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Sep 04

The National Hurricane Center Is A Trusted Source As Worrisome Hurricane Irma Looms

Ok, folks, I am officially concerned, and I usually try to be measured. It is Labor Day, and many people are enjoying the day off. There is a group of professionals, however, that is working very hard today as the increasingly worrisome threat of Hurricane Irma looms. For colleagues at the National Hurricane Center, the peak in the Atlantic basin hurricane season is approaching. This has been an active year, as predicted. Irma has me and other meteorologists particularly concerned. Over the weekend, I sat back on Twitter and watched the sheer volume of tweets, updates, opinions, hyperbole, hype, excitement, and dread associated with Irma. There was even one unfortunate “article” that made the rounds talking about hurricane categories that do not even exist. All of this made me wonder how the non-meteorologically attentive public (people like my mother or Barber) can stay focused on a clear signal with such overload of information. The National Hurricane Center is a trusted source that I wanted to highlight on this Labor Day as Hurricane Irma grabs the news cycle.

NOAA NHC

5-day forecast as of Labor Day morning.

However, it is prudent to provide an update on Irma. Hurricane Irma is a grave threat to residents in the Caribbean region and looks to be an equally worrisome threat for the contiguous United States. Irma is a category 3 hurricane and just to the east of Leeward Islands where hurricane watches have been issued. The latest 5-day forecast (above) is ominous, and I have distilled some important points from the 5:00 am AST NHC forecast discussion,

the global models have been trending toward quickly lifting the trough out over New England and eastern Canada on days 4 and 5, with the subtropical ridge building westward toward Florida. As a result, it’s becoming increasingly likely that Irma would maintain a west-northwestward heading on days 3 through 5, and the track guidance shifted significantly westward on this cycle during that period. Remarkably, the track models are very tightly clustered through day 5, which increases the confidence in the westward shift of the latest NHC forecast.

As the National Hurricane Center notes, it is too early to know the specific “where and when” of downstream impacts on the U.S. mainland. However, the statement about models being clustered indicates that there is growing consensus on how meteorological patterns are setting up to steer the storm. My meteorological “eye” sees a threat to Florida to the Carolinas (and possibly even a slight chance of moving into the Gulf of Mexico). I also see the potential for Irma maintaining category 3 or greater intensity. Tropical storm force winds could be impacting some of these regions within the next 1-5 days.

NWS NHC

Tropical storm wind speed probabilities (4.5 days)

Ok, let’s get back to National Hurricane Center (NHC) “101”. The NHC is actually a part of the National Weather Service (NWS). When I tweeted my thoughts on sifting through “hurricane information overload,” NWS Storm Prediction Center meteorologist Roger Edwards responded, “If more and more of us directly to the sole official forecast source (NHC), the info asymptotically approaches consistency.” There is certainly value in multiple messaging from different sources and colleagues so do not miss what I am saying. However, when you have people posting fake hurricane tracks or articles about category 7 hurricanes, Roger’s point is well-taken. NHC’s website points out,

NHC is a component of the National Centers for Environmental Prediction (NCEP) located at Florida International University in Miami, Florida. The NHC mission is to save lives, mitigate property loss, and improve economic efficiency by issuing the best watches, warnings, forecasts, and analyses of hazardous tropical weather and by increasing understanding of these hazards. The NHC vision is to be America’s calm, clear, and trusted voice in the eye of the storm and, with its partners, enable communities to be safe from tropical weather threats.

 

NOAA NWS

NWS Organizational Chart

NHC is broken up into several units and has a Director (or currently an Acting Director in Dr. Ed Rappaport). These units as described on the NHC website are:

The Hurricane Specialist Unit (HSU) maintains a continuous watch on tropical cyclones and areas of disturbed weather within the North Atlantic and eastern North Pacific basins. The HSU prepares and issues analyses and forecasts in the form of text advisories and graphical products. The HSU issues coastal tropical cyclone watches and warnings for the United States and its Caribbean territories and provides watch and warning recommendations to other World Meteorological Organization (WMO) Region IV meteorological services.

The Tropical Analysis and Forecast Branch (TAFB)generates analyses and forecasts over the tropical and subtropical eastern North and South Pacific and the North Atlantic basins year-round.

The Technology & Science Branch (TSB), often in conjunction with other government and academic entities, develops and transitions new tools and techniques into operations for tropical weather prediction.

Dr. Marshall Shepherd, Dir., Atmospheric Sciences Program/GA Athletic Assoc. Distinguished Professor (Univ of Georgia), Host, Weather Channel’s Sunday Talk Show, Weather (Wx) Geeks, 2013 AMS President

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