AXPZ20 KNHC 291655

1605 UTC SUN MAY 29 2016

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 1200 UTC surface analysis and satellite imagery through 1430 UTC.


A tropical wave is along 82W, moving westward at 10 to 15 knots. Scattered to numerous strong convection is present from 03N to 07N between 77W and 81W.


The monsoon trough passes through 11N86W to a 1010 mb low pressure center near 10N95W, to 09N100W, to 13N115W, to a 1010 mb low pressure center near 11N121W, and to 10N125W. The ITCZ continues from 10N125W to 08N131W, and to 06N140W. Scattered moderate to isolated strong convection is found from 06N to 13N between 100W and 108W. Scattered moderate convection is located from 04N to 07N between 138W and 140W.

A 1010 mb low pressure center is near 11N121W. Numerous strong convection exists within 120 nm nw and se of the monsoon trough between 118W and 125W.


Northerly winds are continuing to the north of the area along the California coast as a cold front moves inland. Latest ASCAT imagery shows fresh to strong north winds from 33N to 42N east of 128W. Latest altimetry shows an area of combined seas between 8 and 11 feet just to the north of the forecast area. As the cold front moves farther inland...winds and seas will subside. North swell will maintain sea heights of 8 to 9 feet north of 27N between 122W and 128W today. Seas are expected to subside below 8 feet tonight. Winds and seas will continue to subside north of 23N through Tuesday night.

A surface ridge extends northwestward from 21N119W to beyond 32N137W. Surface high pressure covers the eastern Pacific Ocean from 16N northward from 115W westward. Latest ASCAT winds generally show light to moderate north to northeast winds north of the the ITCZ and monsoon trough to 22N from 118W westward.

A 1010 mb low pressure center is near 11N121W. The latest scatterometer data from 29/0500 utc showed 20 to 25 knot wind speeds near the low center. Model guidance quickly weakens the low. Convection associated with the low has begun to decrease. Maintained 20 to 25 knot winds in the vicinity of the low in the forecast for the next 6 hours. After 6 hours the area of seas associated with the low merges with the area of seas associated with southern hemisphere swell. After this low weakens...model guidance does not develop any areas of fresh to moderate winds in the vicinity of the trough through Friday.

Latest altimetry showed 10 to 12 foot seas associated with long period S to SW swell beginning to arrive from the southern hemisphere. The only model capturing these sea heights well was the European model. Accordingly...the latest wave height forecast for the eastern Pacific during the next 48 hours heavily favors European model guidance. All of the forecast models agree that the long period swell have begun to decay and that seas across the basin will subside below 8 ft by Thursday evening.

$$ McElroy