000
AXPZ20 KNHC 250313
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED AUG 25 2010

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0115 UTC.

...SPECIAL FEATURE...

TROPICAL STORM FRANK CENTERED NEAR 16.0N 102.9W AT 25/0300 UTC 
MOVING W-NW AT 8 KT. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH 
GUSTS TO 65 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 992 MB. 
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. NUMEROUS MODERATE TO 
STRONG CONVECTION IS WITHIN 120 NM W SEMICIRCLE WITH SCATTERED 
MODERATE CONVECTION FOUND WITHIN 75 NM NE QUADRANT AND ELSEWHERE 
WITHIN 300 NM SW SEMICIRCLE OF FRANK. STRONG EASTERLY SHEAR IS 
IMPACTING FRANK BUT IS EXPECTED TO DECREASE OVER THE NEXT FEW 
DAYS. THE LATEST NHC FORECAST GUIDANCE TRACK HAS FRANK MOVING IN 
A GENERAL WNW DIRECTION PARALLEL TO THE MEXICAN COAST AND IT IS 
EXPECTED TO BECOME A HURRICANE ON THU AS VERTICAL WIND SHEAR 
ALOFT LIGHTENS ALLOWING FOR A MORE FAVORABLE ENVIRONMENT FOR 
INTENSIFICATION TO MATERIALIZE.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 09N84W 
TO 13N102W TO 11N110W TO 12N130W TO 09N140W. SCATTERED MODERATE 
CONVECTION IS WITHIN 150 NM S OF THE ITCZ AXIS BETWEEN 99W AND 
105W.

...DISCUSSION...

BROAD ANTICYCLONIC FLOW ALOFT IS CENTERED OVER THE U.S. DESERT 
SW AND ENCOMPASSES MUCH OF THE AREA N OF 15N E OF 137W. TWO WEAK 
UPPER LOWS ARE EMBEDDED IN THIS FLOW. THE EASTERN LOW IS NEAR 
24N118W AND THE WESTERN LOW IS NEAR 31N129W. THESE LOWS ARE 
FORECAST TO MOVE NW OUT OF THE FORECAST AREA OVER THE NEXT 24 
HOURS AS THE ANTICYCLONE MOVES SW THROUGH THE CENTRAL GULF OF 
CALIFORNIA AND OFF THE BAJA COAST ON THU. THE BUILDING RIDGE 
ALOFT WILL BE A MAJOR FACTOR IN THE STEERING OF FRANK PRIMARILY 
TO THE W AND AWAY FROM THE COAST OVER THE NEXT FEW DAYS.  
SATELLITE WATER VAPOR IMAGERY SHOWS MOSTLY MODERATE SUBSIDENCE 
WITH RESULTANT DRY AIR PRESENT OVER A LARGE PORTION OF THE AREA 
OUTSIDE THE ITCZ AND THESE UPPER LEVEL LOW PRES SYSTEMS W OF 
116W. E-NE WINDS IN THE 20-30 KT RANGE CAN BE FOUND OVER MUCH OF 
THE PACIFIC WATERS S OF 23N E OF 110W. THIS WIND SHEAR IS 
LIMITING THE DEVELOPMENT OF DEEP CONVECTION ASIDE FROM THAT 
ASSOCIATED WITH FRANK.

AT THE SURFACE...A RIDGE ENTERS THE REGION THROUGH 30N130W AND 
REACHES TO 25N118W. A 1011 MB LOW IS EMBEDDED IN THE ITCZ NEAR 
12N133W. THERE IS NO SIGNIFICANT DEEP CONVECTION CURRENTLY 
ASSOCIATED WITH THIS LOW AND IT IS FORECAST TO MOVE W AROUND 
5-10 KT AND DISSIPATE TO A TROUGH OVER THE NEXT 24 HOURS AS 25 
KT OF EAST-SOUTHEASTERLY SHEAR MOVES OVER THE SYSTEM. FARTHER 
E...A TROUGH IS EMBEDDED IN THE ITCZ FROM 14N118W TO 10N120W. A 
SMALL AREA OF SCATTERED MODERATE CONVECTION IS WITHIN 60 NM W OF 
TROUGH FROM 11N TO 13N. THE 1738 UTC ASCAT PASS SHOWED WINDS TO 
20 KT MAINLY ON THE SOUTHERN SIDE OF THIS TROUGH. THE TROUGH AND 
THE WINDS ARE FORECAST TO DISSIPATE OVER THE NEXT 24-36 
HOURS...WITH WINDS DROPPING BELOW 20 KT BY THU MORNING.

CROSS EQUATORIAL S AND SW SWELLS WITH PEAK WAVE PERIODS OF 15-17 
SECONDS CONTINUE TO BRING SEAS TO THE 8-11 FT RANGE OVER MUCH 
OVER THE AREA W OF 80W TO LINE FROM 10N140W TO 21N105W. THIS 
AREA OF SEAS OVER 8 FT WILL SHRINK SLIGHTLY SOUTHEASTWARD OVER 
THE NEXT TWO DAYS AS PERIODS SHORTEN TO THE 13-15 SECOND RANGE. 

$$
SCHAUER