000
AXPZ20 KNHC 251501
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN OCT 25 2009

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 
1330 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE CAN BE FOUND ALONG THE LINE 
FROM 10N86W TO 09N96W TO 12N11W TO 08N130W TO 10N140W. SCATTERED 
MODERATE WITH ISOLATED STRONG CONVECTION LIES WITHIN 180 NM S 
AND 45 NM N OF THE ITCZ AXIS BETWEEN 100W AND 110W AS WELL AS 
WITHIN 75 NM S AND 120 NM N OF THE ITCZ AXIS BETWEEN 114W AND 
119W.

...DISCUSSION...

A LONGWAVE MID TO UPPER LEVEL TROUGH FROM SOUTH TEXAS NEAR 
27N99W THROUGH MEXICO TO 18N110W TO 16N125W WILL BE RELOADED BY 
THE SHORTWAVE ENERGY CURRENTLY PASSING INTO THE BACKSIDE OF THIS 
LONGWAVE TROUGH OVER THE U.S. WESTERN STATES. THE COLD FRONT AT 
THE SURFACE ASSOCIATED WITH THIS TROUGH IS CURRENTLY DISSIPATING 
IN THE VICINITY OF THE BAY OF CAMPECHE AND THE ACCELERATED WINDS 
THROUGH THE ISTHMUS OF TEHUANTEPEC...CURRENTLY AT 20 KT WITHIN 
120 NM S OF THE COAST OF THE GULF OF TEHUANTEPEC ACCORDING TO 
THE 1250 UTC QUIKSCAT PASS...SHOULD DIMINISH LATER TODAY. A 
SECONDARY COLD FRONT ASSOCIATED WITH THE REINFORCING SHORTWAVE 
ENERGY IS CURRENTLY PASSING S THROUGH THE GREAT BASIN AND SHOULD 
MOVE INTO NORTHERN MEXICO BY SUNRISE TOMORROW. SOME OF THE 
MODELS SHOW WINDS IN THE NORTHERN GULF OF CALIFORNIA INCREASING 
TO THE 20 TO 25 KT RANGE EARLY MON MORNING WITH THE FRONTAL 
PASSAGE AND QUICKLY DIMINISH BELOW 20 KT BY MID DAY. IF WINDS DO 
EXCEED 20 KT...THE EVENT WILL BE SHORT LIVED.  IN 
ADDITION...BECAUSE THE REINFORCING SHORTWAVE ENERGY IS EXPECTED 
TO PUSH E INTO THE PLAINS EARLY MON WITH THE TROUGH AMPLIFYING 
WELL E OF THE GULF OF CALIFORNIA...IT APPEARS THAT THE WIND 
DIRECTION IN THE NORTHERN GULF OF CALIFORNIA SHOULD BE MORE N TO 
NE RATHER THAN THE NW TO N DIRECTION THAT FAVORS FUNNELING WINDS 
DOWN THE LENGTH OF THE GULF.  

SW FLOW ON THE EASTERN EDGE OF THE MID TO UPPER LEVEL TROUGH 
AXIS IS TRANSPORTING TROPICAL MOISTURE NE INTO MEXICO WITH A 
LINE OF CIRRUS EVIDENT ON SATELLITE IMAGERY WITHIN 150 NM OF 
LINE FROM 20N100W TO 11N112W WHERE A STATIONARY SURFACE TROUGH 
RESIDES. THIS TROUGH LIES IN THE VICINITY OF THE REAR RIGHT 
QUADRANT ON THE UPPER JET AND CONVECTION HAS BEEN ENHANCED NEAR 
THE TROUGH AND ALONG THE ITCZ IS THIS AREA OF LOW LEVEL 
CONVERGENCE AND UPPER LEVEL DIFFLUENCE. THIS AREA SHOULD REMAIN 
A FAVORED REGION FOR CONVECTION THE NEXT DAY OR SO AS THE MID TO 
UPPER LEVEL TROUGH RELOADS.

OVER N AND W WATERS...RELATIVELY STRONG RIDGING IS IN PLACE IN 
THE MID TO LOW LEVELS. NORTHERLY FLOW BETWEEN THE EASTERN EDGE 
OF THE RIDGE AND ENHANCED TROUGHING OVER THE SOUTHERN U.S. 
PLAINS AND NORTHERN MEXICO IS IN THE 20 TO 25 KT RANGE ACCORDING 
TO THE 0124 QUIKSCAT AND THE 0620 UTC ASCAT PASSES. NE TO E 
TRADE WINDS ON THE SOUTH SIDE OF THE RIDGE AXIS ARE ALSO IN THE 
20 TO 25 KT RANGE ACCORDING TO THE ASCAT AND QUIKSCAT PASSES. 
THE RIDGE IS EXPECTED TO AMPLIFY SLIGHTLY OVER THE NEXT TWO DAYS 
WITH LITTLE CHANGE IN WIND AND SEA CONDITIONS. SCATTERED TO 
BROKEN STRATOCUMULUS N OF 18N AND NW OF LINE FROM 18N125W TO THE 
WESTERN BAJA CALIFORNIA COAST NEAR 27N113W WILL ALSO REMAIN IN 
PLACE FOR THE NEXT TWO DAYS.

CLOSER TO THE COAST...SCATTERED MODERATE CONVECTION CAN BE FOUND 
WITHIN 75 NM E SEMICIRCLE OF A 1007 MB LOW PRES SYSTEM NEAR 
09N88W WITH ISOLATED MODERATE CONVECTION ELSEWHERE WITHIN 210 NM 
SE QUADRANT OF THE LOW. THIS SYSTEM LIES IN A REGION OF STRONG 
UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER RIDGE AXIS EXTENDING 
FROM AN ANTICYCLONE NEAR 06N97W TO 04N82W AND A CARIBBEAN UPPER 
LOW NEAR 19N79W. THE LOW LEVEL CENTER WAS IDENTIFIABLE ON NIGHT 
CHANNEL VISIBLE SATELLITE IMAGERY OVERNIGHT AND CONVECTION FIRED 
NEAR THE CENTER OF THE SYSTEM BETWEEN 0800 AND 1100 UTC THAT HAS 
SINCE DISSIPATED. THIS LOW IS NOT EXPECTED TO DEVELOP FURTHER 
AND WILL MOVE SLOWLY TO THE N OVER THE NEXT DAY OR TWO UNDER 
DEEP LAYER SOUTHERLY STEERING FLOW GENERATED BY THE AMPLIFYING 
MID TO UPPER LEVEL PATTERN BETWEEN THE TROUGH TO ITS NW AND 
RIDGING OVER THE SW N ATLC AND CARIBBEAN. UNFORTUNATELY...THE 
1108 AND 1248 UTC QUIKSCAT PASSES MISSED THE LOW. WINDS HERE ARE 
BELIEVED TO BE UNDER 20 KT BASED ON AN EARLIER ASCAT PASS AND 
THE LACK OF ORGANIZED CONVECTION.

$$
SCHAUER