Hurricane Center Changes Policy to Include Sandy-like Storms; AMS Forum Assists

April 5, 2013 · 0 comments

If another storm like Sandy threatens land while on the cusp between tropical and extratropical classification, National Hurricane Center (NHC) forecasters will have a green light to issue or maintain watches and warnings as well as advisories, even after transition.

That’s the policy change NWS/NHC made this week after months of animated debate among forecasters, weather broadcasters, and emergency managers. The changes will take effect at the start of the 2013 Atlantic hurricane season, June 1.

The shift—from watches, warnings, and advisories only being posted by NHC when a storm was expected to be strictly tropical as it came ashore to now being allowed for what it terms “post-tropical” storms at landfall—was borne of a critical firestorm.

Despite the enormous threat from Sandy last October, NWS and NHC decided not to hoist hurricane watches and warnings for the northeastern coast of the United States because the monster storm wasn’t forecast to land its center on shore while still a hurricane. The re-classification of Sandy as post-tropical would have forced such alerts to be dropped mid storm, which they argued would cause confusion.

Critics of the decision claimed that people in harm’s way didn’t take the storm seriously because there weren’t any hurricane warnings in place. Nearly 70 people died in the United States directly from Sandy’s surge and wind.

The fallout included broad discussions of the difficulty forecasting Sandy. At an AMS Town Hall Meeting in Austin, Texas, in January, Louis Uccellini (then director of NOAA’s National Center for Environmental Prediction) said that NWS and NHC forecasters had anticipated Sandy transitioning from a hurricane to an extratropical storm, but they expected it to happen sooner than it actually did. In his presentation, he also noted that the primary operational forecast model used by the NWS (the Global Forecast System, or GFS, model) had performed the best of all models during the 2012 Atlantic hurricane season, but when it counted—with the season’s only two landfalling U.S. storms of hurricane intensity (Isaac and Sandy)—it had the worst forecasts.

“When you don’t hit the big one, people notice,” he said.

Compounding the uncertain model forecasts was what to do with the warnings if the transition occurred prior to landfall. NHC Director Rick Knabb discussed this at the same AMS Town Hall meeting, calling it the “Sandy warning dilemma.” He agreed that hurricane warnings would have been best, because they’re familiar and grab your attention. But, because of the looming transition, discussions among NHC and NWS forecasters as well as emergency managers and local and state authorities, including one governor, stressed that the warning type not change during the storm for fear of confusing the message during critical times of preparation and evacuation. Due to the structure for hurricane warnings in place at the time, which would have forced NHC to drop them once the transition occurred, NHC and NWS forecasters opted not to issue a hurricane warning for Sandy.

“We wanted to make sure the warning didn’t change midstream, and we could focus on the hazards.”

Ultimately, calls settled on a way to effectively communicate the threat of dangerous winds and high water regardless of a storm’s meteorological definition. A proposal surfaced during the Town Hall that would broaden the definition of tropical storm and hurricane watches and warnings and include post-tropical cyclones, whose impacts still pose a serious threat to life and property.

Knabb credits the candid nature of the months-long debate, with its criticisms and recommendations, for the now-approved proposal. He says it will allow NHC and NWS forecasters as well as the emergency management community to focus on what they do best.

“Keeping communities safe when a storm threatens is truly a team effort and this change reflects that collaboration.”