TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
151 PM EST FRI NOV 06 2009
 
AT 15UTC...TD IDA CENTERED NEAR 15.0N 84.0W...WITH MINIMAL CENTRAL
PRESSURE OF 1007 HPA AND MAXIMUM SUSTAINED WINDS OF 40KT. SEE TPC
BULLETIN FOR UPDATES.

DISCUSSION FROM NOV 06/0000 UTC. AT MID/UPPER LEVELS...A SOUTHERN
STREAM SHORT WAVE TROUGH WILL ENTER THE NORTHWEST STATES OF MEXICO
THROUGH 42-48 HRS...WITH CLOSED CIRCULATION ALONG THE BORDER
BETWEEN ARIZONA-SONORA MEXICO. THROUGH 72 HRS THE LOW WILL LIFT TO
THE NORTHWEST... DRAGGING THE TROUGH ACROSS NORTHEAST MEXICO.
ALTHOUGH MODELS SHOW STRONG ROTATION IN ASSOCIATION WITH THIS
SYSTEM...AVAILABLE MOISTURE IS LACKING. THE REGIONAL NAM IS THE
ONLY MODEL THAT SHOWS SIGNIFICANT RAINFALL AMOUNTS ON THE NORTHERN
STATES OF CHIHUAHUA-COAHUILA...WITH ACCUMULATION OF 05-10MM/DAY
AND MAXIMA OF 15-25MM. THE GFS...IN CONTRAST...ONLY SHOWS TRACE
RAINFALL AMOUNTS... AND IN OUR FORECAST WE ARE GOING WITH THE
LESSER AMOUNTS. 

AS THE 500 HPA TROUGH ENTERS MEXICO...IT WILL INTERACT WITH A
MEANDERING SHORT WAVE TROUGH OVER THE WESTERN GULF/ SOUTHERN
MEXICO. EARLY IN THE PERIOD THE TROUGH WILL REMAIN NEARLY
STATIONARY ALONG 96W/97W TO 10N. BY 42-48 HRS... HOWEVER...IT WILL
START TO PULL EAST AND NORTH ALONG 92W/93W...AND BY 72 HRS IT IS
TO RAPIDLY DAMPEN WHILE SHEARING TO THE NORTHEAST. AT LOW
LEVELS...IT SUPPORTS AN INDUCED/INVERTED TROUGH ALONG 90W/92W.
CONSISTENT WITH THE PREVIOUS FORECASTS...THIS FEATURE IS FORECAST
TO WEAKEN THROUGH 36-48 HRS WHILE GRADUALLY TILTING FROM SOUTHEAST
TO NORTHWEST ACROSS THE GULF. AN ILL ORGANIZED LOW/TROUGH WILL
THEN REMAIN TO THE EAST OF VERACRUZ MEXICO. AS THE TROUGH
WEAKENS/TILTS...THE FLOW ACROSS SOUTHERN MEXICO WILL SHIFT AND
BECOME NEARLY PARALLEL TO THE GULF COAST. THE WINDS ARE TO ALSO
DECREASE IN INTENSITY. THIS WILL LEAD TO A DECREASE IN
OROGRAPHICALLY INDUCED CONVECTION ACROSS SOUTHERN MEXICO. ACROSS
TABASCO-CENTRAL/NORTHERN CHIAPAS-NORTHERN OAXACA AND SOUTHERN
VERACRUZ EXPECT RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM/DAY THROUGH 36-42 HRS. AFTERWARDS...MOST INTENSE
CONVECTION IS EXPECTED OFF THE COAST.

FURTHERMORE...AS THE MID/UPPER TROUGH DEEPENS ACROSS THE SOUTHWEST
USA/NORTHWEST MEXICO...IT WILL SUSTAIN THE NORTHWARD AMPLIFICATION
OF A RIDGE ACROSS THE SOUTHEAST/ EASTERN USA TO THE WESTERN
ATLANTIC. THE MID/UPPER LEVEL RIDGE WILL REACH MAXIMUM AMPLITUDE
BETWEEN 48-72 HRS. A POLAR TROUGH LIES TO THE EAST...AND AS THE
RIDGE OVER THE CONTINENT AMPLIFIES...THE TROUGH IS THEN FORECAST
TO DEEPEN. AT 24 HRS THE TROUGH WILL EXTEND BETWEEN 55W-85W AND TO
THE NORTH OF 26N. AT 60-72 HRS...THE TROUGH IS TO THEN AMPLIFY
ALONG 35N 50W...25N 60W TO NORTH OF HISPANIOLA. AT 96-108 HRS A
CLOSED LOW WILL FORM ALONG THE BASE OF THE TROUGH NEAR 23N
60W...WITH AXIS TO SIMULTANEOUSLY DEEPEN INTO THE EASTERN
CARIBBEAN/OFF THE COAST OF VENEZUELA. THIS WILL BRING COLD AIR
ADVECTION ALOFT TO THE NORTHEAST CARIBBEAN ISLANDS...MOST
SIGNIFICANT ACROSS THE DOMINICAN REPUBLIC-PUERTO RICO...WHERE IT
IS LIKELY TO SUSTAIN AN INCREASE IN CONVECTION. AT LOW LEVELS AN
ELONGATED FRONT TRAILS ACROSS THE NORTHWEST BAHAMAS-FLORIDA KEYS
TO THE GULF OF MEXICO. THROUGH 30-36 HRS IT WILL MOVE TO THE
NORTHWEST/CENTRAL BAHAMAS...ALONG THE NORTHWEST COAST OF
CUBA/STRAITS OF FLORIDA TO THE WESTERN GULF OF MEXICO. BY 36-48
HRS IT WILL MEANDER ACROSS THE CENTRAL BAHAMAS...THEN WEST ALONG
22N THROUGH CUBA TO THE GULF. AT 48-60 HRS IT WILL LIE ACROSS THE
TURKS/SOUTHEAST BAHAMAS-MEANDERING WEST ACROSS CUBA ALONG 22N INTO
THE GULF OF MEXICO. BY 72-84 HRS THE FRONT WILL START BOWING
TOWARDS NORTHERN HISPANIOLA...WHILE PIVOTING OVER THE TURKS/
SOUTHEAST BAHAMAS-CENTRAL/WESTERN CUBA TO THE GULF OF MEXICO. OVER
THE NORTHWEST-CENTRAL BAHAMAS IT IS TO INITIALLY FAVOR RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY IN ISOLATED TO
SCATTERED CONVECTION. ACROSS THE CENTRAL/SOUTHEAST BAHAMAS THIS
WILL INCREASE TO 20-35MM/DAY...WITH LOCALIZED MAXIMA IN EXCESS OF
50MM QUITE POSSIBLE BY 60-72 HRS.

FURTHERMORE...THE GFS SHOWS A FRONTAL SHEARLINE DEVELOPING AHEAD
OF THIS FRONT...WITH BOUNDARY AT 1000 HPA FORECAST TO MOVE FROM
THE SOUTHEAST BAHAMAS/HAITI EARLY IN THE CYCLE TO PUERTO
RICO/EASTERN HISPANIOLA BY 24-36 HRS. IT IS TO THEN MEANDER
BETWEEN EASTERN HISPANIOLA/WESTERN PUERTO RICO THROUGH 48-60
HRS...AND BY 72-84 HRS IT WILL SHIFT ACROSS THE VIRGIN
ISLANDS-EASTERN PUERTO RICO. IN ADDITION TO SUSTAINING A SLIGHT
INCREASE IN LOW LEVEL CONVERGENCE... THIS WILL SUSTAIN A SYNOPTIC
SCALE NORTHEASTERLY FLOW ACROSS THE NORTHEAST CARIBBEAN ISLANDS.
ACROSS THE DOMINICAN REPUBLIC-PUERTO RICO AND THE VIRGIN ISLANDS
WE EXPECT A SLIGHT INCREASE IN CONVECTION...WITH RAINFALL AMOUNTS
OF 05-10MM/DAY. MAXIMA OF 15-25MM WILL CONCENTRATE OVER THE
DOMINICAN REPUBLIC AND PUERTO RICO ON DAY 02...TO INCREASE TO
20-35MM/DAY ON DAY 03.

AN UPPER LEVEL RIDGE IS INITIALIZED OVER NORTHERN SOUTH
AMERICA/CENTRAL-EASTERN CARIBBEAN...WITH AXIS CENTERING ON A
CLOSED 250 HPA HIGH NORTH OF LA GUAJIRA PENINSULA. THE RIDGE
PATTERN WILL PERSIST THROUGH 72 HRS...BUT IT TENDS TO WEAKEN NORTH
OF THE ISLANDS AS THE AFOREMENTIONED TROUGH AMPLIFIES TO THE
SOUTH. AT 500 HPA IT REFLECTS AS A SHORT WAVE RIDGE OVER THE
EASTERN/CENTRAL CARIBBEAN. THIS SUSTAINS A WEAK SUBSIDENCE CAP
ACROSS THE EASTERN CARIBBEAN ISLANDS...WITH LOCAL RADIOSONDE
OBSERVATIONS SHOWING INVERSION HEIGHT AROUND 700-650 HPA. THE GFS
IS FORECASTING THIS PATTERN TO PERSIST DURING THE NEXT 60-72
HRS...WITH WEAKENING BY 72-96 HRS AS THE TROUGH INTRUDES THE
NORTHEAST CARIBBEAN.

TD IDA...OVER NORTHEAST HONDURAS/NICARAGUA...WILL MOVE TO THE
WESTERN CARIBBEAN EARLY THIS PERIOD. AS INDICATED BY THE TPC...THE
SYSTEM IS EXPECTED TO GRADUALLY STRENGTHEN WHILE MOVING TO THE
NORTHWEST TOWARDS THE YUCATAN CHANNEL DURING THE NEXT THREE DAYS.
SOME RESIDUAL CONVECTION IS EXPECTED ACROSS NORTHEAST NICARAGUA TO
RESULT IN ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM/DAY.
OVER NORTHEAST HONDURAS...TO CONCENTRATE BETWEEN ROATAN/LA
CEIBA-PUERTO LEMPIRA...EXPECT ACCUMULATION OF 10-15MM/DAY AND
MAXIMA OF 20-40MM/DAY. AS THE SYSTEM EMERGES OVER THE WESTERN
CARIBBEAN...CONVECTION IS EXPECTED TO INCREASE ACROSS THE CAYMAN
ISLANDS AND THE YUCATAN PENINSULA. OVER THE CAYMAN ISLANDS EXPECT
ACCUMULATION OF 15-25MM/DAY AND MAXIMA OF 40-70MM...WHILE OVER THE
YUCATAN/NORTHERN BELIZE INITIALLY EXPECT ACCUMULATION OF
10-15MM/DAY AND MAXIMA OF 20-35MM. ON DAY 03 THIS WILL INCREASE TO
15-25MM/DAY AND MAXIMA OF 40-70MM/DAY WHILE CONCENTRATING ACROSS
QUINTANA ROO/NORTHERN BELIZE TO EASTERN YUCATAN. OTHER ACTIVITY IS
EXPECTED ACROSS WESTERN CUBA...WITH MOST INTENSE EXPECTED BETWEEN
CIUDAD HABANA-PINAR DEL RIO AND ISLA DE LA JUVENTUD...WITH
ACCUMULATION OF 75-150MM/DAY AND MAXIMA OF 250-350MM/DAY. IN THIS
AREA CONSIDER POSSIBILITY OF STRONG MECHANICAL FORCING AS THE
TROPICAL CYCLONE STARTS TO INTERACT WITH THE AFOREMENTIONED
SURFACE FRONT OVER THE ISLAND. ALTHOUGH SOME OF THE MODELS
FORECAST THE FRONT TO RETROGRESS UNDER INFLUENCE OF THE
STORM...ENOUGH MECHANICAL FORCING MIGHT REMAIN TO RESULT IN
EXCESSIVE RAINFALL AMOUNTS. IN NEARLY IDEAL CONDITIONS...AND AS A
WORST CASE SCENARIO...THE MAXIMA IN THIS AREA COULD PEAK AT
500-750MM. 

FARTHER SOUTH...OVER THE EASTERN PACIFIC...A LOW ALONG THE ITCZ
NEAR 12N 92W CONTINUES TO FAVOR MOISTURE ADVECTION INTO SOUTHERN
GUATEMALA-EL SALVADOR/SOUTHERN HONDURAS AND WESTERN NICARAGUA.
MODELS ARE HAVING A HARD TIME DEALING WITH THIS LOW...AND THEY
FAIL TO MAINTAIN CONTINUITY WITH PREVIOUS FORECASTS.
WE...HOWEVER...STILL BELIEVE THAT AS TD IDA STRENGTHENS OVER THE
WESTERN CARIBBEAN...IT IS GOING TO DRAW THE EASTERN PACIFIC LOW TO
THE NORTHEAST ACROSS EL SALVADOR/SOUTHERN HONDURAS BY 36-48 HRS.
INITIALLY EXPECT RAINFALL AMOUNTS OF 10-20MM/DAY AND MAXIMA OF
40-60MM. THROUGH 48 HRS THIS WILL INCREASE TO 15-25MM/DAY AND
MAXIMA OF 40-70MM. THE MOST INTENSE IS TO CONCENTRATE OVER GULF OF
FONSECA REGION/TEGUCIGALPA...WITH MAXIMA TO PEAK AROUND 100MM.

AS THE TROPICAL CYCLONES MODULATE THE EASTERN PACIFIC
ITCZ...CONVECTION ACROSS SOUTHERN CENTRAL AMERICA IS TO REMAIN
GENERALLY SPARSE WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF
15MM. ACROSS THE ABC ISLANDS...LA GUAJIRA PENINSULA/NORTHWEST
VENEZUELA-NORTHERN COLOMBIA/EJE CAFETERO/THE DARIEN IN EASTERN
PANAMA...EXPECT ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM
IN A DIURNAL PATTERN. LOCALLY HIGHER AMOUNTS ARE EXPECTED ACROSS
EJE CAFETERO/ SANTANDERES COLOMBIA-LAKE MARACAIBO REGION...WHERE
THE DAILY MAXIMA COULD PEAK AT 25-50MM/DAY. OTHER LOCALIZED
MAXIMUM ARE EXPECTED ALONG THE PACIFIC COAST OF COLOMBIA BETWEEN
CHOCO AND VALLE DEL CAUCA.

A TUTT TO THE EAST OF THE ISLANDS AND NORTH OF THE GUIANAS IS TO
PERSIST DURING THE NEXT 48 HRS...THEN START TO WEAKEN BY 60-72 HRS
AS THE POLAR TROUGH PATTERN NORTH OF THE ISLANDS INTENSIFIES. BY
THE END OF THE CYCLE THE TUTT WILL SHEAR TO THE EAST-NORTHEAST.
MOST ACTIVE CONVECTION WITH THIS FEATURE IS DEVELOPING TO THE EAST
OF 45W AS IT ENHANCES ITCZ RELATED CONVECTION OVER THE TROPICAL
ATLANTIC. OVER THE SOUTHERN WINDWARD ISLANDS/ORINOCO DELTA REGION
ITCZ RELATED CONVECTION WILL RANGE BETWEEN 05-10MM/DAY...WITH
WIDELY ISOLATED MAXIMA OF 15-25MM/DAY.

PUERTO RICO AND THE USVI: AS A SUBSIDENCE PATTERN ESTABLISHES AT
UPPER LEVELS...WE EXPECT A RELATIVELY DRY AND STABLE PATTERN TO
ESTABLISH INTO THE WEEKEND. A SLIGHT INCREASE IN ACTIVITY IS
POSSIBLE UNDER INFLUENCE OF THE FRONTAL SHEAR LINE...BUT MOST
ACTIVE IS GOING TO BE ACROSS THE WESTERN/INTERIOR PORTIONS OF THE
ISLAND. ON SUNDAY TO MONDAY...AS THE SURFACE FRONT
APPROACHES...AND THE MID/UPPER TROUGH DEEPENS...CONDITIONS WILL
BECOME MORE FAVORABLE FOR ORGANIZED CONVECTION TO DEVELOP...SO THE
GENERAL TREND IS FOR HIGHER RAINFALL AMOUNTS.

INVERTED TROUGHS IN THE EASTERLIES (INITIALIZED AT 12Z)

INITIAL      F24   F36   F48   F60   F72   F84
NONE

CANALES...SMN (HONDURAS)
DAVISON...NCEP (USA)