Visible satellite imagery is widely used by operational weather forecast centers for tropical and extratropical cyclone analysis and marine forecasting. The absence of visible imagery at night can significantly degrade forecast capabilities, such as determining tropical cyclone center locations or tracking warm-topped convective clusters. This paper documents ProxyVis imagery, an infrared-based proxy for daytime visible imagery developed to address the lack of visible satellite imagery at night and the limitations of existing nighttime visible options. ProxyVis was trained on the VIIRS day/night band imagery at times close to the full moon using VIIRS IR channels with closely matching GOES - 16 / 17 / 18 , Himawari - 8 / 9 , and Meteosat - 9 / 10 / 11 channels. The final operational product applies the ProxyVis algorithms to geostationary satellite data and combines daytime visible and nighttime ProxyVis data to create full-disk animated GeoProxyVis imagery. The simple versions of the ProxyVis algorithm enable its generation from earlier GOES and Meteosat satellite imagery. ProxyVis offers significant improvement over existing operational products for tracking nighttime oceanic low-level clouds. Further, it is qualitatively similar to visible imagery for a wide range of backgrounds and synoptic conditions and phenomena, enabling forecasters to use it without special training. ProxyVis was first introduced to National Hurricane Center (NHC) operations in 2018 and was found to be extremely useful by forecasters becoming part of their standard operational satellite product suite in 2019. Currently, ProxyVis implemented for GOES - 16 / 18 , Himawari - 9 , and Meteosat - 9 / 10 / 11 is being used in operational settings and evaluated for transition to operations at multiple NWS offices and the Joint Typhoon Warning Center. Significance Statement This paper describes ProxyVis imagery, a new method for combining infrared channels to qualitatively mimic daytime visible imagery at nighttime. ProxyVis demonstrates that a simple linear regression can combine just a few commonly available infrared channels to develop a nighttime proxy for visible imagery that significantly improves a forecaster’s ability to track low-level oceanic clouds and circulation features at night, works for all current geostationary satellites, and is useful across a wide range of backgrounds and meteorological scenarios. Animated ProxyVis geostationary imagery has been operational at the National Hurricane Center since 2019 and is also currently being transitioned to operations at other NWS offices and the Joint Typhoon Warning Center.

A reanalysis of 1969's Hurricane Camille has been completed as part of the Atlantic Hurricane Database Reanalysis Project. The reanalysis of Hurricane Camille has been expedited to allow for a homogeneous comparison of all four of the U.S.-landfalling Saffir-Simpson hurricane wind scale category 5 hurricanes since 1900. A review of the available ship, station, radar, aircraft, and satellite observations is presented, along with the reanalysis methodology. Highlights of the Best-Track Change Committee approved changes to Camille's genesis, track, intensity, and dissipation are discussed. As part of the preparation for the reanalysis, research on Hurricane Camille uncovered new data useful to the reanalysis. Focus was placed on understanding the internal structure in a modern context, especially whether eyewall replacement cycles occurred, including comparisons with a similar hurricane used as a proxy. A more detailed understanding was gained of the tropical wave and genesis phases. In addition, a 901-mb dropsonde that was later rejected was reanalyzed to find out why and to see if an accurate central pressure could be determined. New landfall surface pressures along the Mississippi coast were discovered and a significant revision is made to the U.S.-landfall central pressure and intensity (maximum sustained surface winds). Additionally, a radar "loop" was constructed from archived Weather Surveillance Radar-1957 (WSR-57) film, including landfall, marking the very first time that this historic hurricane can be viewed in a time-lapse movie format.

AbstractThe Dvorak technique is used operationally worldwide for tropical cyclone intensity analysis. This study tests Dvorak intensity change constraints, using a database of simultaneous aircraft and satellite fixes for tropical cyclones (TCs) in the 1998–2012 period. Results indicate that, in the vast majority of cases, Dvorak intensity constraints are valid with only a small percentage of strengthening TCs violating the constraints. Of the small sample that broke the constraints, most had initial intensities ranging from moderately strong tropical storms to minimal hurricanes.

Hurricane Sandy – a tropical cyclone that transitioned into an extratropical cyclone near the time of landfall along the east coast of the United States – caused historic damage in many regions which rarely receive such a direct hit from a storm of this magnitude, including many of the large metropolitan areas along the U.S. eastern seaboard. Specifically, Sandy generated record low-pressure, a large wind field with corresponding storm surge and copious amounts of precipitation in some areas, including record snowfall in mountainous regions. Sandy presented several forecast challenges to the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS). Satellites played an integral role in the analysis and forecast of Sandy's track and intensity. The NOAA National Hurricane Center, Ocean Prediction Center, and Weather Prediction Center all relied on information from satellites to make critical warning decisions using various satellite products that assist with diagnosing tropical cyclone intensity, surface winds over the ocean, and heavy precipitation. All of the skillful global forecast models used satellite data for initiation to better forecast the track and intensity of Sandy. As part of the Geostationary Operational Environmental Satellite — R-series (GOES-R) and Joint Polar Satellite System (JPSS) Proving Ground activities, new satellite products were available to forecasters at these national centers in experimental form to assist with observing this unique, high impact event. This paper will demonstrate how the current satellite products assisted NOAA forecasters during Sandy and introduce some new satellite products that could be used to analyze and predict future high impact weather systems.

The 2010 Atlantic hurricane season was marked by above-average tropical cyclone activity with the formation of 19 tropical storms. A total of 12 of the storms became hurricanes and 5 became major hurricanes (category 3 or higher on the Saffir-Simpson hurricane wind scale). In addition, there were two tropical depressions that did not reach storm strength. These totals were well above the long-term averages of 11 named storms, 6 hurricanes, and 2 major hurricanes. The areas most affected by the 2010 storms were eastern Mexico, Central America, and the island nations of the western Caribbean Sea, where multiple strikes occurred. In addition, two hurricanes struck eastern Canada. Despite the high level of activity, no hurricanes made landfall in the United States in 2010. The death toll from the 2010 Atlantic tropical cyclones was 189. A verification of National Hurricane Center official forecasts during 2010 is also presented. The 2010 mean track errors were slightly larger than the previous 5-yr average at 12 and 24 h and much smaller at the other forecast times, even though the 2010 track forecasts were more difficult than normal. The 2010 mean intensity forecast errors were larger than the previous 5-yr average at 12-48 h, smaller at the longer forecast times, and had a high bias at all forecast times. As with the track forecasts, the 2010 intensity forecasts were more difficult than normal at all forecast times.

This paper details the event, recording instrumentation, and verification of a new world extreme three-second average wind gust record of 113.3 m s(-1), measured on Barrow Island, Australia, during the passage of tropical cyclone Olivia in April 1996, and the public and media reaction to that verification. This record supersedes the previous extreme of 103.3 m s(-1) measured at the Mount Washington Observatory in New Hampshire, USA, in April 1934. Members of a World Meteorological Organization evaluation committee critically reviewed the data of the Olivia event, determined the Barrow Island wind measurement was valid and established the record. With the announcement of the record, interesting public reaction has occurred and is discussed, as well as the concept of more detailed classification of wind extremes. Although Olivia now holds the record for having the highest wind gust ever measured, this record doesn't imply that Olivia is the most intense cyclone recorded. However, planners should be aware that extreme gusts well above the 'typical' gusts quoted on the intensity scale are possible for tropical cyclones, particularly for category 4 and 5 tropical cyclones.

MODIS image of Hurricane Earl off the southeastern coast of the United States on September 2, 2010. With contributions from Lixion Avila, Robbie Berg, Michael Brennan, Dan Brown, John Cangialosi, T...

The Best Track Change Committee of the National Hurricane Center evaluates proposed changes to the Hurricane Database (HURDAT) in the Atlantic and eastern North Pacific basins. In the companion paper, Gruskin documents a possible tropical cyclone that affected portions of the eastern United States on 27-28 June 2006 and proposes that it be added to HURDAT. The committee reviewed the aircraft, radar, rawin-sonde, satellite, and surface data available on this system and found it to be a challenging and complex system. Areconnaissance aircraft flying in the system in real time failed to find a closed circulation before landfall, and kinematic parameters suggest the system was more likely to have the structure of an open wave, with any surface circulation at best being poorly defined. Because of the lack of conclusive evidence regarding the existence of a closed surface circulation before landfall, the committee has decided not to add this system to HURDAT as a tropical cyclone.

Abstract The satellite-based Dvorak technique (DVKT) is the most widely available and readily used tool for operationally estimating the maximum wind speeds associated with tropical cyclones. The DVKT itself produces internally consistent results, is reproducible, and has shown practical accuracy given the high cost of in situ or airborne observations. For these reasons, the DVKT has been used in a reasonably uniform manner globally for approximately 20 years. Despite the nearly universal use of this technique, relatively few systematic verifications of the DVKT have been conducted. This study, which makes use of 20 yr of subjectively determined DVKT-based intensity estimates and best-track intensity estimates influenced by aircraft observations (i.e., ±2 h) in the Atlantic basin, seeks to 1) identify the factors (intensity, intensity trends, radius of outer closed isobar, storm speed, and latitude) that bias the DVKT-based intensity estimates, 2) quantify those biases as well as the general error charact...

The 2008 Atlantic hurricane season is summarized and the year's tropical cyclones are described. Sixteen named storms formed in 2008. Of these, eight became hurricanes with five of them strengthening into major hurricanes (category 3 or higher on the Saffir-Simpson hurricane scale). There was also one tropical depression that did not attain tropical storm strength. These totals are above the long-term means of 11 named storms, 6 hurricanes, and 2 major hurricanes. The 2008 Atlantic basin tropical cyclones produced significant impacts from the Greater Antilles to the Turks and Caicos Islands as well as along portions of the U.S. Gulf Coast. Hurricanes Gustav, Ike, and Paloma hit Cuba, as did Tropical Storm Fay. Haiti was hit by Gustav and adversely affected by heavy rains from Fay, Ike, and Hanna. Paloma struck the Cayman Islands as a major hurricane, while Omar was a major hurricane when it passed near the northern Leeward Islands. Six consecutive cyclones hit the United States, including Hurricanes Dolly, Gustav, and Ike. The death toll from the Atlantic tropical cyclones is approximately 750.A verification of National Hurricane Center official forecasts during 2008 is also presented. Official track forecasts set records for accuracy at all lead times from 12 to 120 h, and forecast skill was also at record levels for all lead times. Official intensity forecast errors in 2008 were below the previous 5-yr mean errors and set records at 72-120 h.

The hurricane season of 2006 in the eastern North Pacific basin is summarized, and the individual tropical cyclones are described. Also, the official track and intensity forecasts of these cyclones are verified and evaluated. The 2006 eastern North Pacific season was an active one, in which 18 tropical storms formed. Of these, 10 became hurricanes and 5 became major hurricanes. A total of 2 hurricanes and 1 tropical depression made landfall in Mexico, causing 13 direct deaths in that country along with significant property damage. On average, the official track forecasts in the eastern Pacific for 2006 were quite skillful. No appreciable improvement in mean intensity forecasts was noted, however.

Abstract The National Hurricane Center issues analyses, forecasts, and warnings over large parts of the North Atlantic and Pacific Oceans, and in support of many nearby countries. Advances in observational capabilities, operational numerical weather prediction, and forecaster tools and support systems over the past 15–20 yr have enabled the center to make more accurate forecasts, extend forecast lead times, and provide new products and services. Important limitations, however, persist. This paper discusses the current workings and state of the nation’s hurricane warning program, and highlights recent improvements and the enabling science and technology. It concludes with a look ahead at opportunities to address challenges.