000
AXPZ20 KNHC 190346
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU MAR 19 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...ITCZ...
THE ITCZ AXIS LIES ALONG A LINE FROM 02N78W TO 04N89W TO 01N104W 
01N117W TO 01N128W TO 06N140W. NO SIGNIFICANT CONVECTION IS 
NOTED ALONG THE ITCZ.

...DISCUSSION...

THE UPPER LEVEL FLOW CONTINUES TO AMPLIFY N OF THE DISCUSSION 
AREA AS A DEEP LOW OVER THE GULF OF ALASKA PROPAGATES 
SOUTHEASTWARD CARVING OUT A DEEP TROUGH N OF THE DISCUSSION 
AREA. THE PREVIOUSLY STATIONARY FRONT N OF THE AREA IS NOW 
ADVANCING SOUTHWARD...AND IS FORECAST TO ENTER THE NORTHERN 
WATERS BY SUNDAY. NORTHWESTERLY WINDS OF 20 TO 30 KT WILL AFFECT 
AREAS IN THE WAKE OF THE FRONT...WHERE WAVE HEIGHTS OVER 12 FT 
IN NORTHWESTERLY SWELL WILL BE PRESENT. 

IN THE MEANTIME...A 1026 MB SURFACE HIGH N OF THE AREA NEAR 
34N132W WILL CONTINUE TO WEAKEN IN RESPONSE TO DECREASING DEEP 
LAYER SUBSIDENCE WITH THE AMPLIFICATION OF THE UPPER TROUGH. THE 
PRESSURE GRADIENT BETWEEN THE HIGH AND A SURFACE TROUGH OVER THE 
SW CONUS CONTINUES TO DRIVE NW TO N WINDS OF UP TO 20 KT IN A 
NARROW SWATH W OF THE BAJA COAST. WAVE HEIGHTS UP TO 10 FT IN 
NORTHWESTERLY SWELL CONTINUE IN THIS AREA...BUT CONTINUE 
SUBSIDING AS THEY DEPART THEIR SOURCE REGION. THE ENHANCED 
SURFACE PRESSURE GRADIENT AT THE SOUTHERN PERIPHERY OF THE 
SURFACE HIGH ALSO IS ENHANCING NE TO E TRADES ACROSS THE REGION. 
THE HIGH RESOLUTION QUIKSCAT PASS AROUND 18/1500 UTC SHOWED NE 
TO E WINDS UP TO 20 KT FROM 09N TO 18N W OF 128W...WITH 
WAVEWATCH GUIDANCE INDICATING SEAS TO 10 FT IN THIS AREA WITH 
CONTINUING NE SWELL. THE TRADES IN THIS AREA ARE EXPECTED TO 
PICK UP SUBSTANTIALLY BY SUNDAY AS A SURFACE HIGH BUILDS 
SOUTHWARD IN THE WAKE OF THE AFOREMENTIONED COLD FRONT.

AS FOR CONVECTIVE ACTIVITY...UPPER LEVEL DIFFLUENCE N OF THE 
ITCZ AXIS IS SUPPORTING SCATTERED MODERATE CONVECTION FROM 15N 
TO 18N BETWEEN 118W AND 123W AND SCATTERED MODERATE CONVECTION 
FROM 11N TO 16N W OF 135W. THE DIFFLUENCE IS EMBEDDED WITHIN AN 
UPPER TROUGH LOCATED S OF 19N W OF 110W. FARTHER TO THE E...DEEP 
LAYER DRY AIR AND STABLE ATMOSPHERIC CONDITIONS EMBEDDED WITHIN 
AN UPPER RIDGE ARE RESULTING IN FAIR WEATHER CONDITIONS.

GAP WINDS...
A PERSISTENT RIDGE OF SURFACE HIGH PRESSURE OVER MEXICO AND THE 
GULF OF MEXICO WILL SUPPORT A RELATIVELY STRONG SURFACE PRESSURE 
GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC DURING THE NEXT FEW 
DAYS. CORRESPONDINGLY...THE HIGH RESOLUTION QUIKSCAT PASS AROUND 
19/0050 UTC DEPICTED N TO NE WINDS OF 20 TO 25 KT FUNNELING INTO 
THE GULF OF TEHUANTEPEC. THESE WINDS ARE WITHIN 90 NM EITHER 
SIDE OF A LINE FROM 16N94.5W TO 12N96W TO 09N100W...WITH N TO NE 
WINDS UP TO 30 KT WITHIN 60 NM OF THE COAST. A SHIP OBSERVATION 
NEAR 12N95.5W WAS REPORTING NORTH-NORTHEAST WINDS NEAR 20 KT AS 
OF 19/0000 UTC. COMPUTER MODEL GUIDANCE INDICATES THESE WINDS 
WILL CONTINUE DURING THE NEXT DAY GENERALLY WITHIN 90 NM OF THE 
COAST. HOWEVER STRONG SURFACE HIGH PRESSURE BUILDING SOUTHWARD 
FROM THE CANADIAN PRAIRIES WILL STEEPEN THE PRESSURE GRADIENT 
ACROSS THE ISTHMUS OF TEHUANTEPEC EVEN FURTHER ON FRIDAY...WHEN 
WINDS WILL INCREASE ACROSS A LARGER AREA IN THE GULF OF 
TEHUANTEPEC...WITH N TO NE WINDS APPROACHING 30 KT. HOWEVER... 
THE ABSENCE OF ANY REMARKABLE SURFACE FRONTS IN THE WESTERN GULF 
OF MEXICO WILL PRECLUDE THE THREAT FOR GALES. SEAS WILL BUILD 
OVER 10 FT DOWNWIND OF THE GULF OF TEHUANTEPEC BY SATURDAY. 
ALSO...TRADE WINDS ACROSS THE CARIBBEAN CONTINUE WITH A 
PERSISTENT SURFACE LOW OVER NW COLOMBIA. THESE WINDS CONTINUE TO 
BLEED INTO THE GULF OF PAPAGAYO. GAP WINDS AROUND THE GULFS OF 
TEHUANTEPEC AND PAPAGAYO ARE FORECAST TO BE STRONGEST LATE AT 
NIGHT WHEN DRAINAGE FLOW OFF HIGHER TERRAIN IS MAXIMIZED IN THE 
PRESENCE OF DEEP LAYER DRY AIR.

$$

COHEN