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484
FXCA20 KWBC 181836
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT THU SEP 18 2014

AT 15 UTC HURRICANE POLO CENTERED NEAR 17.3N 105.7W...WITH MAXIMUM
SUSTAINED WINDS OF 65KT AND CENTRAL PRESSURE OF 988 HPA...MOVING
TO THE NORTHWEST AT 7KT.

DISCUSSION FROM SEPTEMBER 18/00UTC: AT 250 HPA...WEST OVER THE
DOMAIN... BROAD RIDGE PATTERN CONTINUES TO DOMINATE UPPER LEVEL
CIRCULATION. THE RIDGE ANCHORS ON A CLOSED HIGH OVER NORTHWEST
MEXICO AND SPANS BETWEEN THE NORTHERN STATES OF MEXICO AND THE
WESTERN USA. THE RIDGE PROVIDES THE VENTILATION ALOFT AND STEERING
FLOW TO HURRICANE POLO. THE NHC FORECASTS THIS HURRICANE TO
CONTINUE TRACKING TO THE NORTHWEST...SLOWLY MOVING AWAY FROM LAND
THROUGH MIDDAY ON FRIDAY. MEANWHILE...THIS IS TO ENHANCE
CONVECTIVE DEVELOPMENT ACROSS THE SOUTHWEST STATES OF
MEXICO...BETWEEN SOUTHERN SINALOA TO COLIMA/NAYARIT...WHERE WE
EXPECT RAINFALL AMOUNTS OF XX-25-50MM/DAY AND MAXIMA OF 75-125MM
THROUGH FRIDAY MORNING. A SLIGHT INCREASE IS THEN EXPECTED OVER
SOUTHERN BAJA ON SATURDAY...WITH RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-35MM. THE RIDGE ALOFT IS TO ALSO VENT DEEP
CONVECTION ALONG THE SIERRA MADRE BETWEEN SONORA/WESTERN CHIHUAHUA
AND NORTHERN SINALOA...WHERE WE EXPECT RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. SIMILAR AMOUNTS ARE EXPECTED ON
THE CENTRAL-SOUTHERN STATES OF MEXICO TO GUATEMALA/EL SALVADOR.

A HIGH AMPLITUDE TROUGH LIES TO THE EAST OF THE CONTINENTAL
RIDGE...WITH MID/UPPER LEVEL TROUGH EXTENDING ACROSS THE EASTERN
USA TO THE FLORIDA PENINSULA/STRAITS OF FLORIDA. STRONG SHORT WAVE
TROUGH IS FORECAST TO ROUND THE BASE OF THE LONG WAVE LATER ON
FRIDAY/EARLY SATURDAY MORNING. THIS IS TO THEN INDUCE THE
SOUTHWARD AMPLIFICATION OF THE TROUGH TO THE WESTERN TIP OF CUBA
AND THE NORTHERN YUCATAN LATER IN THE DAY. AT LOW LEVELS THIS IS
TO SUSTAIN A TROUGH ACROSS SOUTHERN FLORIDA/NORTHWEST BAHAMAS TO
THE NORTHERN GULF OF MEXICO. AS UPPER TROUGH PATTERN DEEPENS THE
SURFACE TROUGH IS TO ALIGN FROM NORTHEAST TO SOUTHWEST. OVER THE
WESTERN CARIBBEAN IS TO THEN SUSTAIN AN INDUCED TROUGH THAT
RETROGRESSES ACROSS BELIZE/QUINTANA ROO MEXICO TO THE YUCATAN.
ACROSS THE NORTHWEST BAHAMAS THIS IS TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH SATURDAY THE MAXIMA
INCREASES TO 25-50MM. OVER CUBA EXPECTING ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15-25MM IN SCATTERED DIURNAL CONVECTION.
OVER BELIZE-QUINTANA ROO...MOST ACTIVE CONVECTION IS THEN EXPECTED
ON FRIDAY-SATURDAY...WHEN THE INVERTED TROUGH IS TO SUSTAIN
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM.

ALSO OVER THE WESTERN CARIBBEAN...A TUTT LOW LIES TO THE
SOUTH-SOUTHWEST OF THE CAYMAN ISLANDS...WITH ASSOCIATED TROUGH
INTO HONDURAS/NORTHEAST NICARAGUA. UNDER INFLUENCE OF DEEP
MID/UPPER LEVEL TROUGH OVER THE EASTERN USA...THE TUTT IS TO
SLOWLY LIFT NORTH...WEAKENING ACROSS CENTRAL CUBA LATER ON
SATURDAY/EARLY SUNDAY. EARLY IN THE CYCLE THIS IS TO ENHANCE
CONVECTIVE DEVELOPMENT ACROSS EASTERN NICARAGUA/NORTHEAST
HONDURAS...TO RESULT IN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA
OF 20-40MM. THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-25MM.
ACROSS CUBA IT IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM AND
MAXIMA OF 20-30MM.

AS THE TUTT WEAKENS...THE EASTERN PACIFIC ITCZ RETURNS TO ITS
CLIMATOLOGICAL POSITION. THIS IS TO THEN EXTENDS ACROSS COSTA
RICA-PANAMA TO NORTHERN SOUTH AMERICA. AS IT MEANDERS OVER THE
ISTHMUS...A LOW ALONG THE ITCZ WEST OF COSTA RICA IS TO ENHANCE
LOW LEVEL MOISTURE CONVERGENCE...TO RESULT IN RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM. THE SURFACE LOW MEANDERS WEST
AS THE CYCLE PROGRESSES. AS IT MOVES AWAY...WE EXPECT RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. ACROSS
WESTERN-NORTHERN COLOMBIA...NEAR EQUATORIAL TROUGH MOISTURE
CONVERGENCE IS TO FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA
OF 25-50MM.

EAST OF THIS TROUGH...AT 250 HPA...A CELL OF THE SUBEQUATORIAL
RIDGE LIES ACROSS THE CENTRAL TO EASTERN CARIBBEAN. THIS RIDGE
REMAINS NEARLY UNCHANGED THROUGH FRIDAY EVENING...THEN STARTS TO
WEAKEN THROUGH SATURDAY MORNING AS TROUGH OVER THE EASTERN USA
DEEPENS INTO THE WESTERN CARIBBEAN. A TUTT LIES TO THE EAST OF
THIS RIDGE...WITH AXIS SOUTH ACROSS THE LESSER ANTILLES. THIS IS
TO MEANDER OVER THE LESSER ANTILLES THROUGH FRIDAY EVENING...WITH
A CLOSED LOW FORECAST TO FORM OVER THE LEEWARD/NORTHEAST CARIBBEAN
ON SATURDAY. GLOBAL MODELS ARE SLOWLY REACHING A CONSENSUS ON
WHERE THIS LOW IS TO FORM...WITH THE LATEST RUN OF THE GFS
TRENDING TOWARDS THE ECMWF. AT MID LEVELS...A RIDGE EXTENDS TO THE
SOUTHWEST ACROSS THE LEEWARD ISLES/PUERTO RICO TO THE EASTERN
CARIBBEAN. MID LEVEL RIDGE IS TO SLOWLY LIFT NORTH OF THE LEEWARD
ISLES/PUERTO RICO LATER ON THURSDAY. AS IT PULLS AWAY...MID LEVEL
CAP INVERSION OVER THE NORTHEAST CARIBBEAN IS TO WEAKEN. THROUGH
FRIDAY ENVIRONMENTAL CONDITIONS ARE FORECAST TO BECOME MORE
FAVORABLE AND CONDUCIVE TO DEEP CONVECTION AS A SHORT WAVE TROUGH
APPROACHES FROM THE EAST. THIS WILL COMBINE WITH TROPICAL WAVE TO
FAVOR ORGANIZED CONVECTION (SEE BELOW FOR DETAILS). OTHER
ENHANCEMENT IS EXPECTED TO THE SOUTH ALONG THE NEAR EQUATORIAL
TROUGH AS IT MEANDERS OVER NORTHEAST VENEZUELA TO THE SOUTHERN
WINDWARD ISLES...WERE WE EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15-25MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE
44W     47W    49W    51W    53W    56W    59W    61W     TW
63W     66W    68W    71W    73W    76W    78W    80W     TW

TROPICAL WAVE ALONG 36W MOVES NORTH OF THE GUIANAS LATER ON
FRIDAY/EARLY SATURDAY MORNING...WITH MOST ACTIVE CONVECTION
EXPECTED ALONG AND NORTH OF THE ITCZ TO THE NORTH. IT IS TO ENTER
THE LESSER ANTILLES DURING LATE MORNING ON SATURDAY...TO TRIGGER
SCATTERED DEEP CONVECTION WITH ACCUMULATION OF 10-15MM/DAY AND
MAXIMA OF 20-35MM.

TROPICAL WAVE ALONG 63W CONTINUES TO INTERACT WITH TUTT NORTH OF
THE ISLANDS. AS IT MOVES ACROSS THE VIRGIN ISLES TO EASTERN PUERTO
RICO LATER THIS AFTERNOON IT IS TO SUSTAIN RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-45MM. MEANWHILE...MOIST PLUME
TRAILING THIS WAVE IS TO MEANDER ACROSS BARBADOS-FRENCH/LEEWARD
ISLANDS...WHERE IT IS TO SUSTAIN ADDITIONAL CONVECTION WITH
ACCUMULATION OF 10-15MM/DAY 20-30MM. ACROSS THE DOMINICAN REPUBLIC
TO HAITI IT IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM...WHILE OVER JAMAICA IT IS TO SUSTAIN RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ACROSS CENTRAL
VENEZUELA...IN INTERACTION WITH THE NET...EXPECT RAINFALL AMOUNTS
OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER NORTHWEST VENEZUELA TO
NORTHERN COLOMBIA THIS INCREASES TO 15-20MM/DAY AND MAXIMA OF
25-50MM.

VALVERDE...IMN (COSTA RICA)
MEDINA...ONAMET (REPUBLICA DOMINICANA)
DAVISON...WPC (USA)
$$






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