Tropical Weather Discussion
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000
AXPZ20 KNHC 310300
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI JUL 31 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0245 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM GUILLERMO AT 31/0300 UTC WAS NEAR
10.8N 129.3W 991 MB...MOVING WNW OR 295 DEG AT 12 KT. MAXIMUM
SUSTAINED WINDS HAVE INCREASED TO 60 KT WITH GUSTS TO 75 KT.
GUILLERMO CONTINUES TO BECOME BETTER ORGANIZED AS IT REMAINS IN
AN ENVIRONMENT CONDUCIVE FOR FURTHER STRENGTHENING AND IS
FORECAST TO BECOME A HURRICANE BY FRI MORNING. NUMEROUS STRONG
CONVECTION WAS NOTED WITHIN 90 NM OF THE CENTER...EXCEPT 120 NM
IN THE NE QUADRANT. ELSEWHERE SCATTERED MODERATE TO STRONG
CONVECTION WAS NOTED WITHIN 180 NM IN THE N AND 210 NM IN THE S
SEMICIRCLES. PLEASE READ THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADER MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.

THE CENTER OF POST-TROPICAL CYCLONE EIGHT-E CONTINUES TO MOVE
WESTWARD AWAY FROM THE AREA WITH THE LOW LEVEL CIRCULATION
WEAKENING. THE SURFACE PRESSURE GRADIENT TO THE NORTH INDUCED BY
THE NE PACIFIC RIDGE MAINTAINING A NARROWING ZONE OF 20-25 KT
WINDS AND SEAS TO 10 FT OVER THE FORECAST WATERS FROM 17N TO 24N
W OF 135W. THESE WINDS AND SEAS ARE EXPECTED TO SUBSIDE AND MOVE
W OF THE AREA OVERNIGHT OR EARLY FRI.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 94W N OF 09N MOVING WEST 15-20 KT. THE
CONVECTIVE PRECIPITATION ASSOCIATED WITH THE WAVE IS DESCRIBED
IN THE MONSOON TROUGH SECTION.

TROPICAL WAVE ALONG 107W FROM 05N TO 14N MOVING WEST 15 KNOTS.
CONVECTIVE PRECIPITATION ASSOCIATED WITH THE WAVE IS DESCRIBED
IN THE MONSOON TROUGH SECTION.

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

MONSOON TROUGH FROM 10N85W TO 09N95W TO 06N106W. SCATTERED
MODERATE TO STRONG FROM 06N TO THE COAST OF COSTA RICA BETWEEN
83W AND 88W. SCATTERED MODERATE WITHIN 90 NM OF THE AXIS BETWEEN
92W AND 95W...AND FROM 09N TO 14N BETWEEN 100W AND 104W.

...DISCUSSION...

A WEAKENED SURFACE RIDGE CENTERED ACROSS THE NE PACIFIC EXTENDS
SE INTO THE AREA AND PASSES THROUGH 30N134W TO 21N113W. THE
SLACKENED PRESSURE GRADIENT BETWEEN THE RIDGE AND THE TYPICAL
TROUGH THAT IS SEEN ALONG BAJA CALIFORNIA HAS ALLOWED NW WINDS
TO SUBSIDE DURING THE PAST 12-24 HOURS TO THE 10-15 KT RANGE
WITHIN ABOUT 180 NM W OF THE BAJA CALIFORNIA PENINSULA WITH
RESULTANT SEAS OF 5 TO 6 FT. THE RIDGE WILL BEGIN TO SLOWLY
STRENGTHEN ACROSS THIS REGION BEGINNING TONIGHT...WITH THE NWLY
FLOW SLOWLY INCREASING OFFSHORE OF THE BAJA PENINSULA...POSSIBLY
REACHING 20 KT WITH POCKETS TO 25 KT LATE FRI AFTERNOON AND
NIGHT...WITH SEAS BUILDING TO NEAR 8 FT.

AS MENTIONED ABOVE...THE SURFACE PRESSURE GRADIENT THAT EXISTS
BETWEEN THE SUBTROPICAL RIDGE AND LOWER SURFACE PRESSURES
ASSOCIATED WITH TROPICAL DEPRESSION EIGHT-E IS RESULTING A
SWATH OF 20 TO 25 KT TRADE WINDS IN THE FAR WESTERN PART OF THE
AREA FROM 17N TO 24N AND TO THE WEST OF 135W. THE WINDS WILL
GRADUALLY MOVE W OF THE AREA BY FRI...BEFORE FRESHENING AGAIN S
OF 20N ON FRI AS GUILLERMO CONTINUES WNW AND TRACKS W OF 130W.

GAP WINDS...
THE GULF OF PAPAGAYO...STRONG TRADE WINDS ACROSS THE SOUTHERN
CARIBBEAN CONTINUE TO FUNNEL ACROSS THE HIGHER TERRAIN OF
CENTRAL AMERICA AND SPILL ACROSS THE PACIFIC COASTAL WATERS THAT
ARE TO THE EAST OF 90W. THE WINDS IN THIS AREA HAVE INCREASED
AGAIN OVERNIGHT TO 20-25 KT ACROSS THE NICARAGUAN COASTAL WATERS
IN THE LEE OF LAKES NICARAGUA AND MANAGUA...WILL DIMINISH BY
LATE AFTERNOON...AND THEN INCREASE AGAIN TO AROUND 20 KT WITH
ISOLATED AREAS TO 25 KT FRIDAY NIGHT. SEAS DOWNWIND OF THIS
REGION WILL FLUCTUATE AT 6 TO 8 FT OVER THE NEXT 36 HOURS.

A NARROW PLUME OF NORTHERLY WINDS HAS DECREASED IN THE GULF OF
TEHUANTEPEC LEAVING A SWATH OF 8 FT SEAS. THE SEAS WILL SUBSIDE
TO LESS THAN 8 FT TONIGHT. THE NEXT PULSE WILL OCCUR FRI NIGHT
INTO SAT WITH NORTHERLY WINDS OF ABOUT 20 KT AND SEAS LESS
THAN 8 FT EXPECTED.

$$
COBB


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