000
AXPZ20 KNHC 081007
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU OCT 08 2009

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 
0930 UTC.

...TROPICAL WAVE... 

A TROPICAL WAVE WAS ANALYZED ALONG 102W N OF 07N TO THE MEXICAN 
COAST....AND ESTIMATED TO BE MOVING W AROUND 15 KT. THIS WAVE 
HAS ENTERED THE EASTERN END OF A BROAD AND ELONGATED LOW TO MID 
LEVEL CYCLONIC GYRE DURING THE PAST 24 HOURS...MAKING ITS 
PRECISE LOCATION COMPLEX. HOWEVER TOTAL PRECIPITABLE WATER 
IMAGERY AND GFS ANALYSIS FROM SUNY ALBANY SUGGEST THE WAVE MAY 
BE A BIT FARTHER TO THE E ALONG 97/98W...WITH A NORTHERN 
EXTENSION OF THIS WAVE AND ASSOCIATED MOISTURE HAVING BEEN 
SHEARED AWAY TO THE NW IN THE PAST 2-3 DAYS...AND HAS MOVED 
ACROSS THE FAR SW GULF OF MEXICO AND INTO NE MEXICO AND EXTREME 
SE TEXAS. AN OVERNIGHT QUIKSCAT PASS SHOWED A SWATH OF ESE WINDS 
OF 15-20 KT WITH ISOLATED AREAS NEAR 20 KT...AND HIGHER IN 
CONVECTION...N OF THE ITCZ IN THIS AREA TO THE COAST OF MEXICO. 
GLOBAL MODELS HAVE BEGUN TO INDICATED THE DEVELOPMENT OF A LARGE 
AND BROAD SURFACE LOW TO DEVELOP OUT OF THIS CYCLONIC GYRE 
DURING THE NEXT 2-3 DAYS...AS IT SHIFTS OFF TO THE NW. THE ECMWF 
HAS SHOWN A DECIDED BIAS TOWARD CYCLOGENESIS ACROSS THIS REGION 
THIS SEASON...AND IS THE MOST AGGRESSIVE MODEL WITH THIS SYSTEM. 

...ITCZ...

THE ITCZ AXIS WAS CENTERED ALONG 08N78W TO 09N90W TO 12N101W TO 
12N112W TO 11N125W TO 07N140W. ISOLATED TO SCATTERED MODERATE 
CONVECTION WAS WITHIN 90 NM N AND 240 NM S OF AXIS E OF 
83W...AND BETWEEN 92W AND 125W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION WAS WITHIN 180 NM EITHER SIDE OF AXIS W OF 
127W. 

...DISCUSSION...

A BROAD ANTICYCLONIC CIRCULATION E OF THE AREA OVER THE NRN
GULF OF MEXICO EXTENDS A RIDGE SW TO ACROSS CENTRAL MEXICO TO 
NEAR 16N116W. THIS RIDGE WILL SHIFT E AND WEAKEN...AHEAD OF A 
MID TO UPPER LEVEL TROUGH THAT STRETCHES FROM A L/W MID/UPPER 
LEVEL TROUGH N OF THE AREA...S THROUGH SRN CALIFORNIA...THEN  
SSW THROUGH 23N119W...CONTINUING SSW TO 18N124W. TO THE W OF THE 
TAIL END OF THIS TROUGH IS A MID/UPPER LEVEL ANTICYCLONIC 
CIRCULATION NEAR 15N135W...WITH A BROAD RIDGE EXTENDS NORTHWARD 
FROM THIS ANTICYCLONE TO N OF THE AREA AT 32N135W. A SWLY JET 
STREAM BRANCH BETWEEN THE FIRST RIDGE AND TROUGH AS SEEN IN 
WATER VAPOR IMAGERY WILL CONTINUE TO ADVECT UPPER LEVEL MOISTURE 
IN THE FORM OF SCATTERED THIN CIRRUS ACROSS SRN BAJA CALIFORNIA 
AND CENTRAL MEXICO...WHILE MORE SIGNIFICANT CONVECTIVE DEBRIS 
WAS BEING PULLED N AND NE FROM THE W COAST OF MEXICO ACROSS THE 
BORDER OF MEXICO AND SW TEXAS. 

S OF THE GULF OF MEXICO RIDGE WAS A TUTT LOW OVER CENTRAL 
AMERICA CENTERED NEAR 14N89W AND SHIFTING W INTO THE EPAC. UPPER 
DIVERGENCE TO THE W OF THIS LOW AND UNDERNEATH AN UPPER LEVEL 
MESO HIGH NEAR 19N104W WAS VENTILATING AND SUSTAINING DEEP 
CONVECTION ALONG THE W COAST OF MEXICO ASSOCIATED WITH THE 
CYCLONIC GYRE MENTIONED ABOVE.

A SURFACE RIDGE ENTERS THE REGION THROUGH 32N135W AND EXTENDS SE 
TO NEAR 22N116W. SCATTEROMETER WINDS OVERNIGHT SHOWED NW WIND OF 
20 KT DUE TO A TIGHTER PRES GRADIENT ALONG THE W COAST OF BAJA 
CALIFORNIA...DUE TO THE RIDGE BUILDING SE. HOWEVER...THE RIDGE 
IS FORECAST TO WEAKEN AFTER 48 HOURS AS A COLD FRONT APPROACHES 
THE FAR NW CORNER OF THE REGION.

OVER THE SRN PORTION...A 1010 MB LOW IS NOTED ALONG THE ITCZ
NEAR 114W. THE LOW IS FORECAST TO MOVE W OVER THE NEXT COUPLE OF 
DAYS AS IT INTERACTS WITH THE RIDGE TO THE N. TO THE N OF THE 
LOW...NE TRADES OF 20 KT WERE SEEN FROM 12N TO 23N W OF 112W 
WITH SEAS TO 10 FT IN NE WIND WAVES. THESE SEAS ARE FORECAST BY 
LATEST WAVEWATCH MODEL GUIDANCE TO REMAIN 8 TO 10 FT THROUGH 48 
HOURS...THEN SUBSIDE 8 TO 9 FT ON SAT.

$$
STRIPLING