000
AXPZ20 KNHC 292133
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU JUL 29 2010

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2000 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE IS ANALYZED ALONG A LINE FROM 
10N86W TO 08N96W TO 14N103W TO 10N126W TO 10N140W. SCATTERED 
MODERATE CONVECTION LIES WITHIN 90 NM N AND 60 NM S OF THE ITCZ 
AXIS BETWEEN 87W AND 91W...WITHIN 180 NM S OF THE ITCZ AXIS 
BETWEEN 100W AND 104W...AND WITHIN 60 NM EITHER SIDE OF THE ITCZ 
AXIS BETWEEN 106W AND 112W.


...DISCUSSION...

AN UPPER LEVEL TROUGH AXIS PASSES THROUGH 30N134W TO 26N140W. A 
30-50 KT UPPER LEVEL JET STREAM IS WITHIN 750 NM TO THE EAST OF 
THE TROUGH AXIS FROM 27N TO 30N. ELSEWHERE...UPPER LEVEL 
ANTICYCLONIC FLOW COVERS MUCH OF THE AREA TO THE NORTH OF 10N W 
OF 110W. A WEAK UPPER TROUGH LIES NEAR THE W CENTRAL COAST OF 
MEXICO FROM 25N104W TO 15N111W. THIS PATTERN IS EXPECTED TO 
RETROGRADE SLIGHTLY WESTWARD DURING THE NEXT COUPLE OF DAYS. DRY 
AIR IN SUBSIDENCE CAN BE FOUND IN MOST OF THE REGION N OF A LINE 
FROM 13N140W TO 13N130W TO 30N116W...BUT SOME MOISTURE ALOFT IS 
BEGINNING TO CROSS THIS LINE FROM THE SE AND MOVE INTO THE 
ENTRANCE REGION OF THE AFOREMENTIONED UPPER JET. BROAD SURFACE 
ANTICYCLONIC FLOW COVERS THE AREA TO THE NORTH OF 15N TO THE 
WEST OF 115W. A SURFACE TROUGH IS ANALYZED FROM 13N115W TO 
11N119W. SOUTHERLY SWELLS TO 9 FEET ARE LOCATED NEAR THIS TROUGH 
AND IN GENERAL TO THE SOUTH OF 10N W OF 100W.

MODERATE EASTERLY TO NORTHEASTERLY WINDS ALOFT COVER THE EASTERN 
PORTION OF THE DISCUSSION AREA. AT THE SURFACE...A LOW IS 
EMBEDDED IN THE ITCZ NEAR 09N94W. SCATTERED MODERATE CONVECTION 
IS WITHIN 120 NM N SEMICIRCLE OF THE LOW. THE AVERAGE OF SEVERAL 
SHIP OBSERVATIONS IN THE NE SEMICIRCLE OF THE LOW SHOW WINDS 
AROUND 20-25 KT. THE PRES GRADIENT BETWEEN THIS LOW AND HIGH 
PRES EXTENDING FROM THE N CENTRAL GULF OF MEXICO INTO THE 
YUCATAN PENINSULA AND NORTHERN CENTRAL AMERICA HAS INCREASED 
THE WINDS HERE...BUT LOOK FOR THE GRADIENT TO WEAKEN FRI AND SAT 
AS THE HIGH PRES TO THE N OF THE LOW WEAKENS. SOME OF THE 
COMPUTER MODEL GUIDANCE SUGGESTS THAT SHORTWAVE ENERGY NEAR THE 
BAY OF CAMPECHE WILL SEEP SOUTHWARD THROUGH THE GULF OF 
TEHUANTEPEC INTO THE WESTERN SIDE OF THIS PACIFIC LOW. THE 
PASSAGE OF THE SHORTWAVE ENERGY IS EXPECTED TO INCREASE NORTH TO 
NORTHEAST WINDS TO 25 KT DOWNWIND OF THE GULF OF TEHUANTEPEC BY 
FRI MORNING.

$$
HUFFMAN/SCHAUER