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AXPZ20 KNHC 272125
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC.


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

THE ITCZ AXIS EXTENDS FROM 06N89W TO 13N105W TO LOW PRESSURE NEAR 07N118W TO 04N125W TO 07N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 03N TO 06N BETWEEN 90W AND 95W...FROM 04N TO 08N BETWEEN 100W AND 105W...WITHIN 300 NM SE OF AXIS BETWEEN 104W AND 113W...AND WITHIN 360 NM IN THE SE SEMICIRCLE OF THE LOW.


...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. RECENT SHIP OBSERVATIONS AND SCATTEROMETER DATA INDICATE MAINLY 10-20 KT NW FLOW OFF THE PACIFIC COAST OF BAJA CALIFORNIA NORTE TO THE SOUTH OF 30N... BETWEEN 1025 MB HIGH PRES CENTERED NEAR 31N134W 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 WINDS PERSIST WITH 8 TO 9 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 1008 MB SURFACE LOW CENTERED NEAR 07N118W. 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 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 1024 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 RECENT ALTIMETER IMAGERY...COVERING A LARGE AREA FROM 06N TO 15N W OF 115W. 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 10 FT.

$$ LEWITSKY/CHRISTENSEN

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