NWS increasing services to help officials better prepare for storms
Published 8:31 pm Wednesday, May 31, 2017
With the 2017 Atlantic Ocean hurricane season beginning today, the National Weather Service is providing several services and products related to hurricane forecasting to better serve emergency-management personnel and residents in assessing a storm’s threats.
During the hurricane season, which ends Nov. 30, the NWS will issue storm surge watches and warnings to highlight areas along the Gulf and Atlantic coasts of the continental United States that have a significant risk of life-threatening inundation from a tropical cyclone, subtropical cyclone, post-tropical cyclone, or a potential tropical cyclone. Storm surge might not occur at the same time a storm’s winds pose a hazard, according to the NWS.
“Having separate warnings for these two hazards will save lives by better identifying the specific tropical cyclone hazards communities face, and by enhancing public response to instructions from local officials,” according to a NWS publication.
NWS also plans to implement an experimental time of arrival tropical-storm-force-winds graphic.
“The arrival of sustained tropical-force winds is a critical planning threshold for coastal communities, as many preparedness activities become difficult or dangerous once winds reach tropical storm force,” read the publication. “The primary graphic displays the ‘earliest reasonable’ arrival time, identifying the time window that users at individual locations can safely assume will be free from tropical-storm force winds.”
If the NWS approves, this hurricane season the National Hurricane Center will have the option to issue advisories, watches and warnings for disturbances that are not yet a tropical cyclone, but which pose the threat of bringing tropical storm or hurricane conditions to land areas within 48 hours, according to the publication. “Under previous longstanding NWS policy, it has not been permitted to issue a hurricane or tropical storm watch or warning until after a tropical cyclone had formed,” according to the document.
NWS officials indicate the hurricane-tracking forecast cone will be smaller than in past year. “The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of imaginary circles placed along the forecast track (at 12, 24, 36 hours, etc.),” reads the publication. “The size of each circle is set so that two-thirds of historical official forecast errors over the previous five years (2012-2016) fall within the circle.”
NWS forecasters predict a 70-percent likelihood of 11 to 17 named storms (winds of 39 mph or higher), of which five to nine of them could become hurricanes (winds of 74 mph or higher), including two to four major hurricanes (Categories 3, 4 or 5; winds of 111 mph or higher). An average season produces 12 named storms of which six become hurricanes, including three major hurricanes, according to the National Hurricane Center.
The National Hurricane Center’s storm-surge group can be followed on Twitter at @NHC_Surge. The National Hurricane Center’s Facebook page: www.facebook.com/NWSNHC. The National Hurricane Center Twitter page: www.nhc.noaa.gov/twitter.shtml.