Tue AM East Pac Tropical Weather Discussion

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE AUG 26 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM
THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0915 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION JULIO IS CENTERED OVER GULF OF CALIFORNIA
NEAR 28.0N 112.7W AT 26/0900 UTC MOVING NNW OR 345 DEG AT 06 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED
WIND SPEED IS 30 KT WITH GUSTS TO 45 KT. THE CENTER OF JULIO IS
EVIDENT IN NIGHTTIME VISIBLE IMAGERY AS A SWIRL OF LOW CLOUDS
JUST INSIDE THE GULF OF CALIFORNIA...ENTIRELY DEVOID OF DEEP
CONVECTION. IN FACT...THE NEAREST DEEP CONVECTION IS NEARLY 75
NM TO THE ESE ALONG THE MEXICAN COAST. JULIOS RAPID WEAKENING
SEEMS CONSISTENT WITH CIMSS SHEAR ANALYSES WHICH INDICATE AROUND
20 KT OF WSW SHEAR...A MARKED INCREASE FROM THIS TIME YESTERDAY.
SEE THE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS.

...TROPICAL WAVE...

A TROPICAL WAVE S OF 20N ALONG 87W MOVING W AT ABOUT 15 KT. A
BROAD MID-LEVEL CYCLONIC TURNING IS APPARENT IN SATELLITE
IMAGERY ALONG THE NORTHERN END OF THE WAVE. A RECENT INCREASE IN
CONVECTION OVER THIS AREA IS ALSO NOTED...POSSIBLY ENHANCED BY
AFTERNOON CONVECTION MOVING OFFSHORE THE ADJACENT CENTRAL
AMERICAN COAST. HOWEVER...THE LOW-LEVEL FLOW THROUGH THIS AREA
IS UNIDIRECTIONAL FROM THE W...WITH NO SIGNS OF INCIPIENT LOW
PRESSURE.

...ITCZ...

ITCZ AXIS LIES ALONG 11N86W TO 06N106W THEN FROM 21N111W TO
15N120W TO 08N140W. SCATTERED MODERATE CONVECTION WITHIN 180 NM
N OF AXIS BETWEEN 86W AND 93W. SCATTERED MODERATE CONVECTION
WITHIN 180 NM SE OF AXIS BETWEEN W OF 121W.

.NUMEROUS MODERATE ISOLATED STRONG CONVECTION WITHIN 60 NM
EITHER SIDE OF LINE FROM 11N88W TO 14N93W.

.NUMEROUS SCATTERED SCATTERED STRONG CONVECTION WITHIN 60 NM OF
15.5N101W.

...DISCUSSION...

THE WESTERN END OF THE ITCZ IN THE TROPICAL EAST PACIFIC
CONTINUES TO LIE UNUSUALLY FAR N FOR THE LAST WEEK OF AUGUST
...WITH A POSITION EXTENDING FROM AROUND 21N111W THROUGH 17N116W
TO 12N130W. OVER THE LAST SEVERAL DAYS A LARGE SWATH OF SW TO W
WINDS OF 20 TO 30 KT HAVE BEEN BLOWING WITHIN 300 NM SE OF THE
ITCZ AND PRODUCING SEAS OF 8 TO 13 FT. THESE WINDS AND THEIR
AREAL COVERAGE HAVE BEEN GRADUALLY DECREASING DURING THE PAST 24
HOURS BUT ARE STILL HAVE AN IMPACT...WITH THE LATEST QUIKSCAT
PASS INDICATING SW 20 KT WINDS WITHIN ABOUT 240 NM SE OF THE
ITCZ BETWEEN 120W AND 130W. SEAS ARE ESTIMATED UP TO 11 FT.
GLOBAL MODELS CONTINUE TO INDICATE THAT THESE WINDS WILL WEAKEN
WHILE SHRINKING IN AREAL COVERAGE SE OF THE ITCZ OVER THE NEXT
48 HOURS.

WITHIN THE ITCZ...SATELLITE PICTURES INDICATE A SEPARATE AREA OF
CYCLONIC TURNING NEAR 16N121W...WHICH IS NOT LIKELY RELATED TO
THE REMNANTS OF TROPICAL STORM ISELLE ANY LONGER. ALTHOUGH
GLOBAL MODELS PERSIST THIS WEAK ARE OF LOW PRESSURE...THEY DO
WEAKEN IT OVER THE NEXT FEW DAYS POSSIBLY IN RESPONSE TO STEADY
HIGH EASTERLY SHEAR ENVIRONMENT IN WHICH IT IS EMBEDDED.

ELSEWHERE...A SHORTWAVE TROUGH MOVING INTO THE NW U.S. HAS
DRIVEN A COLD FRONT FROM NORTHERN CALIFORNIA SW INTO THE NE
PACIFIC...JUST N OF THE AREA. AS HIGH PRESSURE BUILDS BEHIND THE
FRONT...NW TO NW WINDS OF UP TO 20 KT HAVE SPREAD AS FAR S AS
27N BETWEEN 119W AND 127W. DURING THE NEXT 24 TO 48 HOURS...NW
SWELL GENERATED BY THESE WINDS SHOULD ARRIVE AND CAUSE WAVE
HEIGHTS TO BUILD TO 8 TO 9 FT N OF 27N BETWEEN 118W AND 131W.

FINALLY...LONG PERIOD SW SWELL GENERATED BY A STORM SYSTEM IN
THE SOUTHERN HEMISPHERE MID-LATITUDES HAS ALREADY BEGUN TO
ENGULF THE TROPICAL EAST PACIFIC WATERS AND SHOULD REACH THE
COAST OF MEXICO BY EARLY WED. WAVE HEIGHTS ARE FORECAST TO BUILD
TO 8 TO 10 FT OVER SOUTHERN WATERS GENERALLY S OF 10N BETWEEN
91W AND 127W BUT SHOULD LEVEL OFF AND BEGIN TO SUBSIDE BY THU.


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