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000
AXPZ20 KNHC 280338
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC TUE APR 28 2015

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0215 UTC.


...SPECIAL FEATURES...

GULF OF TEHUANTEPEC GALE WARNING...MODEL GUIDANCE IS IN GOOD AGREEMENT REGARDING WEAK LOW PRES DEVELOPING SE OF TEHUANTEPEC LIKELY INDUCED BY MID/UPPER LEVEL DYNAMICS APPROACHING THE AREA. ALONG WITH HIGH PRES BUILDING OVER NE MEXICO IN THE WAKE OF A GULF OF MEXICO COLD FRONT...THIS WILL TIGHTEN THE PRES GRADIENT AND SUPPORT GALE CONDITIONS THROUGH THE GULF OF TEHUANTEPEC BY WED AFTERNOON CONTINUING INTO EARLY THU MORNING. SEAS WILL BUILD TO UP TO 12 TO 13 FT DURING THE GALE FORCE WINDS BY LATE WED NIGHT.


...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM 10N100W TO LOW PRES NEAR 08N117W THEN CONTINUES AS THE ITCZ FROM THE LOW TO 06N140W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 07N TO 09N BETWEEN 91W AND 100W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN AN AREA BOUNDED BY A LINE FROM 16N108W TO 05N100W TO 04N116W TO 16N108W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM IN THE N AND SE QUADRANTS OF THE LOW...AND ALSO WITHIN 150 NM N OF THE AXIS BETWEEN 122W AND 127W.


...DISCUSSION...

E OF 120W...

TROUGHING ALOFT AND AN ASSOCIATED UPPER LOW MOVING ACROSS NEW MEXICO INTO W TEXAS IS SUPPORTING RELATIVELY LOW PRES OVER NW MEXICO INCLUDING BAJA CALIFORNIA NORTE. THIS PRES PATTERN HAS RELAXED SINCE YESTERDAY WHEN GALE FORCE WINDS WERE OCCURRING HOWEVER SOME RESIDUAL NORTHERLY SWELL PERSISTS WITH SEAS TO 8 FT REACHING AS FAR SOUTH AS 24N OFF BAJA. VARIOUS WAVE MODEL GUIDANCE REMAINS IN GOOD AGREEMENT SHOWING THESE SEAS SUBSIDING TO LESS THAN 8 FT OVERNIGHT.

FARTHER SOUTH...THE TROPICAL EPAC IS STARTING TO TRANSITION TO ITS LATE SPRING/SUMMER PATTERN...WITH SIGNIFICANT MID LATITUDE INFLUENCES. WHAT WAS A COHERENT ITCZ IS BREAKING DOWN INTO A LARGE AREA OF EAST TO WEST ORIENTED TROUGHING ALONG ROUGHLY 10N...ALTHOUGH WITH FAIRLY WEAK AND INCONSISTENT SOUTHERLY FLOW. A MID/UPPER LEVEL SHORT WAVE TROUGH IS EVIDENT ON WATER VAPOR IMAGERY APPROACHING FROM THE NW...PROVIDING SUPPORT TO A LARGE AREA OF MODERATE TO STRONG CONVECTION AROUND A 1008 MB SURFACE LOW CENTERED NEAR 08N117W. GUIDANCE INDICATES THIS LOW PRES WILL WEAKEN AND DISSIPATE THROUGH 48 TO 72 HOURS AS IT DRIFTS W...AND AS THE SUPPORTING UPPER DYNAMICS SHIFT EAST.

SEAS ARE GENERALLY 4 TO 6 FT OVER THE TROPICAL EPAC WITH LITTLE CHANGE EXPECTED UNTIL LATER IN THE WEEK WHEN LONG PERIOD SW SWELL WITH WAVE HEIGHTS OF 8 TO 10 FT MOVES ACROSS THE EQUATOR IN THE WATERS W OF THE GALAPAGOS.

W OF 120W...

A SPLIT FLOW PATTERN IS NOTED ALOFT AHEAD OF SHARP UPPER TROUGHING APPROACHING FROM THE NW. THE TROUGH WILL SHIFT EASTWARD TO THE NORTH OF 25N...WEAKENING THE DEEP LAYER RIDGING AHEAD OF IT TO INCLUDE A WEAKENING 1020 MB HIGH PRES AREA CENTERED NEAR 31N134W. THIS IN TURN WILL ALLOW PERSISTENT FRESH TRADE WIND FLOW FARTHER SOUTH TO DIMINISH BY TUE AFTERNOON. HOWEVER THE SUBTROPICAL RIDGE BUILDS EASTWARD FROM THE CENTRAL PACIFIC TONIGHT BEHIND THE TROUGH. PERSISTENT TRADE WIND FLOW ALONG WITH COMPONENTS OF NW SWELL ARE CONTRIBUTING TO 8 TO 10 FT SEAS NOTED IN EARLIER ALTIMETER IMAGERY...COVERING AN AREA FROM 08N TO 16N W OF 124W. THESE SEAS WILL SUBSIDE IN HEIGHTS AND COVERAGE THROUGH 48 HOURS AS THE TRADE WIND FLOW DIMINISHES. WAVE GUIDANCE INDICATES LONG PERIOD NW SWELL WILL MOVE INTO THE NW CORNER OF THE AREA BY TUE MORNING PROPAGATING TO THE SE THROUGH WED WITH SEAS OF 8 TO 11 FT.

$$ LEWITSKY

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