000
AXPZ20 KNHC 150920
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE SEP 15 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 
0845 UTC.

...SPECIAL FEATURE...

A SURFACE LOW 16N111W 1008 MB MOVING WNW 8 KT. LOW IS PART OF A 
LARGE AREA OF LOW PRESSURE THAT EXTENDS OUT ABOUT 400 NM FROM 
THE POINT 15N113W. UPPER DIFFLUENT FLOW IS CONTRIBUTING TO THE 
LOW LEVEL CONVERGENCE THAT IS INCREASING THE CYCLONIC 
CIRCULATION IN THE LOW LEVELS. WIDESPREAD MULTI LEVEL CLOUDS AND 
EMBEDDED AREAS OF CONVECTION ARE WITHIN THIS AREA. SCATTERED 
MODERATE TO STRONG CONVECTION IS WITHIN 150 NM IN THE NORTH 
QUADRANT OF THE LOW. IT IS POSSIBLE THAT A TROPICAL CYCLONE MAY 
FORM WITHIN THIS BROAD AREA OR THE LOW ITSELF MAY DEVELOP INTO A 
TROPICAL CYCLONE OVER THE NEXT 48 HOURS.

...TROPICAL WAVE...

TROPICAL WAVE ALONG 106W FROM 08N TO 18N MOVE WEST 15 KT. NO 
CONVECTION IS NEAR THE WAVE AT THIS TIME. 

TROPICAL WAVE ALONG 120W FROM 08N TO 16N MOVE WEST 15 KT. SOME 
CONVECTION IS NEAR THE WAVE IN THE ITCZ. THE CONVECTION IS NOT 
ORGANIZED BY CYCLONIC FLOW.

...THE ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE 07N77W TO 
09N100W TO 10N120W TO 06N140W. SCATTERED MODERATE TO STRONG 
CONVECTION IS WITHIN 60 NM EITHER SIDE OF THE ITCZ AXIS E OF 
80W. SCATTERED MODERATE CONVECTION IS WITHIN THE AREA 60 NM 
EITHER SIDE OF A LINE FROM 14N112.5W TO 10N121W.

...DISCUSSION...

TROUGH OVER THE SOUTHWEST UNITED STATES EXTENDS OVER NORTHWEST 
MEXICO AND THE NORTHEAST PART OF THE PACIFIC OCEAN NORTH OF 25N 
EAST OF 123W. CLOUDS IN THIS ARE ARE BROKEN TO OVERCAST 
STRATOCUMULUS OVER THE OCEAN AND THE COASTAL AREAS OF BAJA 
CALIFORNIA. THE TROUGH IS FORECAST TO REMAIN OVER THE SOUTHWEST 
UNITED STATES AND CONTINUE TO BE OVER NORTHERN MEXICO THROUGH 
THE NEXT SEVERAL DAYS. 

A STRONG MIDDLE LATITUDE TROUGH IS MOVING OVER THE FAR NORTHWEST 
PART OF THE AREA. THE TROUGH IS FORECAST TO REMAIN MOSTLY NORTH 
OF THE AREA AND TO PULL FURTHER NORTH AFTER A COUPLE OF DAYS. 
SOME MULTI LEVEL LAYERED CLOUDINESS IS ASSOCIATED WITH THE 
TROUGH BUT THESE CLOUDS ARE EXPECTED TO REMAIN MOSTLY NORTH OF 
32N.

BETWEEN THE TWO TROUGHS A SHARP RIDGE EXTENDS NORTH OF 25N. THIS 
RIDGE IS PART OF A LARGE ANTICYCLONIC FLOW THAT COVERS MOST OF 
THE PACIFIC REGION. THE RIDGE EXTENDS EAST TO A LINE FROM 
NORTHWESTERN YUCATAN PENINSULA TO THE ITCZ NEAR 100W. THIS RIDGE 
IS DIFFLUENT ALOFT TO THE SOUTH OF A LINE THAT EXTENDS FROM NEAR 
25N105W TO THE ITCZ AT 140W. NORTHWEST OF THE LINE MIDDLE AND 
UPPER LEVEL SUBSIDENCE IS KEEPING THE MIDDLE AND UPPER LEVELS 
DRY AND CLOUD FREE. BROKEN TO OVERCAST STRATOCUMULUS ARE WITHIN 
THIS AREA NORTH OF 20N. THE DIFFLUENT AREA INCLUDES THE SPECIAL 
FEATURES AREA AND ALSO WIDESPREAD MULTI LEVEL CLOUDINESS NEAR 
THE ITCZ WEST OF 125W.
 
WEAK SURFACE RIDGE IS NORTH OF 23N FROM 118W TO 135W. ELSEWHERE 
EXCEPT FOR THE BROAD LOW A WEAK FLAT PRESSURE GRADIENT IS 
ANALYZED.

$$
LL