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AXPZ20 KNHC 181602
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Fri Aug 18 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 1200 UTC surface analysis and satellite imagery through 1545 UTC.


...SPECIAL FEATURE...

Hurricane Warning...Tropical Depression 13-E has formed at 14.8N 116.5W, or about 705 miles SW of the southern tip of the Baja California Peninsula. Central pressure is estimated at 1006 mb. Maximum sustained winds are 30 kt with gusts to 40 kt. Scattered strong convection is currently observed in bands within 180 nm over the N, and within 240 nm over the S semicircles of the center. The system is expected to strengthen to a tropical storm within 12 hours, and then gradually strengthen to a minimal hurricane in 48 hours. Refer to National Hurricane Center Forecast Advisory under WMO/AWIPS headers WTPZ23 KNHC/MIATCMEP3, and the High Seas Forecast under WMO/AWIPS headers FZPN03 KNHC/MIAHSFEP2 for additional information.


..TROPICAL WAVES AND TROPICAL LOWS...

A tropical wave is analyzed to the N of 05N between 95W AND 97W. This wave has been progressing W at about 18 kts over the past 24 hours, but is expected to slow it's forward speed somewhat over the next few days. Scattered moderate isolated strong convection is observed within 150 nm E, and within 240 nm W of the wave axis.

A tropical wave is analyzed from 13N112W to 23N109W, and has moved W at 15 kt over the past 24 hours. Scattered moderate and isolated strong convection is observed to the N of 20N within 60 nm either side of the wave axis.

A 1009 mb surface low is analyzed N of the monsoon trough at 17N128W. Fresh NE to E winds are observed within 390 nm over the NW semicircle of the low with seas of 6 to 7 ft. Isolated strong convection has been flaring intermittently within 180 nm over the S semicircle. The low is forecast to move w and weaken into to open trough tonight.

The remnants of former tropical cyclone Jova continue to spin near 18N140W with a pressure of about 1010 mb. Scattered moderate convection is currently noted within 120 nm over the NE quadrant of the low. The pressure gradient is supporting moderate to locally fresh N to NE winds and 6 to 7 ft seas within 420 nm over the NE quadrant of the low. The low is forecast to move W of 140W today.


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

The monsoon trough extends W across the far SW Caribbean from 09N76W to across the northern Gulf of Panama to the Pacific Coast of Costa Rica at 09N84W, then turns slightly W-SW to 07N103W, then NW to 08N108W where it loses identity. The monsoon trough resumes SW of the newly formed TD 13-E and extends SW to 10N125W, then W to 11N134W, then NW to beyond 13N140W.

Except as previously mentioned, scattered moderate isolated strong convection is noted off the Pacific Coast of Colombia from 02N to 08N to the of 82W. Similar convection is noted along the monsoon trough within 75 nm either side of a line from 09N83W to 07N98W to 10N102W, within 75 nm of 08.5N110W, and within 180 nm either side of a line from 07N117W to 11N124W to 09N140W.
...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A NW to SE orientated low level trough will meander E to W across the Baja California Peninsula and Gulf of California through Mon night with a surface low developing intermittently along the trough over the far northern Gulf of California waters. A NW to SE orientated ridge extends across the offshore waters W of the southern tip of Baja. A moderate NW breeze is forecast through the weekend to the W of the Baja California Peninsula, except the pressure gradient will tighten each evening with fresh NW flow within 90 nm of the Baja coast with 3 to 6 ft seas.

Gulf of California...light to gentle southerly flow will persist across the Gulf of California through the upcoming weekend, except a moderate to locally fresh breeze will surround the low pressure center over the waters N of 29.5N.

Gulf of Tehuantepec: fresh to locally brief and strong N drainage winds are forecast during the overnight hours with seas building to 8 ft downstream of the Gulf waters near 15N95W.

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

Gulf of Papagayo: moderate nocturnal drainage forecast through the weekend.

Otherwise, light and variable to gentle NE to E flow expected N of the monsoon trough throughearly Mon, while moderate to locally fresh southerly winds are expected S of the monsoon trough axis with 3 to 6 ft seas throughout.

REMAINDER OF THE AREA...

The subtropical ridge extends from 32N136W to near 23N116W. Except as previously mentioned in the above paragraphs, moderate to locally fresh anticyclonic flow is forecast N of the monsoon trough and W of 120W.

$$ Nelson

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