000
AXPZ20 KNHC 010908
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED JUL 01 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 0700 UTC.


...TROPICAL WAVE...

A TROPICAL WAVE IS ALONG 96W N OF 04N MOVING WEST AT 10 TO 15 
KT. 20 TO 30 KT UPPER LEVEL NE WINDS OVER THE SYSTEM ARE 
LIMITING DEEP CONVECTION OVER FORECAST WATERS. SHOWERS AND 
THUNDERSTORMS CAN BE FOUND NEAR THE WAVE PRIMARILY OVER SOUTHERN 
MEXICO WITH SCATTERED MODERATE CONVECTION WITHIN 75 NM OF THE 
MEXICAN COAST FROM 94W TO 101W AND WITHIN 45 NM OF THE COSTA 
RICA...NICARAGUA...AND EL SALVADOR COAST FROM 10N TO 13N. THE 
FORECAST FOR THIS WAVE IS HIGHLIGHTED IN THE DISCUSSION BELOW.


...ITCZ...

THE ITCZ LIES ALONG AN AXIS FROM 08N78W TO 07N82W TO 12N106W TO 
08N120W TO 06N140W. SCATTERED MODERATE CONVECTION CAN BE FOUND 
ALONG THE NW COAST OF PANAMA AND EXTREME SW COAST OF COSTA RICA  
WITHIN 90 NM S AND 75 NM N OF THE ITCZ AXIS BETWEEN 80W AND 84W. 


...DISCUSSION...

TROPICS...
THE AFOREMENTIONED TROPICAL WAVE IS EXPECTED TO MOVE UNDER A 
REGION OF STRONG UPPER LEVEL DIFFLUENCE OVER THE NEXT FEW 
DAYS...MAKING CONDITIONS MORE FAVORABLE FOR DEEP CONVECTION TO 
DEVELOP. AT THE SAME TIME...LOW TO MID LEVEL RIDGING IS EXPECTED 
TO BUILD OVER NORTHERN MEXICO AND THE GULF OF MEXICO THAT WILL 
ALLOW EASTERLY FLOW TO BUILD THROUGH THE WESTERN CARIBBEAN AND 
INTO THE EASTERN PACIFIC. THE 30-40 KT MID LEVEL EASTERLY JET 
WILL BE CENTERED NEAR 13N AND COULD HELP ENHANCE THE VORTICITY 
ASSOCIATED WITH THE TROPICAL WAVE. THE FORECAST CALLS FOR A 
SURFACE LOW TO DEVELOP ALONG THE WAVE TONIGHT AND BECOME THE 
DOMINANT FEATURE BY THU NIGHT AS IT APPROACHES 100W. WINDS ARE 
EXPECTED TO INCREASE TO 20 KT IN THE SE QUADRANT BY THU NIGHT AS 
THE PRESSURE GRADIENT INCREASES BETWEEN THE STRONG SUBTROPICAL 
RIDGE IN THE SE PACIFIC AND THIS 1008 MB LOW. CROSS-EQUATORIAL S 
WINDS TO 20 KT ARE ALREADY OBSERVED S OF 05N BETWEEN 82W AND 97W 
WHERE THE PRESSURE GRADIENT IS SUFFICIENT. CROSS-EQUATORIAL 
WINDS ABOVE 20 KT ARE ALSO NOTED IN FAR SW WATERS. A STRONG 
SOUTHERN HEMISPHERE STORM WILL BRING LONG PERIOD SW SWELL INTO 
FORECAST WATERS S OF 06N BETWEEN 100W AND 130W BEGINNING THIS 
EVENING.

SUBTROPICS...
THE UPPER LEVEL ANTICYCLONE CENTERED OVER W WATERS NEAR 15N130W 
WILL MOVE NORTHWARD OVER THE NEXT FEW DAYS. THIS WILL FORCE THE 
BROAD UPPER TROUGH CURRENTLY OVER NW WATERS N OF THE AREA. 
HOWEVER...EXPECT THE ASSOCIATED SURFACE TROUGH FOUND FROM 
31N122W TO 28N128W TO LINGER OVER THIS REGION THE NEXT FEW DAYS 
AS THE DEEP LAYER TROUGH IS PUSHED NE. THE SURFACE RIDGE WILL 
BUILD TO THE SOUTH OF THIS TROUGH...ALLOWING FOR AN INCREASED 
PRESSURE GRADIENT BETWEEN IT AND CLIMATOLOGICAL LOW PRESSURE 
OVER THE SW U.S. WINDS OFF THE W COAST OF BAJA CALIFORNIA MAY 
BRIEFLY RISE ABOVE 20 KT IN THE AFTERNOON/EVENING HOURS WHEN 
SURFACE PRESSURES IN THE DESERT SW ARE LOWEST. STRONG SOUTHERLY 
FLOW ON THE LEADING EDGE OF THE TROUGH HAS TRANSPORTED SOME MID 
TO UPPER LEVEL MOISTURE/CLOUDINESS INTO THE REGION S OF 25N W OF 
125W BUT THIS CLOUDINESS SHOULD WANE AS THE BUILDING DEEP LAYER 
HIGH ENHANCES SUBSIDENCE OVER THE REGION. 

$$
SCHAUER CLARK