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Eastern Pacific Tropical Weather Discussion



000
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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Page last modified: Monday, 27-Apr-2015 21:25:40 UTC