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733
AXPZ20 KNHC 230403
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
220 UTC Mon Jul 23 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 0000 UTC surface analysis and satellite imagery through 0245 UTC.


...TROPICAL WAVES...

A low-latitude tropical wave has an axis extending from 01S80W to 10N80W, moving westward around 20 kt. The wave remains evident in tropical wave model diagnostics as well as a maximum in total precipitable water satellite imagery. Numerous moderate and scattered strong convection is seen from 07n to 10n between 81W and 84W. Scattered moderate and isolated strong convection is evident elsewhere from 05N to 10N between 78W and 89W.

A tropical wave has an axis reaching from 04N95W to the Isthmus of Tehuantepec near 17N94W, moving westward around 20 kt. The wave is evident in 700 mb model guidance streamlines as well as a pronounced maximum in total precipitable water satellite imagery. Numerous moderate and scattered strong convection is occurring within 30 nm either side of a line from 14N97W to 12N100W. Scattered moderate and isolated strong convection is seen elsewhere from 07N to 14N between 92W and 101W.

A tropical wave has an axis extending from 07N125W to newly formed low pressure 1010 mb near 10N125W to 18N124W, moving westward around 20 kt. The wave is associated with broad troughing at 700 mb as depicted in model guidance. Scattered moderate and isolated strong convection is seen from 08N to 11N between 123W and 130W.


...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough axis extends from NW Colombia near 09N73W to just NW of the Panama Canal near 10N80W to 07N93W to 11N113W to 11N123W, then resumes from 10N127W to 10N130W to 12N140W. Aside from convection associated with the tropical waves, scattered moderate and isolated strong convection is observed from 10N to 13N between 108W and 111W and from 08N to 14N between 114W and 123W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A broad and weak high pres ridge extends SE from 32N140W to ESE of the Revillagigedo Islands near 16N106W. The ridge is maintaining light to moderate NW winds across the Mexican offshore waters, except for the Gulf of Tehuantepec area as discussed below. Little change is expected in these conditions during the next several days. A long period SW cross-equatorial swell is affecting the waters S of 20N. This extensive swell event will continue spreading northward, and will cause seas to build to the range of 7-9 ft in the open waters for all the forecast zones through Tue night.

Gulf of Tehuantepec: fresh to strong north winds will pulse over the Gulf one more time through Mon morning before diminishing to light to moderate early Mon afternoon, gentle S to SW Mon night and gentle variable winds Tue. Wind waves generated by the north winds are interacting with the SW swell event resulting in mixed seas south of the Gulf, with sea heights maxing out around 9 ft. This area of 8 ft seas will merge with the much larger area of 8 ft seas approaching from the S on Mon, then seas will gradually subside Tue and Wed.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR...

Gulf of Papagayo: Fresh to strong NE to E winds will pulse during the late night and morning hours through Wed morning before diminishing to fresh. Seas from these NE to E winds will interact with the SW swell event to produce mixed seas in the Gulf as high as high as 10 ft on Mon before seas begin to slowly subside on Tue.

Gentle to moderate NE to E winds are forecast elsewhere N of the monsoon trough which will meander west of Central America between 07N- 10N. Moderate to fresh S to SW winds are generally expected S of the trough axis during the next several days.

A long-period SW cross-equatorial swell event is already affecting the region. Seas along the equator are will peak tonight and Mon between 11 and 12 ft. Seas will then gradually subside Tue through Fri, with the highest seas expected to the west of Ecuador.

REMAINDER OF THE AREA...

A weak surface ridge extends ESE from 32N140W to ESE of the Revillagigedo Islands near 16N106W. The gradient between the ridge and the monsoon trough is generally maintaining moderate trade winds north of the monsoon trough, south of 20N and west of 115W. Little change in this pattern is expected for the upcoming week. Swell producing wave heights to a maximum of 8 ft generated by strong winds N of the area is propagating southward encompassing the discussion waters N of 28.5N and W of 131W. This swell will continue to affect this region while slowly shifting westward and subsiding through Mon evening.

Newly formed low pressure of 1010 mb is located along the tropical wave that extends from 07N125W to 18N124W. The low will generate fresh to strong winds as it tracks WNW to near 12N134W by Wed evening. Fresh to strong winds are forecast from 12N- 15N between 131W- 134W, with seas of 8-10 ft by Wed.

Large long-period SW swell is crossing the equator, with seas of 8 to 11 ft affecting almost all of the waters S of 20N as confirmed by satellite-derived sea height data. The swell will continue to propagate N and cause seas to build to 8 ft or above across most of the area to the south of 25N and east of 133W on Mon. The swell will decay and allow seas to subside Tue through Thu.

$$ CAM

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