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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1136Z Sep 25, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
736 AM EDT THU SEP 25 2014

DISCUSSION FROM SEPTEMBER 24/00UTC: AT 250 HPA...A WANING RIDGE
OVER MEXICO IS TO RAPIDLY CRUMBLE THROUGH THURSDAY EVENING AS A
HIGH AMPLITUDE TROUGH DEEPENS ACROSS NORTH AMERICA. EARLY IN THE
CYCLE THE AMPLIFYING TROUGH IS TO FOCUS SHORT WAVE ENERGY ACROSS
NEW MEXICO TO NORTHERN CHIHUAHUA/SONORA IN NORTHWEST MEXICO. LATER
ON THURSDAY THE TROUGH REACHES MAXIMUM AMPLITUDE... AS IT IS TO
EXTEND ACROSS THE NORTHERN STATES OF MEXICO. AS THE TROUGH ENTERS
NORTHWEST MEXICO THIS IS TO SUSTAIN AN INCREASE IN CONVECTION
ALONG THE SIERRA MADRE OCCIDENTAL...WITH CONVECTION BETWEEN
CHIHUAHUA-SONORA AND SINALOA TO PEAK AT 30-60MM. BUT AS THE TROUGH
DEEPENS...THE FOCUS OF THE CONVECTION SHIFTS TO CENTRAL-NORTHEAST
STATES OF MEXICO...WHERE IT IS TO FAVOR RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM.

ANOTHER TROUGH LIES TO THE EAST...WITH AXIS ALOFT ACROSS THE
EASTERN USA TO THE YUCATAN PENINSULA. BUT AS THE RIDGE TO THE WEST
OVER MEXICO WEAKENS EARLY IN THE CYCLE...THE TROUGH IS TO QUICKLY
LIFT. THROUGH MIDDAY ON THURSDAY THE TROUGH IS FORECAST TO PULL
AWAY. AT LOW/MID LEVELS THIS SUSTAINS A TROUGH ACROSS THE YUCATAN
TO THE EASTERN GULF OF MEXICO. BUT AS THE TROUGH ALOFT
WEAKENS...THIS IS TO GRADUALLY FILL THROUGH THURSDAY MORNING.
MEANWHILE...THE TROUGH IS TO ENHANCE CONVECTIVE DEVELOPMENT ACROSS
THE YUCATAN-BELIZE-GUATEMALA TO THE SOUTHERN STATES OF MEXICO. IN
THIS AREA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM.

ALSO AT 250 HPA...A BROAD CELL OF THE SUBTROPICAL RIDGE LIES OVER
THE WESTERN ATLANTIC/NORTH OF THE GREATER ANTILLES. A CELL OF THE
SUBEQUATORIAL RIDGE TO THE SOUTH CONFINES TO THE WESTERN/CENTRAL
CARIBBEAN AND PORTIONS OF CENTRAL AMERICA. AS THE MID/UPPER TROUGH
OVER THE EASTERN USA/GULF OF MEXICO WEAKENS...THE SUBTROPICAL
RIDGE IS TO MEANDER WEST INTO THE BAHAMAS/OFF THE EAST COAST OF
THE USA...WHILE THE SUBEQUATORIAL RIDGE MOVES TO NORTHERN CENTRAL
AMERICA/SOUTHERN STATES OF MEXICO. AT MID LEVELS...THE SUBTROPICAL
RIDGE ANCHORS ON A HIGH NEAR 32N 68W...WHILE EXTENDING A RIDGE TO
THE BAHAMAS/NORTH OF THE ISLANDS. THROUGH FRIDAY EVENING THE HIGH
IS TO MIGRATE TO 30N 71W WHILE ASSOCIATED RIDGE BUILD ACROSS CUBA.
AS THE RIDGE BUILDS... TRADE WINDS CAP ACROSS THE BAHAMAS-CUBA IS
TO GRADUALLY STRENGTHEN. THIS WILL THEN LEAD TO GRADUAL EROSION OF
AVAILABLE MOISTURE FROM THE EAST. THIS BECOMES MORE PRONOUNCED
THROUGH FRIDAY MORNING. EARLY IN THE CYCLE...DIURNAL CONVECTION
ACROSS CUBA WILL FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA
OF 25-50MM. THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-30MM ON
FRIDAY. ACROSS THE BAHAMAS EXPECTING ACCUMULATION OF 15-20MM/DAY
AND MAXIMA OF 25-50MM THROUGH THURSDAY MORNING...THEN 05-10MM/DAY
AND MAXIMA OF 15-20MM ON THURSDAY TO FRIDAY. THE SUBEQUATORIAL
RIDGE TO THE SOUTH...MEANWHILE...IS TO VENT CONVECTION ALONG THE
CONTINENTAL DIVIDE OVER HONDURAS/EL SALVADOR-GUATEMALA...WITH
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ACROSS
NORTHEAST HONDURAS-EASTERN NICARAGUA EXPECTING ACCUMULATION OF
10-15MM/DAY AND MAXIMA OF 20-40MM. THROUGH FRIDAY MAXIMA DECREASES
20-30MM.

DOWNSTREAM FROM THE SUBTROPICAL RIDGE...A TUTT LOW NEAR 27N 55W
EXTENDS A TROUGH TO THE SOUTHWEST INTO THE NORTHEAST CARIBBEAN.
UNDER INFLUENCE OF THE RIDGE TO THE WEST...TUTT LOW IS TO REMAIN
NORTH OF THE ISLANDS...WHILE TROUGH IS TO GRADUALLY AMPLIFY ACROSS
THE NORTHEAST CARIBBEAN ISLES TO THE CENTRAL/EASTERN
CARIBBEAN-NORTHERN SOUTH AMERICA. AS THE TROUGH AMPLIFIES... IT IS
TO FOCUS A SERIES OF SHORT WAVE VORTICES ACROSS THE NORTHEAST
CARIBBEAN ISLES. INFLOW OF CYCLONIC VORTICITY IS TO START EARLY ON
FRIDAY...AND IT IS EXPECTED TO PEAK ON SATURDAY WHEN A STRONG
VORTEX PULLS ACROSS PUERTO RICO TO THE MONA PASSAGE/EASTERN
HISPANIOLA. DEEP TROUGH PATTERN ALOFT IS INTERACTING WITH THE
ATLANTIC ITCZ...MODULATING THE CONVERGENCE ZONE NORTH INTO THE
NORTHERN WINDWARD/FRENCH ISLES. AS THE ITCZ MEANDERS NORTH OF ITS
CLIMATOLOGICAL POSITION...THIS IS TO SUSTAIN HIGH PWAT CONTENT
OVER THE NEXT FEW DAYS. FURTHERMORE...THE DEEPENING TUTT ALOFT IS
TO MODULATE THE LOW LEVEL EASTERLY TRADES...WITH WINDS TO VEER TO
THE SOUTH-SOUTHEAST EARLY ON FRIDAY. SOUTHERLY WINDS ARE TO THEN
PERSIST THROUGH THE WEEKEND...ENHANCING MOISTURE
TRANSPORTS/CONVERGENCE ACROSS THE VIRGIN ISLES-PUERTO RICO AND THE
DOMINICAN REPUBLIC. ACROSS THE LEEWARD/FRENCH ISLES EXPECTING
ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 25-50MM. OVER PUERTO
RICO AND THE DOMINICAN REPUBLIC EXPECTING RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 25-50MM THROUGH THURSDAY MORNING. ON
FRIDAY TO SATURDAY THIS IS TO INCREASE TO 15-20MM/DAY AND MAXIMA
OF 35-70MM. DURING THIS PERIOD CONDITIONS APPEAR FAVORABLE FOR
GENERATION OF AN MCS ACROSS THE NORTHEAST CARIBBEAN ISLES...WITH
HIGHER RAINFALL AMOUNTS HIGHLY LIKELY.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE
50W     51W    52W    53W    54W    55W    56W    58W  TUTT INDCD.

72W     74W    75W    76W    77W    78W    79W    80W     TW
85W     86W    87W    88W    89W    90W    91W    92W     TW

TUTT INDUCED PERTURBATION ALONG 50W IS TO REMAIN EAST OF THE
ISLANDS.

TROPICAL WAVE ALONG 72W IS TO ENHANCE CONVECTION ACROSS HISPANIOLA
EARLY THIS CYCLE...TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM. AS IT ENTERS JAMAICA/EASTERN CUBA IT IS TO THEN
FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. OVER
WESTERN COLOMBIA...IN INTERACTION WITH THE NET...EXPECTING
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM...WHILE OVER
NORTHWEST VENEZUELA/NORTHERN COLOMBIA MAXIMA PEAKS AT 15-20MM.
ACROSS PANAMA IT IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-40MM.

TROPICAL WAVE ALONG 85W MOVES ACROSS NICARAGUA TO HONDURAS EARLY
IN THE CYCLE...TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-40MM. ACROSS SOUTHERN HONDURAS/EL SALVADOR IT IS TO
THEN FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM...WHILE OVER NORTHERN GUATEMALA/BELIZE AND YUCATAN IT IS
TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-30MM.
OVER SOUTHERN GUATEMALA TO SOUTHERN MEXICO THE MAXIMA PEAKS AT
30-60MM.

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