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Laupattarakasem P.,University of Central Florida | Laupattarakasem P.,Webster University | Jones W.L.,University of Central Florida | Hennon C.C.,University of North Carolina at Asheville | And 4 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

The SeaWinds scatterometer, onboard the QuikSCAT satellite, infers global ocean vector winds (OVWs); however, for a number of reasons, these measurements in hurricanes are significantly degraded. This paper presents an improved hurricane OVW retrieval approach, known as Q-Winds, which is derived from combined SeaWinds active and passive measurements. In this technique, the effects of rain are implicitly included in a new geophysical model function, which relates oceanic brightness temperature and radar backscatter measurements (at the top of the atmosphere) to the surface wind vector under both clear sky and in the presence of light to moderate rain. This approach extends the useful wind speed measurement range for tropical cyclones beyond that exhibited by the standard SeaWinds Project Level-2B (L2B) 12.5-km wind vector algorithm. A description of the Q-Winds algorithm is given, and examples of OVW retrievals are presented for the Q-Winds and L2B 12.5-km algorithms for ten hurricane overpasses in 20032008. These data are also compared to independent surface wind vector estimates from the National Oceanic and Atmospheric Administration Hurricane Research Division's objective hurricane surface wind analysis technique known as H*Wind. These comparisons suggest that the Q-Winds OVW product agrees better with independently derived H*Wind analysis winds than does the conventional L2B OVW product. © 2006 IEEE. Source


Edwards R.,Storm Prediction Center | La Due J.G.,NWS Warning Decision Training Branch | Ferree J.T.,NWS Office of Climate | Scharfenberg K.,NWS Office of Climate | And 2 more authors.
Bulletin of the American Meteorological Society | Year: 2013

An enhanced Fujita (EF) scale stakeholder's meeting (EFSSM) was convened in March 2010 to evaluate the EF scale, to understand new techniques in estimating damaging wind strength, and to map out a plan for future improvements. Discussion topics included variations in construction practices and structural integrity within any given DI, changes in vulnerability of single damage indicator (DIs) based on directional wind angle and vertical velocity, full-scale testing facilities for wind effects on structures, inconsistencies in building codes and enforcement thereof, the effects of flying debris and surrounding surface roughness, and the weakest points of structural failure. The international colleagues expressed concern that the diversity of construction habits among the DIs would force modifications to the EF scale prior to adoption. Given this diversity, one proposal was forwarded to consider all countries to adopt a more universal, physically derived wind speed scale, which could serve as a focus to bind all other wind speed and damage scales. Source


News Article | April 26, 2016
Site: http://www.techtimes.com/rss/sections/environment.xml

Large swaths of central United States will be hit by violent tornadoes and hail bigger than baseballs beginning Tuesday, weather forecasters in Oklahoma warned. The severe weather outbreak will target areas spanning from southern Nebraska, central Kansas to central Oklahoma and northern Texas. This has prompted the National Weather Service Storm Prediction Center (SPC) to mark these places as "moderate risk" zones -- the second highest of the five categories for potentially strong storm systems. More specifically, cities in the forecast area include the following: Bill Bunting, the agency's Chief of Operations, said the severe storm system will produce strong thunderstorms and ferocious straight-line winds of up to 70 miles per hour. Expect the tornado threat to start Tuesday afternoon and peak in the evening, Bunting said. Severe weather will last into the night. Some of the tornadoes have the potential to be intense and strong. "An EF-2 or greater, which is winds over 110 mph, [is] strong enough to cause structural damage to well-built homes," he said. Andrew Gagnon of AccuWeather said Tuesday's storm outbreaks can potentially produce numerous tornadoes, including strong wedge tornadoes that could remain on the ground for an extended period of time. Wedge tornadoes are at least as wide as they are tall, and can damage a lot of territory, according to AccuWeather. Allison Chinchar, CNN Meteorologist, said the storm outbreak is not just a tornado or two. She said multiple tornadoes can hit multiple states. "Several have the possibility to be long-lived or long-tracked, meaning they're on the ground for long periods of time," said Chinchar. Most tornadoes stay on the ground for 10 to 15 minutes on average, but the ones predicted this Tuesday could last on the ground for half an hour or longer, she added. 1. Bunting advises residents in storm-threatened areas to prepare. He said it is important for families to have a severe weather plan and practice it. 2. It is also vital to have several ways of receiving weather alerts and information about the storm, including weather apps on smartphones or weather radio. 3. Knowing where to find shelter in your building or home is important. AccuWeather recommends finding shelter locations: underground safe room, basement, small interior room. 4. Have a secure way to communicate with friends and family, or set a specific meeting point, to let them know your state after the storm. 5. Prepare a survival kit containing non-perishable food, potable water, flashlights, extra batteries, extra medications, and an extra pair of shoes. 7. During the storm: do not seek shelter in a car, mobile home, bridge, or overpass. Stay as safe as possible. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.


Naylor J.,University of North Dakota | Gilmore M.S.,University of North Dakota | Thompson R.L.,Storm Prediction Center | Edwards R.,Storm Prediction Center | Wilhelmson R.B.,University of Illinois at Urbana - Champaign
Monthly Weather Review | Year: 2012

The accuracy, reliability, and skill of several objective supercell identification methods are evaluated using 113 simulations from an idealized cloud model with 1-km horizontal grid spacing. Horizontal cross sections of vorticity and radar reflectivity at both mid- and low levels were analyzed for the presence of a supercell, every 5min of simulation time, to develop a "truth" database. Supercells were identified using well-known characteristics such as hook echoes, inflow notches, bounded weak-echo regions (BWERs), and the presence of significant vertical vorticity. The three objective supercell identification techniques compared were the Pearson correlation (PC) using an analysis window centered on the midlevel storm updraft; a modified Pearson correlation (MPC), which calculates the PC at every point in the horizontal using a small 3km 3 3km analysis window; and updraft helicity (UH). Results show that the UHmethod integrated from 2 to 5km AGL, and using a threshold value of 180 m2 s22, was equally as accurate as the MPC technique-averaged from 2 to 5km AGL and using a minimum updraft threshold of 7 m s21 with a detection threshold of 0.3-in discriminating between supercells and nonsupercells for 1-km horizontal grid spacing simulations. At courser resolutions, the UH technique performed best, while the MPC technique produced the largest threat scores for higher-resolution simulations. In addition, requiring that the supercell detection thresholds last at least 20min reduced the number of false alarms. © 2012 American Meteorological Society. Source


News Article
Site: http://www.reuters.com

The National Weather Service has issued a flash flood watch stretching from Arkansas to Georgia, and put parts of southern Alabama and western Florida under a tornado watch. The severe weather is being caused by a moist and unstable air mass ahead of a cold front that has been moving through Arkansas and Louisiana, said Greg Garrett, a forecaster with the NWS in Jackson, Mississippi. He said sunny skies in parts of the region in the morning could cause the air mass to destabilize even more in the afternoon. "When we start to have thunderstorms developing this afternoon, there is a good chance they could be widespread and severe again, similar to last night," he said. On Wednesday night, emergency crews near Little Rock, Arkansas, performed a high-water rescue for a woman whose car was caught in floods. At least four tornadoes were reported in Tulsa and Rogers counties in Oklahoma, according to the Storm Prediction Center. Another was reported in southern Kansas. On Thursday, four schools were closed in Tulsa because of storm damage and a loss of power, local officials said. In southern Mississippi, Alabama and western Florida, the NWS said there was a significant threat of tornadoes, damaging wind gusts and large hail on Thursday from the storm system. The weather service said large parts of region could get about 3 inches of rain on Thursday, bringing significant risks of flooding in low-lying areas.

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