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| #1025406 (Received by flhurricane at: 4:06 AM 15.Nov.2020) TCDAT1 Hurricane Iota Discussion Number 8 NWS National Hurricane Center Miami FL AL312020 400 AM EST Sun Nov 15 2020 Iota has continued to rapidly intensify, strengthening 35 kt during the past 24 hours. Deep convection has increased in vertical depth and has also expanded, producing a symmetrical Central Dense Overcast (CDO) with a large area of cloud tops colder than -80C surrounding the center. Upper-level outflow has also improved in all quadrants as the deep-layer vertical wind shear has finally abated. An Air Force Reserve reconnaissance investigating Iota early this morning measured a peak 700-mb flight-level wind speed of 76 kt on its outbound leg, which equates to about a 68-kt equivalent surface wind speed. The second center dropsonde pressure was 987 mb with a 21-kt surface wind, which equals about 985 mb, a pressure drop of 4 mb in a little more than an hour. Based on these data, the intensity has been increased to 70 kt for this advisory. Iota has recently wobbled to the northwest, but the best motion estimate is 280/05 kt. An expansive ridge extending westward from the Atlantic across Florida and over the Gulf of Mexico will keep Iota moving in a westward to west-northwestward motion for the next few days, resulting in a Central America landfall in about 48 hours, close to where former Hurricane Eta made landfall earlier this month. As low-level ridging increases southward across the Gulf of Mexico on days 3 and 4, Iota is expected to move westward farther inland over Central America and dissipate by day 5. The new NHC model guidance remains in good agreement on this developing track scenario. The new official track forecast is a little north of the previous advisory track, primarily due to the more northward initial position, and lies along the southern edge of the guidance between the consensus models TVCN, NOAA-HCCA, and FSSE. The atmospheric and oceanic conditions are expected to be very conducive for continued rapid strengthening, characterized by low shear less than 5 kt, moist mid-tropospheric air, and sea-surface temperatures of 28.5-29.0 deg C. Therefore, rapid intensification is explicitly forecast for the next 48 hours, with Iota expected to become a category 4 hurricane before it reaches central America. The official intensity forecast is very similar to the bulk of the intensity guidance, but lies a little below the Decay-SHIPS and LGEM models, which bring Iota to 120-125 kt just prior to landfall. The slightly lower intensity is due to the warm water east of Nicaragua becoming a more shallow, which could result in some cold some upwelling, plus a possible eyewall replacement cycle (ERC) occurring. After Iota moves inland, rapid weakening is forecast as the hurricane moves over the rugged terrain of Nicaragua and southern Honduras. The new NHC intensity forecast is similar to a blend of the IVCN, HCCA, and FSSE consensus models. Key Messages: 1. Iota is expected to rapidly intensify and be a major hurricane when it approaches the coast of Central America. A Hurricane Warning has been issued for portions of the coast of Nicaragua and Honduras, and hurricane conditions and a dangerous storm surge are expected there beginning Monday. 2. Hurricane conditions are expected and storm surge impacts are possible on Providencia beginning late Sunday night. Tropical storm conditions are expected and hurricane conditions are possible by Sunday evening on San Andres. 3. Through Thursday, heavy rainfall from Iota will likely lead to life-threatening flash flooding and river flooding across portions of northern Colombia and Central America. Flooding and mudslides in Honduras and Nicaragua could be exacerbated by Hurricane Etas recent effects there, resulting in significant to potentially catastrophic impacts. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 13.1N 77.3W 70 KT 80 MPH 12H 15/1800Z 13.4N 78.4W 80 KT 90 MPH 24H 16/0600Z 13.7N 80.1W 95 KT 110 MPH 36H 16/1800Z 14.1N 81.7W 110 KT 125 MPH 48H 17/0600Z 14.3N 83.1W 115 KT 130 MPH 60H 17/1800Z 14.3N 84.4W 65 KT 75 MPH...INLAND 72H 18/0600Z 14.2N 85.7W 35 KT 40 MPH...INLAND 96H 19/0600Z 13.9N 88.7W 20 KT 25 MPH...INLAND 120H 20/0600Z...DISSIPATED $$ Forecaster Stewart |
