Mon AM East Pac Tropical Weather Discussion

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON AUG 25 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 STORM JULIO CENTERED NEAR 25.8N 111.8W AT 25/0900 UTC
MOVING NNW OR 335 DEG AT 13 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1002 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH
GUSTS TO 45 KT. SATELLITE IMAGERY REVEALS A LARGE AND
INCREASINGLY MORE SYMMETRIC CONVECTIVE MASS ASSOCIATED WITH
JULIO...EVEN THOUGH THE CENTER HAS BEEN TRAVERSING SOUTHERN BAJA
CALIFORNIA FOR ABOUT 12 HOURS NOW. CIMSS ANALYSES ESTIMATE ONLY
LIGHT SOUTHWESTERLY SHEAR OVER THE TROPICAL CYCLONE...A DRAMATIC
CHANGE FROM THE STRONG EASTERLY SHEAR HINDERING DEVELOPMENT THE
LAST FEW DAYS. EVEN THOUGH JULIO STILL APPEARS FAIRLY WELL-
ORGANIZED...THE FORECAST SHEAR IS EXPECTED TO BE RATHER STRONG
WITHIN 24 HOURS AND ITS TRACK SHOULD KEEP IT MOSTLY OVER LAND.
GIVEN THESE TWO FACTORS...THE FORECAST CALLS FOR GRADUAL
WEAKENING AS IT HEADS ON A MOSTLY NNW TO N TRACK UNTIL
DISSIPATION. SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS.

...ITCZ...

.INTERTROPICAL CONVERGENCE ZONE LIES ALONG AXIS 09N82W TO 06N92W
TO 06N105W THEN 21N110W TO 17N114W TO 14N123W TO 11N140W.
SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 240 NM S OF
AXIS BETWEEN 82W AND 102W. SCATTERED MODERATE ISOLATED STRONG
CONVECTION WITHIN 300 NM SE OF AXIS BETWEEN 114W AND 130W.
NUMEROUS MODERATE ISOLATED STRONG CONVECTION S OF 06N E OF 80W.

...DISCUSSION...

THE ITCZ IN THE TROPICAL EASTERN PACIFIC HAS RECENTLY BECOME
DISCONTINUOUS...WITH THE EASTERN END OF IT RUNNING FROM 09N94W
TO 06N105W AND THE WESTERN END DROPPING SW FROM JULIO THROUGH
17N114W TO 14N123W TO 11N140W. LIKE YESTERDAY...QUIKSCAT AND
ASCAT DATA INDICATE A LARGE SWATH OF S TO SW 20 TO 25 KT WINDS
WITHIN ABOUT 330 NM E OF THE ITCZ BETWEEN 114W AND 131W. THESE
WINDS HAVE BEEN BLOWING FAIRLY STEADILY FOR AT LEAST 2 TO 3 DAYS
AND HAVE LIKELY CAUSED SEAS TO BUILD HIGHER THAN WHAT LATEST
GUIDANCE IS INDICATING. THE BEST ESTIMATE IS THAT THERE EXISTS A
LARGE AREA OF GREATER THAN 8 FT SEAS OVER THE ABOVE AREA...AND A
WAVE NOMOGRAM ANALYSIS YIELDS FULLY DEVELOPED SEAS OF NEARLY 13
FT.

GLOBAL MODELS FORECAST THE ITCZ TO GRADUALLY SINK SOUTHWARD OVER
THE NEXT 2 TO 3 DAYS...ATTEMPTING TO SETTLE INTO A MORE
CLIMATOLOGICAL POSITION. ALTHOUGH NOT COMPLETELY ACCURATE...
MODEL GUIDANCE SUGGESTS A CONTINUATION OF THE STRONG SW FLOW
NEAR AND SE OF THE ITCZ FOR AT LEAST THE NEXT 24 HOURS FOLLOWED
BY A GRADUAL DIMINUTION OF WINDS THEREAFTER. UNTIL THEN...
MARINERS CAN EXPECT A LARGE AREA OF 8 TO POSSIBLY 13 FT SEAS
WITHIN 300 NM SE OF THE ITCZ BETWEEN 115W AND 130W.

QUIKSCAT ALSO INDICATED A LARGE AREA OF SOUTHERLY 20 KT WINDS S
OF THE EASTERN END OF THE ITCZ GENERALLY E OF 103W. THE
DEVELOPMENT OF ENHANCED SOUTHERLY WINDS OVER THIS AREA SEEMS TO
BE A NEW PHENOMENON...WITH NONE OF THE GUIDANCE INDICATING THESE
CONDITIONS. WAVE HEIGHTS OF 5 TO 7 FT GENERALLY PREVAIL OVER
THIS AREA BUT COULD BE AS HIGH AS 8 FT IN SPOTS.

FINALLY...A STRONG SHORTWAVE TROUGH REACHING THE W COAST TODAY
SHOULD HELP ENHANCE NW TO N WINDS OFFSHORE THE CALIFORNIA COAST
BEGINNING TODAY AND FOR THE NEXT FEW DAYS. AS A RESULT OF THE
STRONG WINDS...LONG PERIOD NW SWELL SHOULD BEGIN TO PROPAGATE
INTO THE FAR NORTHERN WATERS W OF THE BAJA PENINSULA WITH WAVE
HEIGHTS PEAKING AROUND 8 TO 9 FT N OF 26N BETWEEN 118W AND 130W
WED.


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