000
AXPZ20 KNHC 250918
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED AUG 25 2010

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 
0900 UTC.

...SPECIAL FEATURE...

AT 25/0900 UTC...TROPICAL STORM FRANK IS CENTERED NEAR 16.2N 
103.6W MOVING W-NW OR 285 DEGREES AT 8 KT. MAXIMUM SUSTAINED 
WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SOME STRENGTHENING IS 
POSSIBLE AND FRANK COULD BECOME A HURRICANE TODAY. ESTIMATED 
MINIMUM CENTRAL PRESSURE IS 991 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 AND 30 NM E SEMICIRCLES. SIMILAR CONVECTION IS NOTED IN A 150 
NM WIDE BAND TO THE W OF THE CENTER ALONG 20N106W TO 14N106W. 
STRONG EASTERLY SHEAR CONTINUES TO IMPACT THE CYCLONE BUT IS 
FORECAST TO DECREASE SOMEWHAT OVER THE NEXT DAY OR SO GIVING 
FRANK AN OPPORTUNITY TO STRENGTHEN. THE LATEST NHC FORECAST 
GUIDANCE TRACK HAS FRANK MOVING IN A GENERAL W-NW DIRECTION 
THROUGH FRIDAY. ON THIS TRACK...THE CENTER OF FRANK WILL 
CONTINUE TO MOVE AWAY FROM THE SOUTHWESTERN COAST OF MEXICO.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED ALONG 09N84W 
TO 08N94W THEN RESUMES AT 12N106W TO 11N120W TO 11N130W TO 
09N140W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM EITHER 
SIDE OF AXIS FROM 114W TO 116W...AND FROM 08N TO 11N W OF 134W.

...DISCUSSION...

BROAD ANTICYCLONIC CIRCULATION LOCATED OVER THE SW CONUS EXTENDS 
A RIDGE OVER THE FORECAST WATERS COVERING THE AREA N OF 15N E OF 
137W. TWO WEAK UPPER-LEVEL LOWS ARE EMBEDDED IN THIS FLOW. THE 
EASTERN LOW IS NEAR 25N119W AND THE WESTERN LOW IS JUST N OF 
AREA NEAR 31N130W. T.S. FRANK IS MOVING AROUND THE SOUTHERN 
PERIPHERY OF THIS DEEP-LAYER RIDGE. 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 DOMINATES ROUGHLY THE REGION N OF 20N W 
OF 120W. A PAIR OF 1010 MB WEAK LOWS ARE EMBEDDED WITHIN THE 
ITCZ. THE FIRST ONE IS NEAR 13N118W. AN ASCAT PASS FROM 0442 UTC 
SHOWED SW TO W WINDS OF 20 KT ON THE SOUTHERN SIDE OF THE LOW 
COVERING THE AREA FROM 05N TO 12N BETWEEN 110W AND 125W. THE 
SECOND ONE IS NEAR 12N132W. SCATTERED MODERATE CONVECTION IS 
ASSOCIATED WITH BOTH LOWS. 

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. 

$$
GR