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Tropical Storm Narda Forecast Discussion Number 11
2019-10-01 04:49:34| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Mon Sep 30 2019 000 WTPZ41 KNHC 010249 TCDEP1 Tropical Storm Narda Discussion Number 11 NWS National Hurricane Center Miami FL EP162019 900 PM MDT Mon Sep 30 2019 Passive microwave satellite imagery, especially a recent 2326 UTC SSMI/S pass, continue to show that a small mid-level eye feature has remained close to the northwestern coast of mainland Mexico since the previous advisory, with the center now located just inland near Los Mochis. Earlier scatterometer surface wind data indicated winds to near 40 kt about 40 n mi south of the center, and extrapolation of the position of those winds would place them near the coast now, and justifies lowering the current intensity to 40 kt. Deep convection near the center has also decreased markedly over the past few hours, further suggesting that the intensity has likely decreased. Narda has continued moving northwestward at an unusually fast forward speed, or 325/17 kt. There is no significant change to the previous track forecast or reasoning. The latest model guidance remains in excellent agreement on Narda maintaining a northwestward trajectory around the southwestern periphery of a large deep-layer ridge for the next 48 hours, with the center remaining inland or very near the coast during that time. The new NHC forecast track is essentially on top of the previous advisory track, and lies close to an average of the tightly packed consensus model tracks. Now that Narda's center has moved inland again over the mountainous terrain of coastal Mainland Mexico, steady weakening is expected during the next 48 hours. However, tropical-storm-force winds are still possible, especially due to funneling along some of the concave-shaped coastlines near Huatabampito and Guaymas before Narda weakens to a depression in 24 hours or so. Terrain interaction should result in the small cyclone becoming a remnant low or dissipating by 48 hours. The main threat posed by Narda continues to be very heavy rainfall, due to large amounts of moisture being advected northward and northeastward over Mexico on the eastern side of the cyclone's circulation. These rains, which could total as much as 15 inches in a few locations, will result in life-threatening flash floods and mudslides. Furthermore, the very humid mid- and upper-level remnant moisture plume is expected to spread northeastward across northern Mexico and into portions of the U.S. Southern and Central Plains through at least Wednesday, enhancing the threat for heavy rainfall and flash flooding in these areas. For additional information, please see excessive rainfall products issued by the NOAA Weather Prediction Center at https://www.wpc.ncep.noaa.gov/qpf/excess_rain.shtml. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 25.7N 109.0W 40 KT 45 MPH...INLAND 12H 01/1200Z 26.9N 110.0W 35 KT 40 MPH...OVER WATER NEAR COAST 24H 02/0000Z 28.5N 111.0W 30 KT 35 MPH...INLAND 36H 02/1200Z 29.4N 111.7W 25 KT 30 MPH...INLAND 48H 03/0000Z...DISSIPATED INLAND $$ Forecaster Stewart
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