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Subtropical Storm Alberto Forecast Discussion Number 4

2018-05-26 10:53:25| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Sat May 26 2018 000 WTNT41 KNHC 260853 TCDAT1 Subtropical Storm Alberto Discussion Number 4 NWS National Hurricane Center Miami FL AL012018 400 AM CDT Sat May 26 2018 Alberto is not very well organized this morning. Satellite images indicate that the low-level center is located between widespread showers and thunderstorms well to its northeast and patches of deep convection to its south and east. The struggling cyclone continues to battle westerly shear and dry air. A recent ASCAT pass indicated that winds near the center were not particularly strong. The initial intensity is held at a possibly generous 35 kt pending a sampling of the circulation farther east by an Air Force reconnaissance aircraft in a few hours. Alberto remains subtropical given its sprawling structure and involvement with an upper-level trough. The subtropical storm has now turned north-northeastward at an estimated speed of 6 kt. This general motion with a increase in forward speed is expected throughout the day today, taking the center of Alberto through the Yucatan Channel. A turn to the northwest is forecast on Sunday as the storm rotates around a developing mid- to upper-level low in the central Gulf of Mexico. Alberto is predicted to be very near the northern Gulf Coast in about 72 hours, and should then turn northward and northeastward when it moves inland over the eastern U.S. The models are in fairly good agreement this cycle, but they have trended a bit faster from previous runs. The NHC track forecast has been adjusted accordingly, and lies fairly close to the latest consensus aids. Only slow strengthening is expected today due to the broad nature of the system and continued influences of westerly shear and dry air. There is an opportunity for more significant strengthening tonight and Sunday when the shear is expected to lessen and Alberto moves into a region of upper-level diffluence while it remains over warm SSTs. The models also suggest that Alberto will likely make a transition to a tropical storm in about 36 hours, and that is reflected in the official forecast below. The official intensity forecast is fairly similar to the previous one, and is in line with the IVCN and HCCA consensus models. The HMON model is now the only intensity guidance that makes Alberto a hurricane before it reaches the coast. Although a hurricane watch could still be required for a portion of the Gulf Coast later today, the recent intensity guidance trends suggest that this possibility is decreasing. KEY MESSAGES: 1. Regardless of its exact track and intensity, Alberto is expected to produce heavy rainfall and flash flooding over western Cuba, southern Florida and the Florida Keys. Rainfall and flooding potential will increase across the central U.S. Gulf Coast region and over much of the southeastern United States beginning Sunday. 2. Tropical-storm-force winds and hazardous storm surge are possible along portions of the central and eastern U.S. Gulf Coast beginning on Sunday, including areas well east of the track of Alberto's center, and tropical storm and storm surge watches are in effect for portions of these areas. Residents in the watch areas are encouraged not to focus on the details of the forecast track of Alberto and should follow any guidance given by their local government officials. 3. Dangerous surf and rip current conditions are affecting portions of the Yucatan Peninsula and western Cuba and will likely spread along the eastern and central U.S. Gulf Coast later today and tonight. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 19.9N 85.6W 35 KT 40 MPH 12H 26/1800Z 21.6N 85.1W 35 KT 40 MPH 24H 27/0600Z 24.3N 85.0W 40 KT 45 MPH 36H 27/1800Z 26.2N 85.9W 50 KT 60 MPH...TROPICAL STORM 48H 28/0600Z 27.5N 86.8W 55 KT 65 MPH...TROPICAL STORM 72H 29/0600Z 30.4N 87.9W 50 KT 60 MPH...NEAR THE COAST 96H 30/0600Z 33.3N 88.1W 25 KT 30 MPH...INLAND 120H 31/0600Z 38.0N 85.0W 20 KT 25 MPH...INLAND $$ Forecaster Cangialosi/Berg

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Subtropical Storm Alberto Forecast Discussion Number 3

2018-05-26 04:45:22| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Fri May 25 2018 000 WTNT41 KNHC 260245 TCDAT1 Subtropical Storm Alberto Discussion Number 3 NWS National Hurricane Center Miami FL AL012018 1000 PM CDT Fri May 25 2018 Satellite imagery, earlier aircraft data, and surface observations indicate that Alberto is rather disorganized. A prominent mid-level center is near the western tip of Cuba, with the convection somewhat organized around it. However, the low-level center is about 170 n mi south-southwest of the mid-level center. There are no recent observations of gale-force winds, so the initial intensity will remain an uncertain 35 kt. An upper-level trough just to the west and northwest of the cyclone is advecting cool and dry air into Alberto, and thus the system remains a subtropical cyclone at this time. The initial motion is a somewhat uncertain 090/4. Alberto should turn northward during the next 12 h or so in response to the nearby upper-level trough, with this motion continuing through about 36 h. After that, a north-northwestward motion is likely as the aforementioned trough becomes a closed low over the central Gulf of Mexico and Alberto moves around the northeast side. This evolution should cause Alberto to move through the eastern Gulf of Mexico during the next 2-3 days, and then make landfall on the northern Gulf Coast between 72-96 h. After landfall, Alberto should continue northward through the southeastern United States. The new forecast track is nudged a bit to the east of the previous track during the first 36 h based on the initial position, and it lies just to the west of the consensus models. One uncertainty in the track forecast is the possibility that the center could re-form to the north, which at the least could change the timing of the forecast track. The dynamical models forecast Alberto to reach an area of stronger upper-level divergence in about 24 h, with the models agreeing on more significant development starting about that time. The intensity forecast shows a slower development rate for the first 24 h than the previous forecast, then shows a faster development to the 55-kt peak intensity of the previous forecast. After landfall, Alberto should quickly weaken over land. The new intensity forecast is near the intensity consensus and the SHIPS model. Some of the intensity guidance suggests that Alberto could become a hurricane before landfall. If the guidance trends stronger, a hurricane watch could be needed for a portion of the Gulf Coast on Saturday. KEY MESSAGES: 1. Regardless of its exact track and intensity, Alberto is expected to produce heavy rainfall and flash flooding over the northeastern Yucatan Peninsula of Mexico, western Cuba, southern Florida and the Florida Keys. Rainfall and flooding potential will increase across the central U.S. Gulf Coast region and the southeastern United States later this weekend and early next week when Alberto is expected to slow down after it moves inland. 2. Tropical-storm-force winds and hazardous storm surge are possible along portions of the central and eastern U.S. Gulf Coast beginning on Sunday, including areas well east of the track of Alberto's center, and tropical storm and storm surge watches are in effect for portions of these areas. Residents in the watch areas are encouraged not to focus on the details of the forecast track of Alberto and should follow any guidance given by their local government officials. 3. Dangerous surf and rip current conditions are affecting portions of the Yucatan Peninsula and western Cuba and will likely spread along the eastern and central U.S. Gulf Coast later this weekend. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 19.4N 85.7W 35 KT 40 MPH 12H 26/1200Z 20.7N 85.4W 35 KT 40 MPH 24H 27/0000Z 22.9N 85.1W 40 KT 45 MPH 36H 27/1200Z 25.4N 85.4W 50 KT 60 MPH 48H 28/0000Z 27.0N 86.3W 55 KT 65 MPH...TROPICAL CYCLONE 72H 29/0000Z 29.5N 87.5W 55 KT 65 MPH...TROPICAL CYCLONE 96H 30/0000Z 32.5N 88.0W 30 KT 35 MPH...INLAND 120H 31/0000Z 36.5N 85.5W 20 KT 25 MPH...INLAND $$ Forecaster Beven

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Subtropical Storm Alberto Forecast Discussion Number 2

2018-05-25 22:58:19| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Fri May 25 2018 000 WTNT41 KNHC 252058 TCDAT1 Subtropical Storm Alberto Discussion Number 2 NWS National Hurricane Center Miami FL AL012018 400 PM CDT Fri May 25 2018 The inner-core low-level wind field of Alberto has changed little since the previous advisory based on recent data from an Air Force Reserve reconnaissance aircraft, along with land and ship observations. However, the convective structure of the cyclone has degraded over the past several hours due a pronounced intrusion of dry mid-/upper-level air and the cloud pattern continues to exhibit the structure of a subtropical cyclone. The lowest pressure measured thus far by the aircraft has been 1006 mb. The initial position is a little north of the recon position of a pronounced swirl due to the broad overall nature of the low-level circulation. The initial motion estimate is 090/02 kt, but this is considered to be a short-term motion. A gradual turn toward the north should begin later tonight due to a strong ridge located to the east across the Greater Antilles. A steadier northward motion is forecast to occur by Saturday evening and continue into Sunday as a sharp mid/upper-level trough digging southward into the central Gulf of Mexico combines with southerly flow around the western portion of a large subtropical ridge to produce deep-layer southerly flow across Alberto. By 48 hours and continuing through 72 hours, the developing mid/upper-level low over the central Gulf should cause the cyclone to turn northwestward and accelerate until it nears the Gulf Coast by Monday night. After that, steering currents are forecast to collapse as a broad weakness develops in the subtropical ridge axis located along the Gulf coast. Slow but steady recurvature into the westerlies across the Deep South is expected to begin by 96-120 h. The new NHC forecast track is similar to the previous advisory, and closely follows the consensus models TVCN and HCCA, and the Florida State Superensemble (FSSE) model. The broad nature of the inner-core wind field, along with strong westerly wind shear in excess of 20 kt is forecast to continue for the next 24 hours. The latest model runs actually decrease the shear sooner than previously forecast, but the ragged nature of the wind field should prevent any significant intensification until after 48 hours. As a result, only slow but steady strengthening is expected for the next 3 days, and Alberto could peak around 60 kt around 60 hours when the storm will be in a low wind shear regime and over SSTs greater than 28 deg C. However, proximity to dry mid- level air around landfall could hinder any additional strengthening, and the NHC intensity forecast remains similar to the previous advisory, closely following a blend of the HCCA and ICON consensus models and the FSSE model. The new NHC forecast necessitates the issuance of tropical storm and storm surge watches for portions of the U.S. Gulf Coast at this time. Note that if the intensity forecast increases with later advisories, a hurricane watch could be needed for a portion of the Gulf Coast. KEY MESSAGES: 1. Regardless of its exact track and intensity, Alberto is expected to produce heavy rainfall and flash flooding over the northeaster Yucatan Peninsula of Mexico, western Cuba, southern Florida and the Florida Keys. Rainfall and flooding potential will increase across the central U.S. Gulf Coast region and the southeastern United States later this weekend and early next week when Alberto is expected to slow down after it moves inland. 2. Tropical-storm-force winds and hazardous storm surge are possible along portions of the central and eastern U.S. Gulf Coast beginning on Sunday, including areas well east of the track of Alberto's center, and tropical storm and storm surge watches have been issued for portions of these areas. Residents in the watch areas are encouraged not to focus on the details of the forecast track of Alberto and should follow any guidance given by their local government officials. 3. Dangerous surf and rip current conditions are affecting portions of the Yucatan Peninsula and western Cuba and will likely spread along the eastern and central U.S. Gulf Coast later this weekend. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 19.4N 86.3W 35 KT 40 MPH 12H 26/0600Z 20.7N 86.0W 40 KT 45 MPH 24H 26/1800Z 22.5N 85.7W 45 KT 50 MPH 36H 27/0600Z 24.8N 85.6W 50 KT 60 MPH 48H 27/1800Z 26.8N 86.2W 55 KT 65 MPH...TROPICAL STORM 72H 28/1800Z 29.0N 87.8W 55 KT 65 MPH...TROPICAL STORM 96H 29/1800Z 31.7N 88.6W 30 KT 35 MPH...INLAND 120H 30/1800Z 35.2N 87.6W 20 KT 25 MPH...INLAND $$ Forecaster Stewart

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Subtropical Storm Alberto Forecast Discussion Number 1

2018-05-25 16:44:13| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Fri May 25 2018 000 WTNT41 KNHC 251444 TCDAT1 Subtropical Storm Alberto Discussion Number 1 NWS National Hurricane Center Miami FL AL012018 1000 AM CDT Fri May 25 2018 The broad low pressure system that the NHC has been tracking for the past several days over the Yucatan Peninsula has finally moved offshore over the waters of the northwestern Caribbean Sea. Although the system possesses multiple low-level circulations, the overall larger circulation has improved since yesterday. Given that the system has been interacting with a sharp upper-level trough, the strongly sheared low has been designated a subtropical storm. The initial intensity is based on buoy and ship observations of 30-35 kt. Ship 3ETA7 located just northeast of the center at 1100Z reported 45-kt winds at 50 meters elevation. Those winds equate to 35-40 kt at 10 meters elevation. An Air Force Reserve Hurricane Hunter Aircraft is scheduled to investigate Alberto later this afternoon and provide more information on the storm's structure and intensity. The initial motion estimate is an uncertain 020/05 kt. The broad inner-core wind field and multiple swirls makes the short-term motion forecast a little tricky. However, a large subtropical ridge to the east should generally induce a slow north to north- northeastward motion for the next 24 hours or so. After that, the ridge across the western Atlantic and Florida, along with a mid/upper-level low forecast to develop over the central Gulf of Mexico, should result in a faster northward motion at 36-48 hours, followed by a gradual turn toward the northwest around the northern fringe of the aforementioned mid/upper-level low. By 96 hours, the cyclone is forecast to slow down significantly as it nears the north-central Gulf Coast due to a large weakness in the subtropical ridge forecast to develop over the Deep South. The official forecast track closely follows the consensus models TVCN and HCCA. Given the broad inner-core wind field and belligerent westerly wind shear forecast to persist for the next 48 hours or so, only gradual intensification is expected. By 72 hours, however, when the cyclone is forecast to move slowly over above-normal SSTs of 28-29C and into an upper-level col and weak wind shear, some additional strengthening could occur. For now, the intensity forecast will remain conservative due to possible intrusion of dry mid-level air before landfall, and closely follows the HCCA consensus model. KEY MESSAGES: 1. Regardless of its exact track and intensity, Alberto is expected to produce heavy rainfall and flash flooding over the northeastern Yucatan Peninsula of Mexico, western Cuba, southern Florida and the Florida Keys. Rainfall and flooding potential will increase across the central Gulf Coast region and the southeastern United States later this weekend and early next week when Alberto is expected to slow down after it moves inland. 2. Alberto could bring tropical storm conditions and storm surge to portions of the central and eastern Gulf Coast later this weekend and early next week, although it is too soon to specify the exact location and magnitude of these impacts. Residents in these areas should monitor the progress of Alberto, as tropical storm and storm surge watches may be required later today or tonight. 3. Dangerous surf and rip current conditions are affecting portions of the Yucatan Peninsula and western Cuba and will likely spread along the eastern and central U.S. Gulf Coast later this weekend. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 19.7N 86.8W 35 KT 40 MPH 12H 26/0000Z 20.5N 86.6W 35 KT 40 MPH 24H 26/1200Z 22.0N 86.2W 40 KT 45 MPH 36H 27/0000Z 24.1N 85.8W 45 KT 50 MPH 48H 27/1200Z 26.7N 86.1W 50 KT 60 MPH 72H 28/1200Z 29.3N 87.9W 55 KT 65 MPH 96H 29/1200Z 31.0N 89.1W 30 KT 35 MPH...INLAND 120H 30/1200Z 33.6N 88.7W 20 KT 25 MPH...INLAND $$ Forecaster Stewart

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Listen in on the City's arts and culture discussion

2018-05-21 19:03:37| PortlandOnline

Tags: discussion arts culture listen

 

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