000
AXPZ20 KNHC 232142
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON AUG 23 2010

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...SPECIAL FEATURE...

TROPICAL STORM FRANK CENTERED NEAR 14.9N 99.3W AT 23/2100 UTC 
MOVING WNW AT 8 KT. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH 
GUSTS TO 55 KT. ESTIMATED MINIMUM CENTRAL PRESSURE HAS RISEN 
SLIGHTLY TO 1000 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER 
AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. 
SATELLITE IMAGERY DURING THE AFTERNOON DEPICTS THAT THE CYCLONE 
IS UNDERGOING VERTICAL WIND SHEAR AS NOTED BY THE DISPLACEMENT 
OF LOW CLOUD LINES WITHIN 90 NM OF THE CENTER IN THE NE 
SEMICIRCLE. SCATTERED MODERATE TO STRONG CONVECTION...IN SMALL 
CLUSTERS...IS NOTED WITHIN 270 NM OF THE CENTER IN THE SW AND NW 
QUADRANTS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 
30 NM OF LINE FROM 11N110W TO 13N98W DENOTES WHAT APPEARS TO BE 
A DETACHED BAND. LATEST NHC FORECAST GUIDANCE TRACK HAS FRANK 
MOVING IN A GENERAL WNW DIRECTION PARALLEL TO THE MEXICAN COAST 
WHILE SLOWLY GAINING STRENGTH...BUT NOT EXPECTED TO BECOME A 
HURRICANE UNTIL AFTER 48 HOURS AS VERTICAL WIND SHEAR IS NOT 
FORECAST TO DIMINISH SIGNIFICANTLY DURING THIS PERIOD.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED FROM 9N84W 
TO 12N93W...THEN RESUMES AT 13N100W 11N110W 13N120W 12N126W 
10N140W. SCATTERED MODERATE CONVECTION IS SE OF THE AXIS WITHIN 
30 NM OF 6N82W.

...DISCUSSION...

A MID/UPPER RIDGE EXTENDS FROM SOUTHERN PLAINS TO OVER THE SW 
SECTOR OF THE CONUS...THEN CONTINUES SW TO AN ANTICYCLONIC 
CENTER NEAR 31N131W...AND SW TO NEAR 21N140W. THIS IS THE SAME 
RIDGE THAT IS THE FORECAST PLAYER IN THE TRACK OF TROPICAL STORM 
FRANK THROUGH AT LEAST THE NEXT 48 HOURS. TO THE SE OF THE RIDGE 
AN INVERTED MID TO UPPER LEVEL TROUGH MOVING WNW STRETCHES FROM 
31N124W TO 22N133W. A CYCLONIC CIRCULATION IS ALONG THE TROUGH 
NEAR 28N125W. MOISTURE ASSOCIATED WITH THE TROUGH AND THE 
CYCLONIC CIRCULATION IS CONFINED S OF THE RIDGE TO 19N AND 
BETWEEN 121W-137W. SATELLITE WATER VAPOR IMAGERY SHOWS MOSTLY 
MODERATE SUBSIDENCE WITH RESULTANT DRY AIR PRESENT OVER A LARGE 
PORTION OF THE AREA OUTSIDE THE ITCZ W OF 114W. AN UPPER-LEVEL 
LOW MOVING NW AT 20 KT IS NEAR 22N111W...BUT WITH ASSOCIATED 
MOISTURE LIMITED TO THE MID LEVELS NO SHOWER/TSTMS ARE PRESENTLY 
BEING DETECTED WITH THIS FEATURE. AS THE LOW MOVES WNW...AND A 
SMALL ANTICYCLONE EMBEDDED IN A LARGE SCALE ANTICYCLONE OVER THE 
CENTRAL SECTION OF THE U.S. MOVES SW OVER FAR SOUTHERN TEXAS THE 
UPPER LEVEL FLOW IS ACCELERATED ACROSS THE FAR EASTERN PART OF 
THE AREA TO THE E AND SE OF THE UPPER LOW INCLUDING THE 
ENVIRONMENT OVER AND NEAR FRANK. ELSEWHERE E OF 103W...THE UPPER 
LEVEL WIND FLOW REGIME IS FROM THE NE AS IT IS DRIVEN AROUND THE 
E SIDE OF THE LARGE SCALE ANTICYCLONE OVER THE CENTRAL U.S. AND 
FURTHER ACCELERATED IN RESPONSE TO AN UPPER LEVEL LOW WELL TO 
ITS SE. THIS FLOW IS ADVECTING CIRRUS BLOW OFF FROM ITCZ 
CONVECTION S AND SW TO 6N AND E OF FRANK.

AT THE SURFACE...A RIDGE ENTERS THE REGION THROUGH 32N136W...AND
STRETCHES TO 27N128W TO NEAR 23N122W. HIGH PRES COVERS THE AREA 
N OF 19N AND W OF 120W. A 1010 MB LOW IS ON THE ITCZ AXIS NEAR 
13N123W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE 
LOW. WINDS OF 20 KT ARE OCCURRING WITHIN 180 NM OF THE LOW IN
THE S SEMICIRCLE. THE LOW IS FORECAST TO REMAIN ABOUT STATIONARY 
THROUGH THE NEXT 24 HOURS. A TROUGH IS ANALYZED FROM 15N133W TO 
12N131W. AN ASCAT PASS FROM CLOSE TO 1800 UTC SHOWED A SWATH OF 
N-NE 15-20 KT WINDS WITHIN 150 NM NE OF THE TROUGH. ONLY 
ISOLATED SHOWERS ARE WITHIN 30-45 NM OF THE TROUGH FROM 13N TO 
15N. ANOTHER TROUGH IS OVER THE FAR EASTERN PART OF THE AREA TO 
THE E OF FRANK...AND EXTENDS FROM THE FAR NW YUCATAN PENINSULA S 
TO 11N91W. IT IS UNDER AN AREA WHERE THE UPPER LEVEL NE FLOW 
TENDS TO BECOME SOMEWHAT DIFFLUENT...LEADING TO SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION BETWEEN IT AND FRANK WITHIN 
75 NM EITHER SIDE OF LINE FROM 13N93W TO 14N97W.

WITH RESPECT TO MARINE ISSUES...CROSS EQUATORIAL S AND SW SWELLS 
WITH PEAK WAVE PERIODS OF 18-20 SECONDS CONTINUE TO AFFECT THE 
WATERS SE OF A LINE FROM 20N105W TO 20N130W TO 9N140W PRODUCING 
SEAS OF UP TO 9 FT IN SW SWELL. THIS SWELL EVENT WILL CONTINUE 
TO PROPAGATE AND EXPAND TO S TO 20N BETWEEN 90W-130W IN ABOUT 48 
HOURS AT WHICH TIME SEAS ARE EXPECTED TO BE IN THE 8-10 FT RANGE.

$$
AGUIRRE