.
ISOLATED THUNDERSTORMS IN EASTERN MEXICO/SIERRA MADRE ORIENTAL
WILL PRODUCE 05-10MM/DAY AND MAXIMA OF 15MM. SIMILAR AMOUNTS ARE
EXPECTED ALONG THE SIERRA MADRE OCCIDENTAL ON
SATURDAY-SUNDAY...WHILE A MARKED DECREASE IS EXPECTED IN EASTERN
AND SOUTHERN MEXICO IN ASSOCIATION WITH A DRIER AIR MASS ARRIVING
FROM THE GULF OF MEXICO.

TO THE SOUTHEAST OF THE GULF OF MEXICO...AN IMPRESSIVE STRONG TUTT
LOW IS RETROGRESSING. THE TUTT LOW IS FORECAST TO CENTER OVER
SOUTHEASTERN CUBA BY THURSDAY EVENING...WESTERN CUBA BY FRIDAY
EVENING...AND JUST TO THE NORTH OF CANCUN BY SATURDAY EVENING. THE
STRONG TUTT WILL STIMULATE CONVECTION ESPECIALLY ALONG ITS EASTERN
PERIPHERY...WHERE IT IS INTERACTING WITH A DEEP MOIST LAYER AND A
TUTT INDUCED TROUGH IN THE TRADES. THIS IS A REGION PRONE FOR
HEAVY RAINFALL THROUGH THE CYCLE...INCLUDING THE RISK FOR
NOCTURNAL MCS FORMATION. ON THURSDAY THROUGH EARLY
FRIDAY...LARGEST ACCUMULATIONS WILL CLUSTER OVER HISPANIOLA WHERE
EXPECTING 15-30MM/DAY AND MAXIMA OF 40-80MM. NORTH ACROSS THE
TURKS AND CAICOS EXPECTING 10-15MM/DAY AND MAXIMA OF 20-40MM. IN
PUERTO RICO AND THE VIRGIN ISLANDS EXPECTING 15-30MM/DAY AND
MAXIMA OF 40-80MM...ALTHOUGH PRECIPITATION RATES ARE DECREASING
AND THE STRONGEST CONVECTION IS EXITING THE AREA TO THE NORTHEAST.
BY FRIDAY-SATURDAY LARGEST ACCUMULATIONS ARE TO CLUSTER ACROSS
EASTERN/CENTRAL CUBA AND THE BAHAMAS...WHERE EXPECTING 15-20MM/DAY
AND MAXIMA OF 35-70MM. MOST WIDESPREAD CONVECTION IS EXPECTED
ACROSS THE BAHAMAS. ACROSS JAMAICA EXPECTING 10-15MM/DAY AND
MAXIMA OF 20-45MM. BY SATURDAY-SUNDAY...LARGEST ACCUMULATIONS ARE
EXPECTED IN THE NORTHERN BAHAMAS WHERE AMOUNTS WILL REACH
15-20MM/DAY AND MAXIMA OF 35-70MM. IN WESTERN CUBA EXPECTING
15-20MM/DAY AND MAXIMA OF 25-50MM.

IN THE CARIBBEAN...THE CONCERN ARE THE STRONG TROPICAL WAVES
APPROACHING FROM THE TROPICAL ATLANTIC. THE FIRST WAVE TO ARRIVE
WILL ENTER THE ARC OF THE LESSER ANTILLES LATE ON THURSDAY. THE
NHC IS MONITORING THIS SYSTEM FOR POTENTIAL TROPICAL CYCLONE
FORMATION. GIVEN THE EXPECTED TRACK...LARGEST ACCUMULATIONS ARE
EXPECTED ACROSS BARBADOS/SAINT VINCENT AND NORTH INTO MARTINIQUE
AND DOMINICA. THROUGH EARLY FRIDAY EXPECTING AMOUNTS OF
20-40MM/DAY AND MAXIMA OF 75-125MM. NOTE THAT THERE IS THE
POTENTIAL FOR ISOLATED HIGHER AMOUNTS IN REGIONS OF OROGRAPHIC
FORCING ALONG EASTERN SLOPES. BY FRIDAY-SATURDAY TRAILING
CONVECTION WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 25-50MM ACROSS
THE CENTRAL LESSER ANTILLES. BY SATURDAY-SUNDAY...STRONGEST
CONVECTION WITH THE WAVE SHOULD CLUSTER OVER OPEN WATERS OF THE
CARIBBEAN. YET...IT WILL STIMULATE MOISTURE CONVERGENCE ACROSS
NORTHERN COLOMBIA TO SUSTAIN ACCUMULATIONS OF 15-20MM/DAY AND
MAXIMA OF 30-60MM...WHILE IN SOUTHERN HISPANIOLA EXPECTING
10-15MM/DAY AND MAXIMA OF 20-30MM.

THE NEXT DISTURBANCE OF INTEREST FOR THE EASTERN CARIBBEAN IS A
TROPICAL WAVE LOCATED AT 43W. CONVECTION WITH THIS WAVE IS
FORECAST TO DRIFT FURTHER NORTH DUE TO A WEAKNESS IN THE MID-UPPER
RIDGE TO ITS NORTH. THUS EXPECTING MARGINAL ENHANCEMENT OF
ACTIVITY ONCE IT REACHES THE LESSER ANTILLES. THIS WILL PRODUCE
05-10MM/DAY AND MAXIMA OF 15-20MM ACROSS THE LEEWARD ISLANDS AND
VIRGIN ISLANDS ON SATURDAY-SUNDAY.

ACROSS NORTHERN SOUTH AMERICA...MOST ACTIVE CONVECTION IS EXPECTED
ACROSS COLOMBIA AND WESTERN VENEZUELA...AS A PERSISTENT UPPER
DIFFLUENT/DIVERGENT PATTERN REMAIN IN PLACE IN A REGION OF
ENHANCED CONVECTIVE INSTABILITY. TO THE EAST OF 65W...A DRIER AIR
MASS OF SOUTHERN ATLANTIC ORIGINS WILL LIMIT THE DEVELOPMENT OF
DEEP CONVECTION...THUS EXPECTING LIGHT ACCUMULATIONS ACROSS THE
GUIANAS. IN COLOMBIA...EXPECTING AMOUNTS OF 10-15MM/DAY AND MAXIMA
OF 20-40MM ON THURSDAY-EARLY FRIDAY INCREASING TO 15-20MM/DAY AND
MAXIMA OF 35-70MM ON FRIDAY-SUNDAY ACROSS THE CARIBBEAN COAST AND
PLAINS/NORTHERN ANDES. HEAVY RAINFALL WILL SPREAD INTO PANAMA AND
COSTA RICA ON SATURDAY TO PRODUCE 15-20MM/DAY AND MAXIMA OF
30-60MM. ACROSS CENTRAL/NORTHEASTERN COLOMBIA AND THE WESTERN
VENEZUELAN LLANOS EXPECTING AMOUNTS IN THE ORDER OF 10-15MM/DAY
AND MAXIMA OF 20-30MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24    36    48    60    72    84    96  TYPE
43W      46W   50W   54W   58W   62W   65W   68W  TW
53W      56W   60W   63W   67W   71W   75W   79W  TW
68W      71W   75W   78W   81W   84W   86W   88W TUTT INDCD
82W      85W   88W   91W   DISSIPATES             TW
89W      DISSIPATES                               EW

A TROPICAL WAVE ALONG 43W IS FORECAST TO REACH THE ARC OF THE
LESSER ANTILLES DURING THE DAY ON SATURDAY. STRONGEST
CONVECTION...HOWEVER...IS FORECAST TO DRIFT NORTH OF THE CARIBBEAN
BASIN...THUS EXPECTING AMOUNTS IN THE ORDER OF 05-10MM/DAY AND
ISOLATED MAXIMA OF 15-20MM/DAY.

A TROPICAL WAVE ALONG 53W IS BEING MONITORED BY THE NHC FOR
POTENTIAL TROPICAL CYCLONE FORMATION. THIS WAVE WILL LEAD TO HEAVY
RAINFALL ACROSS THE CENTRAL LESSER ANTILLES WHERE IT WILL LEAD TO
20-40MM/DAY AND MAXIMA OF 75-125MM...ALTHOUGH LARGER AMOUNTS ARE
POSSIBLE IN REGIONS OF OROGRAPHIC UPLIFT.

RETROGRESSING TUTT ACROSS SOUTHEASTERN CUBA SUSTAINS AN INDUCED
TROUGH IN THE EASTERLY TRADES...WITH AXIS NORTH ALONG 68W. THE
WAVE IS ENHANCING MOISTURE TRANSPORT/CONVERGENCE ACROSS
HISPANIOLA...WHERE MOST ACTIVE CONVECTION IS EXPECTED ON FRIDAY
WITH AMOUNTS OF 15-30MM/DAY AND MAXIMA OF 40-80MM. AS THE WAVE
MEANDERS NORTHWESTWARD IN UNISON WITH THE ASSOCIATED TUTT...IT
WILL LEAD TO AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 35-70MM ACROSS
EASTERN AND CENTRAL CUBA/BAHAMAS ON FRIDAY...AND THE NORTHERN
BAHAMAS ON SATURDAY. ACROSS WESTERN CUBA...IT WILL PRODUCE
15-20MM/DAY AND MAXIMA OF 25-50MM ON SATURDAY.

A TROPICAL WAVE ALONG 82W IS FORECAST TO DISSIPATE WEST OF 91W ON
FRIDAY. IN THE MEAN TIME...IT WILL FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40 IN SOUTHERN CENTRAL AMERICA.

AN EASTERLY WAVE AT 89W HAS LOST DEFINITION.

GUY...NMS (BELIZE)
DAVISON/GALVEZ...WPC (USA)

$$





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