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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1826Z Sep 25, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EDT THU SEP 25 2014

DISCUSSION FROM SEPTEMBER 25/00UTC: AT 250 HPA...RIDGE OVER MEXICO
IS YIELDING TO AN AMPLIFYING TROUGH OVER NORTH AMERICA. THROUGH
THURSDAY EVENING THE TROUGH REACHES MAXIMUM AMPLITUDE...AS IT IS
TO EXTEND TO THE SOUTHWEST ACROSS THE USA TO THE NORTHERN STATES
OF MEXICO. DURING THE NEXT TWO DAYS...THE BEST INFLOW OF SHORT
WAVE ENERGY IS EXPECTED ALONG THE USA/MEXICO BORDER-COAHUILA-NUEVO
LEON/TAMAULIPAS. LATER ON SATURDAY...AS RIDGE BEGINS TO BUILD
ACROSS MEXICO...THE TROUGH IS TO LIFT INTO EASTERN TEXAS/NORTHWEST
GULF OF MEXICO. ACROSS SINALOA-SOUTHWEST MEXICO...AS THE TROUGH
MEANDERS OVER MEXICO...EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY
AND MAXIMA OF 25-50MM. OVER NORTHEAST
MEXICO...MEANWHILE...EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY AND
MAXIMA OF 30-60MM. THROUGH SATURDAY...AS THE TROUGH WEAKENS...THIS
DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-40MM. ACROSS
CENTRAL-SOUTHERN MEXICO EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-40MM.

SOUTH AND EAST OF THE UPPER LEVEL TROUGH OVER NORTH AMERICA...A
RIDGE EXTENDS TO THE NORTHEAST FROM GUATEMALA/THE YUCATAN...ACROSS
WESTERN CUBA TO THE WESTERN ATLANTIC. AT 250 HPA THE RIDGE ANCHORS
ON TWO CLOSED HIGHS... WITH ONE OVER BELIZE/QUINTANA ROO MEXICO
AND THE OTHER OVER THE ATLANTIC NEAR 28N 85W. AT MID LEVELS THIS
SUSTAINS A BROAD RIDGE ACROSS THE WESTERN ATLANTIC/NORTH OF THE
GREATER ANTILLES. THIS IS FORECAST TO BUILD SOUTH AND WEST ACROSS
THE BAHAMAS-CUBA. THE BUILDING MID LEVEL RIDGE WILL STRENGTHEN THE
TRADE WINDS CAP ACROSS THE BAHAMAS-CUBA...WHILE OVER NORTHERN
CENTRAL AMERICA DEEP LAYER CONVECTIVE INSTABILITY IS TO PERSIST.
ACROSS THE BAHAMAS-CUBA THIS WILL THEN LEAD TO GRADUAL EROSION OF
AVAILABLE MOISTURE FROM THE EAST...AND THIS IS TO BECOME MORE
PRONOUNCED EARLY ON FRIDAY. ACROSS CUBA EXPECTING DIURNAL
CONVECTION TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM THROUGH THIS EVENING...AND 05-10MM/DAY AND MAXIMA OF 15MM
LATER ON FRIDAY TO SATURDAY. ACROSS THE BAHAMAS EXPECTING
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM ON THURSDAY TO
EARLY FRIDAY MORNING. OVER NORTHERN CENTRAL AMERICA...UPPER RIDGE
IS TO VENT CONVECTION ALONG THE CONTINENTAL DIVIDE OVER
HONDURAS/EL SALVADOR-GUATEMALA...WITH RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 30-60MM. ACROSS NORTHEAST
HONDURAS-EASTERN NICARAGUA EXPECTING ACCUMULATION OF 10-15MM/DAY
AND MAXIMA OF 20-30MM.

EAST OVER THE DOMAIN...THE TUTT PATTERN ALOFT CONTINUES TO
STRENGTHEN...WITH TUTT LOW NEAR 25N 55W EXTENDING A SHORT WAVE
TROUGH TO THE NORTHEAST CARIBBEAN ISLES. THIS IS ENHANCING
CONVECTIVE INSTABILITY ACROSS THE NORTHEAST CARIBBEAN ISLES WHILE
FAVORING GENERATION OF ORGANIZED DEEP CONVECTION. MODELS FORECAST
THE TUTT TO AMPLIFY FARTHER WEST AND SOUTH INTO THE CARIBBEAN
THROUGH MIDDAY ON FRIDAY...WHEN IT IS TO EXTEND ACROSS A LOW OVER
PUERTO RICO/VIRGIN ISLES TO NORTHERN COLOMBIA/NORTHWEST VENEZUELA.
BEST INFLOW OF SHORT WAVE ENERGY IS EXPECTED ACROSS THE NORTHEAST
CARIBBEAN ISLES THROUGH SATURDAY EVENING/EARLY SUNDAY MORNING. THE
INFLOW OF COLD AIR ALOFT WILL FAVOR LIFTED INDEX VALUES OF -6 TO
-9 AND TTI OF 50 OVER THE NEXT FEW DAYS. AT LOW LEVELS...DEEPENING
MID/UPPER LEVEL TROUGH WILL SUSTAIN AN INDUCED TROUGH IN THE
EASTERLY TRADES LATER THIS EVENING. UNDER INFLUENCE OF THIS
TROUGH...THE WINDS WILL VEER TO THE SOUTH-SOUTHEAST THROUGH FRIDAY
MORNING...FOCUSING CYCLONIC VORTICITY ACROSS THE VIRGIN
ISLES/SOUTHEAST PUERTO RICO. THIS FLOW IS TO ALSO ADVECT ITCZ
MOISTURE ACROSS THE FRENCH/LEEWARD ISLES INTO THE NORTHEAST
CARIBBEAN ISLES...WITH PWAT EXPECTED TO PEAK IN EXCESS OF 50MM
THROUGH SUNDAY MORNING. ALTHOUGH DYNAMICAL FORCING IS STRONG AND
DEEP MOISTURE IS AVAILABLE...THE GLOBAL AND REGIONAL MODELS ARE
NOT RESPONDING TO THIS PATTERN. IN THIS PATTERN...POTENTIAL FOR
HEAVY CONVECTION IS HIGH...WITH RISK OF AN MCS FORMING BETWEEN
EASTERN PUERTO RICO AND THE LEEWARD ISLES EARLY ON FRIDAY. LATER
ON...INTERACTION BETWEEN DIURNAL HEATING/SEA BREEZE CONVERGENCE
WILL FAVOR HEAVY PRECIPITATION FROM PUERTO RICO TO EASTERN
HISPANIOLA. ACROSS THE NORTHERN LEEWARD-VIRGIN ISLES EXPECTING
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM...WHILE
ACROSS PUERTO RICO TO EASTERN HISPANIOLA EXPECT ACCUMULATION OF
15-30MM/DAY AND MAXIMA OF 75-125MM. ALTHOUGH DYNAMICAL FORCING
WANES ON SUNDAY TO MONDAY...DEEP LAYER CONVECTIVE INSTABILITY IS
EXPECTED TO CONTINUE FAVORING STRONG CONVECTION IN ASSOCIATION
WITH SEA BREEZE CONVERGENCE. ACROSS NORTHERN COLOMBIA/NORTHWEST
VENEZUELA...AS THE UPPER TROUGH INTERACTS WITH THE NEAR EQUATORIAL
TROUGH...EXPECTING 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
52W     53W    54W    55W    56W    DISP.              TUTT INDCD.

74W     75W    76W    77W    78W    79W    80W    81W     TW
87W     88W    89W    90W    91W    92W    93W    94W     TW

WEAK TROPICAL WAVE ALONG 74W IS TO MOVE ACROSS HAITI THROUGH
FRIDAY MORNING...TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM. AS IT ENTERS JAMAICA IT IS TO THEN FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER
WESTERN COLOMBIA...IN INTERACTION WITH THE NET... EXPECTING
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM. ACROSS
PANAMA IT IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-40MM.

TROPICAL WAVE ALONG 87W MOVES ACROSS WESTERN NICARAGUA TO EL
SALVADOR/ HONDURAS EARLY IN THE CYCLE...WHERE IT IS TO FAVOR
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM. 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 30-70MM.

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