Thursday, September 9, 2010

The $700,000,000 Weather Forecast

Hurricane Earl at a time when it was moving directly toward Florida (upper left)

Remember last week at this time when Category 4 Hurricane Earl was threatening the East Coast of the United States?

The memory has probably already started to fade because Earl just brushed the coast at the outer banks of North Carolina and far east Massachusetts. Total coastal miles put under hurricane warnings? According to the NOAA's National Hurricane Center, 450. There were no mass evacuations, just some selective evacuations in areas most threatened by the storm. Earl was an inconvenience, not a disaster -- just as it should have been, right?

Rewind 11 years. Above is a photo of Category 5 Hurricane Floyd in roughly the same geographic position as Earl. In 1999, virtually the entire East Coast of the U.S. was put under a hurricane warning. Again, according to NHC (thanks, Dennis Feltgen), the number of coastal miles of hurricane warning was 1,500.  There were mass evacuations that overwhelmed highways and local authorities --  to the extent that one scientist wrote an essay, "Floyd the Fire Drill."

Given the similar paths north of Hispanola, why was there such a difference in preparations between Earl and Floyd? The answer is simple:  The great improvement in the quality of hurricane track forecasts in the last decade.

Below is the Hurricane Center's forecast path from about the time Earl was north of Hispanola.
Instead of warning the entire East Coast as we had to during Floyd, the science of meteorology correctly identified that only the two areas (outer banks and far east Massachusetts) were at risk and warned accordingly. The forecast change in Earl's direction of movement and rate of weakening were both remarkably good considering this forecast was two days out.

Why is this important?  It is further evidence that meteorology has "tamed the weather."

NOAA estimates that an evacuation costs between $600,000 and $1 million per mile of evacuated coast. These costs include transportation, lost wages of the evacuees, preparations (i.e., cost of lumber to board up windows, pulling boats out of the water), lost income (tourists that cancel), etc.

Lets do a little hurricane warning math:  Floyd (1500 warned miles) - Earl (450 miles) = 1050 correctly unwarned miles due to the improvement in hurricane forecasting.

OK, now take those 1,050 miles and multiply them by a conservative figure of $700,000 in savings for each mile that correctly was not warned = $735 million dollars! Given the current weak economy, that is a tremendous value to the U.S. and its people!

And, when you figure in the value-added private sector hurricane forecasts issued by companies like WeatherData and its parent company AccuWeather, the savings grow further, perhaps approaching a billion dollars in total when the correct landfall forecast for Canada is factored in.  I chose to go with a more conservative number in the headline.

This is the story I tell (without math!) in Warnings: The True Story of How Science Tamed the Weather. We certainly have not "conquered" the weather, but we have tamed it -- that is, we have removed a lot of its sting through more accurate forecasts, warnings, and advice that people and businesses can use to make appropriate decisions in critical situations.  The story behind this unnoticed miracle of science and technology is fascinating and I hope you will consider checking out Warnings. 

In the meantime, congratulations to my fellow meteorologists in general and, in particular, the meteorologists at the National Hurricane Center and my colleagues at WeatherData and AccuWeather.

UPDATE: 10AM Friday:  The American Meteorological Society has more here.


  1. Apples and oranges--hurricane force winds from Floyd in fact came very close to Florida, which would make a warning justifiable. Earl was never anywhere near Florida.

  2. Agree with above comment. There were no US watches on Floyd until it was in the Bahamas, and Floyd tracked right up the coast whereas Earl never particularly threatened anything beyond Cape Cod and Cape Hatteras. NHC did not issue any CONUS watches for *either* storm when it was N/NE of Puerto Rico.

    More similar storms should be used to make the comparison the author is trying here. Earl had fewer coastline miles warned because it was less of a threat. Floyd had more miles warned not because of more forecast uncertainty 11 years ago, but because it tracked right on the coast.

    The author's point may be valid, but the example chosen does not show it.

  3. Actually, I believe the examples do in fact demonstrate my point.

    At the time of the photo of Hurricane Floyd, the Miami Herald was running a huge front page story quoting NHC discussing that south Florida might be hit by a category 5 hurricane. Of course, it did not strike south Florida.

    The reason we knew "Earl" -- at the same geographic location -- was not a threat was become of the improved confidence in our forecast skill.