Prognostic Meteorological Discussion
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
315 PM EDT FRI AUG 18 2017

AT 15 UTC...TROPICAL STORM HARVEY CENTERS AT 13.1N 61.3W. CENTRAL
PRESSURE IS 1005 HPA. MAXIMUM SUSTAINED WINDS ARE AT 35KT WITH
GUSTS UP TO 45KT. THE SYSTEM IS MOVING WESTWARD OR AT 270 DEGREES
AND AT 18KT.

TROPICAL DISCUSSION FROM AUG 18/12 UTC: A TUTT LOW IS MEANDERING
TO THE SOUTH WEST ACROSS CENTRAL MEXICO...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
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....

AN IMPRESSIVE STRONG TUTT LOW IS RETROGRESSING ACROSS
CUBA/BAHAMAS. BY FRIDAY EVENING THE TUTT LOW WILL CENTER OVER
WESTERN CUBA...BY SATURDAY EVENING JUST TO THE NORTH OF THE
YUCATAN CHANNEL...BY SUNDAY EVENING OVER THE EASTERN GULF OF
MEXICO...AND BY MONDAY EVENING JUST TO THE SOUTH OF LOUISIANA. 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. BY FRIDAY-SATURDAY LARGEST
ACCUMULATIONS ARE TO CLUSTER ACROSS EASTERN/CENTRAL CUBA AND THE
BAHAMAS. IN CUBA EXPECTING 15-20MM/DAY AND MAXIMA OF 35-70MM IN
STRONGEST THUNDERSTORMS. OVER THE BAHAMAS EXPECTING 10-15MM/DAY
AND MAXIMA OF 20-45MM. DURING SATURDAY-SUNDAY...EXPECTING
ACCUMULATIONS OF 15-20MM/DAY AND MAXIMA OF 25-50MM IN WESTERN
CUBA...WHILE OVER THE BAHAMAS EXPECTING 15-20MM/DAY AND MAXIMA OF
35-70MM WITH THE RISK OF MCS FORMATION. BY SUNDAY-MONDAY...

IN THE CARIBBEAN...THE CONCERN ARE TROPICAL STORM HARVEY AND A
STRONG TROPICAL WAVE THAT TRAILS BEHIND. GIVEN THE PROJECTED PATH
OF HARVEY (SEE NHC WEBSITE)...HEAVY PRECIPITATION WILL REACH
NORTHERN CENTRAL AMERICA ON MONDAY. WE ARE EXPECTING LARGEST
ACCUMULATIONS IN HONDURAS/NORTHERN NICARAGUA/BELIZE/GUATEMALA.
LOCALLY HEAVY RAINFALL IS ALSO EXPECTED IN THE GULF OF FONSECA/EL
SALVADOR/SOUTHERN GUATEMALA REGIONS IN ASSOCIATION WITH FEEDER
BAND CONVERGENCE/SOUTHWESTERLY TRADES ENHANCING MOISTURE
CONVERGENCE. ALTHOUGH THE DETAILS ON THE STRUCTURE OF THE SYSTEM
AND THE POSITION ARE STILL NOT CLEAR...WE ANTICIPATE ACCUMULATIONS
IN THE ORDER OF 20-40MM/DAY AND MAXIMA OF 75-125MM IN REGIONS OF
OROGRAPHICALLY-INDUCED ASCENT. ALTHOUGH THE CYCLONE IS NOT
FORECAST TO AFFECT SOUTH AMERICA DIRECTLY...FEEDER BAND
CONVERGENCE WILL ENHANCE ACCUMULATIONS IN EXTREME NORTHERN SOUTH
AMERICA AND SOUTHERN CENTRAL AMERICA. THROUGH EARLY SATURDAY
EXPECTING 15-20MM/DAY AND MAXIMA OF 25-50MM IN NORTHEASTERN
VENEZUELA...AND 10-15MM/DAY AND MAXIMA OF 20-35MM ACROSS
NORTHWESTERN/NORTH-CENTRAL VENEZUELA. IN NORTHERN COLOMBIA
EXPECTING 15-20MM/DAY AND MAXIMA OF 35-70MM. BY
SATURDAY-SUNDAY...EXPECTING ACCUMULATIONS OF 20-40MM/DAY AND
MAXIMA OF 60-100MM IN WESTERN COLOMBIA...AND 15-20MM/DAY WITH
MAXIMA OF 30-60MM IN SOUTHERN COSTA RICA/SOUTHWESTERN PANAMA AND
NORTHERN COLOMBIA. BY SUNDAY-MONDAY...LARGEST ACCUMULATIONS WILL
CONCENTRATE ACROSS COSTA RICA AN PANAMA WHERE EXPECTING
15-20MM/DAY AND MAXIMA OF 25-50MM. ALSO...FEEDER BAND CONVERGENCE
IN JAMAICA WILL LEAD TO RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA
OF 25-50MM.

REGARDING THE TROPICAL WAVE TRAILING BEHIND HARVEY...MODELS AGREE
IN STRONGEST ACTIVITY DRIFTING NORTHWARDS. YET...DEEP-LAYER
MOISTURE AND INSTABILITY WILL ENTER THE NORTHERN CARIBBEAN TO
PRODUCE MODERATE RAINFALL IN THE LEEWARD ISLANDS AND GREATER
ANTILLES. BY SATURDAY-SUNDAY EXPECTING AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM ACROSS THE LEEWARD ISLANDS. BY
SUNDAY-MONDAY...THE WAVE WILL ENHANCE CONVECTION ACROSS THE ENTIRE
ARC OF THE LESSER ANTILLES. ACTIVITY WILL MOVE VERY RAPIDLY...THUS
EXPECTING AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM IN AREAS OF
OROGRAPHIC INTERACTIONS. IN PUERTO RICO...EXPECTING AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM. IN HISPANIOLA...EXPECTING
ACCUMULATIONS OF 15-20MM/DAY AND MAXIMA OF 25-50MM MOSTLY ALONG
THE SOUTHERN AND EASTERN PORTIONS OF THE ISLAND.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24    36    48    60    72    84    96  TYPE       SOF

35W      38W   42W   46W   49W   53W   57W   59W  TW         25N
50W      53W   56W   60W   64W   67W   70W   74W  TW         22N
75W      77W   79W   82W   84W   86W   88W   90W  TUTT INDCD 27N

A TROPICAL WAVE IS INITIALIZED AT 35W...AND IS FORECAST TO ENTER
THE GUIANAS ON SUNDAY AND THE ARC OF THE LESSER ANTILLES LATE ON
MONDAY...WITH LIMITED EFFECTS IN PRECIPITATION.

A TROPICAL WAVE ALONG 50W 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. THE SOUTHERN TIER OF THIS WAVE IS FORECAST TO ENHANCE
CONVECTION IN THE CARIBBEAN BASIN. BY SATURDAY-SUNDAY EXPECTING
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM ACROSS THE LEEWARD
ISLANDS. BY SUNDAY-MONDAY...THE WAVE WILL ENHANCE CONVECTION
ACROSS THE ENTIRE ARC OF THE LESSER ANTILLES. ACTIVITY WILL MOVE
VERY RAPIDLY...THUS EXPECTING AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM IN AREAS OF OROGRAPHIC INTERACTIONS. IN PUERTO
RICO...EXPECTING AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. IN
HISPANIOLA...EXPECTING ACCUMULATIONS OF 15-20MM/DAY AND MAXIMA OF
25-50MM MOSTLY ALONG THE SOUTHERN AND EASTERN PORTIONS OF THE
ISLAND.

RETROGRESSING TUTT ACROSS SOUTHEASTERN CUBA SUSTAINS AN INDUCED
TROUGH IN THE EASTERLY TRADES...WITH AXIS NORTH ALONG 75W. THIS
TUTT-INDUCED WAVE WILL ENHANCE ACTIVITY ACROSS THE BAHAMAS AND
CUBA THROUGH THE CYCLE...IN INTERACTION WITH THE UPPER TROUGH.

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

$$





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