000
AXPZ20 KNHC 190929
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT APR 19 2008

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 
0900 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 07N77W 04N85W 07N108W 02N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION FROM 2N TO 4N 
BETWEEN 80W AND 82W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION WITHIN 120 NM S OF AXIS BETWEEN 110W AND 115W.

...DISCUSSION...

E OF 105W...WINDS WILL INCREASE OVER THE GULF OF TEHUANTEPEC 
LATER TODAY...THE RESULT OF STRONG GRADIENT FLOW FUNNELING INTO 
THE BAY OF CAMPECHE AND THROUGH THE TEHUANTEPEC ISTHMUS. 25 TO 
30 KT N FLOW WAS OBSERVED AT COATZACOALCOS...MMMT...EARLIER THIS 
EVENING...LENDING CREDENCE TO STRONG NLY FLOW IN SOUTHERN GULF 
OF MEXICO IN RECENT SCATTEROMETER DATA. EXPECT ONLY AROUND 20 KT 
IN GULF OF TEHUANTEPEC AND THE EVENT WILL BE FAIRLY SHORT LIVED. 
GULF OF PAPAGAYO REMAINS QUIET PER AN EVENING QUIKSCAT 
PASS...BUT GIVEN STRENGTH OF TRADES IN CARIBBEAN...GLOBAL MODELS 
CONTINUE TO INDICATED PUFFS OF 20 KT GAP WIND FLOW THROUGH 48 
HOURS. ALOFT...A STATIONARY MID LEVEL RIDGE CENTERED OVER 
SOUTHERN MEXICO DOMINATES THE PATTERN OVER THE AREA...WITH THE 
RIDGE AXIS EXTENDING THROUGH NW MEXICO. ASSOCIATED SUBSIDENCE IS 
SUPPRESSING MAJOR CONVECTION EXCEPT FOR AREAS MENTIONED ALONG 
ITCZ. HOWEVER...DEEP LAYER MOISTURE IS SLOWLY INCREASING INTO 
NORTHERN MEXICO SOUTHERLY MID LEVEL FLOW. GFS SHOWS ONGOING 
CONVECTION ALONG THE ITCZ N AND NE OF GALAPAGOS INCREASING BY 
SUNDAY AS AN UPPER TROUGH CUTS OFF OVER THE ITCZ NEAR 105W S OF 
THE MAIN RIDGE BY EARLY SUNDAY...ALLOWING SLIGHTLY BETTER UPPER 
DIVERGENCE.

W OF 105W...ANIMATED WATER VAPOR IMAGERY SHOWS REINFORCING 
ENERGY DIGGING INTO A SHORT TROUGH OFF THE CALIFORNIA COAST 
ALONG ROUGHLY 125W. THIS SEEMS TO BE CUTTING OFF AN UPPER 
CYCLONE NEAR 23N140W...SOUTH OF A MID/UPPER RIDGE ALONG ROUGHLY 
142W...TO FORM A WEAK REX BLOCK PATTERN NE OF HAWAII. THE 
PATTERN DEAMPLIFIES SLIGHTLY AS THE SHORT WAVE ALONG 125W LIFTS 
OUT OVER A BLOCKING RIDGE OVER MEXICO. THE CUT OFF UPPER CYCLONE 
OPENS UP SAT AND LIFTS OUT TO THE NE AS THE RIDGE TO THE N 
SHIFTS SE AHEAD OF A STRONGER SHORT WAVE IN THE N CENTRAL 
PACIFIC. A SURFACE HIGH OFF THE WEST COAST WEAKENS ACCORDING BUT 
SHIFTS SOUTHWARD WITH ITS SUPPORTING UPPER RIDGE. THIS WILL 
MAINTAIN TRADE WIND FLOW AS WELL AS INCREASE THE PRESSURE 
GRADIENT OFF THE NRN BAJA COAST BY LATE SAT INTO SUN. EXPECT 
INCREASED NLY FLOW AND SWELL TO 12 FT BY MID SUNDAY OFF NRN BAJA 
AS A RESULT. MEANWHILE ANOTHER UPPER TROUGH IS EVIDENT FURTHER 
S...ORIENTED NW TO SE FROM 15N130W TO 3N110W...RUNNING PARALLEL 
AND SW OF AN UPPER RIDGE OVER MEXICO. DIVERGENCE ALOFT AT THE 
BASE OF THIS TROUGH CONTINUES TO ENHANCE ITCZ CONVECTION BETWEEN 
105W AND 110W. GFS HINTS OF MODEST CONVECTION SPARKING ALONG THE 
ITCZ BETWEEN 120W AND 130W BY SUNDAY DUE TO INCREASED DIVERGENCE 
ALOFT.

$$
CHRISTENSEN