000
AXPZ20 KNHC 092111
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN SEP 09 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1930 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH AXIS WAS ANALYZED FROM 09N83W TO 11N93W TO 
11N107W TO 10N113W TO 10N126W. THE ITCZ AXIS WAS ANALYZED FROM 
10N126W TO 09N131W TO 10N136W TO 09N140W. SCATTERED MODERATE 
CONVECTION WAS WITHIN 180 NM N AND 210 NM S OF THE AXIS BETWEEN 
90W AND 107W AS WELL AS WITHIN 120 NM S OF THE AXIS BETWEEN 111W 
AND 122W. SCATTERED MODERATE CONVECTION WAS WITHIN 180 NM N AND 
FROM 60 NM TO 210 NM S OF THE ITCZ AXIS W OF 130W.

...DISCUSSION...

A DEEP LAYERED LOW LIES OVER BAJA CALIFORNIA NORTE. SOUTHERLY 
FLOW ON THE EASTERN SIDE OF THIS LOW IS PUMPING MOISTURE 
NORTHWARD ALONG THE W COAST OF MEXICO INTO THE GULF OF 
CALIFORNIA. SCATTERED MODERATE CONVECTION WAS WITHIN 60 NM N AND 
90 NM S SEMICIRCLES OF THE LOW. THERE IS ALSO SCATTERED MODERATE 
CONVECTION OVER THE SIERRA MADRE OCCIDENTALS FROM 27N TO 31N 
BETWEEN THIS LOW AND A COLD FRONT THAT IS DRAPED OVER MAINLAND 
MEXICO ALONG 25N E OF 104W. 

AN UPPER LEVEL ANTICYCLONE NEAR 22N113W EXTENDS RIDGE AXES 
SOUTHWESTWARD TO ANOTHER ANTICYCLONE NEAR 16N133W AND EASTWARD 
ACROSS CENTRAL MEXICO TO THIRD ANTICYCLONE NEAR 22N98W. A 25-35 
KT EASTERLY JET LIES S OF THE UPPER RIDGE WITHIN 120 NM EITHER 
SIDE OF A LINE FROM 06N130W TO 02N100W. THIS SHEAR IS INHIBITING 
THE DEVELOPMENT OF DEEP CONVECTION...BUT A BROAD AREA OF 
DIFFLUENCE ALOFT NE OF THIS JET IS ENHANCING THE SCATTERED 
MODERATE CONVECTION ALONG THE MONSOON TROUGH DESCRIBED IN THE 
SECTION ABOVE. AN UPPER LOW TROUGH LIES W OF THE AREA ALONG 144W 
FROM 07N TO 15N. THE SURFACE REFLECTION OF THIS TROUGH IS 
DEPICTED AS A NORTHWARD BEND ALONG THE ITCZ NEAR 136W. 

THE 1031 MB SUBTROPICAL HIGH WAS ANALYZED NEAR 37N153W. THE HIGH 
IS CURRENTLY BEING ENCROACHED UPON BY A FRONT TO ITS N. THIS 
FRONT AND THE HIGH ARE FORECAST TO MOVE EASTWARD OVER THE NEXT 
FEW DAYS. THE 1824 UTC ASCAT PASS SHOWED FRESH TO STRONG TRADE 
WINDS HAVE BUILT OVER FAR W WATERS WHERE THE PRES GRADIENT IS 
STRONGEST JUST N OF THE AFOREMENTIONED NORTHWARD BEND IN THE 
ITCZ. WINDS AND SEAS HERE SHOULD DIMINISH BELOW ADVISORY 
CRITERIA BY EARLY TUE AS THE DEEP LAYERED TROUGH CONTINUES TO 
MOVE W. THE 1644 UTC ASCAT PASS SHOWED A REGION OF FRESH TO 
STRONG S-SW WINDS S OF THE MONSOON TROUGH TO 05N BETWEEN 105W 
AND 115W...FORCED BY THE PRES GRADIENT BETWEEN THE MONSOON 
TROUGH AND STRONG HIGH PRES OVER THE SOUTH PACIFIC. THESE WINDS 
ARE EXPECTED TO DIMINISH BELOW ADVISORY CRITERIA AS THE HIGH 
PRES TO THE S WEAKENS OVERNIGHT. S SWELL TO 8 FT CURRENTLY IN 
THIS REGION OF FRESH TO STRONG WINDS WILL SHIFT NORTHWARD OVER 
THE NEXT FEW DAYS TOWARD THE MEXICAN COAST. AT THE SAME 
TIME...THE NUMERICAL GUIDANCE AGREES ON DEVELOPING A BROAD AREA 
OF LOW PRES SW OF THE GULF OF TEHUANTEPEC BY MON AFTERNOON AND 
INCREASING WINDS TO FRESH TO STRONG ON ITS NORTHERN SIDE BETWEEN 
THE MEXICAN COAST AND 12N WHERE THE S SWELL WILL HAVE ALREADY 
BUILT THE SEAS ABOVE ADVISORY CRITERIA. THIS LOW IS FORECAST TO 
STRENGTHEN AS IT MOVES NW AROUND 10 KT THROUGH TUE AFTERNOON.

$$
SCHAUER