000
AXPZ20 KNHC 310307
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT OCT 31 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE WAS CENTERED ALONG THE LINE 
...09N83W TO 09N125W TO 07N130W TO 08N140W. SCATTERED MODERATE 
TO STRONG CONVECTION IS WITHIN 120 NM OF THE POINT 09N105W. 
SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION IS WITHIN 75 
NM OF THE POINT 08.5N128W.

...DISCUSSION...

STRONG DEEP LAYER TROUGH IS OVER MEXICO NORTH OF 22N. THE TROUGH 
IS FORECAST TO WEAKEN SOME AND MOVE EAST REACHING THE WESTERN 
GULF OF MEXICO MIDDAY SATURDAY. A WEAKER MOSTLY UPPER TROUGH 
EXTENDS FROM THE MAIN TROUGH WEST SOUTHWEST OVER THE PACIFIC 
FROM NEAR THE COAST OF MEXICO AT 21N TO 20N127W TO 10N140W. MOST 
OF THE AREA NORTHWEST OF THE TROUGH IS DOMINATED BY A LARGE 
RIDGE OVER THE NORTHWEST PART OF THE PACIFIC OCEAN AREA. THE 
RIDGE IS WEAKENING AND A LARGE WEAK DEEP LAYER CYCLONIC 
CIRCULATION IS FORECAST TO FORM OF THE WESTERN PART OF THE 
PACIFIC OCEAN AREA. THIS SHOULD HAVE LITTLE AFFECT ON THE 
WEATHER BESIDES MOISTENING THE MIDDLE AND UPPER LEVELS IN THIS 
REGION. AT THE PRESENT TIME DRY MIDDLE AND UPPER LEVELS WITHIN 
THE RIDGE INDICATES SUBSIDENCE IN THIS LARGE AREA. IN THE LOWER 
LEVELS BROKEN TO OVERCAST STRATOCUMULUS IS FROM 16N TO 23N WEST 
OF 120W AND BROKEN STRATOCUMULUS NORTH OF 23N WEST OF 125W. 
SOUTH OF THE UPPER TROUGH TO THE ITCZ THE ATMOSPHERE IS MOIST IN 
THE DEEP LAYER WITH MULTI LEVEL CLOUDS FROM MOISTURE EMANATING 
FROM ITCZ CONVECTION.

EXCEPT FOR THE FEATURE IN THE NEXT PARAGRAPH THE REGION NORTH OF 
THE ITCZ EAST OF 105W TO 85W AND SOUTHEAST OF THE ABOVE TROUGH 
IS DIFFLUENT ALOFT WITH DEEP LAYER MOISTURE WITH MULTI LEVEL 
CLOUDS AND EMBEDDED AREAS OF CONVECTION. CONVECTION WITHIN THIS 
AREA IS CONFINED TO SOUTH OF 12N AND IS MENTIONED IN THE ITCZ 
SECTION. BROAD LOW PRESSURE IS IN THIS AREA WITH A 1007 MB 
CENTER ANALYZED NEAR 11N94W. 

A LARGE CYCLONIC CIRCULATION IS OVER GUATEMALA AND TO THE WEST 
OF THE CENTER TO 96W OVER EASTERN MEXICO AND ABOUT 200 NM FROM 
THE COAST THE ATMOSPHERE IS DRY IN THE MIDDLE AND UPPER LEVELS 
WITH CLEAR SKIES IN THE MIDDLE AND UPPER LEVELS. THIS FEATURE 
EXTENDS WESTWARD OVER THE EASTERN PART OF MEXICO EAST OF 96W 
WITH ISOLATED CONVECTION OVER THE LAND AREAS DEVELOPING WITHIN 
THE LAST SEVERAL HOURS. THE CENTER OF THE CYCLONIC CIRCULATION 
IS MOVING SLOWLY WEST. SOME MOISTURE IS EAST OF THE CIRCULATION.
MORE EXTENSIVE CONVECTION IS FURTHER EAST IN THE WESTERN 
CARIBBEAN. EAST OF 85W THE MIDDLE AND UPPER LEVELS ARE DRY AND 
MOSTLY CLOUD FREE. 

MODERATE SURFACE RIDGE IS NORTH OF 15N WEST OF 115W. THE SURFACE 
HIGH IS FORECAST TO WEAKEN AND CONTRACT IN SIZE WHILE A COLD 
FRONT APPROACHES FROM THE NORTHWEST. BESIDES THE LOW MENTIONED 
ABOVE...ELSEWHERE AT THE SURFACE A BROAD TROUGH IS ANALYZED.

GAP WINDS...
HIGH PRES BUILDING SE ACROSS SOUTHERN MEXICO IN THE WAKE OF A 
COLD FRONT OVER THE WESTERN GULF OF MEXICO WILL USHER N-NE
WINDS OF 20-30 KT THROUGH THE GULF OF TEHUANTEPEC BEGINNING 
LATE SAT AFTERNOON OR EARLY SAT EVENING...THEN INCREASING TO
GALE FORCE BY DAYBREAK SUN MORNING WITH SEAS BUILDING UP TO
13 FT.

$$