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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1826Z Apr 15, 2015)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EDT WED APR 15 2015

DISCUSSION FROM APRIL 15/12 UTC: LARGE UPPER TROUGH OVER THE
WESTERN UNITED STATES IS SLOWLY PUSHING TO THE SOUTHEAST. THIS IS
PRESSING INTO AN UPPER RIDGE THAT EXTENDS FROM THE EASTERN PACIFIC
SOUTHWEST OF MEXICO INTO THE GULF OF MEXICO/NORTHERN CENTRAL
AMERICA. UNDER THIS PATTERN...EXPECTING SEVERAL SHORT WAVE
VORTICES TO STREAM OVER CENTRAL/NORTHEAST MEXICO THROUGH THE CYCLE
STIMULATING CONVECTIVE DEVELOPMENT. AT LOW-LEVELS...LARGEST
MOISTURE CONTENT REMAINS ALONG THE GULF OF MEXICO BASIN. THIS WILL
LEAD TO LARGEST RAINFALL AMOUNTS ALONG THE EASTERN SLOPES OF THE
SIERRA MADRE ORIENTAL/COASTAL PLAIN THROUGH THE CYCLE. THROUGH
EARLY THURSDAY EXPECTING ISOLATED MAXIMA OF 15-20MM/DAY IN PARTS
OF THE SIERRA MADRE ORIENTAL. MAXIMA WILL DECREASE TO 15MM/DAY
AFTERWARDS. NOTE THAT ISOLATED HIGHER AMOUNTS ARE POSSIBLE NEAR
TEXAS BORDER BY FRIDAY INTO EARLY SATURDAY.

ACROSS CENTRAL AMERICA...MOST ACTIVE CONVECTION IS TO REMAIN
ACROSS SOUTHERN GUATEMALA/EL SALVADOR INTO THE CONTINENTAL
DIVIDE...AND OVER COSTA RICA AND PANAMA. AT MID AND UPPER
LEVELS...RIDGE WILL CONTINUE DOMINATING NORTHERN CENTRAL AMERICA.
AS THE RIDGE HOLDS...EXPECTING A GRADUAL STRENGTHENING OF THE
SUBSIDENCE CAP OVER THE REGION. THIS WILL LIMIT BUT NOT SUPPRESS
RAINFALL AMOUNTS IN NORTHERN CENTRAL AMERICA SUSTAINING A
DECREASING TREND. ACROSS GUATEMALA/EL SALVADOR...THROUGH EARLY
THURSDAY EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM/DAY...WITH
MAXIMA DECREASING TO 15MM/DAY AND BECOMING MORE ISOLATED
AFTERWARDS. TO THE SOUTH OVER COSTA RICA/WESTERN
PANAMA...EXPECTING MAXIMA OF 15MM/DAY THROUGH EARLY THURSDAY
DECREASING TO MAXIMA OF 10MM/DAY AFTERWARDS.

QUIET PATTERN IS DOMINATING MOST OF THE CARIBBEAN BASIN AND THE
BAHAMAS/GULF OF MEXICO REGION. MID-UPPER RIDGE CONTINUES
DOMINATING THE AREA...BUT MORE SO A DRY AIR MASS THAT CAN BE SEEN
AS LOW AS 925 HPA IN SOME LOCATIONS. THIS WILL CONTINUE LIMITING
ACCUMULATIONS ACROSS MOST OF THE GREATER ANTILLES. ISOLATED HIGHER
AMOUNTS ARE POSSIBLE IN PARTS OF CUBA AND PARTS OF HISPANIOLA
WHERE CONVECTIVE INSTABILITY WILL BE SLIGHTLY HIGHER THAN IN OTHER
LOCATIONS. YET...EXPECTING GENERALIZED MAXIMA TO REMAIN NEAR OR
UNDER 10MM/DAY. ISOLATED HIGHER AMOUNTS ARE EXPECTED IN PARTS OF
THE LEEWARDS/FRENCH ISLES THROUGH EARLY THURSDAY UNDER THE
INFLUENCE OF UPPER TROUGH THAT EXTENDS FROM THE CENTRAL ATLANTIC
INTO THE REGION.

TO THE SOUTHEAST...OVER THE WINDWARD ISLANDS AND INTO NORTHEASTERN
SOUTH AMERICA A SLIGHTLY WETTER PATTERN IS EXPECTED. AT UPPER
LEVELS...SUBEQUATORIAL RIDGE EXTENDS ALONG 03N-06N FROM THE
TROPICAL ATLANTIC INTO SOUTHERN VENEZUELA. THIS IS LEADING TO
INCREASED UPPER DIVERGENCE TO THE SOUTH IN COMBINATION WITH THE
SUBTROPICAL RIDGE CENTERING OVER MATO GROSSO IN SOUTH AMERICA.
THIS IS INTERACTING WITH THE ATLANTIC ITCZ AND THE NET LEADING TO
SCATTERED DEEP CONVECTION. THROUGH EARLY THURSDAY...EXPECTING
MAXIMA OF 30-60MM/DAY IN THE SOUTHERN REGION OF THE GUIANAS. A
WEAK WAVE IN THE TRADES WILL BRING IN ITCZ MOISTURE INTO MOST OF
SURINAME AND ALL OF FRENCH GUIANA ON THURSDAY INTO EARLY FRIDAY
WHERE EXPECTING SIMILAR AMOUNTS.BY FRIDAY INTO EARLY SATURDAY
EXPECTING MAXIMA OF 20-30MM/DAY ACROSS MOST OF THE GUIANAS INTO
EASTERN VENEZUELA. ACROSS NORTHERN GUYANA AND NORTHEASTERN
VENEZUELA/TRINIDAD AND TOBAGO...AMOUNTS WILL GENERALLY REMAIN
UNDER THE 15MM/DAY RANGE...WITH ISOLATED MAXIMA OF 15-25MM/DAY IN
CONTINENTAL REGIONS.

OVER NORTHWESTERN SOUTH AMERICA...AN UPPER DIVERGENT PATTERN AND
WIDESPREAD CONVECTIVE INSTABILITY WILL CONTINUE LEADING TO A
SEASONALLY ACTIVE PATTERN OF CONVECTION. FURTHERMORE...FAVORABLE
MADDEN-JULIAN OSCILLATION CONDITIONS WILL ENHANCE THE COVERAGE AND
INTENSITY OF ACTIVITY. ACROSS CENTRAL/NORTHWESTERN COLOMBIA
EXPECTING AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM/DAY THROUGH
THE CYCLE. ACROSS NORTHEASTERN COLOMBIA INTO NORTHWESTERN
VENEZUELA EXPECTING MAXIMA OF 15-30MM/DAY THROUGH EARLY THURSDAY
INCREASING TO MAXIMA OF 25-50MM/DAY BY FRIDAY INTO EARLY SATURDAY.
ISOLATED HIGHER AMOUNTS ARE ALWAYS POSSIBLE IN INTERACTION WITH
THE COMPLEX OROGRAPHY OF THE REGION. TO THE SOUTHEAST OVER THE
LLANOS/AMAZON PLAINS...EXPECTING ALSO AN ACTIVE PATTERN OF
CONVECTION WITH MAXIMA OF 20-40MM/DAY THROUGH EARLY THURSDAY
INCREASING TO MAXIMA OF 30-60MM/DAY AFTERWARDS...WITH REGION OF
STRONGEST CONVECTION GRADUALLY SPREADING NORTHWARDS.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96        TYPE
NONE

CRAIG...TTMS (TRINIDAD AND TOBAGO)
SAMUEL...MDS (SURINAME)
DAVISON...WPC (USA)
GALVEZ...WPC (USA)