Prognostic Meteorological Discussion
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FXCA20 KWBC 231827
PMDCA

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EDT WED JUL 23 2014

DISCUSSION FROM JULY 23/00UTC: WEST OVER THE DOMAIN...BROAD CELL
OF THE SUBTROPICAL RIDGE EXTENDS ACROSS THE SOUTHWEST USA TO THE
NORTHERN STATES OF MEXICO. AT 250 HPA IT IS TO ANCHOR ON A CLOSED
HIGH OVER ARIZONA/NEW MEXICO IN THE SOUTHWEST USA. AN ELONGATED
TROUGH LIES TO THE EAST...WITH AXIS SOUTHWEST ACROSS THE SOUTHEAST
USA-WESTERN GULF OF MEXICO TO A LOW OVER NAYARIT/COLIMA IN
SOUTHWEST MEXICO. UNDER INFLUENCE OF THE RIDGE TO THE NORTH THE
LOW IS TO SPLIT FROM MAIN TROUGH AXIS. EARLY IN THE CYCLE IT IS TO
MEANDER OFF THE SOUTHWEST COAST OF MEXICO...BUT THROUGH FRIDAY
AFTERNOON IT WILL BEGIN TO LIFT INTO THE BAJA PENINSULA. THE
INFLOW OF SHORT WAVE ENERGY AND COLD AIR ALOFT IS TO ENHANCE
CONVECTIVE INSTABILITY ACROSS SOUTHWEST MEXICO. THIS WILL COMBINE
WITH DIURNAL HEATING TO SUSTAIN AN INCREASE IN CONVECTION...WITH
MOST ACTIVE EXPECTED BETWEEN NAYARIT/COLIMA AND GUERRERO/OAXACA
LATER ON WEDNESDAY-THURSDAY...TO RESULT IN RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM. ACTIVITY THEN SPREADS NORTH
INTO SINALOA THROUGH FRIDAY EVENING. THE RIDGE ALOFT...AS IT
MEANDERS OVER NORTHERN MEXICO...IS TO VENT DIURNAL CONVECTION
ALONG THE SIERRA MADRE OCCIDENTAL OF MEXICO...TO FAVOR RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. THROUGH THURSDAY
EVENING THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF 15-30MM AS THE
TUTT LOW LIFTS ALONG THE COAST.

ALSO AT UPPER LEVELS...ANOTHER RIDGE LIES OVER THE WESTERN
ATLANTIC/NORTH OF THE ISLANDS WHILE CENTERING ON A CLOSED HIGH
NEAR 30N 70W. THIS IS TO REMAIN NEARLY STATIONARY THROUGH THURSDAY
AFTERNOON...THEN STARTS TO ERODE LATER ON FRIDAY AS A POLAR TROUGH
AMPLIFIES ACROSS THE EASTERN USA. THE RIDGE
ALOFT...MEANWHILE...WILL PROVIDE THE STEERING FLOW TO A TUTT OVER
THE NORTHWEST CARIBBEAN. THE LOW CENTERS OVER THE CAYMAN
ISLANDS...AND THROUGH THURSDAY AFTERNOON IT IS TO LIFT ACROSS
WESTERN CUBA...INTO THE SOUTHEAST GULF OF MEXICO/FLORIDA PENINSULA
LATER ON FRIDAY. EARLY IN THE CYCLE...AS THE TUTT MEANDERS OVER
THE CAYMAN ISLES...IT IS TO TRIGGER ISOLATED TO SCATTERED
CONVECTION WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15MM.
OVER CENTRAL-WESTERN CUBA THIS IS TO FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-30MM THROUGH THURSDAY MORNING...AND
10-15MM/DAY AND MAXIMA OF 20-40MM ON THURSDAY TO EARLY FRIDAY.

ALTHOUGH A MID/UPPER LEVEL TUTT LOW REMAINS NORTH OF THE
VIRGIN/LEEWARD ISLES...IT IS HAVING LITTLE TO NO IMPACT ON WEATHER
CONDITIONS ACROSS THE NORTHEAST CARIBBEAN ISLANDS. TUTT IS TO
REMAIN NORTH OF THE ISLANDS THROUGH DAY 04. AT LOW LEVELS...BROAD
RIDGE DOMINATES FLOW ACROSS THE ATLANTIC BASIN INTO THE CARIBBEAN.
THIS RIDGE FAVORS A TIGHT GRADIENT AND STRONG EASTERLY WINDS
ACROSS THE CARIBBEAN...WITH 850-800 HPA WINDS PEAKING BETWEEN
35-45KT OVER THE SOUTHERN CARIBBEAN INTO CENTRAL AMERICA. UNDER
INFLUENCE OF THE RIDGE A TRADE WINDS CAP PERSISTS ACROSS THE
ISLAND CHAIN INTO THE EASTERN CARIBBEAN. THIS...AN UNFAVORABLE MJO
CONDITIONS...GENERALLY FAVORS A DRYING TREND ACROSS NORTHERN SOUTH
AMERICA INTO THE WESTERN CARIBBEAN. IN THIS PATTERN WE ARE NOW
FORECASTING LESSER AMOUNTS ACROSS THE FORECAST AREA.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE
56W     59W    64W    68W    71W    75W    78W    81W     TW
68W     72W    76W    78W    81W    83W    85W    88W     TW
87W     91W    95W    99W   102W   105W   108W   111W     TW

TD-TWO WEAKENED TO A TROPICAL WAVE ALONG 56W. THROUGH THIS
AFTERNOON IT IS TO ENTER BARBADOS-THE FRENCH/LEEWARD ISLES...WHERE
IT IS TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-30MM. THROUGH THURSDAY MORNING IT WILL MOVE ACROSS THE VIRGIN
ISLES TO EASTERN PUERTO RICO...WHERE WE EXPECT RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM. OVER THE DOMINICAN
REPUBLIC-HAITI IT IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-35MM EARLY ON FRIDAY. OVER THE GUIANAS-NORTHEAST
VENEZUELA THIS IS TO HAVE LITTLE TO NO IMPACT ON CONVECTION. BUT
AS IT MOVES ACROSS CENTRAL/WESTERN VENEZUELA THE GLOBAL MODEL
GUIDANCE CONSISTENTLY SHOWING AN INCREASE IN CONVECTION...WITH
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER
JAMAICA-EASTERN CUBA IT IS TO THEN FAVOR RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM LATER ON FRIDAY...SIMILARLY
ACROSS COLOMBIA TO THE DARIEN IN PANAMA.

A WEAK TROPICAL WAVE IS INITIALIZED ALONG 68W. AS IT MOVES ACROSS
WESTERN VENEZUELA TO COLOMBIA IT IS TO SUSTAIN SCATTERED
CONVECTION WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM.
ACROSS PANAMA TO COSTA RICA/SOUTHERN NICARAGUA IT IS TO INTERACT
WITH THE EASTERN PACIFIC ITCZ IN SUPPORT OF SCATTERED CONVECTION
WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM.

TROPICAL WAVE ALONG 87W CONTINUES TO WEAKEN AT IT PULLS ACROSS
NORTHERN CENTRAL AMERICA TO SOUTHERN MEXICO. MOST ACTIVE
CONVECTION WITH THIS FEATURE IS NOW EXPECTED ALONG THE EASTERN
PACIFIC ITCZ. OVER GUATEMALA-CHIAPAS MEXICO WE NOW EXPECT RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-30MM. OVER
GUERRERO-CENTRAL MEXICO IT IS TO SUSTAIN RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-40MM.

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




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