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Hurricane Nate Forecast Discussion Number 13

2017-10-07 17:04:35| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Sat Oct 07 2017 000 WTNT41 KNHC 071504 CCA TCDAT1 Hurricane Nate Discussion Number 13...Corrected NWS National Hurricane Center Miami FL AL162017 1000 AM CDT Sat Oct 07 2017 Corrected 24 kt motion to 23 kt motion in third paragraph Nate is showing improved organization in satellite imagery this morning, with the formation of a symmetric central dense overcast with cloud tops colder than -80C. In addition, Air Force Reserve and NOAA Hurricane Hunter aircraft have reported a central pressure near 984 mb inside a 25 n mi wide eye that is starting to form under the overcast. The planes have reported 700-mb flight level winds of up to 88 kt and surface wind estimates from the SFMR instrument between 75-85 kt. Based on these data, the initial intensity is increased to a possibly conservative 80 kt. Conditions appear favorable for Nate to continue strengthening for the next 12 h or so before it encounters land and increasing shear. The new intensity forecast thus follows the SHIPS model in showing Nate become a Category 2 hurricane before landfall on the central Gulf Coast. After landfall, Nate should weaken rapidly as it moves through the eastern United States. The cyclone is now forecast to become extratropical near the 72 hr point and dissipate completely by 96 h. The initial motion is toward the north-northwest at a very rapid 23 kt. The hurricane is being steered by the flow between a large cyclonic gyre over the southwestern Gulf of Mexico and a mid-level ridge over the western Atlantic. In addition, a mid-latitude trough in the westerlies is moving eastward through the central United States. This pattern is expected to cause Nate to turn northward during the next 12-18 h as it rounds the western end of the ridge, followed by a turn toward the northeast as it enters the westerlies. The new forecast track is nudged a little to the left of the previous track, and it lies near the center of the tightly clustered guidance. KEY MESSAGES: 1. Nate is expected to bring life-threatening storm surge flooding near and well east of where the center makes landfall, and a storm surge warning is in effect from Morgan City, Louisiana, to the Okaloosa/Walton county line in Florida. Maximum flooding of 7 to 11 feet above ground level is expected in portions of southeastern Louisiana and along the Mississippi coast. Residents in these areas should immediately heed any evacuation instructions given by local officials. 2. Nate is forecast to reach Category 2 intensity before landfall. A hurricane warning is in effect for portions of the northern Gulf Coast from Louisiana to Alabama, with the strongest winds expected to occur primarily to the east of the center. Preparations to protect life and property should be rushed to completion in these areas, as tropical storm conditions will first arrive in the warning area this afternoon. 3. Nate's fast forward speed after landfall will bring tropical- storm-force winds well inland across portions of the southeastern U.S. Tropical storm watches and warnings are in effect for portions of southeastern Mississippi, Alabama, and western Georgia. 4. Nate will bring heavy rainfall of 3 to 6 inches with isolated totals of 10 inches east of the Mississippi River from the central Gulf Coast into the Deep South, eastern Tennessee Valley, and southern Appalachians through Monday, resulting in the potential for flash flooding in these areas. 5. Moisture from Nate interacting with a frontal zone will also bring 2 to 4 inches of rain with isolated totals of 6 inches across the Ohio Valley and central Appalachians Sunday and Monday, which will increase the risk for flash flooding across these locations. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 26.6N 88.4W 80 KT 90 MPH 12H 08/0000Z 29.1N 89.0W 90 KT 105 MPH 24H 08/1200Z 32.1N 88.3W 60 KT 70 MPH...INLAND 36H 09/0000Z 35.7N 85.5W 35 KT 40 MPH...INLAND 48H 09/1200Z 39.2N 80.6W 30 KT 35 MPH...INLAND 72H 10/1200Z 44.5N 67.5W 25 KT 30 MPH...POST-TROP/EXTRATROP 96H 11/1200Z...DISSIPATED $$ Forecaster Beven

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Hurricane Nate Forecast Discussion Number 12

2017-10-07 10:58:01| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Sat Oct 07 2017 000 WTNT41 KNHC 070857 TCDAT1 Hurricane Nate Discussion Number 12 NWS National Hurricane Center Miami FL AL162017 400 AM CDT Sat Oct 07 2017 An Air Force reconnaissance plane investigated Nate a couple of hours ago and measured peak flight-level winds of 89 kt at 850 mb to the east of the center. No hurricane force winds were reported west of the center. The SFMR winds from that mission yielded an initial intensity of 70 kt. Since the plane left, the satellite presentation has changed little, so the winds remains with the same value in this advisory. Another reconnaissance plane is currently approaching Nate. The outflow is well established suggesting that the shear is low, while the atmospheric conditions favor some additional strengthening. On this basis, the NHC forecast calls for some slight increase in the winds, however, the SHIPS/LGEM models forecast Nate to be a little bit stronger just before landfall. After landfall, weakening is anticipated and Nate is forecast to dissipate in 96 hours or sooner. Nate is moving rapidly toward the north-northwest at about 19 kt. The hurricane is being steered by the flow between a large cyclonic gyre over the southwestern Gulf of Mexico and a developing mid-level ridge over the western Atlantic. This pattern should continue to force Nate on a general north-northwest fast track for the next 24 hours. After that time, the hurricane will recurve northeastward with additional increase in forward speed as it encounters the mid-latitude westerlies. The NHC track forecast has not changed much from the previous one and is and is very close the HFIP corrected consensus HCCA. This model has been very skillful this season. KEY MESSAGES: 1. Life-threatening storm surge flooding is likely along portions of the northern Gulf Coast, and a storm surge warning is in effect from Morgan City, Louisiana, to the Okaloosa/Walton county line in Florida. Residents in these areas should heed any evacuation instructions given by local officials. 2. A hurricane warning is in effect for portions of the northern Gulf Coast from Louisiana to Alabama, and preparations to protect life and property should be rushed to completion in these areas. 3. Nate will bring heavy rainfall of 3 to 6 inches with isolated totals of 10 inches east of the Mississippi River from the central Gulf Coast into the Deep South, eastern Tennessee Valley, and southern Appalachians through Monday, resulting in the potential for flash flooding in these areas. 4. Moisture from Nate interacting with a frontal zone will also bring 2 to 4 inches with isolated totals of 6 inches across the Ohio Valley into the central Appalachians Sunday into Monday, which will also increase the risk for flash flooding across these locations. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 24.5N 87.0W 70 KT 80 MPH 12H 07/1800Z 27.3N 88.3W 75 KT 85 MPH 24H 08/0600Z 30.4N 88.8W 80 KT 90 MPH 36H 08/1800Z 33.8N 86.6W 40 KT 45 MPH...INLAND 48H 09/0600Z 37.0N 83.0W 30 KT 35 MPH...INLAND 72H 10/0600Z 43.0N 70.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 11/0600Z...DISSIPATED $$ Forecaster Avila

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Tropical Storm Nate Forecast Discussion Number 10

2017-10-06 23:02:00| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Fri Oct 06 2017 000 WTNT41 KNHC 062101 CCA TCDAT1 Tropical Storm Nate Discussion Number 10...Corrected NWS National Hurricane Center Miami FL AL162017 400 PM CDT Fri Oct 06 2017 CORRECTED MAX RAINFALL AMOUNT IN KEY MESSAGES Satellite imagery this afternoon indicates that convection associated with Nate is becoming better organized, with a strong convective band now wrapping about three-quarters of the way around the center. Recent data from NOAA buoy 42056 near the center suggest the central pressure has fallen to near 993 mb, and the buoy just reported a 1-minute average wind of 49 kt. Based on this, the initial intensity is increased to a possibly conservative 50 kt. The next aircraft investigating Nate is scheduled to arrive near 22Z. The initial motion is north-northwestward or 340/18 kt. Nate remains between a complex deep-layer low pressure area over the western Gulf of Mexico and Central America and a building ridge of high pressure over the western Atlantic. This combination should steer the storm quickly north-northwestward for the next 24 h or so. After that, Nate should turn northward and northeastward as it goes around the western edge of the ridge and recurves into the mid-latitude westerlies. The guidance remains in good agreement with the direction of motion, and it has come into better agreement on the speed. Thus, the new forecast track is similar to, but slightly to the west of the the previous track, and it calls for the center of Nate to pass near or over the northeastern tip of the Yucatan Peninsula in about 6 h, followed by landfall on the northern Gulf Coast around the 36-h point. It should be noted that the ECMWF and GFS are both a little to the left of the current track. Conditions appear favorable for continued strengthening up to landfall on the northern Gulf Coast, and Nate is expected to make landfall there as a hurricane. The new intensity forecast, which is an update of the previous one, lies near the upper edge of the intensity guidance. Given the current developments, there is still a possibility of a period of rapid intensification as Nate crosses the Gulf of Mexico. As alternative scenarios to the actual forecast of steady strengthening, the ECMWF forecasts no additional strengthening as Nate crosses the Gulf of Mexico, and the GFS/UKMET forecast little additional strengthening until the last 12 h before landfall. KEY MESSAGES: 1. Nate could be near hurricane intensity when it passes near or over the Yucatan Peninsula during the next several hours bringing direct impacts from wind, storm surge, and heavy rainfall. A tropical storm warning and a hurricane watch are in effect for a portion of this area, and life-threatening flash flooding is also possible. 2. Life-threatening storm surge flooding is likely along portions of the northern Gulf Coast, and a storm surge warning is now in effect from Morgan City, Louisiana, to the Okaloosa/Walton county line in Florida. Residents in these areas should heed any evacuation instructions given by local officials. 3. A hurricane warning is in effect for portions of the northern Gulf Coast from Louisiana to Alabama, and preparations to protect life and property should be rushed to completion in these areas. 4. Nate will bring heavy rainfall of 3 to 6 inches with isolated totals of 10 inches from the central Gulf Coast states into the eastern Tennessee Valley and southern Appalachians through this weekend, resulting in the possibility of flash flooding in these areas. 5. Heavy rainfall from Nate will continue to be a threat in portions of Central America, with life-threatening flash flooding and mud slides possible in portions of Nicaragua, Honduras, Costa Rica, Panama, and Belize through tonight. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 20.3N 85.7W 50 KT 60 MPH 12H 07/0600Z 23.0N 87.2W 55 KT 65 MPH 24H 07/1800Z 26.8N 88.9W 60 KT 70 MPH 36H 08/0600Z 29.9N 89.1W 70 KT 80 MPH 48H 08/1800Z 33.1N 87.2W 45 KT 50 MPH...INLAND 72H 09/1800Z 39.5N 78.5W 25 KT 30 MPH...INLAND 96H 10/1800Z 43.5N 66.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 11/1800Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm Nate Forecast Discussion Number 9

2017-10-06 16:56:25| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Fri Oct 06 2017 000 WTNT41 KNHC 061456 TCDAT1 Tropical Storm Nate Discussion Number 9 NWS National Hurricane Center Miami FL AL162017 1000 AM CDT Fri Oct 06 2017 Reports from Air Force Reserve and NOAA Hurricane Hunter aircraft indicate that Nate lacks an inner wind core at the present time, with the maximum winds located about 50 n mi from the center. The central pressure is fluctuating near 996 mb, and the aircraft- reported winds support an initial intensity of 45 kt. This is in good agreement with the satellite intensity estimates from TAFB and SAB. Satellite imagery shows that convection associated with Nate has been increasing during the past several hours, and that the storm has good outflow in the western semicircle. The center has moved generally northward during the past 12 hr. However, the latest recon fixes and satellite imagery suggest that a north-northwestward motion is resuming at about 18 kt. Nate is between a complex deep-layer low pressure area over the western Gulf of Mexico and Central America and a building ridge of high pressure over the western Atlantic. This combination should steer the storm quickly north-northwestward for the next 36 h or so. After that, Nate should turn northward and northeastward as it goes around the western edge of the ridge and recurves into the mid-latitude westerlies. While the guidance is in good agreement with this scenario, there has been a rightward shift to the latest guidance, likely due to the recent northward motion. The new forecast track is thus also shifted to the east of the previous forecast, and it now calls for the center of Nate to pass near or over the northeastern tip of the Yucatan Peninsula in about 12 h, followed by landfall on the northern Gulf Coast between 36-48 h. The new track is in the center of the guidance envelope in good agreement with the various consensus models. Conditions appear favorable for strengthening up to landfall on the northern Gulf Coast, and Nate is expected to make landfall there as a hurricane. The new intensity forecast, which is an update of the previous one, lies near the upper edge of the intensity guidance. It should be noted that the Rapid Intensification Index of the SHIPS model continues to indicate an above normal chance of rapid intensification. However, the current structure of the cyclone does not favor rapid development. KEY MESSAGES: 1. Nate could be near hurricane intensity when it approaches the Yucatan Peninsula later today bringing direct impacts from wind, storm surge, and heavy rainfall. A tropical storm warning and a hurricane watch are in effect for a portion of this area, and life-threatening flash flooding is also possible. 2. Life-threatening storm surge flooding is likely along portions of the northern Gulf Coast, and a storm surge warning has been issued from Morgan City, Louisiana, to the Alabama/Florida border. Residents in these areas should heed any evacuation instructions given by local officials. 3. A hurricane warning has been has been issued for portions of the northern Gulf Coast from Louisiana to Alabama, and preparations to protect life and property should be rushed to completion in these areas. 4. Nate will bring heavy rainfall of 3 to 6 inches with isolated totals of 12 inches from the central Gulf Coast states into the eastern Tennessee Valley and southern Appalachians through this weekend, resulting in the possibility of flash flooding in these areas. 5. Heavy rainfall from Nate will continue to be a threat in portions of Central America, with life-threatening flash flooding and mud slides possible in portions of Nicaragua, Honduras, Costa Rica, Panama, and Belize through tonight. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 18.7N 85.0W 45 KT 50 MPH 12H 07/0000Z 21.3N 86.3W 50 KT 60 MPH 24H 07/1200Z 24.8N 88.3W 60 KT 70 MPH 36H 08/0000Z 28.1N 89.3W 70 KT 80 MPH 48H 08/1200Z 31.1N 88.1W 60 KT 70 MPH...INLAND 72H 09/1200Z 37.5N 80.5W 30 KT 35 MPH...INLAND 96H 10/1200Z 42.0N 70.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 11/1200Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm Nate Forecast Discussion Number 8

2017-10-06 10:43:30| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Fri Oct 06 2017 000 WTNT41 KNHC 060843 TCDAT1 Tropical Storm Nate Discussion Number 8 NWS National Hurricane Center Miami FL AL162017 400 AM CDT Fri Oct 06 2017 An Air Force plane fixed the center of Nate as it was moving back over the waters of the Gulf of Honduras a few hours ago. The minimum central pressure was estimated at 999 mb, and a combination of flight-level and the SFMR winds yield an intensity of 40 kt. The surface circulation is broad, and the strongest winds are within a cyclonically curved band in the eastern semicircle. Radar from Honduras also helped to track the center when the cyclone was over Honduras. Nate is moving toward the very warm waters of the northwestern Caribbean Sea and within an environment of light shear. On this basis, the NHC forecast calls for some strengthening through the next 48 hours, and Nate is expected to be a Category one hurricane by the time it is close to the U.S. coast. The interaction with the Yucatan peninsula, however, could halt the strengthening temporarily in the 12 to 24 hour period. Once Nate moves inland over the U.S., weakening is anticipated and the cyclone most likely will dissipate by the end of the forecast period. Nate is moving toward the north-northwest or 340 degrees at 12 kt. The cyclone is sandwiched between a large cyclonic gyre over Central America and a developing subtropical ridge over the western Atlantic. This flow pattern should steer Nate on the same general north-northwest track with a marked increase in forward speed for the next 2 days. After that time, Nate should be on the northern edge of the subtropical high and become steered toward the northeast by the mid-latitude westerly flow. The confidence in the track forecast is high since most of the reliable guidance have come to a very good agreement, and models are tightly clustered at least for the next 2 to 3 days. The NHC forecast is in the middle of the envelope. KEY MESSAGES: 1. Heavy rainfall is the main threat from Nate in portions of Central America, with life-threatening flash flooding and mud slides possible in portions of Nicaragua, Honduras, Costa Rica, Panama, and Belize through tonight. 2. There is a possibility that Nate could be near hurricane intensity when it approaches the Yucatan Peninsula later today bringing direct impacts from wind, storm surge, and heavy rainfall. A tropical storm warning and a hurricane watch are in effect for a portion of this area, and life-threatening flash flooding is also possible. 3. Nate is forecast to reach the northern Gulf Coast late Saturday or Sunday morning as a hurricane, and the threat of direct impacts from wind, storm surge, and heavy rainfall is increasing from Louisiana through the western Florida Panhandle. Hurricane and tropical storm watches, as well as a storm surge watch, are in effect for a portion of the northern Gulf Coast, and residents in these areas should monitor the progress of Nate, heeding any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 16.9N 85.1W 40 KT 45 MPH 12H 06/1800Z 19.2N 85.9W 50 KT 60 MPH 24H 07/0600Z 22.7N 87.8W 50 KT 60 MPH 36H 07/1800Z 26.4N 89.5W 60 KT 70 MPH 48H 08/0600Z 29.3N 89.6W 70 KT 80 MPH 72H 09/0600Z 36.0N 84.0W 30 KT 35 MPH...INLAND 96H 10/0600Z 40.5N 74.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 11/0600Z...DISSIPATED $$ Forecaster Avila

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