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Hurricane Ida Forecast Discussion Number 11
2021-08-29 04:50:24| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Sat Aug 28 2021 000 WTNT44 KNHC 290250 TCDAT4 Hurricane Ida Discussion Number 11 NWS National Hurricane Center Miami FL AL092021 1000 PM CDT Sat Aug 28 2021 The NOAA Hurricane Hunters investigated Ida earlier this evening and found that the maximum winds were still around 90 kt. Although the peak winds appear to have leveled off for now, the minimum pressure has continued to fall and was down to 966 mb at the last pass through the center an hour or two ago. In fact, the pressure has been dropping by about 2 mb per hour based on the aircraft data. In addition, tail Doppler Radar data from the aircraft indicate that the vortex has become more symmetric and that the inner core has contracted from the mission earlier today. These are signals that Ida is poised to strengthen further, and based on recent satellite images it appears that strengthening is imminent. Flight-level and SFMR observations also indicate that Ida's wind field has expanded and there is some indication of a double-wind maximum. The tropical-storm-force winds now extend outward up to 120 n mi from the center and hurricane-force winds up to 35 n mi from the eye. Ida continues to move steadily to the northwest at about 14 kt. There has been little change to the track forecast rationale. A subtropical ridge situated near the southeast U.S. coast is expected to shift westward during the next day or two. This feature should continue to steer Ida northwestward toward the Louisiana coast. The latest runs of the numerical models bring the center of Ida to southeast or south-central Louisiana Sunday afternoon. Although landfall is not expected for about 18 hours, impacts will begin well before that time. Tropical-storm-force winds are likely to begin overnight, therefore, all preparations to protect life and property must be rushed to completion. The new track forecast is just a little to the east of the previous one through landfall. After Ida moves inland, a turn to the north and then the northeast is expected as the storm moves in the flow on the northwest and north sides of the ridge. Ida remains over waters with high oceanic heat content, and in an atmospheric environment of low wind shear and abundant moisture. These conditions, combined with the improved structure of the hurricane, should allow Ida to rapidly intensify until it makes landfall. The models remain in fairly good agreement, and the NHC forecast holds steady and brings Ida to a dangerous major hurricane prior to landfall. After the storm moves inland on Sunday, rapid weakening is forecast due to a combination of land interaction, drier air and some increase in wind shear. Users are again reminded to not focus on the exact details of the track forecast as storm surge, wind, and rainfall impacts will extend far from the center. Rainfall impacts will also spread inland across the Lower Mississippi and Tennessee Valleys through early next week. Key Messages: 1. There is a danger of life-threatening storm surge inundation Sunday along the coasts of Louisiana, Mississippi, and Alabama within the Storm Surge Warning area. Extremely life-threatening inundation of 9 feet or greater above ground level is possible somewhere within the area from Morgan City, Louisiana, to the coast of Mississippi. Overtopping of local levees outside of the Hurricane and Storm Damage Risk Reduction System is possible where local inundation values may be higher. Interests throughout the warning area should follow any advice given by local officials. 2. Ida is expected to be an extremely dangerous major hurricane when it reaches the coast of Louisiana. Hurricane-force winds are expected Sunday in portions of the Hurricane Warning area along the Louisiana coast, including metropolitan New Orleans, with potentially catastrophic wind damage possible where the core of Ida moves onshore. Actions to protect life and property should be rushed to completion in the warning area. 3. Damaging winds, especially in gusts, will spread inland near the track of the center of Ida across portions of southeastern Louisiana and southwestern Mississippi Sunday night and early Monday. These winds will likely lead to widespread tree damage and power outages. 4. Ida is likely to produce heavy rainfall Sunday into Monday across the central Gulf Coast from southeast Louisiana, coastal Mississippi, and far southwestern Alabama, resulting in considerable to life-threatening flash and urban flooding and significant river flooding impacts. As Ida moves inland, significant flooding impacts are possible across portions of the Lower Mississippi, Tennessee, and Ohio Valleys through Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 27.2N 88.0W 90 KT 105 MPH 12H 29/1200Z 28.4N 89.4W 115 KT 130 MPH 24H 30/0000Z 29.9N 90.7W 85 KT 100 MPH...INLAND 36H 30/1200Z 31.4N 91.2W 45 KT 50 MPH...INLAND 48H 31/0000Z 33.1N 90.6W 30 KT 35 MPH...INLAND 60H 31/1200Z 34.8N 89.1W 25 KT 30 MPH...INLAND 72H 01/0000Z 36.3N 86.7W 20 KT 25 MPH...INLAND 96H 02/0000Z 38.6N 80.6W 20 KT 25 MPH...POST-TROP/INLAND 120H 03/0000Z...DISSIPATED $$ Forecaster Cangialosi
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Tropical Depression Eleven Forecast Discussion Number 1
2021-08-29 04:49:54| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sat Aug 28 2021 023 WTNT41 KNHC 290249 TCDAT1 Tropical Depression Eleven Discussion Number 1 NWS National Hurricane Center Miami FL AL112021 1100 PM AST Sat Aug 28 2021 Before sunset this evening, visible satellite images showed that a well-defined low level circulation was developing in association with the disturbance over the subtropical central Atlantic. However, up until a couple of hours ago, the system lacked sufficient organized deep convection to be considered a tropical cyclone by definition. Since that time, a deep convective burst has increased in size near, and to the east of the estimated center. In addition, a curved band has begun to develop over the southeastern portion of the circulation. Based on this increase in convective organization, advisories are being initiated on Tropical Depression Eleven. There was no ASCAT data this evening over the cyclone, so the initial intensity of 30 kt is based on the latest Dvorak CI number from TAFB. The initial motion of the depression is 050/10 kt. The cyclone is embedded in southwesterly flow to the southeast of a mid- to upper-level trough and an associated cold front. This flow is forecast to increase as the cold front approaches the cyclone, resulting in the system accelerating northeastward over the next day or so. Once the cyclone interacts with this frontal boundary in a couple of days, a turn to the north is expected. The model guidance is in very good agreement on this scenario, and the NHC track forecast lies in the middle of the consensus tracks. Baroclinic forcing and upper-level diffluence should aid in intensifying the depression over the next 24 h, despite increasing shear. By 36 h, the combination of interaction with the cold front and passage over much cooler waters should result in extratropical transition. The system is then forecast to become absorbed by a larger low pressure system by midweek. The NHC intensity forecast is near the various multi-model consensus solutions. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 33.0N 49.7W 30 KT 35 MPH 12H 29/1200Z 34.6N 47.1W 35 KT 40 MPH 24H 30/0000Z 36.8N 43.4W 45 KT 50 MPH 36H 30/1200Z 39.5N 39.2W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 31/0000Z 43.4N 36.4W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 31/1200Z 47.9N 36.3W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 01/0000Z...DISSIPATED $$ Forecaster Latto
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Tropical Depression Ten Forecast Discussion Number 4
2021-08-29 04:35:53| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sat Aug 28 2021 941 WTNT45 KNHC 290235 TCDAT5 Tropical Depression Ten Discussion Number 4 NWS National Hurricane Center Miami FL AL102021 1100 PM AST Sat Aug 28 2021 The center of the tropical depression remained exposed for much of the evening, though in the past hour or so the center has become located closer to a small, ragged area of convection. A more pronounced curved band can also be seen east of the depression though this feature is located over 120 n mi away. This structure is due to ongoing west-southwesterly shear and the presence of some dry air that continues to plague the cyclone. The latest Dvorak intensity estimate from TAFB and wind data from a recent ASCAT-B overpass indicate the initial intensity remains 30 kt. Some slight strengthening is possible later tonight through Sunday morning as a slight decrease in shear combined with the diurnal convective maximum may allow the depression to become a tropical storm. Thereafter through 60 h, the shear is forecast to increase, while the system moves into an drier environment. Thus, no further strengthening is forecast during this period, and the cyclone could weaken back into a tropical depression. By around 72 h, global models are suggesting that the shear will decrease again. So, some gradual strengthening is forecast after that time. It should also be noted that the GFS, which earlier forecast the system to degenerate into a remnant low in a few days, now keeps the cyclone in tact and deepens it when the shear lessens toward the end of the 5-day forecast period. The latest NHC intensity forecast is close to the previous one through 24 h, but is higher beyond 24 h. This forecast is a blend of the SHIPS and IVCN guidance through 72 h, but is lower than those solutions after that time. The depression is moving toward the north at 9 kt toward a weakness in the subtropical ridge, carved out by a mid- to upper-level trough over the north-central Atlantic. This trough and associated ridge weakness is forecast to remain in place for the next few days, resulting in the cyclone continuing a general northward motion. By late in the forecast period, the trough is expected to lift out of the region and be replaced by a ridge, which would result in the system turning northwestward. The latest NHC track forecast is little changed from the previous one and lies near the various multi-model consensus tracks. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 16.6N 49.9W 30 KT 35 MPH 12H 29/1200Z 17.7N 49.9W 35 KT 40 MPH 24H 30/0000Z 19.4N 49.9W 35 KT 40 MPH 36H 30/1200Z 20.8N 49.7W 35 KT 40 MPH 48H 31/0000Z 22.3N 49.2W 35 KT 40 MPH 60H 31/1200Z 23.5N 49.0W 35 KT 40 MPH 72H 01/0000Z 25.0N 49.2W 40 KT 45 MPH 96H 02/0000Z 28.2N 50.6W 40 KT 45 MPH 120H 03/0000Z 31.5N 51.7W 45 KT 50 MPH $$ Forecaster Latto
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Hurricane Nora Forecast Discussion Number 13
2021-08-28 22:54:20| National Hurricane Center (East Pacific)
Issued at 400 PM CDT Sat Aug 28 2021 000 WTPZ44 KNHC 282054 TCDEP4 Hurricane Nora Discussion Number 13 NWS National Hurricane Center Miami FL EP142021 400 PM CDT Sat Aug 28 2021 Nora developed a cloud-filled eye during the past few hours, with the center now grazing the coast and the eyewall moving across western Jalisco, Mexico. An Air Force Reserve Hurricane Hunter aircraft has been investigating the hurricane, but unfortunately the storm is now too close to the mountainous coastline for the plane to safely locate the surface center or sample the likely-stronger wind field on the eastern side of the circulation. Based mainly on T4.5/77 kt Dvorak estimates from TAFB and SAB, the initial intensity is estimated to be 75 kt. The center has been moving a little faster to the west of due north, or 350/12 kt. The track models are in agreement that Nora should turn toward the north-northwest and northwest during the next few days, generally keeping the center of the hurricane over the waters of the Gulf of California. However, due to the complex geography and mountainous topography of the region, the track forecast is challenging, and it's almost impossible to know if Nora's center will remain over water or graze the coastlines of Nayarit and Sinaloa over the next few days. By days 4 and 5, Nora's center is forecast to move inland over Sonora after traversing a significant length of the Gulf of California. Assuming a path that keeps Nora just offshore, low shear and very warm sea surface temperatures in the Gulf of California should be sufficient to at least maintain hurricane intensity for the next 3 days. However, any slight deviations of the track could cause Nora to weaken and fall below hurricane intensity sooner than is indicated in the official forecast. Given the uncertainties, however, the government of Mexico has extended the hurricane warning farther north along the coasts of Nayarit and Sinaloa out of an abundance of caution. Weakening will become more likely the farther north Nora gets up the Gulf of California, both due to possible land interaction and ingestion of drier air off the Mexican plateau. Key Messages: 1. Nora is forecast to be a hurricane while it moves near or along the coasts of the Mexican states of Jalisco, Nayarit, and Sinaloa through Monday, and hurricane warnings are in effect for portions of that coastline. Interests in these areas should closely monitor the progress of Nora and subsequent updates to the forecast. 2. Heavy rain associated with Nora is expected across the west coast of Mexico from the Mexican states of Guerrero, northward to southern Sonora, including Baja California Sur. This rain will likely result in life-threatening flash flooding and mudslides across these regions. Rainfall from Nora may spread into the southwestern U.S. and central Rockies during the middle to latter portion of next week. 3. Nora is forecast to continue moving northward over the Gulf of California Tuesday and Wednesday, bringing a risk of wind impacts to portions of the Mexican states of Baja California Sur, northern Sinaloa, and Sonora. Given the above-average uncertainty in the forecast intensity, confidence is not high enough to determine the magnitude and location of these potential impacts. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 19.7N 105.4W 75 KT 85 MPH...ON THE COAST 12H 29/0600Z 21.5N 105.9W 75 KT 85 MPH 24H 29/1800Z 22.9N 106.7W 75 KT 85 MPH 36H 30/0600Z 23.5N 107.4W 75 KT 85 MPH 48H 30/1800Z 24.2N 108.1W 75 KT 85 MPH 60H 31/0600Z 24.8N 108.9W 70 KT 80 MPH 72H 31/1800Z 25.6N 109.5W 70 KT 80 MPH 96H 01/1800Z 27.6N 110.4W 55 KT 65 MPH...INLAND 120H 02/1800Z 29.4N 110.6W 30 KT 35 MPH...INLAND $$ Forecaster Berg
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Hurricane Ida Forecast Discussion Number 10
2021-08-28 22:51:19| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Sat Aug 28 2021 000 WTNT44 KNHC 282051 TCDAT4 Hurricane Ida Discussion Number 10 NWS National Hurricane Center Miami FL AL092021 400 PM CDT Sat Aug 28 2021 Ida's satellite presentation has continued to improve this afternoon, with the eye becoming more apparent in both infrared and visible satellite imagery. The eye is surrounded by a symmetric ring of cold cloud tops and new convection with lightning as seen by the GOES-16 GLM sensor has been rotating around the western portion of the eyewall within the past few hours. The upper-level outflow has also become well established over the hurricane and several spiral bands are noted over the northern semicircle. Subjective Dvorak satellite intensity estimates have increased to T5.0 and these support increasing the initial intensity to 90 kt for this advisory. Both NOAA and Air Force Reserve reconnaissance aircraft are scheduled to be in the hurricane within the next few hours and should provide additional information on Ida's current strength. Earlier aircraft and satellite wind data indicate that the tropical-storm-force wind field has continued to expand over the eastern semicircle and the initial wind radii have been adjusted outward. The hurricane appears to have begun its anticipated rapid intensification phase. A favorable upper-level wind pattern, warm waters along the track, and a moist atmosphere are expected to allow for additional rapid strengthening overnight and early Sunday. This is again supported by the majority of the intensity models, and the NHC wind speed forecast continues to call for rapid strengthening, bringing Ida to Category 4 status within 12 to 18 hours. An eyewall replacement cycle could occur as Ida nears the northern Gulf coast, so some fluctuations in intensity are possible during that time. After landfall, rapid weakening is expected, and Ida is forecast to become a post-tropical cyclone by day 4, and it is likely to be absorbed along a frontal zone by day 5. Ida has moved a little to the right of the previous track, but the long-term motion motion is still northwestward or 320/14 kt. The track forecast philosophy remains unchanged. Ida is expected to continue on a northwestward heading through late Sunday as it is steered around the southwestern portion of a deep-layer ridge near the southeastern United Stated coast. After landfall, Ida's forward motion is forecast to slow when it turns northward around the western extent of the aforementioned ridge. By Tuesday, the cyclone should reach the southern extent of the mid-latitude westerlies, causing it to turn north-northeastward across the Lower Mississippi and Tennessee Valleys. The track guidance has nudged slightly eastward during the first 12-24 hours, primarily due to the more northeastward initial position, and this has required a slight rightward adjustment in the new official forecast at those times. The remainder of the NHC forecast is largely unchanged from before, and lies near various consensus models and the GFS ensemble mean. Users are again reminded to not focus on the exact details of the track forecast as storm surge, wind, and rainfall impacts will extend far from the center. Rainfall impacts will also spread inland across the Lower Mississippi and Tennessee Valleys through early next week after Ida makes landfall. Key Messages: 1. There is a danger of life-threatening storm surge inundation Sunday along the coasts of Louisiana, Mississippi, and Alabama within the Storm Surge Warning area. Extremely life-threatening inundation of 9 feet or greater above ground level is possible somewhere within the area from Morgan City, Louisiana, to the coast of Mississippi. Overtopping of local levees outside of the Hurricane and Storm Damage Risk Reduction System is possible where local inundation values may be higher. Interests throughout the warning area should follow any advice given by local officials. 2. Ida is expected to be an extremely dangerous major hurricane when it reaches the coast of Louisiana. Hurricane-force winds are expected Sunday in portions of the Hurricane Warning area along the Louisiana coast, including metropolitan New Orleans, with potentially catastrophic wind damage possible where the core of Ida moves onshore. Actions to protect life and property should be rushed to completion in the warning area. 3. Damaging winds, especially in gusts, will spread inland near the track of the center of Ida across portions of southeastern Louisiana and southwestern Mississippi Sunday night and early Monday. These winds will likely lead to widespread tree damage and power outages. 4. Ida is likely to produce heavy rainfall Sunday into Monday across the central Gulf Coast from southeast Louisiana, coastal Mississippi, and far southwestern Alabama, resulting in considerable to life-threatening flash and urban flooding and significant river flooding impacts. As Ida moves inland, significant flooding impacts are possible across portions of the Lower Mississippi, Tennessee, and Ohio Valleys through Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 26.2N 87.0W 90 KT 105 MPH 12H 29/0600Z 27.5N 88.6W 110 KT 125 MPH 24H 29/1800Z 29.1N 90.4W 115 KT 130 MPH 36H 30/0600Z 30.5N 91.3W 65 KT 75 MPH...INLAND 48H 30/1800Z 32.2N 91.2W 35 KT 40 MPH...INLAND 60H 31/0600Z 34.0N 90.1W 25 KT 30 MPH...INLAND 72H 31/1800Z 35.7N 88.1W 20 KT 25 MPH...INLAND 96H 01/1800Z 38.0N 82.5W 20 KT 25 MPH...POST-TROP/INLAND 120H 02/1800Z...DISSIPATED $$ Forecaster Brown
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