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Eastern Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 012200
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
2205 UTC WED JUL 01 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 
2330 UTC. 

...TROPICAL WAVES...

TROPICAL WAVE FROM 07N TO 13N NEAR 98W/99W NEAR THE EASTERN END 
OF AN UPPER TROUGH EXTENDING EAST TO WEST ALONG 21N. THIS ALONG 
WITH LEFTOVER BOUNDARIES MOVING OFF THE MEXICAN COAST ARE 
ENHANCING SCATTERED SHOWERS AND THUNDERSTORMS ALONG THE NORTHERN 
END OF THE WAVE FROM 13N TO 15N BETWEEN 95W AND 100W. THE WAVE 
DOES NOT SHOW UP WELL IN SURFACE OR LOWER LEVEL DATA AND 
POSITION IS BASED ON CONTINUITY.

TROPICAL WAVE FROM 09N TO 15N NEAR 105W/106W IS DISPLAYED 
RELATIVELY WELL IN THE LOWER TO MID LEVELS OF THE ATMOSPHERE 
BASED ON ANIMATED PRECIPITABLE WATER IMAGERY AND GOES DERIVED 
HIGH DENSITY WINDS...BUT SHOWS UP POORLY AT THE SURFACE BASED ON 
A PAIR OF RECENT SCATTEROMETER PASSES. NO SIGNIFICANT CONVECTION 
IS NOTED WITH THIS WAVE.

TROPICAL WAVE FROM 05N TO 14N ALONG 128W/129W IS EMBEDDED IN A 
LARGE AREA OF SHOWERS AND THUNDERSTORMS ALONG THE ITCZ RELATED 
TO UPPER LEVEL DIVERGENCE AND WEAK TRADE WIND CONVERGENCE. THE 
WAVE IS POORLY PRESENTED AT THE SURFACE AND LOWER LEVELS OF THE 
ATMOSPHERE. 

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

NO MONSOONAL CIRCULATION IS CURRENTLY EVIDENT. THE ITCZ EXTENDS 
FROM 05N105W TO 10N135W TO BEYOND 10N140W. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION NOTED WITHIN 180 NM N OF THE ITCZ 
AXIS...AND 270 NM S OF THE ITCZ AXIS BETWEEN 115W AND 135W.

...DISCUSSION...

N OF 15N E OF 120W...WEAK 1013 MB LOW PRES W OF THE AREA NEAR 
16N125W HAS INTERRUPTED THE SUBTROPICAL RIDGE OVER THE 
AREA...AND IS MAINTAINING A LIGHT PRESSURE PATTERN OVER THE 
REGION...AS NOTED IN RECENT SCATTEROMETER DATA...INCLUDING 
ANOMALOUS SE FLOW OFF THE BAJA CALIFORNIA COAST. THIS WAS 
CONFIRMED A SHIP OBSERVATION FROM EARLIER THIS MORNING. A PAIR 
OF ALTIMETER PASSES FROM 11 UTC AND 13 UTC INDICATED SEAS OF 
GENERALLY 3 TO 5 FT OFF THE BAJA PENINSULA. THE SURFACE LOW IS 
RELATED TO AN UPPER LEVEL LOW IN THE SAME AREA WITH A SHARP 
UPPER TROUGH REACHING ACROSS THE SOUTHERN TIP OF THE BAJA 
PENINSULA TO CABO CORRIENTES. DRY SUBSIDENT FLOW WRAPPING INTO 
WEST AND SW SIDE OF THE UPPER LOW IS SUPPRESSING CONVECTION 
ACROSS THE REGION. FARTHER SOUTH...A PULSE OF STRONG GAP WINDS 
WILL OCCUR THROUGH THE GULF OF TEHUANTEPEC TONIGHT...BUT WILL 
END QUICKLY AND NOT RESULTS IN SEAS 8 FT OR HIGHER. LOOKING 
AHEAD...THE LOW WEST OF THE AREA WILL DRIFT FARTHER WEST 
ALLOWING THE SUBTROPICAL RIDGE TO BUILD NEAR 25N120W. A SURFACE 
TROUGH OVER NORTHERN BAJA CALIFORNIA NORTE RELATED TO AN UPPER 
IMPULSE N OF THE AREA WILL ALLOW STRONG WINDS OFF THE SOUTHERN 
COAST OF BAJA CALIFORNIA NORTE FRI NIGHT.

S OF 15N E OF 110W...A 16 UTC ASCAT PASS VERIFIED STRONG GAP 
WIND FLOW THROUGH THE GULF OF PAPAGAYO...RELATED TO STRONG TRADE 
WIND FLOW OVER THE SW CARIBBEAN. WIND CONVERGENCE ON THE LEADING 
EDGE OF THIS PLUME OF GAP WINDS WAS RESULTING IN A FEW SHOWERS 
AND THUNDERSTORMS ALONG A LINE FROM 07N85W TO 10N90W. AN EARLIER 
ALTIMETER PASS INDICATED SEAS TO 10 FT DOWNSTREAM OF THE 
PLUME...BUT THIS LIKELY MISSED THE AREA OF PEAK WAVE HEIGHTS 
WITHIN THE PLUME WHICH MAY HAVE BEEN IN EXCESS OF 11 FT. ANOTHER 
PULSE OF GAP WINDS THROUGH PAPAGAYO IS EXPECTED TONIGHT AS SHORT 
PERIOD SWELL FROM THE EARLIER PLUME PROPAGATES WEST AND 
SUBSIDES. SIMILARLY FRESH NORTHERLY GAP WIND FLOW WILL PERSIST 
INTO THE GULF OF PANAMA TONIGHT AND THU NIGHT. 

ELSEWHERE...AN UPPER LOW REMAINS CENTERED NEAR 27N125W MOVING 
WEST. DIVERGENCE ALOFT ON THE SOUTHERN PERIPHERY OF THE UPPER 
LOW AND ANTICYCLONIC FLOW ALOFT S OF 12N INTERACTING WITH WEAK 
TRADE WIND CONVERGENCE TO SUPPORT CLUSTERS OF SHOWERS AND 
THUNDERSTORMS ALONG THE ITCZ BETWEEN 115W AND 135W. AN AREA OF 
NE SWELL TO 8 FT IS NOTED ON AN EARLIER ALTIMETER FROM 10N TO 
15N W OF 136W. WINDS WERE 20 TO 25 KT EARLIER...RELATED TO A AN 
TROPICAL WAVE THAT MOVE THROUGH THE THE AREA YESTERDAY...BUT 
THESE WINDS APPEAR TO HAVE DIMINISHED AS NOTED IN A RECENT  
ASCAT PASS. THE SWELL IS EXPECTED TO SUBSIDE BELOW 8 FT 
ACCORDINGLY WITHIN THE NEXT 18 TO 24 HOURS. ONLY MODERATE TRADE 
WINDS ARE NOTED DUE TO A WEAKENED SUBTROPICAL RIDGE N OF THE 
AREA...DUE THE PRESENCE OF THE DEEP LAYER LOW. AS THE UPPER LOW 
WILL DRIFT WEST THROUGH LATE WEEK...THERE IS SOME UNCERTAINTY 
CONCERNING THE DEVELOPMENT OF LOW PRES IN THE DEEP TROPICS. THE 
LATEST GFS AND ECMWF INDICATE DEVELOPMENT OF AT LEAST TWO AREAS 
OF LOW PRES ALONG THE ITCZ W OF 130W THROUGH LATE FRI...THE 
LATEST GFS IS FASTER AND MORE AGGRESSIVE. THE OFFICIAL FORECAST 
DOES NOT INCLUDE ANY CHANGES YET IN THIS AREA THROUGH 48 
HOURS...BUT THIS WILL BE REVIEWED WITH SUBSEQUENT MODEL RUNS.

$$ 
CHRISTENSEN


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Page last modified: Wednesday, 01-Jul-2015 22:01:03 UTC