000
AXPZ20 KNHC 212200
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT MAR 21 2009

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 
2145 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 08N78W TO 05N90W TO 04N100W TO 
04N140W. NO SIGNIFICANT CONVECTION IS NOTED.

...DISCUSSION...

THE UPPER LEVEL FLOW CONTINUES TO AMPLIFY N OF THE DISCUSSION 
AREA AS AN UPPER LEVEL JET MAXIMUM DIVES SOUTHEASTWARD...FORCING 
A RATHER VIGOROUS MID/UPPER LEVEL TROUGH TO PUSH SEWD INTO THE 
FAR NW CORNER OF THE AREA. A MID/UPPER LEVEL CYCLONIC 
CIRCULATION IS BECOMING EVIDENT ON THE SOUTHERN PORTION OF 
THROUGH W OF THE AREA NEAR 20N146W. THE ASSOCIATED SURFACE 
DISSIPATING COLD FRONT ENTERS THE FAR NW WATERS THROUGH 
32N127W...AND REACHES TO 28N140W. THE FRONT IS FORECAST TO 
FURTHER WEAKEN OVER THE NEXT 24 HOURS AS IT PROGRESSES FURTHER S 
INTO THE NORTHERN WATERS. STRONG HIGH PRES BUILDS IN BEHIND IT 
ON MONDAY. LATEST MODEL GUIDANCE IS SHOWING N WINDS INCREASING 
TO 20 TO 25 KT BEHIND THE FRONT WITH OCCASIONAL GUSTS TO 30 KT 
ESPECIALLY IN THE FAR NE PORTION OF THE AREA NEAR THE BAJA 
CALIFORNIA WHERE GRADIENT IS EXPECTED TO BE THE TIGHTEST. LATEST 
WAVEWATCH GUIDANCE INDICATES SEAS BUILDING UP TO 12 OR 13 FT IN 
THE FAR NORTHERN WATERS.

A WEAK SURFACE RIDGE N OF THE DISCUSSION AREA CONTINUES TO
WEAKEN IN RESPONSE TO DECREASING DEEP LAYER SUBSIDENCE WITH THE 
AMPLIFICATION OF THE MID/UPPER TROUGH.
 
E OF THE MID/UPPER TROUGH...BROAD ANTICYCLONE FLOW PATTERN
DOMINATES THE AREA WITH A MEAN RIDGE AXIS ALONG THROUGH 32N116W 
TO 26N113W TO 18N11W. EXTENSIVE MID/UPPER LEVEL MOISTURE 
CONTINUES TO BE ADVECTED ENE IN DIFFLUENT FLOW PATTERN E OF THE 
MID/UPPER TROUGH AND E ACROSS THE RIDGE TOWARDS BAJA CALIFORNIA 
AND THE SW U.S. AT THE SURFACE...A RIDGE EXTENDS SE FROM 28N128W 
TO 21N111W. THE ENHANCED SURFACE PRESSURE GRADIENT AT THE 
SOUTHERN PERIPHERY OF THE 1030 MB SURFACE HIGH AT 35N150W IS 
ENHANCING NE TO E TRADE WINDS ACROSS THE REGION FROM 8N TO 17N W 
OF 125W WHERE NE WINDS OF 20 TO 25 KT ARE FOUND WITH SEAS TO 9 
FT. THESE TRADES ARE EXPECTED TO INCREASE IN AREAL COVERAGE ON 
SUN AS THE STRONG HIGH BEHIND THE FRONT SURGES SWD.

THE UPPER LEVEL DIFFLUENT FLOW E OF THE ABOVE MENTIONED TROUGH 
IS SUPPORTING SCATTERED MODERATE CONVECTION FROM 10N TO 15N 
BETWEEN 123W AND 130W.  SCATTERED MODERATE FROM 07N TO 11N 
BETWEEN 130W AND 137W. 

FARTHER TO THE E...DEEP LAYER DRY AIR AND STABLE ATMOSPHERIC 
CONDITIONS EMBEDDED WITHIN AN UPPER RIDGE ARE RESULTING IN FAIR 
WEATHER CONDITIONS S OF 16N E OF 96W.

GAP WINDS...
A PERSISTENT RIDGE OF SURFACE HIGH PRESSURE OVER MEXICO AND THE 
GULF OF MEXICO CONTINUES TO SUPPORT A RELATIVELY STRONG SURFACE 
PRES GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC DURING THE NEXT 
FEW DAYS. QUIKSCAT DATA SHOWED WINDS OF 30 TO 35 KT THROUGH THE 
GULF. WINDS WILL DIMINISH TO LESS THEN GALE FORCE IN ABOUT 18 
HOURS.

ALSO...TRADE WINDS ACROSS THE CARIBBEAN CONTINUE WITH A 
PERSISTENT SURFACE LOW OVER NW COLOMBIA...AND ARE FILTERING
THROUGH THE GULFS OF PAPAGAYO AND PANAMA. EXPECT THESE WINDS 
CONTINUE THROUGH THE GULF OF PAPAGAYO OVER THE NEXT 48 HOURS
...BUT DECREASE SOME AND DIMINISH IN THE GULF OF PANAMA IN
48 HOURS. THE GAP WINDS ARE FORECAST TO BE STRONGEST LATE AT 
NIGHT WHEN DRAINAGE FLOW OFF HIGHER TERRAIN IS MAXIMIZED IN THE 
PRESENCE OF DEEP LAYER DRY AIR.

$$
FORMOSA