Myles Blog: Sandy’s Spaghetti

Posted at 10:25 AM, Oct 23, 2012
and last updated 2012-10-23 12:43:38-04

When it comes to tropical systems you often hear meteorologists talking about spaghetti models. It’s an odd name for something that is a key part of forecasting tropical cyclones.

First off… What are spaghetti models? Spaghetti models (also called spaghetti plots) are the nickname given to the multiple computer models when shown together because the individual model tracks can somewhat resemble strands of spaghetti. Every day meteorologists look at dozens of computer models both for tropical weather and “everyday” weather. Each model factors in and calculates a different set of data, resulting in a unique forecast. It’s our job as meteorologists to digest this data output, sort through the bad, and find the good to help us shape a forecast.

Another question… Why would viewers want to see spaghetti models? For a developing storm system that has not officially become a tropical depression or a tropical storm, spaghetti models can give you an early heads up as to where they may track. Once a storm is official, the National Hurricane Center releases an official forecast path based on their analysis. But it is often useful to compare the NHC forecast cone and the spaghetti plots to get a better picture of the uncertainty within a storm track.

What about (now) Tropical Storm Sandy’s spaghetti models? For days now, I have received several emails and Facebook posts from weather enthusiasts proclaiming “Sandy is going to wreck the East Coast” or “Sandy is only a fish storm, why are you talking about it”. Each post with a “look at this!” type of picture. That is the issue with the computer models, each one is different and often times widely different.

Follow Sandy with our interactive hurricane tracker

I have posted a picture of the spaghetti models for TS Sandy from Tuesday morning. Notice the tight grouping through Jamaica, Cuba, and the Bahamas. The models are lining up… that’s good news for forecast confidence. Now notice what happens after the Bahamas… the “spaghetti” has now spilled all over the “Atlantic kitchen table”. One extreme has Sandy making landfall in Virginia Beach, the other extreme keeps Sandy southeast of Bermuda and 1000+ miles away from the east coast.

This spread in the models is common with tropical systems, but Sandy’s spaghetti has gotten more buzz because the extremes aren’t coming together quickly. Think of it like two stubborn siblings who refuse to agree. Who’s right? Who’s wrong? Is a compromise the right answer? Sometimes the best solution is to sit back and wait it out.

-Meteorologist Myles Henderson