AXPZ20 KNHC 190936

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Mon Mar 19 2018

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 0600 UTC surface analysis and satellite imagery through 0915 UTC.


Gale Warning: A weakening cold front over the far northwest portion of the area along a position from 32N137W to 26N140W is preceded by strong southerly flow north of 25N and within 420 nm to its east, along with seas of 8 to 10 ft. A deepening surface low pres system currently northwest of the area at 36N143W will drop southeastward to near 32N140W on Mon night behind this initial cold front, and drag a second cold front into the discussion area accompanied by a strong to near gale southwest- west-northwest wind shift. The pressure gradient will tighten around the southwest semicircle of the low increasing the westerly winds to minimal gale force winds in the range of 30 to 35 kt over the discussion waters from 29N to 30N west of 139W near 0900 UTC on Tue, with the associated seas of 14 to 19 ft forecast from 26N to 32N between 136W and 140W. The low pres will lift north of the area on Tue afternoon, with associated winds diminishing to 20 kt or less south of 32N on Wed evening. The associated NW swell, in the form of 7 to 10 ft seas, will propagate southeastward through the waters covering the area west of a line from the Central Baja peninsula to 06N140W on Sat. Please refer to the Pacific high seas forecast for more details on this upcoming event under AWIPS/WMO headers MIAHSFEP2/FZPN03


A surface trough axis is analyzed from low pres over NW Colombia westward to across northern Panama and to just offshore the border between Costa Rica and Panama continuing to 06N90W to 06N97W, where latest scatterometer winds indicate the ITCZ axis begins and continues to 06N110W to 07N125W and to beyond 07N140W. Scattered moderate isolated strong convection is noted within 180 nm S of the axis between 86W and 88W, also within 60 nm N of the axis between 115W and 118W and within 30 nm of the axis between 118W and 122W.



A north-northwest to south-southeast ridge extending from 30N121W to 17N110W to 13N94W will shift slightly to the southwest through Tue. Fresh to locally strong northerly winds will set up south of 25N and east of the ridge briefly on Mon and Mon night with the pressure gradient then relaxing some on Tue. Light to gentle northerly winds and 3 to 4 ft seas are then expected west of the Baja Peninsula through Wed. Broken to scattered mid and high level clouds are advecting eastward towards northern and central Baja California north of 26N as well as to the northeast in the direction of southern California.

Gulf of California: Moderate to fresh northwest flow is forecast across the entire gulf waters today, with narrow swaths of strong northwest winds expected across the far southern gulf waters late Mon. Seas may build to 6 ft in the longer fetch waters.

Fresh to locally strong northwest to north flow expected across the open Pacific waters from 18N to 23N east of 110W through late tonight with seas building to 8 ft.

Gulf of Tehuantepec: Strong north flow will surge through the gulf waters on Tue evening, increasing to minimal gale force Wed evening. Gale conditions are then expected to continue through Thu morning, with seas building to a maximum of around 14 ft downstream from the gulf near 14.5N95.5W on Wed night.


Gulf of Papagayo: Fresh to locally strong NE nocturnal winds will diminish to moderate winds this afternoon, then increase to strong winds again briefly on Tue night with seas building to 7 ft downstream. A stronger drainage event is forecast to begin on Wed night, and persist into the upcoming weekend.

Gulf of Panama: Fresh northerly winds will diminish to moderate winds this afternoon. Fresh to strong north nocturnal winds are expected to resume on Wed night.

Elsewhere, gentle to moderate offshore flow will prevail N of 07N while light to gentle SW winds are forecast S of 07N.


Please see see Special Features Section above for details on upcoming gale force winds to impact the far NW portion of the area in the short-term.

A very progressive pattern will continue to impact the the northwest portion of the area well into this week. The deep layer low pres system located to the northwest of the area and its related trough is preceded by mid to upper level moisture in the form of overcast cloudiness. Areas of rain along with scattered showers and isolated thunderstorms under upper level divergence that is present to the the east and southeast of this low have moved over the area north of about 27N and west of 120W. These clouds and precipitation will continue advancing eastward towards the general area of southern California and also northern and central Baja California through Wed per model moisture guidance fields.

$$ Aguirre