Tropical Weather Discussion
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000
AXPZ20 KNHC 301032
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU JUL 30 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0900 UTC.

...SPECIAL FEATURES...

THE CENTER OF NEWLY UPGRADED TROPICAL STORM GUILLERMO WAS
ESTIMATED NEAR 8.5N 126.3W AT 0900 UTC MOVING WNW OR 285 DEG AT
13 KT. MAXIMUM SUSTAINED WINDS 35 KT GUSTS 45 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE 1003 MB. CONVECTION HAS INCREASED NEAR
THE CENTER OR GUILLERMO DURING THE PAST SEVERAL HOURS...
ESPECIALLY ACROSS THE WESTERN SEMICIRCLE. SCATTERED TO NUMEROUS
MODERATE TO STRONG CONVECTION WAS NOTED WITHIN 270 NM SW
SEMICIRCLE WHILE SCATTERED MODERATE TO STRONG CONVECTION WAS
WITHIN 330 NM NE SEMICIRCLE. GUILLERMO IS EXPECTED TO CONTINUE
ON THIS WEST NORTHWEST TRAJECTORY DURING THE NEXT TWO TO THREE
DAYS. WARM SST`S AND FAVORABLE ATMOSPHERIC CONDITIONS SHOULD
ALLOW THE SYSTEM TO GRADUALLY STRENGTHEN TO A HURRICANE BY 36-48
HOURS. AFTER 72 HOURS...GUILLERMO WILL BE MOVING OVER COOLER
SST`S AND A PERIOD OF WEAKENING IS THEN LIKELY. INCREASING WINDS
AND QUICKLY BUILDING SEAS WILL BE SEEN ACROSS THE NORTHERN
SEMICIRCLE OF GUILLERMO DURING THE NEXT FEW DAYS. PLEASE READ
THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.

THE CENTER OF TROPICAL DEPRESSION EIGHT-E WAS NEAR 16.5N 138.5W
AT 0900 UTC MOVING W OR 270 DEG AT 13 KT. MAXIMUM SUSTAINED
WINDS 25 KT GUSTS 35 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 1007
MB. THE LOW LEVEL CIRCULATION OF THE DEPRESSION CONTINUES TO
SLOWLY WEAKEN...WITH THE PRESSURE GRADIENT TO THE NORTH INDUCED
BY THE NE PACIFIC RIDGE MAINTAINING A BROAD ZONE OF 20-25 KT
WINDS ACROSS THE N SEMICIRCLE. VERY LIMITED CONVECTION IS
OCCURRING WITH A LONE CLUSTER OF MODERATE TO STRONG
THUNDERSTORMS NOTED FROM 120 TO 240 NM ACROSS THE NE QUADRANT.
THIS LOW WILL CONTINUE TO MOVE WEST SOUTHWEST OVER THE NEXT FEW
DAYS AND GRADUALLY WEAKEN TO AN OPEN TROUGH WITHIN 24-36 HOURS
AS IT MOVES BEYOND THE DISCUSSION AREA. PLEASE READ THE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMEP3/WTPZ23
KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE INVOF 84W-87W HAS ENTERED THE EASTERN PACIFIC IN
THE PAST 24 HOURS AND CONTINUES TO MOVE ACROSS CENTRAL
AMERICA...MOVING W 10-15 KT. CONVECTION ASSOCIATED WITH THIS
WAVE IS DESCRIBED BELOW ASSOCIATED WITH THE MONSOON TROUGH...BUT
CURRENTLY IS BEHIND THE WAVE AXIS AND AFFECTING CENTRAL AMERICA.

TROPICAL WAVE INVOF 94W-97W IS MOVING WEST AT 15 KNOTS.
CONVECTION ASSOCIATED WITH THIS WAVE IS MAINLY OCCURRING NEAR
THE MONSOON TROUGH AS DESCRIBED BELOW...BUT IS ALSO OCCURRING S
OF THE GULF OF TEHUANTEPEC. RECENT SCATTEROMETER DATA SUGGESTS A
BROAD AND WEAK LOW PRESSURE CENTER ASSOCIATED WITH THIS WAVE
ALONG THE MONSOON TROUGH NEAR 08N96W...WHERE ELY WINDS 15-20 KT
ARE SHIFTING WWD ACROSS THE NE PORTIONS OF THE LOW AND BEHIND
THE WAVE. SEAS ARE 7-8 FT IN THIS REGION.

TROPICAL WAVE INVOF 120W-121W IS BECOMING ABSORBED INTO THE E
PORTIONS OF THE BROADER CIRCULATION OF TROPICAL STORM GUILLERMO.
SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED IN A LONG BAND
FROM 12N TO 14N BETWEEN 115W AND 121.5W. THIS WAVE HAS BEEN
DROPPED FROM THE SURFACE MAPS AND WILL BECOME ENTRAINED INTO THE
CIRCULATION OF GUILLERMO.

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

MONSOON TROUGH EXTENDS FROM 09N80W TO 09N86W TO 07N97W TO
06.5N112W...WHERE IT TERMINATES. SCATTERED MODERATE TO STRONG
CONVECTION NOTED WITHIN 150 NM N AND 300 NM S OF TROUGH BETWEEN
80W AND 100W. WIDELY SCATTERED MODERATE ISOLATE STRONG
CONVECTION NOTED WITHIN 180 NM S OF TROUGH BETWEEN 105W AND
112W.

...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
EVENING...WITH SEAS BUILDING 6-8 FT THERE.

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 BROAD
SWATH OF 20 TO 25 KT TRADE WINDS  IN THE WESTERN PART OF THE
AREA FROM 17N TO 22N AND TO THE WEST OF 132W. THE WINDS WILL
GRADUALLY MOVE W OF THE AREA LATE TODAY...BEFORE FRESHENING
AGAIN S OF 20N ON FRI AS GUILLERMO CONTINUES WNW AND TRACK 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 IN THE RANGE OF 20 TO 25 KNOTS
WAS DEPICTED BY OVERNIGHT SCATTEROMETER DATA...AND EXTENDED SOUTH
SOUTHWEST TO NEAR 15N95W...WHERE SEAS BUILT TO 7-8 FT. THESE
WINDS WILL ALSO DIMINISH SLIGHTLY BY AFTERNOON AND THEN PULSE
AGAIN TO 20 TO 25 KNOTS TONIGHT INTO THE MORNING HOURS ON FRI.

$$
STRIPLING


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