000
AXPZ20 KNHC 241556
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE AUG 24 2010

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...SPECIAL FEATURE...

TROPICAL STORM FRANK CENTERED NEAR 15.4N 101.4W AT 24/1500 UTC 
MOVING WNW AT 6 KT. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH 
GUSTS TO 65 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. FIRST VISIBLE SATELLITE 
IMAGERY FROM THIS MORNING SHOW THAT THE OVERALL STRUCTURE OF THE 
CYCLONE HAS QUICKLY BECOME MORE SYMMETRICAL AS SUPPORTED BY THE
VAST EXPANDING CDO (CENTRAL DENSE OVERCAST) FEATURE OVER THE
CENTER. CONVECTION CONSISTS OF THE SCATTERED STRONG WITHIN 90 NM
IN THE NW AND 60 NM SW QUADRANTS OF THE CENTER. SCATTERED 
MODERATE CONVECTION IS ELSEWHERE WITHIN 120 NM OF THE CENTER IN 
THE WESTERN SEMICIRCLE. THE MAIN FEEDER BAND INTO FRANK IS 
LOCATED WITHIN 200 TO 400 NM TO ITS W AND NW...AND CONSISTS OF 
SCATTERED STRONG CONVECTION WITHIN 45 NM EITHER SIDE OF A LINE 
FROM 18N106W TO 16N104W WHERE IT BECOMES SOMEWHAT DETACHED FROM 
THE CORE OF THE CYCLONE. LATEST NHC FORECAST GUIDANCE TRACK HAS 
FRANK MOVING IN A GENERAL WNW DIRECTION PARALLEL TO THE MEXICAN 
COAST AND SLOWLY GAINING STRENGTH THROUGH AT LEAST THE NEXT 48 
HOURS. FRANK IS NOW EXPECTED TO ACHIEVE HURRICANE INTENSITY IN 
24 HOURS AS VERTICAL WIND SHEAR ALOFT LIGHTENS ALLOWING FOR A 
MORE FAVORABLE ENVIRONMENT FOR INTENSIFICATION TO MATERIALIZE.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED FROM 9N85W
TO 12N96W...THEN RESUMES AT 12N106W 12N120W 10N130W 10N140W. 
SCATTERED MODERATE ISOLATED CONVECTION IS WITHIN 90 NM S OF THE 
AXIS 85W-93W..

...DISCUSSION...

A MID/UPPER RIDGE EXTENDS FROM SOUTHERN PLAINS TO OVER THE SW 
SECTOR OF THE CONUS...THEN EXTENDS NW TO A COL REGION NEAR
34N127W. TO THE SW OF THE COL...AN UPPER LEVEL ANTICYCLONIC IS 
IDENTIFIED NEAR 31N135W WITH A RIDGE SSW TO 25N140W. THIS FEATURE
WILL BE A MAIN PLAYER IN THE FUTURE STEERING OF TROPICAL STORM 
FRANK THROUGH AT LEAST THE NEXT 48 HOURS AS IT TRACKS PARALLEL
TO THE MEXICAN COAST. TO THE SE OF THE RIDGE...AN INVERTED MID 
TO UPPER LEVEL TROUGH MOVING WNW STRETCHES FROM 32N126W TO 
25N130W. A WEAK CYCLONIC CIRCULATION IS EVIDENT ON THE TROUGH 
29N127W. MOISTURE ASSOCIATED WITH THE TROUGH AND THE CYCLONIC 
CIRCULATION IS CONFINED TO SE AND S OF THE RIDGE TO 20N AND 
BETWEEN 124W-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. ANOTHER 
MID/UPPER LEVEL TROUGH MOVING WNW EXTENDS FROM NORTHERN BAJA 
CALIFORNIA SSW TO NEAR 21N117W...BUT WITH ASSOCIATED MOISTURE 
LIMITED TO THE MID LEVELS THERE IS NO SIGNIFICANT SHOWER 
ACTIVITY NOTED WITH THIS FEATURE. AS THE TROUGH ADVANCES 
WNW...AND A SMALL ANTICYCLONE EMBEDDED IN A LARGE SCALE RIDGE 
OVER THE CENTRAL SECTION OF THE U.S. MOVES SW OVER FAR 
SOUTHEASTERN TEXAS THE EFFECTS ON THE UPPER LEVEL FLOW IS TO 
ACCELERATE IT AS NE-E WINDS ACROSS THE FAR EASTERN PART OF
THE AREA TO THE E AND SE OF THE MID/UPPER LEVEL TROUGH INCLUDING 
THE UPPER ENVIRONMENT FOUND TO THE W AND NW OF FRANK. ACTUALLY
...THE UPPER LEVEL FLOW OVER THE EASTERN PORTION BECOMES 
DIFFLUENT E OF FRANK PROVIDING ADDITIONAL IMPETUS TO IS RELATED 
CONVECTION...AND WITH THAT OCCURRING E OF IT AND N OF THE ITCZ 
WHICH IS ADDING TO THE INCREASE FLOOD THREAT OVER PORTIONS OF 
SOUTHERN MEXICO AND CENTRAL AMERICA. THE UPPER FLOW FOUND IN THE 
EASTERN PORTION IS ALSO RESPONSIBLE FOR ADVECTING CIRRUS BLOW 
FROM THE CONVECTION OCCURRING THERE SW TO 4N BEFORE IT DISSOLVES 
IN MODERATE DRY AIR.

AT THE SURFACE...A RIDGE ENTERS THE REGION THROUGH 32N136W...AND 
REACHES TO 27N130W TO NEAR 23N124W. HIGH PRES COVERS THE AREA N 
OF 19N AND W OF 125W. A NEARLY STATIONARY 1010 MB LOW IS ON THE 
ITCZ AXIS NEAR 13N123W. SCATTERED MODERATE CONVECTION IS WITHIN 
150 NM OF THE LOW IN THE E QUADRANT...AND WITHIN 90 NM OF THE
LOW IN THE NE QUADRANT. WINDS OF 20 KT ARE OCCURRING WITHIN 360 
NM OF THE LOW IN THE SE QUADRANT. THE LOW IS FORECAST TO REMAIN 
ABOUT STATIONARY THROUGH THE NEXT 12-18 HOURS...THEN DISSIPATE 
CLOSE TO WITHIN 24 HOURS. A 1012 MB LOW IS CENTERED JUST N OF 
THE ITCZ NEAR 13N123W...MOVING SW 5-10 KT. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS WITHIN 120 NM NE OF THE LOW. A 
SURFACE TROUGH IS JUST INLAND THE BORDER OF SE MEXICO AND 
GUATEMALA.

WITH RESPECT TO MARINE SPECIFIC SWELL ISSUES...CROSS EQUATORIAL 
S AND SW SWELLS WITH PEAK WAVE PERIODS OF 18-20 SECONDS CONTINUE 
TO AFFECT THE WATERS PRIMARILY S OF 22N BETWEEN 80W AND 120W 
PRODUCING SEAS OF 8-11 FT. THIS SWELL EVENT WILL CONTINUE TO 
PROPAGATE AND EXPAND NORTHWARD TO NEAR 25N AND E OF 130W
TO THE BAJA CALIFORNIA COAST DURING THE NEXT 24 HOURS...THEN
SUBSIDE BEGINNING BETWEEN 36-48 HOURS WHILE SE TO S SWELLS 
LEADING TO 8 FT SEAS AFFECT THE WATERS S OF 10N AND W OF 130W.

$$
AGUIRRE