000
AXPZ20 KNHC 071530
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT NOV 07 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 
1500 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...10N84W TO 
06N100W TO 09N115W TO 08N140W. SCATTERED MODERATE CONVECTION IS 
WITHIN THE AREA FROM 05N TO 08N FROM 79W TO 81W. SCATTERED 
MODERATE CONVECTION IS WITHIN 45 NM EITHER SIDE OF THE ITCZ AXIS 
FROM 94W TO 102W. 

...DISCUSSION...

STRONG DEEP LAYER SHORTWAVE ALMOST A CUT OFF LOW IS OVER 
NORTHWEST MEXICO. THE SYSTEM IS MOVING EAST AND WILL CROSS INTO 
TEXAS SUNDAY AND WEAKEN SLIGHTLY. MULTI LEVEL BROKEN TO OVERCAST 
CLOUDS ARE OVER NORTHWEST MEXICO NORTH OF 28N FROM 105W TO 
113.5W. SOME LIGHT RAIN MAY BE EMBEDDED WITHIN THE CLOUD AREA. 

A MOSTLY UPPER TROUGH EXTENDS ACROSS THE AREA WITH AN AXIS FROM 
THE COAST OF MEXICO NEAR 20N TO 23N135W THEN SOUTH TO 12N140W. 
THE WESTERN PART OF THIS FEATURE IS PART OF A LARGE UPPER LEVEL 
CYCLONIC CIRCULATION MOSTLY WEST OF THE AREA. NORTH AND WEST OF 
THIS TROUGH AXIS TO 30N THE ATMOSPHERE IS DRY AND CLOUD FREE IN 
THE MIDDLE AND UPPER LEVELS SOUTH OF 30N. NORTH OF 30N SOME 
UPPER MOISTURE IS PRESENT BUT THE MIDDLE AND UPPER LEVELS ARE 
CLOUD FREE. THROUGHOUT MOST OF THIS AREA NORTH OF THE TROUGH 
AXIS THE LOWER LEVELS ARE COVERED BY BROKEN TO OVERCAST 
STRATOCUMULUS CLOUDS. WITHIN 300 NM SOUTH OF THE TROUGH AXIS A 
PLUME OF UPPER MOISTURE IS BEING ADVECTED EASTWARD BUT THE 
ATMOSPHERE IS MOSTLY CLEAR IN THE MIDDLE AND UPPER LEVELS.

A SHARP MOSTLY UPPER TROUGH CONTINUES FROM THE WESTERN GULF OF 
MEXICO ACROSS THE EASTERN PART OF THE ISTHMUS OF TEHUANTEPEC 
CONTINUING TO THE ITCZ NEAR 98W. OUTSIDE THE ITCZ THE AREA OVER 
THE OCEAN IS DRY AND CLOUD FREE IN THE MIDDLE AND UPPER LEVELS. 
OVER MEXICO MULTI LEVEL CLOUDS ARE PRESENT WITH SOME CONVECTION 
OVER SOUTHERN GUATEMALA. THIS CONVECTION IS ASSOCIATED WITH A 
WEAK LOW THAT HAS BEEN OFF THE COAST OF GUATEMALA FOR THE LAST 
SEVERAL DAYS. THE LOW IS FORECAST TO DRIFT NORTH AND THE STRONG 
SOUTHERLY DRY FLOW OVER THE LOW SHOULD PRECLUDE ANY DEVELOPMENT 
OF THE LOW.

LOW NEAR 13N117W WITH A CENTRAL PRESSURE OF 1010 MB IS MOVING 
SLOWLY WEST. CONVECTION HAS BEEN OCCASIONALLY DEVELOPING WITHIN  
ABOUT 120 NM OF THE CENTER BUT HAS NOT PERSISTED. THE COMPUTER 
MODELS WEAKEN THE SYSTEM AS IT SLOWLY MOVES WEST.
 
REMAINDER OF THE MIDDLE AND UPPER LEVELS IS BROAD ANTICYCLONIC 
FLOW.

MODERATE SURFACE RIDGE IS NORTH OF 15N WEST OF 113W. ELSEWHERE 
BESIDES THE TWO LOWS MENTIONED ABOVE A BROAD TROUGH IS ANALYZED 
AT THE SURFACE.

WINDS HAVE DIMINISHED IN THE GULF OF TEHUANTEPEC REGION TO LESS 
THAN GALE FORCE AND ARE FORECAST TO DIMINISH TO LESS THAN 20 KT 
BY LATE TONIGHT.

$$
LL