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Hurricane Iota Forecast Discussion Number 10

2020-11-15 21:37:21| National Hurricane Center (Atlantic)

Issued at 400 PM EST Sun Nov 15 2020 000 WTNT41 KNHC 152037 TCDAT1 Hurricane Iota Discussion Number 10 NWS National Hurricane Center Miami FL AL312020 400 PM EST Sun Nov 15 2020 The satellite presentation of Iota has continued to improve this afternoon. A ragged eye has become apparent in visible satellite imagery, with excellent banding features surrounding it. An Air Force Reserve Hurricane Hunter aircraft measured a minimum central pressure of 977 mb during its first pass through the center earlier this afternoon, and recorded around 974 mb on its second pass. Somewhat surprisingly, the plane only measured peak 700-mb flight-level winds of 74 kt and SFMR winds of 68 kt. Those winds support an intensity slightly lower than what was previously estimated, but given the low central pressure and downward trend, plus the fact that the plane only made a single pass in each quadrant, it is possible that the maximum winds were not sampled. In addition, the satellite presentation and pressure fall may be preceding the winds slightly. Therefore, the initial is again set at 80 kt. Another Air Force Reserve reconnaissance aircraft is en route and should provide additional information on Iota's intensity this evening. Very favorable atmospheric and oceanic conditions consisting of low vertical wind shear and warm waters are expected to lead to rapid strengthening until the center crosses the coast of Central America. The NHC intensity forecast again calls for Iota to reach major hurricane strength tonight, and become an extremely dangerous category 4 hurricane before it reaches the coast of Central America Monday night. The NHC intensity forecast is similar to the previous advisory and shows a peak slightly above the latest HFIP corrected consensus model. After landfall, rapid weakening should occur as Iota moves over the mountainous terrain of Central America. Iota is moving westward to west-northwestward at about 8 kt. The track forecast philosophy is unchanged from before. A strong mid-level ridge that extends across the western Atlantic and Florida will steer Iota westward to west-northwestward through landfall Monday night. Once Iota moves over Central America, a westward to west-southwestward motion is expected. The updated NHC track forecast has been adjusted southward through 24 hours, but little overall change was required thereafter. The official forecast lies near the middle of the tightly clustered dynamical model envelope. In addition to potentially catastrophic winds, Iota is expected to bring a life-threatening storm surge and extreme rainfall impacts to portions of Central America. This comes less than two weeks after Hurricane Eta significantly impacted the area. Key Messages: 1. Iota is expected to continue to rapidly intensify and be an extremely dangerous category 4 hurricane when it approaches the coast of Central America on Monday. Potentially catastrophic winds and a life-threatening storm surge are expected along portions of the coast of northeastern Nicaragua and eastern Honduras where a hurricane warning is in effect. 2. Hurricane conditions are expected and storm surge impacts are possible on Providencia tonight and Monday. Tropical storm conditions are expected and hurricane conditions are possible on San Andres. 3. Through Friday morning, heavy rainfall from Iota will likely lead to life-threatening flash flooding and river flooding across portions of 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 15/2100Z 13.3N 79.3W 80 KT 90 MPH 12H 16/0600Z 13.6N 80.5W 100 KT 115 MPH 24H 16/1800Z 14.0N 82.1W 120 KT 140 MPH 36H 17/0600Z 14.3N 83.6W 105 KT 120 MPH...INLAND 48H 17/1800Z 14.4N 84.9W 60 KT 70 MPH...INLAND 60H 18/0600Z 14.3N 86.3W 35 KT 40 MPH...INLAND 72H 18/1800Z 14.1N 87.9W 25 KT 30 MPH...INLAND 96H 19/1800Z...DISSIPATED $$ Forecaster Brown

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Hurricane Iota Forecast Discussion Number 9

2020-11-15 15:36:51| National Hurricane Center (Atlantic)

Issued at 1000 AM EST Sun Nov 15 2020 000 WTNT41 KNHC 151436 TCDAT1 Hurricane Iota Discussion Number 9 NWS National Hurricane Center Miami FL AL312020 1000 AM EST Sun Nov 15 2020 Iota continues to rapidly strengthen. The hurricane has an impressive appearance in visible satellite imagery with a very symmetric Central Dense Overcast and excellent banding features in all quadrants. The outflow has become well established and recent microwave satellite imagery has shown a 37-GHz eye feature and a mid-level eye that was not quite closed. A TAFB Dvorak classification of T4.5 was the basis for the 75-kt 1200 UTC analyzed intensity, and with the continued improvement in structure the advisory wind speed is set at 80 kt. An Air Force Reserve Hurricane Hunter aircraft is currently en route to the storm. Iota is located within an extremely conducive environment for strengthening. The upper-level wind pattern is forecast to remain quite favorable while the storm crosses sea surface temperatures of 28.5-29 degrees C. As a result, continued rapid strengthening is expected during the next 24 to 36 hours, and Iota is forecast to become a potentially catastrophic category 4 hurricane before it reaches the coast of northeastern Nicaragua or eastern Honduras. A difficult-to-predict eyewall replacement cycle could cause the intensity to begin to level off when Iota nears the coast. The new NHC intensity forecast calls for continued rapid strengthening and is in good agreement with the SHIPS and HFIP corrected consensus models. After landfall, rapid weakening should occur as Iota moves over the mountainous terrain of Central America. The hurricane has begun moving faster toward the west-northwest, with a long-term motion estimate of 285/8 kt. The steering currents ahead of Iota are well established as a strong mid-level ridge is located over the western Atlantic and Florida. This should keep Iota on a westward to west-northwestward heading through landfall. After landfall, a westward to west-southwestward track is anticipated. The global models are in good agreement on this scenario and the updated NHC track forecast is only adjusted a little north of the previous track to be closer to the latest multi-model consensus aids. Key Messages: 1. Iota is expected to continue to rapidly intensify and be an extremely dangerous category 4 hurricane when it approaches the coast of Central America on Monday. Potentially catastrophic winds and a life-threatening storm surge are expected along portions of the coast of northeastern Nicaragua and eastern Honduras where a hurricane warning is in effect. 2. Hurricane conditions are expected and storm surge impacts are possible on Providencia tonight and Monday. Tropical storm conditions are expected and hurricane conditions are possible by this 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 15/1500Z 13.3N 78.5W 80 KT 90 MPH 12H 16/0000Z 13.8N 79.7W 95 KT 110 MPH 24H 16/1200Z 14.2N 81.4W 110 KT 125 MPH 36H 17/0000Z 14.4N 82.9W 120 KT 140 MPH 48H 17/1200Z 14.5N 84.3W 80 KT 90 MPH...INLAND 60H 18/0000Z 14.4N 85.5W 45 KT 50 MPH...INLAND 72H 18/1200Z 14.3N 86.8W 30 KT 35 MPH...INLAND 96H 19/1200Z 13.8N 89.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 20/1200Z...DISSIPATED $$ Forecaster Brown

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Tropical Depression Theta Forecast Discussion Number 22

2020-11-15 09:37:15| National Hurricane Center (Atlantic)

Issued at 900 AM GMT Sun Nov 15 2020 000 WTNT45 KNHC 150837 TCDAT5 Tropical Depression Theta Discussion Number 22 NWS National Hurricane Center Miami FL AL302020 900 AM GMT Sun Nov 15 2020 Theta is barely a tropical cyclone. The only remnants of deep convection are a small area of warming cloud tops, located around 90 n mi to the southeast of Theta's exposed center. The cyclone has produced little central convection all day, so it is assumed that at least slight weakening has occurred and the intensity is set at 30 kt. This also agrees with a blend of the latest Dvorak Final-T and CI numbers from TAFB. If Theta does not redevelop substantial inner-core convection soon, it will likely become a remnant low later today. The cyclone has slowed down and is moving eastward with an initial motion of 090/4 kt. A continued slow eastward track is expected today, before a ridge centered over northwestern Africa begins to steer the cyclone northward on Monday. Although Theta could continue to produce intermittent bursts of convection, no significant redevelopment is anticipated due to surrounding dry air and cool underlying SSTs. The cyclone is forecast to become a remnant low within 12 h and dissipate in 60 h. No major changes were made to the NHC track or intensity forecasts, both of which are based on the multi-model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 31.8N 18.3W 30 KT 35 MPH 12H 15/1800Z 31.9N 17.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 16/0600Z 33.1N 17.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 16/1800Z 35.5N 16.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 17/0600Z 39.0N 14.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 17/1800Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Storm Theta Forecast Discussion Number 21

2020-11-15 03:36:44| National Hurricane Center (Atlantic)

Issued at 300 AM GMT Sun Nov 15 2020 000 WTNT45 KNHC 150236 TCDAT5 Tropical Storm Theta Discussion Number 21 NWS National Hurricane Center Miami FL AL302020 300 AM GMT Sun Nov 15 2020 Theta remains a highly sheared but resilient tropical cyclone with little change in its satellite appearance since the previous advisory. A persistent band of deep convection to the southeast of Theta remains within about 60 n mi of the storm center, despite a hostile environment characterized by dry mid-level air and 40-50 kt of northerly shear. Unfortunately, several scatterometer passes this evening missed the core of the cyclone. Since the satellite presentation is generally unchanged from earlier today, the initial intensity is held at 35 kt, which is consistent with a T2.5 Dvorak classification received from TAFB. Strong northerly shear and continued dry air entrainment will eventually take a toll on Theta, but recent satellite trends and the latest GFS simulated satellite imagery suggest that the cyclone could remain tropical a little longer than previously forecast. The latest NHC intensity forecast keeps Theta as a 35-kt tropical storm at 12 h before weakening it into a remnant low by 24 h. This follows the consensus of the latest intensity guidance. Thereafter, continued weakening is expected through its dissipation early next week. Theta is still moving eastward at around 4 kt. The cyclone should begin turning northeastward later today, and then accelerate north-northeastward on Monday as the shallow remnant low is steered by a low-level ridge centered over northwestern Africa. The remains of Theta are forecast to open up into a trough and dissipate by 60 h ahead of an approaching cold front over the northeastern Atlantic. The latest NHC track forecast is adjusted slightly to the left of the previous one, which generally follows the latest track consensus aids. On the forecast track, the remnant low of Theta is expected to pass near the island of Madeira late Sunday night or early Monday. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 31.7N 18.7W 35 KT 40 MPH 12H 15/1200Z 31.9N 18.0W 35 KT 40 MPH 24H 16/0000Z 32.6N 17.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 16/1200Z 34.2N 17.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 17/0000Z 36.7N 15.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 17/1200Z...DISSIPATED $$ Forecaster Reinhart/Cangialosi

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Tropical Storm Iota Forecast Discussion Number 7

2020-11-15 03:32:38| National Hurricane Center (Atlantic)

Issued at 1000 PM EST Sat Nov 14 2020 000 WTNT41 KNHC 150232 TCDAT1 Tropical Storm Iota Discussion Number 7 NWS National Hurricane Center Miami FL AL312020 1000 PM EST Sat Nov 14 2020 Iota continues to strengthen. Deep convection has been increasing in coverage and intensity near the center, and microwave images indicate that the inner core is becoming better defined. The Dvorak classifications at 00Z supported an intensity of 55 kt, and since the thunderstorms continue to organize, the initial wind speed is set a little higher to 60 kt. The Air Force Hurricane Hunters will be investigating Iota overnight. Iota has slowed a little and has now turned westward, with the latest initial motion estimated to be 270/4 kt. A ridge over Florida and the western Atlantic is expected to remain to the north of Iota. This high pressure system, and another ridge over Mexico and the western Gulf, should steer the storm westward to west-northwestward during the next couple of days and then westward to west-southwestward after that. This motion should take the core of Iota to the coast of Nicaragua Monday night. The models are in good agreement, and the NHC track forecast is largely an update of the previous one. The atmospheric and oceanic conditions appear quite favorable for Iota to continue strengthening until it reaches the coast in a little more than 2 days. Since the storm appears to be developing an inner core, rapid strengthening during the next couple of days seems likely. All of the intensity models show a significant amount of strengthening before landfall, and are higher than the previous cycle. Based on the latest guidance and favorable conditions, the NHC intensity forecast is above the previous one and shows Iota becoming a hurricane soon and a major hurricane in 36 hours. After Iota moves inland, rapid weakening is forecast as the cyclone moves over the rugged terrain of Nicaragua and southern Honduras. The NHC forecast lies close to the HCCA and IVCN consensus aids. Key Messages: 1. Iota is expected to 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 Central America. Flooding and mudslides in Honduras and Nicaragua could be exacerbated by Hurricane Etas recent effects there, resulting in significant impacts. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 12.7N 77.0W 60 KT 70 MPH 12H 15/1200Z 12.9N 77.9W 75 KT 85 MPH 24H 16/0000Z 13.3N 79.5W 90 KT 105 MPH 36H 16/1200Z 13.7N 81.2W 105 KT 120 MPH 48H 17/0000Z 14.0N 82.7W 110 KT 125 MPH 60H 17/1200Z 14.1N 84.0W 80 KT 90 MPH...INLAND 72H 18/0000Z 14.0N 85.2W 45 KT 50 MPH...INLAND 96H 19/0000Z 13.6N 87.8W 25 KT 30 MPH...INLAND 120H 20/0000Z...DISSIPATED $$ Forecaster Cangialosi

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