Prognostic Meteorological Discussion
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FXCA20 KWBC 271814
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
214 PM EDT MON JUL 27 2015

DISCUSSION FROM JUL 27/12 UTC: PERSISTENT MID/UPPER LEVEL RIDGE
CONTINUES TO DOMINATE THE FLOW OVER THE SOUTHWEST USA/NORTHERN
STATES OF MEXICO. AT 250 HPA TUTT LOWS BOUND THE SOUTHERN FRINGES
OF THIS RIDGE...WITH ONE OVER THE BAJA PENINSULA WHILE ANOTHER
CENTERS SOUTH OF GUATEMALA/CHIAPAS IN SOUTHERN MEXICO. THE ONE
OVER BAJA CALIFORNIA IS TO MEANDER TO THE WEST-NORTHWEST THROUGH
TUESDAY EVENING. MEANWHILE...THIS IS TO ENHANCE CONVECTION ALONG
THE SIERRA MADRE WHERE WE EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15-25MM. ACROSS SOUTHERN BAJA PENINSULA...THIS WILL
FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM
THROUGH TUESDAY MORNING. THE OTHER TUTT LOW...MEANWHILE...IS TO
TRACK TO THE WEST ALONG THE SOUTH COAST OF MEXICO. EARLY IN THE
CYCLE THIS IS LIKELY TO ENHANCE CONVECTION ACROSS
GUERRERO-OAXACA-CENTRAL MEXICO...TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH WEDNESDAY MORNING THIS
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-20MM.

A MID LEVEL TROUGH OVER THE WESTERN ATLANTIC-GULF OF MEXICO
SEPARATES THE CONTINENTAL RIDGE FROM A BROAD CELL OF THE
SUBTROPICAL RIDGE OVER THE BAHAMAS-NORTHERN CARIBBEAN. ALTHOUGH
THE MODELS FORESEE SOME EROSION OF MID LEVEL RIDGE PATTERN TO THE
NORTH...IT IS TO REMAIN STRONG ENOUGH THAT CURRENT DRY AND STABLE
CONDITIONS ARE EXPECTED TO PERSIST OVER THE EASTERN-NORTHERN
CARIBBEAN ISLES. THIS RIDGE IS TO CONTINUE BLOCKING THE TROUGH TO
NORTH OF THE BAHAMAS DURING THE NEXT FEW DAYS...WITH BEST
DYNAMICAL FORCING EXPECTED ACROSS FLORIDA.

THE PERSISTENT MID LEVEL RIDGE PATTERN TO THE NORTH IS TO ALSO
HAVE AN INFLUENCE ON CONVECTIVE ACTIVITY ACROSS CENTRAL
AMERICA-NORTHERN SOUTH AMERICA. ITCZ RELATED CONVECTION IS TO
GENERALLY CONFINE TO COSTA RICA-PANAMA...WHERE WE EXPECT RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM/DAY IN ISOLATED TO
SCATTERED CONVECTION. OVER COLOMBIA-VENEZUELA EXPECTING RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM TO CLUSTER ALONG THE
NEAR EQUATORIAL TROUGH AND THE ANDES. HIGHER AMOUNTS...
HOWEVER...ARE POSSIBLE IN ASSOCIATION WITH TROPICAL WAVES.

A TUTT LOW TO THE EAST OF THE LEEWARD ISLANDS IS TO RETROGRESS
ACROSS THE VIRGIN ISLES TO PUERTO RICO EARLY ON WEDNESDAY
MORNING...AND LATER IN THE DAY IT IS TO MOVE NORTH OF THE
DOMINICAN REPUBLIC. ALTHOUGH WELL DEFINED...THIS WILL NOT BE
STRONG ENOUGH TO OVERCOME NEGATIVE INFLUENCE OF AFOREMENTIONED MID
LEVEL RIDGE PATTERN. CONVECTIVE ENHANCEMENT WITH THIS FEATURE...IF
ANY...IS TO LIMIT TO WESTERN PORTIONS OF PUERTO RICO AND CENTRAL
PORTIONS OF HISPANIOLA...WHERE WE EXPECT RAINFALL AMOUNTS OF
00-05MM/DAY IN ISOLATED CONVECTION.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE
42W      47W    52W    56W    61W    66W    70W    74W       TW
62W      68W    74W    79W    83W    87W    91W    95W    TW/SURGE
78W      83W    86W    91W    94W    97W   100W   103W       TW

TROPICAL WAVE IS INITIALIZED ALONG 42W AND SOUTH OF 22N. THIS
REACHES THE GUIANAS EARLY ON TUESDAY...WHERE IT IS TO FAVOR
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. OVER THE
ISLAND CHAIN MOST ACTIVE IS EXPECTED ACROSS THE NORTHERN
WINDWARD-FRENCH ISLES ON WEDNESDAY...WITH RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM. OVER NORTHEAST-CENTRAL VENEZUELA
THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA
OF 15MM...WHILE OVER NORTHWEST VENEZUELA/NORTHERN COLOMBIA
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

DUSTY AIR TRAILS THE WAVE ALONG 62W AS A SAHARAN AIR LAYER ADVECTS
ACROSS THE TROPICAL ATLANTIC TO THE EASTERN CARIBBEAN. A TRADE
WINDS SURGE ALSO ASSOCIATES WITH THIS PERTURBATION. MOST ACTIVE
CONVECTION WITH THIS WAVE IS EXPECTED AS IT MIGRATES ACROSS
NORTHERN SOUTH AMERICA TO CENTRAL AMERICA. ACROSS VENEZUELA
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM...WHILE OVER NORTHERN COLOMBIA/NORTHWEST VENEZUELA EXPECT
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. OVER
PANAMA-COSTA RICA-SOUTHERN NICARAGUA THIS IS TO THEN FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM EARLY ON
WEDNESDAY...WHILE OVER NORTHEASTERN NICARAGUA-HONDURAS EXPECT
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM.

TROPICAL WAVE ALONG 78W IS IN PHASE WITH TUTT LOW OVER SOUTHERN
MEXICO. THIS IS TO ENHANCE CONVECTION ON THE SOUTHERN STATES EARLY
IN THE CYCLE TO RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM. OVER SOUTHWEST MEXICO THIS IS TO THEN FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM DURING THE
DAY ON WEDNESDAY.

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




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