Prognostic Meteorological Discussion
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FXCA20 KWBC 291818
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
217 PM EDT WED JUL 29 2015

DISCUSSION FROM JUL 29/12 UTC: WEST OVER THE DOMAIN...BROAD RIDGE
IS TO DOMINATE FLOW ACROSS THE SOUTHERN USA-NORTHERN GULF TO THE
NORTHERN STATES OF MEXICO...WHILE ANCHORING ON A MEANDERING HIGH
OVER TEXAS. THE RIDGE IS TO PROVIDE THE STEERING FLOW TO TUTT LOWS
TO THE SOUTH...WITH ONE OFF THE SOUTH COAST OF MEXICO TO MEANDER
WEST ALONG THE SOUTHWEST COAST TO THE EASTERN PACIFIC THROUGH
FRIDAY MORNING. AS IT MEANDERS WEST THIS IS TO ENHANCE DIURNAL
CONVECTION OVER SOUTHWEST MEXICO...WHERE WE EXPECT RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. OTHER CONVECTION ALONG
THE SIERRA MADRE IS TO CLUSTER BETWEEN SINALOA AND
COLIMA/NAYARIT...WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA
OF 15MM. HIGHER AMOUNTS OVER SONORA ARE TO PEAK AT 15-25MM EARLY
IN THE CYCLE.

THE WATER VAPOR IMAGERY SHOWS ANOTHER TUTT OVER THE NORTHWEST
CARIBBEAN/ NORTHERN CENTRAL AMERICA. INFLOW OF SHORT WAVE ENERGY
FROM THE NORTH-NORTHEAST WILL ALLOW THIS TROUGH TO EVOLVE INTO A
CLOSED LOW OFF THE COAST OF HONDURAS EARLY ON THURSDAY. THIS IS TO
THEN MEANDER OVER THE WESTERN CARIBBEAN WHILE EXTENDING A TROUGH
ACROSS GUATEMALA TO THE SOUTHERN STATES OF MEXICO. AS IT MEANDERS
OVER THE WESTERN CARIBBEAN THE SHORT WAVE TROUGH/TUTT LOW IS TO
ENHANCE DIURNAL CONVECTION ACROSS HONDURAS-GUATEMALA...WITH MOST
ACTIVE ON WEDNESDAY-THURSDAY...WHEN WE EXPECT RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-25MM.

MID LEVEL TROUGH TO THE NORTH...MEANWHILE...EXTENDS TO THE
SOUTHWEST FROM A CLOSED LOW OFF THE ATLANTIC COAST OF
FLORIDA...ACROSS THE PENINSULA TO THE EASTERN GULF. THE TROUGH IS
TO PERSIST OVER THE NEXT FEW DAYS...MEANWHILE FOCUSING SHORT WAVE
ENERGY ACROSS BIMINI-GRAND BAHAMA AND GREAT ABACO. THE INFLOW OF
SHORT WAVE ENERGY WILL COMBINE WITH CONVERGENT LOW LEVEL FLOW
PATTERN TO SUSTAIN DEEP LAYER CONVECTIVE INSTABILITY ACROSS THE
NORTHWEST BAHAMAS. IN THIS AREA THE GALVEZ-DAVISON INDEX (GDI)
CONTINUES TO SHOW A GRADUAL INCREASE IN THE RISK OF THUNDERSTORMS
ON THURSDAY TO FRIDAY. IN A SLOW TO EVOLVE PATTERN THERE IS SOME
RISK OF ECHO TRAINING...BUT THIS SEEMS TO BE OF MOST SIGNIFICANCE
JUST TO THE NORTH OF THE ISLANDS. MEANWHILE...OVER GRAND
BAHAMA-GREAT ABACO EXPECTING ACCUMULATION OF 10-15MM/DAY AND
MAXIMA OF 20-35MM...INCREASING TO MAXIMA OF 20-45MM/DAY ON
THURSDAY TO FRIDAY. OVER NEW PROVIDENCE/ELEUTHERA TO NORTHERN
ANDROS EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM.

MID LEVEL RIDGE TO THE SOUTH OF THIS TROUGH DOMINATES FLOW ACROSS
THE NORTHERN CARIBBEAN ISLES. UNDER PRESSURE FROM THE TROUGH TO
THE NORTH THE RIDGE IS TO GRADUALLY COLLAPSE THROUGH FRIDAY
MORNING. BUT ANOTHER RIDGE IS THEN FORECAST TO RAPIDLY BUILD FROM
THE EAST...TO AMPLIFY ACROSS THE CENTRAL ATLANTIC TO THE NORTHERN
CARIBBEAN ISLES LATER ON FRIDAY/EARLY SATURDAY MORNING. AS THE
RIDGE WEAKENS A COUPLE OF MID LEVEL PERTURBATIONS ARE TO MIGRATE
ACROSS THE ISLAND CHAIN TO PUERTO RICO/NORTHEAST CARIBBEAN ISLES
EARLY ON FRIDAY MORNING...REACHING HISPANIOLA/EASTERN CUBA LATER
ON FRIDAY. THIS APPEARS STRONG ENOUGH TO WEAKEN TRADE WINDS CAP
ENVELOPING THE EASTERN CARIBBEAN ISLES...WITH MODELS CONSISTENTLY
SHOWING AN INCREASE IN PWAT AMOUNTS DURING THE DAY ON FRIDAY.
ACROSS THE FRENCH/NORTHERN WINDWARD ISLES-VIRGIN ISLES TO EASTERN
PUERTO RICO THIS IS TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND
MAXIMA OF 10MM ON THURSDAY-FRIDAY. BUILDING RIDGE FROM THE EAST IS
TO THEN SUSTAIN EROSION OF AVAILABLE MOISTURE AND REGENERATION OF
TRADE WINDS CAP.

FARTHER EAST...ANOTHER TUTT LOW IS TO CLOSE NORTH OF FRENCH GUIANA
LATER ON THURSDAY. IN CONTRAST TO PREVIOUS FORECASTS THIS IS NOW
EXPECTED TO REMAIN OFF THE COAST THROUGH THE END OF THE WEEK.
MEANWHILE...IT IS TO INTERACT WITH THE ATLANTIC ITCZ/SEA BREEZE
CONVERGENCE OVER THE NORTHERN GUIANAS. INITIALLY EXPECT RAINFALL
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. THROUGH FRIDAY THIS
INCREASES TO 05-10MM/DAY AND MAXIMA OF 15MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE
22W      25W    28     30W    33W    37W    40W    43W       TW
62W      66W    70W    74W    77W    80W    83W    85W       TW
82W      85W    88W    91W    93W    96W    99W   102W    TW/SURGE
92W      95W    98W   101W   103W   105W   107W   109W       TW

TROPICAL WAVE ALONG 22W IS TO CONFINE TO THE ATLANTIC ITCZ.

TROPICAL WAVE IS INITIALIZED ALONG 62W AND SOUTH OF 19N. A SHALLOW
MOIST PLUME TRAILS THIS WAVE...AND OVER THE NORTHERN
WINDWARD-FRENCH/VIRGIN ISLES IT IS TO FAVOR RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM THROUGH THURSDAY MORNING. ACROSS
EASTERN PUERTO RICO THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM...WHILE OVER HISPANIOLA THE MAXIMA
IS TO PEAK AT 10-15MM ON THURSDAY. MEANWHILE...OVER
NORTHEAST-CENTRAL VENEZUELA THIS IS TO FAVOR RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM THROUGH THURSDAY MORNING...WHILE
OVER NORTHWEST VENEZUELA/NORTHERN COLOMBIA EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-30MM EARLY ON FRIDAY
MORNING. ACROSS PANAMA-COSTA RICA IT IS TO THEN TRIGGER RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM AS IT INTERACTS WITH
THE ITCZ. NORTH ALONG THIS AXIS...OVER JAMAICA-CENTRAL
CUBA...EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF
10MM ON FRIDAY-SATURDAY.

TROPICAL WAVE ALONG 82W IS TO INTERACT WITH THE ITCZ OVER COSTA
RICA-SOUTHERN NICARAGUA TO TRIGGER SCATTERED CONVECTION WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-30MM. ACROSS
NORTHEAST NICARAGUA TO HONDURAS...IN INTERACTION WITH DEEPENING
TUTT LOW TO THE WEST...EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM ON WEDNESDAY TO THURSDAY. SIMILAR AMOUNTS ARE
EXPECTED OVER GUATEMALA-SOUTHERN MEXICO ON THURSDAY TO FRIDAY.
OVER CENTRAL-SOUTHWEST MEXICO THIS INCREASES TO 10-15MM/DAY AND
MAXIMA OF 20-35MM ON FRIDAY TO SATURDAY MORNING.

TROPICAL WAVE ALONG 92W MOVES TO SOUTHERN MEXICO EARLY IN THE
CYCLE...TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM. AS IT MOVES ACROSS SOUTHWEST MEXICO EARLY ON WEDNESDAY THIS
IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-30MM LATER ON THURSDAY THROUGH FRIDAY MORNING.

SALMON...MS (ANTIGUA AND BARBUDA)
SAMUEL...MDS (SURINAME)
DAVISON...WPC (USA)
$$




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