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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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