000 AXPZ20 KNHC 082205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2030 UTC Wed Nov 8 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. ...SPECIAL FEATURES... A tight pressure gradient has set up over southeastern Mexico, and is bringing strong northerly winds through the Isthmus of Tehuantepec and across the Gulf of Tehuantepec. These conditions are expected to continue into Thursday morning. High pressure surging southward behind a cold front moving across the western Gulf of Mexico will push a cooler air mass towards the eastern slopes of the Sierra Oriental mountains along eastern Mexico. This will further intensify the pressure gradient already in place allowing for these winds to increase to gale force by early Thursday afternoon. A gale warning is already in effect for the Gulf of Tehuantepec through 48 hours. Seas are expected to build to the range of 10-15 ft with these gale conditions. Model guidance suggests that this event will last through the next few days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N85W to 09N100W to 08N110W to low pressure near 10N121W 1009 mb to 10N133W where scatterometer winds from this afternoon indicate the ITCZ then begins and continues to beyond 07N140W. Scattered moderate convection is within 180 nm S of the axis between 122W-126W, within 120 nm N of the axis between 114W-117W and also within 30 nm of the axis between 103W-107W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge will dominate the waters W of Baja California through the rest of the week, while a trough will meander between the coast of NW Mexico and the Gulf of California. Moderate to locally fresh NW to N flow will prevail across the waters W of Baja California, increasing to fresh to locally strong offshore of the northern waters Thu night through Fri. A cold front is expected to weaken before reaching the area on Friday, but the associated long-period NW swell inducing seas in the range of 8 to 10 ft will propagate southeastward across the waters N of 23N and to the W of Baja California on Friday, then spread southward through all the waters W of Baja on Saturday while subsiding slightly. Gulf of California: The pressure gradient will tighten a little resulting in a narrow swath of fresh to locally strong NW winds from 25N to 28N by this afternoon. The pressure gradient will relax with moderate NW flow only to the S of 26N by Thursday evening. Mainly light and variable winds and seas of 2 ft or less will then prevail for the end of the week into the upcoming weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: moderate NE winds will pulse during the overnight hours tonight, with seas building to 5 or 6 ft downstream of the Gulf near 11N87W. Light and variable winds and 4 to 6 ft seas, are expected elsewhere to the N of 09N, while moderate to locally fresh southerly winds and 5 to 7 ft seas, are forecast S of 09N through the remainder of the week and the upcoming weekend. REMAINDER OF THE AREA... A 1019 mb high pressure is near 28N125W and extends a ridge SE to near Clarion Island. This system is forecast to remain nearly stationary over the next 24 hours. A surface trough is analyzed across the west-central waters and just N of the monsoon trough. The trough extends from 19N132W to 11N135W. Scattered showers and isolated tstms are near the southern end of the trough axis. A recent altimeter pass indicated seas to 8 ft between the trough axis and 140W. A 1009 mb low pressure system remains embedded within the monsoon trough near 10N121W. An Ascat pass from 1758Z this afternoon highligted winds of 20 kt within 120 nm of the low in the NE quadrant, and within 60 nm of the low in the SE quadrant. Latest satellite imagery shows scattered moderate isolated strong convection within 60 nm NW and SE quadrants of the low. The low is forecast to move NW to near 12N124W by early Thursday afternoon and to near 12N130W by Friday afternoon. A cold front has moved into the far NW corner of the forecast area. The main issue with this front will related to its impacts on wavehieghst. It is followed by a new set of long period NW swell. The front will reach from near 32N130W to 28N134W, and as a weakening stationary front to 28N140W by early Thursday afternoon, then become nearly stationary from 32N130W to 27N140W on Thursday evening and begin to dissipate on Friday. The associated long period NW swell, with seas of 8 to 13 ft seas will propagate SE across the northern forecast waters while decaying. Seas of 8 ft or greater will cover the waters N of 15N W of 115W by late Friday, then begin to subside to near 8 ft throughout the waters by late Sunday. $$ Aguirre