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Eastern Pacific Tropical Weather Discussion



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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Page last modified: Thursday, 30-Jul-2015 10:32:21 UTC