Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXCA20 KWBC 041925
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
224 PM EST WED MAR 04 2015

DISCUSSION FROM MARCH 04/00UTC: AMPLIFYING POLAR TROUGH MOVES
ACROSS THE MIDWESTERN USA EARLY ON WEDNESDAY. AS IT DEEPENS...IT
IS TO MERGE WITH A SHORT WAVE TROUGH ON THE SOUTHERN STREAM OVER
THE SOUTHWEST USA/NORTHERN STATES OF MEXICO. THROUGH THURSDAY
EVENING THE TROUGH IS TO PULL TO THE NORTHEAST WHILE LIFTING OVER
A RIDGE TO THE EAST. AT LOW LEVELS...THE PROGRESSIVE TROUGH IS TO
SUSTAIN A SURFACE FRONT ACROSS NORTH AMERICA... FORECAST TO MOVE
SOUTH ACROSS TEXAS TO THE RIO BRAVO EARLY ON THURSDAY MORNING.
LATER ON THURSDAY THE FRONT MOVES ACROSS THE SOUTHEASTERN USA-THE
GULF OF MEXICO...WHILE TRAILING TO VERACRUZ. AS IT SURGES INTO THE
GULF...A 35-40KT LOW LEVEL JET MAXIMA IS TO DEVELOP ACROSS THE
WESTERN GULF INTO THE SOUTHERN STATES OF MEXICO...FAVORING A
TEHUANTEPECER JET OF 50KT EARLY ON FRIDAY MORNING. THE STRONG
BOUNDARY LAYER WINDS ARE TO THEN PERSIST THROUGH FRIDAY EVENING.
FRONT IS TO THEN STALL OVER CENTRAL FLORIDA-GULF OF MEXICO TO
VERACRUZ/CENTRAL STATES OF MEXICO. AS IT ENTERS
COAHUILA-TAMAULIPAS EARLY ON THURSDAY THIS IS TO FAVOR LIGHT
RAINFALL AMOUNTS...WITH ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF
10MM. BUT AS IT ENTERS SOUTHERN TAMAULIPAS-NORTHERN VERACRUZ ON
THURSDAY THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF 15MM. STRONG
LOW LEVEL NORTHERLIES/HIGH TERRAIN ARE TO COMBINE IN SUPPORT OF
ORGANIZED CONVECTION ACROSS SOUTHERN
VERACRUZ-CHIAPAS/TABASCO...WHERE IT IS TO FAVOR RAINFALL AMOUNTS
OF 15-20MM/DAY AND MAXIMA OF 25-50MM ON THURSDAY...WITH MAXIMA
PEAKING AROUND 35-70MM ON FRIDAY. THROUGH SATURDAY...AS THE
NORTHERLIES WANE...THIS WILL DECREASE TO 00-05MM/DAY AND MAXIMA OF
10MM.

POLAR TROUGH OVER NORTH AMERICA IS TO PRESS AGAINST A BROAD RIDGE
TO THE SOUTH. THE 250 HPA RIDGE EXTENDS TO THE NORTHEAST FROM THE
YUCATAN/NORTHERN CENTRAL AMERICA...ACROSS THE SOUTHEAST USA TO THE
WESTERN ATLANTIC. THROUGH FRIDAY EVENING/SATURDAY MORNING THE
RIDGE IS TO FLATTEN AS THE AFOREMENTIONED POLAR TROUGH LIFTS
ACROSS NORTH AMERICA. AT 500 HPA...BROAD RIDGE DOMINATES THE
CARIBBEAN BASIN-CENTRAL AMERICA. EARLY IN THE CYCLE IT IS TO
ANCHOR ON A CLOSED HIGH OVER THE BAHAMAS. BUT AS THE TROUGH
DEEPENS ACROSS THE USA THE HIGH MOVES TO THE EAST-NORTHEAST NEAR
BERMUDA LATER ON THURSDAY. ALTHOUGH THE HIGH RELOCATES...BROAD MID
LEVEL RIDGE IS TO GENERALLY HOLD ACROSS THE BASIN...HELPING
SUSTAIN STRONG CAP INVERSION ACROSS THE GREATER ANTILLES-CENTRAL
AMERICA.

AT LOW LEVELS...BROAD RIDGE DOMINATES THE CENTRAL-WESTERN
ATLANTIC. THIS SUSTAINS A TIGHT GRADIENT ACROSS THE BASIN...AND A
TRADE WINDS SURGE ACROSS THE LESSER ANTILLES INTO THE CARIBBEAN.
THROUGH SATURDAY THE LOW LEVEL RIDGE PATTERN TENDS TO WEAKEN AS
POLAR FRONT EXITING THE EASTERN USA PRESSES AGAINST THIS RIDGE.
PRESSURE GRADIENT WILL THEN SLACKEN. EARLY IN THE CYCLE THIS IS TO
SUSTAIN 850 HPA WINDS OF 30-35KT ACROSS THE NORTHEAST CARIBBEAN
ISLES...BUT THIS THEN DECREASES TO 20-25KT LATER ON FRIDAY.
STRONGER WINDS ARE EXPECTED TO THE SOUTH ALONG THE COAST OF SOUTH
AMERICA...WITH WINDS TO PEAK AT 25-30KT OVER THE NEXT FEW DAYS.
BRISK EASTERLY TRADES ARE TO FAVOR GENERATION OF STREAMERS ACROSS
THE ISLAND CHAIN...WHILE ALSO ADVECTING THE OCCASIONAL CLOUD
CLUSTER ACROSS THE BASIN. OVER THE NORTHERN LEEWARD-VIRGIN
ISLES-PUERTO RICO AND NORTHERN HISPANIOLA THIS IS TO FAVOR
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. ACROSS THE
SOUTHERN LEEWARD-FRENCH ISLES TO THE ABC ISLANDS EXPECTING HIGHER
AMOUNTS THROUGH THURSDAY MORNING...WITH ACCUMULATION OF
05-10MM/DAY AND ISOLATED MAXIMA OF 15MM. THIS THEN DECREASES TO
00-05MM/DAY WITH WIDELY ISOLATED MAXIMA OF 10MM ON FRIDAY. PLUME
OF MOISTURE ALONG THE SOUTHERN FRINGES OF THE RIDGE IS TO AFFECT
JAMAICA EARLY IN THE CYCLE WITH ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15-20MM.

A TUTT BOUNDS THE EASTERN-SOUTHERN FRINGES OF THE 250 HPA
RIDGE...WITH AXIS WEST-SOUTHWEST ACROSS THE LEEWARD ISLES TO
NORTHERN SOUTH AMERICA/PANAMA. UNDER INFLUENCE OF THE RIDGE THE
TROUGH IS TO STRETCH FARTHER TO THE WEST INTO THE SOUTHERN
CARIBBEAN...WITH A CLOSED LOW TO FORM ALONG THIS AXIS OVER THE
CENTRAL CARIBBEAN LATER ON FRIDAY. THIS IS A DEEP TROUGH PATTERN
WITH STRONG MID LEVEL REFLECTION...AND IT IS TO SUSTAIN AN
INDUCED/INVERTED TROUGH ACROSS PANAMA-GULF OF URABA EARLY ON
SATURDAY. THIS IS TO THEN EVOLVE INTO A CLOSED LOW OVER THE
SOUTHERN CARIBBEAN LATER ON SUNDAY. ALSO AT UPPER LEVELS...A
SUBTROPICAL JET MAXIMA BOUNDS THE SOUTHERN FRINGES OF THIS
TROUGH...TO ALIGN ACROSS NORTHERN COLOMBIA-VENEZUELA AND OVER THE
ISLAND CHAIN. THIS IS LIKELY TO FAVOR AREAS OF UPPER DIVERGENCE AS
IT MEANDERS OVER VENEZUELA-SOUTHEAST CARIBBEAN.

AS THE TUTT MEANDERS OVER THE EASTERN CARIBBEAN THIS IS TO
INTERACT WITH THE NEAR EQUATORIAL TROUGH/ATLANTIC ITCZ...TO VENT
CONVECTION ACROSS THE GUIANAS. ACROSS FRENCH GUIANA-NORTHEAST
SURINAME EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM THROUGH THURSDAY MORNING...INCREASING TO 10-15MM/DAY AND
MAXIMA OF 20-40MM LATER ON THURSDAY/EARLY FRIDAY MORNING. ACROSS
NORTHWEST SURINAME TO GUYANA THIS IS TO THEN FAVOR RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM ON THURSDAY TO
FRIDAY...AND 05-10MM/DAY AND MAXIMA OF 15MM THEREAFTER. AS THE
UPPER LEVEL LOW CLOSES OVER THE CARIBBEAN...IT IS TO THEN ENHANCE
CONVECTION ACROSS AMAZONIA IN SOUTHERN VENEZUELA TO EASTERN
COLOMBIA...WITH RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM...WHILE OVER NORTHWEST VENEZUELA AND SANTANDERES IN
COLOMBIA IT IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA
OF 15-20MM.

FURTHERMORE...THE TROUGH ALOFT...AS IT RETROGRESSES ACROSS
NORTHERN SOUTH AMERICA...IS TO THEN ENHANCE CONVECTIVE DEVELOPMENT
ACROSS THE ANDEAN REGION/WESTERN PLAINS OF COLOMBIA. INITIALLY
EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. BUT AS
THE TROUGH ALOFT ENTERS NORTHERN SOUTH AMERICA THIS INCREASES TO
05-10MM/DAY AND MAXIMA OF 15-25MM ON THURSDAY THROUGH FRIDAY.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE
NONE

CRAIG...TTMS (TRINIDAD AND TOBAGO)
NANDA...MDS (SURINAME)
DAVISON...WPC (USA)
$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.