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Eastern Pacific Tropical Weather Discussion (Text)



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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Page last modified: Monday, 27-Apr-2015 16:08:12 UTC