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Tropical Discussion
 
(Latest Discussion - Issued 1834Z Jul 30, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EDT WED JUL 30 2014

DISCUSSION FROM JULY 30/00UTC: MID/UPPER LEVEL RIDGE CONTINUES TO
DOMINATE MESO/SYNOPTIC FLOW PATTERN ACROSS THE WESTERN
USA-NORTHERN STATES OF MEXICO. THIS RIDGE REMAINS WELL
ENTRENCHED...AND AT 250 HPA IT IS TO ANCHOR ON A CLOSED HIGH OVER
NORTHERN CHIHUAHUA/SOUTHERN ARIZONA. THIS PATTER IS TO HOLD WELL
INTO THE MEDIUM RANGE PERIOD. A TUTT LOW TO THE SOUTH NOW CENTERS
JUST WEST OF COLIMA/NAYARIT...WHILE EXTENDING A SHORT WAVE TROUGH
INTO THE CENTRAL STATES OF MEXICO. UNDER INFLUENCE OF THE RIDGE TO
THE NORTH THE TROUGH/LOW IS TO SLOWLY LIFT ACROSS THE BAJA
PENINSULA. AS IT PULLS NORTH...THE TROUGH IS TO ENHANCE DIURNAL
CONVECTION ALONG THE SIERRA MADRE OCCIDENTAL OF MEXICO. IN THIS
AREA EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF
30-60MM THROUGH THURSDAY MORNING AND AGAIN ON FRIDAY TO SATURDAY.
ON THURSDAY TO FRIDAY THE MAXIMA INCREASES TO 35-70MM.

EAST OF THE CONTINENTAL RIDGE...A POLAR TROUGH EXTENDS ACROSS THE
EASTERN USA TO THE NORTHERN GULF OF MEXICO. THE TROUGH IS TO
GRADUALLY LIFT THROUGH THURSDAY MORNING AS ANOTHER TROUGH DEEPENS
TO THE WEST. THE LATTER IS TO EXPAND INTO THE CENTRAL USA LATER IN
THE DAY...AND THROUGH FRIDAY EVENING IT IS TO TAKE ITS PLACE
ACROSS THE EASTERN USA TO THE NORTHEAST GULF OF MEXICO. AT LOW
LEVELS THE TROUGH ALOFT SUSTAINS A BROAD TROUGH ACROSS THE EASTERN
USA TO THE BAHAMAS. THIS IS ENHANCING LOW LEVEL MOISTURE
CONVERGENCE ACROSS THE NORTHWEST BAHAMAS...A PATTERN EXPECTED TO
PERSIST. THIS IS TO RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM.

ANOTHER TUTT LOW IS INITIALIZED NORTH OF THE ISLANDS NEAR 25N 66W.
THIS EXTENDS A SHORT WAVE TROUGH TO THE NORTHEAST CARIBBEAN. RIDGE
TO THE WEST WILL DRIVE THE LOW TO THE WEST-SOUTHWEST...NEARING
NORTH COAST OF HISPANIOLA LATER ON FRIDAY...WHILE EXTENDING A
SHORT WAVE TROUGH TO THE EASTERN CARIBBEAN. AT MID LEVELS THIS IS
TO INITIALLY REFLECT AS A WELL ORGANIZED CYCLONIC CIRCULATION TO
THE NORTH OF THE ISLANDS. THROUGH THURSDAY EVENING/EARLY FRIDAY
MORNING THIS IS TO WEAKEN TO AN OPEN TROUGH AS IT MEANDERS WEST
TOWARDS THE DOMINICAN REPUBLIC. AT LOW LEVELS IT SUSTAINS INDUCED
PERTURBATIONS IN THE EASTERLY TRADES...SEE BELOW FOR DETAILS. AS
THE TUTT LOW MEANDERS NORTH OF PUERTO RICO-HISPANIOLA IT IS TO
ENHANCE DIURNAL CONVECTION. MOST ACTIVE OVER PUERTO RICO IS
EXPECTED ON WESTERN INTERIOR PORTIONS OF THE ISLAND...WHILE OVER
HISPANIOLA MOST ACTIVE IS TO BUILD ACROSS CENTRAL PORTIONS.
OVERALL EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM.

FURTHERMORE...A THIRD TUTT LOW CENTERS TO THE SOUTH OF THE CAYMAN
ISLES... EXTENDING A SHORT WAVE TROUGH TO THE SOUTHERN CARIBBEAN.
UNDER INFLUENCE OF THE RIDGE TO THE NORTH THIS IS TO RETROGRESS
TOWARDS CENTRAL AMERICA WHILE WEAKENING TO AN OPEN TROUGH. BUT AS
AFOREMENTIONED POLAR TROUGH ESTABLISHES OVER THE EASTERN USA...AND
AN INDUCED TROUGH ESTABLISHES ACROSS THE WESTERN CARIBBEAN...THE
TUTT PATTERN IS TO ONCE AGAIN STRENGTHEN. AS THE TROUGH
RETROGRESSES ACROSS CENTRAL AMERICA IT IS TO INITIALLY FAVOR AN
UPPER CONVERGENT/SUBSIDENT PATTERN. BUT AS THE UPPER TROUGH MOVES
FARTHER INLAND ACROSS HONDURAS-EL SALVADOR DIVERGENCE ALOFT WILL
BRIEFLY ESTABLISH. AS A RESULT...EXPECTING AN INCREASE IN ACTIVITY
THROUGH MIDDAY ON THURSDAY...WHEN THIS IS LIKELY TO ENHANCE
DIURNAL CONVECTION TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM. OTHER CONVECTIVE ENHANCEMENT IS EXPECTED ALONG
THE BASE OF THE TROUGH ACROSS COSTA RICA/NICARAGUA...WHERE IN
INTERACTION WITH THE ITCZ IT IS TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-45MM. AS THE TROUGH DEEPENS LATER IN
THE CYCLE...IT IS TO FAVOR AN INCREASE IN DEEP CONVECTION ACROSS
WESTERN CUBA...TO RESULT IN RAINFALL AMOUNTS OF 15-20MM/DAY AND
MAXIMA OF 30-60MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE
44W     46W    49W    51W    54W    57W    60W    63W     TW
63W     65W    67W    69W    72W    75W    78W    80W     TUTT
INDUCED
72W     73W    74W    75W    77W    78W    DISSIP         TUTT
INDUCED
96W    100W   103W   107W   110W   112W   114W    DISSIP  TW

THE TROPICAL WAVE ALONG 44W REMAINS THE SYSTEM OF CONCERN. THE NHC
CONTINUES TO MONITOR THIS SYSTEM FOR POSSIBLE TROPICAL CYCLONE
FORMATION. DUSTY/DRY AIR TO THE NORTH CONTINUES TO ENTRAIN INTO
THE SYSTEM...AND THEY NOW FORESEE A SLOWER EVOLUTION.
MEANWHILE...IF IT WERE TO REMAIN AN OPEN WAVE...IT SHOULD BE
ENTERING THE LESSER ANTILLES EARLY ON SATURDAY MORNING...WHERE IT
IS FORECAST TO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA
OF 20-40MM.

A TUTT INDUCED PERTURBATION ON THE EASTERLY TRADES ENTERED THE
EASTERN CARIBBEAN EARLY THIS MORNING...WITH AXIS NORTH ALONG 63W.
A MOIST PLUME TRAILS THIS WAVE...FOCUSING MOISTURE ACROSS
BARBADOS-WINDWARD/FRENCH ISLES...WHERE WE EXPECT RAINFALL AMOUNTS
OF 05-10MM/DAY AND MAXIMA OF 15-25MM. THIS IS TO BUILD WEST ACROSS
THE USVI TO PUERTO RICO THROUGH THURSDAY MORNING...WHERE IT IS TO
SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM IN
SCATTERED CONVECTION. ACROSS HISPANIOLA IT IS TO THEN SUSTAIN
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM THROUGH
FRIDAY MORNING...WHILE OVER JAMAICA EXPECTING ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15-25MM ON FRIDAY. HIGHER AMOUNTS ARE
EXPECTED ACROSS EASTERN-CENTRAL CUBA AS IT INTERACTS WITH TUTT TO
THE WEST...TO SUSTAIN MAXIMA OF 30-60MM.

ANOTHER TUTT INDUCED PERTURBATION IS INITIALIZED ALONG 72W. THIS
IS FORECAST TO WEAKEN EARLY ON SATURDAY MORNING.
MEANWHILE...ACROSS HISPANIOLA IT WILL SUSTAIN RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. OVER JAMAICA IT WILL FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM...WHILE
ACROSS EASTERN CUBA MAXIMA PEAKS AT 30-60MM.

TROPICAL WAVE ALONG 96W IS TO SUSTAIN ORGANIZED CONVECTION ACROSS
CENTRAL-SOUTHWEST MEXICO THROUGH THURSDAY MORNING...WITH RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 35-70MM AS IT INTERACTS WITH
TUTT TO THE WEST.

FIGUEROA...MARN (EL SALVADOR)
VALVERDE...IMN (COSTA RICA)
DAVISON...WPC (USA)