One week into the 2016 hurricane season and we’re already three storms down.
With the so-called “spaghetti models” in the spotlight again as we track the paths of storms, time to review what they all mean and where they come from.
National Hurricane Center meteorologists use a slew of sophisticated storm tracking models to determine the official cone of uncertainty watched so closely by cyclone-threatened areas.
The spaghetti models are run by universities, private companies, independent groups and the National Weather Service. They are represented as colorful lines on tracking maps.
But the simplicity in the squiggle belies the millions of dollars dedicated to perfecting some of the models, such as the National Weather Service’s Hurricane Weather Research and Forecasting model, or HWRF.
Already a respected model, HWRF has been undergoing annual improvements, including upgrades that allow the model to process atmosphere more closely and a new supercomputer to interpret the data.
A new HWRF ensemble-based data assimilation system will also be implemented to make better use of aircraft reconnaissance-based Tail Doppler Radar data for improved intensity forecasts.
“It’s now considered the international model of choice,” said Chris Vaccaro, director of NOAA Communications and External Affairs. “For the 2015 hurricane season, HWRF has improved again and is running at a much higher resolution.”
But forecasters caution against focusing on a single model. The National Hurricane Center doesn’t post spaghetti models on its website because it doesn’t want people to be misled
“All models have their biases,” Vaccaro said. “There are strengths and weaknesses and that’s why the human forecasters are so critical.”
Other models considered reliable are the Global Forecast System, or GFS, also from the National Weather Service, and the European model, or ECMWF. Some models average others, such as the TVCN model.
Often, people will be surprised when the National Hurricane Center’s projected path is not where most of the squiggly lines are suggesting the storm will go.
That’s because, along with all the other data they load into their computers, hurricane forecasters weight the models by their track records.
As a result, an image can show 10 lines heading west to West Palm Beach, and two heading to Iceland, and the official track will point north.
Computer models calculate millions of satellite measurements of temperature, air pressure, moisture and wind movements at points around the globe.
Statistical models use data from past storms, as well as what a particular storm has done so far, to extrapolate where it might go next. Hurricane forecasters use the models only as a baseline estimate or not at all, because global climate patterns change constantly, sometimes from hour to hour.
“There are dozens of potential tracks deriving from all the individual models, the various model ensemble members, etc.,” said National Hurricane Center spokesman Dennis Feltgen. “It would be difficult to decide which to show, and we could not display them all clearly. Also, some models are provided to us under the condition we do not share them, and some models are only available every 12 hours, rather than every six hours.”