000 AXPZ20 KNHC 202206 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2059 UTC Thu Apr 20 2017 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A trough axis extends from the Pacific coast of Costa Rica near 08N84W to 06N90W. A weak ITCZ axis extends from 07N113W to 06N124W to 06N133W to 05N140W. Scattered moderate/isolated strong convection is within 30 nm of the axis between 90W and 95W. Scattered moderate convection is within 30 nm of the axis between 126W and 130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Strong high pressure of 1029 mb located north of the area near 36N128W extends a ridge southeastward to near the Revillagigedo Islands. A tight pressure gradient between the ridge and thermal afternoon trough along the Baja California Peninsula is bringing northwest 20 to 25 kt to the waters north of 23N between 115W and 121W, including the Sebastian Vizcaino Bay. These winds are attendant by combined seas in the range of 8 to 11 ft. The high will shift north-northeastward through Friday morning, allowing winds to diminish below 20 kt. These seas will slowly subside to 8 ft by Saturday afternoon as the gradient slackens. The southern portion of a cold front moving into Southern California will reach Baja California Norte early Monday, and swell associated with the front will allow for seas to build to the range of 8 and 10 ft west of Baja California Norte late Sunday night through Tuesday. Gentle to moderate NW winds are expected in the Gulf of California through Friday, becoming light to gentle this weekend with seas in the 1 to 2 ft range, except for pockets of 2 to 3 ft seas in the central and far northern sections through early Saturday. Fresh to locally strong winds southwest to west winds are possible over some of the waters north of 29N Monday through Wednesday. The next significant gap wind event for the Gulf of Tehuantepec is expected to begin Sunday evening as a cold front pushes south along the Sierra Madre Oriental mountains. Model guidance suggests strong to minimal gale force winds Sunday night through Monday morning. Wave model guidance indicates that related combined seas will peak to around 13 or 14 ft with this event. High pressure behind the front will shift eastward by Tuesday allowing for winds and seas to diminish. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds, onshore during the day and offshore at night, and combined seas of 3 to 5 ft in mixed SW and NW swell will prevail through the next several days, associated with a broad low pressure residing over the region. REMAINDER OF THE AREA... Strong high pressure north of the discussion has a ridge extending southeastward to near 23N120W and another one southwestward to beyond the area at 23N140W. The high pressure will shift north-northeastward through Friday evening in response to broad deep layer troughing west of the region, while a new high center of about 1021 mb with attendant ridging forms near 27N132W. The cold front associated with the troughing west of the area is clearly seen on satellite imagery to the northeast of the Hawaiian Islands this afternoon. A tightening pressure gradient between the cold front and the ridging will be enough to initiate strong south to southwest winds with combined seas to 9 ft beginning late tonight to the northwest of a line from 32N136W to 28N140W. By early on Friday, the cold front is forecast to approach the far northwest corner of the discussion area, with the strong south to southwest winds and resultant combined seas of 8 to 12 ft forecast to be to the northwest of a line from 32N136W to 28N140W at that time. The cold front will then reach a position from near 32N138W to 27N140W Friday afternoon, with strong southwest winds forecast by the models to be confined to north of 29N within 120 nm east of the front along with seas of 8 to 11 ft. A large set of northwest swell will propagate into the area behind the front also at that time producing combined seas in the range of 8 to 12 ft. The front will then quickly lose its upper support during Friday and into Saturday as it reaches from near 32N131W to 28N134W, and stalls from there to near 26N140W. Winds near the front will diminish to mostly moderate category on Saturday, however the highest of the seas with the northwest swell is still expected to be peaking to 12 ft in the far northwest corner. Seas of 8 to 11 ft just west of the Baja California Peninsula offshore waters will gradually subside to 8 ft on Saturday afternoon. Moderate to fresh trades will prevail elsewhere north of the ITCZ west of 120W through the weekend with combined seas in the range of 6 to 8 ft, except higher seas to 10 ft arising from the aforementioned northwest swell that follows the cold front into the area are expected north of 12N through Friday before subsiding on Saturday. Over the eastern portion of the area, a mid/upper trough axis extends from southern Baja California to 16N112W to 08N108W to the equator at 111W. Upper level divergence east of the trough is helping to support clusters of scattered moderate convection within 30 nm either side of a line from 07N106W to 09N110W. Similar activity is within 30 nm of 10N109W. This activity is likely to continue into tonight and possibly Friday morning. $$ Aguirre