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000
AXPZ20 KNHC 271608
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON APR 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1500 UTC.


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

THE ITCZ EXTENDS FROM 04N89W TO 12N100W TO LOW PRES NEAR 07N115W 1007 MB TO 02N130W TO 06N140W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 120 NM S OF THE AXIS BETWEEN 90W AND 95W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ALSO IS NOTED WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 105W AND 120W. AN ADDITIONAL AREA OF SCATTERED MODERATE CONVECTION IS OBSERVED FROM FROM 06.5N TO 08.5N BETWEEN 83W AND 87W.


...DISCUSSION...

E OF 120W...

TROUGHING ALOFT ASSOCIATED AN UPPER LOW MOVING ACROSS NEW MEXICO INTO W TEXAS IS SUPPORTING RELATIVELY LOW PRES OVER NW MEXICO INCLUDING BAJA CALIFORNIA NORTE. RECENT SHIP OBSERVATIONS AND SCATTEROMETER DATA INDICATE MAINLY 20 KT NW FLOW OFF THE COAST OF BAJA CALIFORNIA NORTE TO THE SOUTH OF 30N...BETWEEN 1024 MB HIGH PRES CENTERED NEAR 33N130W AND THE LOWER PRESSURE OVER NW MEXICO. THESE WINDS HAVE DIMINISHED SINCE LAST NIGHT AS THE LOW PRES SHIFTS EASTWARD WITH THE UPPER TROUGH...AND THE RIDGE TO THE WEST WEAKENS. RESIDUAL NORTHERLY SWELL GENERATED FROM THE STRONG WINDS PERSIST HOWEVER...WITH 8 TO 10 FT SEAS 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 1007 MB SURFACE LOW CENTERED NEAR 06N116W. 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. BY THURSDAY...GUIDANCE IS IN GOOD AGREEMENT SHOWING ANOTHER 1007 MB LOW PRES SE OF THE GULF OF TEHUANTEPEC...LIKELY INFLUENCED BY THE SAME MID/UPPER DYNAMICS APPROACHING THE AREA CURRENTLY. ALONG WITH HIGH PRES BUILDING OVER NE MEXICO...THIS WILL TIGHTEN THE PRES GRADIENT AND SUPPORT POSSIBLY GALE CONDITIONS THROUGH THE GULF OF TEHUANTEPEC BY WED NIGHT AND THU MORNING. SEAS ARE GENERALLY 4 TO 6 FT OVER THE TROPICAL EPAC WITH LITTLE CHANGE EXPECTED UNTIL LATER IN THE WEEK UNTIL AFTER MID 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 110W...

A SPLIT FLOW PATTERN IS NOTED ALOFT AHEAD OF A SHARP UPPER TROUGH 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 1024 MB HIGH PRES AREA CENTERED NEAR 33N130W. THIS IN TURN WILL ALLOW PERSISTENT FRESH TRADE WIND FLOW FARTHER SOUTH TO DIMINISH LAST NIGHT AND THIS MORNING. HOWEVER THE SUBTROPICAL RIDGE BUILDS EASTWARD FROM THE CENTRAL PACIFIC TONIGHT BEHIND THE TROUGH...ALLOWING FOR A RECOVERY OF FRESH TO STRONG TRADE WINDS FROM 09N TO 11N BETWEEN 130W AND 135W BY EARLY TUE. PERSISTENT TRADE WIND FLOW ALONG WITH COMPONENTS OF NW SWELL ARE CONTRIBUTING TO 8 TO 11 FT SEAS NOTED IN EARLIER ALTIMETER IMAGERY...COVERING A LARGE AREA FROM 06N TO 20N W OF 115W. THE WINDS DIMINISH AGAIN BY WED AND THE SWELL SUBSIDES AND SHRINKS IN AREA TO THE WEST AS A SHORT WAVE TROUGH DIGS INTO THE RIDGE TO THE NORTH. WAVE GUIDANCE INDICATES LONG PERIOD NW SWELL WILL MOVE INTO THE AREA N OF 28N W OF 135W BY TUE NIGHT.

$$ CHRISTENSEN

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