000
AXPZ20 KNHC 280939
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT AUG 28 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 
0845 UTC.

...SPECIAL FEATURES...

TROPICAL STORM FRANK IS CENTERED NEAR 20.3N 112.4W MOVING N-NW 
AT 4 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM 
SUSTAINED WINDS ARE 35 KT WITH GUSTS TO 45 KT. SEE LATEST NHC 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/ WTPZ24 KNHC 
FOR MORE DETAILS. NO ASSOCIATED DEEP CONVECTION REMAINS ONLY A 
LOW LEVEL SWIRL. FRANK IS EXPECTED TO CONTINUE TO WEAKEN AS IT 
WILL REMAIN OVER COOL WATERS. 

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 94W N OF 08N MOVING W NEAR 15 KT. 
SCATTERED STRONG CONVECTION IS W OF WAVE AXIS WITHIN 75 NM OF 
LINE FROM 12N94W TO 15N98W. 

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 09N84W 
TO 06N93W TO 08N105W THEN RESUMES NEAR 12N113W TO 09N119W TO 
11N131W TO 09N140W. NO SIGNIFICANT CONVECTION CURRENTLY LIES 
ALONG THE ITCZ AXIS.

...DISCUSSION...

WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE AND DRY 
AIR ALOFT OVER A LARGE PORTION OF THE AREA NW OF A LINE FROM 
29N112W TO 13N140W. AN UPPER LEVEL ANTICYCLONE IS OVER THE GULF 
OF MEXICO EXTENDING A RIDGE W TO JUST NE OF FRANK NEAR 24N110W. 
DIFFLUENCE ALOFT ASSOCIATED WITH THIS RIDGE AXIS IS ENHANCING 
CONVECTION WITHIN 45 NM ALONG THE COAST OF MEXICO FROM 20N TO 
23N THEN INLAND TO THE SIERRA MADRE OCCIDENTAL MOUNTAINS. A 
SECOND UPPER ANTICYCLONE LIES NEAR 24N133W EXTENDING A RIDGE NE 
TO 29N125W. BETWEEN THESE UPPER RIDGE AXES LIES AN UPPER TROUGH 
FROM 32N120W TO 24N124W. BROAD UPPER TROUGH IS DIGGING S TO 30N 
TO INLAND OVER CALIFORNIA. 

STRONG SURFACE RIDGE COVERS THE AREA N OF 20N W OF 125W AND IS 
EXPECTED TO TIGHTEN THUS INCREASING WINDS TO 20 KT AND BUILDING 
SEAS TO 9 FT OVER THE NEXT 24 HOURS MAINLY N OF 25N BETWEEN 155W 
AND 130W. THE RIDGE WILL THEN RELAX WITH ONLY 20 KT WINDS ALONG 
THE BAJA COASTLINE BY 48 HOURS.  

SURFACE TROUGHING WILL BUILD OVER WESTERN NORTH AMERICA AS FRANK 
IS MOVES NORTHWARD AND THE TROPICAL WAVE CURRENTLY ALONG 94W 
PROGRESSES WESTWARD. IN TURN...THE SURFACE PRES GRADIENT BETWEEN 
THIS MEAN TROUGHING AND HIGHER PRES S OF THE ITCZ WILL BUILD 
INCREASING WINDS TO 20 KT IN THE REGION S OF 10N BETWEEN 90W AND 
100W DURING THE WEEKEND. A SURFACE LOW IS EXPECTED TO FORM ALONG 
THE TROPICAL WAVE BY THE FIRST OF THE WEEK. 

THE LAST ROUND OF S SWELL THAT MOVED NORTHWARD OVER E FORECAST 
WATERS THE PAST FEW DAYS IS BEGINNING TO SUBSIDE. A NEW SURGE OF 
CROSS-EQUATORIAL SWELL IS MOVING INTO THE AREA BUT SEAS WILL 
REMAIN BELOW 9 FT OVER THE EASTERN AND CENTRAL WATERS THROUGH 
SUN NIGHT.

$$
PAW