Fri AM East Pac. Tropical Weather Discussion

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI AUG 22 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.

...TROPICAL WAVES...

A TROPICAL WAVE LOCATED N OF 06N ALONG 81W HAS BEEN MOVING W
AT 10 TO 15 KT OVER THE PAST 24 HOURS. UPPER-AIR TIME SERIES
FROM THE CARIBBEAN THE LAST DAY OR TWO INDICATE THAT THE
AMPLITUDE OF THE WAVE IS ENTIRELY S OF 15N...AND IT IS ASSUMED
THAT LITTLE HAS CHANGED SINCE THEN. ENHANCED CONVECTION OVER THE
SW CARIBBEAN AND DIRECTLY OFFSHORE THE PACIFIC COAST OF COSTA
RICA IS LIKELY BEING ENHANCED BY THIS FEATURE.

AN ACTIVE TROPICAL WAVE LOCATED FROM 06N TO 18N ALONG 103W IS
ESTIMATED TO BE MOVING W AT 10 TO 15 KT. A 0048 UTC QUIKSCAT
PASS REVEALED A BROAD CYCLONIC CENTER ASSOCIATED WITH THE WAVE
NEAR 12.9N102.1W...BUT SATELLITE IMAGERY SHOWS LITTLE TO NO DEEP
CONVECTION. THE NEAREST CONVECTION INSTEAD IS CONCENTRATED
ALONG A CONFLUENT BAND NEARLY 240 NM SE OF THE CIRCULATION
CENTER...WHERE LOW-LEVEL SOUTHERLIES RISING FROM THE EQUATOR
MEET LOW-LEVEL WESTERLIES TO THE N. THE PRESENCE OF THE WAVE HAS
ALSO EXCITED CONVECTION WITHIN THE ITCZ WITHIN ABOUT 5 TO 10
DEGREES OF THE WAVE AXIS.

...ITCZ...

THE ITCZ AXIS EXTENDS ALONG 09N84W TO 13N103W TO 10N110W TO
06N140W. SCATTERED MODERATE FROM 07N TO 10N BETWEEN 82W AND 88W.
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN
120 NM N OF AXIS FROM 105W TO 129W.

ELSEWHERE...SCATTERED MODERATE CONVECTION WITHIN 90 NM EITHER
SIDE OF LINE FROM 11N99W TO 08N101W. NUMEROUS MODERATE SCATTERED
STRONG CONVECTION IS OBSERVED FROM 15N TO 18N BETWEEN 105W AND
108W.

...DISCUSSION...

GLOBAL MODELS KEEP WEAK SURFACE LOW PRESSURE ALONG THE ACTIVE
TROPICAL WAVE CURRENTLY ALONG 103W...AS IT PRESSES WNW TO NW AT
10 TO 15 KT THROUGH 48 HOURS. HOWEVER...UNUSUALLY STRONG UPPER-
LEVEL EASTERLIES FROM THE EQUATOR TO ALMOST 20N BETWEEN 90W AND
130W ARE RESPONSIBLE FOR THE STRONG EASTERLY WIND SHEAR NOW
BEING DIAGNOSED OVER THE MAIN DEVELOPMENT REGION OF THE EAST
PACIFIC BASIN. THE GLOBAL MODELS SEEM TO BE RESPONDING TO THE
STRONG EASTERLY SHEAR BY SHOWING NO APPRECIABLE DEVELOPMENT FOR
AN OTHERWISE GOOD CANDIDATE FOR THE NEXT EASTERN NORTH PACIFIC
TROPICAL CYCLONE.

THAT BEING SAID...QUIKSCAT DATA DID SHOW 20 TO 25 KT WINDS
WITHIN 300 NM OF THE E SEMICIRCLE OF THE ASSOCIATED LOW NOW
ESTIMATED TO LIE NEAR 13.6N102.6W. IN RESPONSE...THE NOAA
WAVEWATCH III SUGGESTS SEAS OF UP TO 8 TO 9 FT OVER THIS AREA.
SIMILAR WINDS AND SEAS ARE EXPECTED TO ACCOMPANY THE LOW AS IT
MOVES WNW TO NW 10 KT AT LEAST THROUGH 24 HOURS...FOLLOWED A
GRADUAL DECREASE AS THE LOW EITHER IS WEAK OR DISSIPATES WITHIN
48 HOURS.

ELSEWHERE...THE REMNANTS OF ISELLE ARE AGAIN SHOWING SIGNS OF
LIFE...WITH MOST RECENT SATELLITE IMAGERY WITHIN ABOUT 270 NM SW
OF THE DIFFUSE CIRCULATION CENTER. IN FACT...CLOUD TOP
TEMPERATURES WITHIN THE BURSTING CONVECTION SW OF THE CENTER HAS
COOLED TO -80C. THIS CURRENT FLARE-UP OF CONVECTION COINCIDES
WITH ISELLE TRACKING OVER 28C WATER...WATER AT LEAST 2-3C WARMER
THAN THAT OF WHICH IT DISSIPATED A FEW DAYS AGO. DESPITE ISELLES
REJUVENATED APPEARANCE...LATEST CIMSS ANALYSES INDICATE AT LEAST
30 KT OF EASTERLY SHEAR. ALTHOUGH GLOBAL MODELS PERSIST LOW
PRESSURE OVER THIS AREA THE NEXT FEW DAYS...THE UNFAVORABLE
ATMOSPHERIC CONDITIONS WOULD SEEM TO PRECLUDE RE-DEVELOPMENT.

FINALLY...EVENING QUIKSCAT DATA FROM YESTERDAY CONTINUED TO SHOW
ENHANCED CROSS-EQUATORIAL S OF 10N BETWEEN 97W AND 122W....WHICH
SHOULD BEGIN TO SHIFT SLIGHTLY W OVER THE NEXT DAY OR TWO. AT
THE SAME TIME...LONG PERIOD SE TO S SWELL PROPAGATING OUT OF THE
SOUTHERN HEMISPHERE IS AFFECTING THE WATERS OF THIS SAME AREA
AND WILL VERY GRADUALLY DIMINISH THE NEXT FEW DAYS. IN
ADDITION...LONG PERIOD NW SWELL COMING OUT OF THE N PACIFIC AND
OFFSHORE THE CALIFORNIA COAST COULD RESULT IN A SIGNIFICANT AREA
OF 8 FT SEAS OVER THE FAR NORTHERN WATERS...GENERALLY N OF 26N
BETWEEN 118W AND 135W. HOWEVER...MODEL GUIDANCE SHOWS 8 FT SEAS
SUBSIDING AS QUICKLY AS THEY BUILT BY EARLY SAT.


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