000
AXPZ20 KNHC 150911
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT SEP 15 2007

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.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 92W/93W N OF 6N MOVING W 10-15 KT. SHORTWAVE 
INFRARED IMAGERY CLEARLY SHOWS A BROAD MID-LEVEL CIRCULATION 
OVER THE WATERS SW OF CENTRAL AMERICA WITH A POSSIBLE VORTICITY 
CENTER NEAR 9N92W. THE ITCZ RUNS THROUGH THIS AREA BUT THERE IS 
NOT YET A CLEAR INDICATION OF A SURFACE LOW. CONVECTION HAS 
FORMED NEAR THE WAVE BUT IS GENERALLY DISPLACED ABOUT 100-200 NM 
AWAY FROM THE VORTICITY CENTER. SCATTERED MODERATE/ISOLATED 
STRONG CONVECTION FROM 6N-16N BETWEEN 89W-98W.

TROPICAL WAVE ALONG 108W/109W S OF 17N MOVING W 5 KT. A 1008 MB 
LOW IS ALONG THE WAVE AXIS NEAR 12N. EASTERLY SHEAR IS AFFECTING 
THE SYSTEM AND THUS A CONVECTIVE BAND HAS FORMED ABOUT 120 NM W 
OF THE LOW. SCATTERED MODERATE/STRONG CONVECTION FROM 8N-14N 
BETWEEN 110W-114W.

TROPICAL WAVE ALONG 139W S OF 16N MOVING W 5-10 KT. A 1009 MB 
LOW IS ALONG THE WAVE AXIS NEAR 11N. ISOLATED SHOWERS FROM 
11N-15N W OF 137W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N77W 13N100W 14N115W 11N140W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 6N-11N E OF 
96W. SCATTERED MODERATE FROM 8N-14N BETWEEN 110W-114W. WIDELY 
SCATTERED MODERATE FROM 11N-16N BETWEEN 120W-128W.

...DISCUSSION...

E OF 110W...
MID/UPPER LEVEL RIDGING REMAINS ANCHORED ACROSS NORTHERN MEXICO 
WITH AN ANTICYCLONIC CENTER NEAR MAZATLAN. THE UPPER FLOW S OF 
THE RIDGE IS MAINLY EASTERLY TO NORTHEASTERLY...EXTENDING FROM 
CENTRAL AMERICA WWD TO 110W. HOWEVER...A DECAYING CYCLONIC SHEAR 
AXIS IS NOTED IN WATER VAPOR IMAGERY FROM THE ISTHMUS OF 
TEHUANTEPEC SW TO 13N99W. ABUNDANT MOISTURE LIES ACROSS THE 
ENTIRE REGION N OF 5N EXTENDING INTO SRN MEXICO...AND SEVERAL 
CLUSTERS OF TSTMS HAVE RECENTLY FORMED OFF THE COAST OFF MEXICO 
AS WELL AS OFF COSTA RICA...LIKELY A RESULT OF LAND BREEZE 
CONVERGENCE. SCATTERED MODERATE/STRONG CONVECTION IS FROM 
13N-17N BETWEEN 92W-104W...AND WITHIN 75 NM OF THE COAST BETWEEN 
18N-24N. A COUPLE OF TROPICAL WAVES ARE MOVING THROUGH THE AREA 
AT THE MOMENT BUT NEITHER APPEARS POISED TO SHOW MUCH 
DEVELOPMENT IN THE COMING DAYS.

W OF 110W...
THE SURFACE RIDGE IS BECOMING RE-ESTABLISHED NEAR 30N AND AS A 
RESULT IS STRENGTHENING THE PRESSURE GRADIENT WITHIN THE TRADE 
WIND BELT FROM BAJA CALIFORNIA SW BETWEEN 16N-25N. 
ELSEWHERE...THE SURFACE WIND FIELD IS MUCH WEAKER WITH 
WESTERLIES NOTED NEAR A DISSIPATING 1013 MB LOW NEAR 19N117W AND 
A NEWLY FORMED 1009 MB LOW NEAR 13N121W. THE SECOND LOW IS 
EXPECTED TO MOVE W OVER THE NEXT FEW DAYS AND LIKELY FURTHER 
INCREASE THE PRESSURE GRADIENT TO ITS NW IN THE TRADE WIND ZONE. 
LOW-LEVEL CONVERGENCE NEAR THE LOW IS CURRENTLY PRODUCING WIDELY 
SCATTERED MODERATE CONVECTION FROM 12N-16N BETWEEN 120W-128W. 
THE UPPER LEVELS ARE DOMINATED BY AN EXTENSIVE RIDGE AXIS FROM 
BAJA CALIFORNIA SW TO 12N140W. A LARGE MID/UPPER LOW IS CENTERED 
NEAR THE CALIFORNIA/OREGON COAST AND THE SUBTROPICAL JET SCRAPES 
BY THE NW PART OF THE AREA WITH MAXIMUM JET SPEEDS NEAR 65 KT.

$$
BERG