Computer models in the weather world can be a funny thing.
Meteorologists use computer model guidance to make a lot of decisions. They can hint at what temperatures will be, when patterns will shift and where storm systems might be headed. There are several different models used by the forecasters, and each model takes a look at the atmosphere several times per day. They change, and the meteorologists have to use their weather knowledge, along with what they see in the models, to tell you what’s going to happen.
You can see how that might get difficult, if the models have a wide range and don’t come to an agreement.
Case in point: Tropical Storm Sandy. Even as it churned south of Jamaica on Tuesday night, the models were busy running their ideas of where they think the storm will go a week from now. One reliable model had Sandy going through Hispaniola, then up near the east coast of Florida on Saturday (though it isn’t expected to have much of an effect on the Georgia-Florida game in Jacksonville, according to Weather Channel Hurricane Specialist Bryan Norcross). But then, it calls for the storm to drift northeast before turning toward New York City and slamming the big cities in the Northeast as a major storm. Forecasters fear it might be a Nor’Easter, but the type of precipitation — whether rain and strong winds, or some possible snow and strong winds — is also yet to be seen.
Forecasters have been hoping another reliable model proves true, instead. It took Sandy up the same path, until it got past Florida. Then, it projected Sandy to drift off to sea, being little more than a rip current threat to the East Coast. But, on Tuesday night…
With 17/20 GFS members now on board, its looking more and more like an historic East Coast storm may happen early next week.
— Eric Holthaus (@WSJweather) October 24, 2012
(The GFS is the model that had Sandy drifting out to sea)
Who knows — the models may change again in the upcoming days, and we may not have a historic storm on our hands. But the weather services are focused on raising the antennae of those in the possible path of the storm, because the words “perfect storm” have been used by some, and this is the time of year we saw The Perfect Storm happen.