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Why Spaghetti Plots Aren’t Always Reliable

6 Sep 2017, 4:43 pm

Now before you go getting all up in arms, let me say– if you live in an area that could potentially see Irma or any hurricane for that matter, the time to prepare is now. Have a plan in place, be ready, communicate that plan with friends and family, and be ready to execute it.

If you need some tips on how to prepare, here are some preparedness tips from Hurricane Awareness Week.

Hurricane Preparedness Week: May 7-13, 2017

Spaghetti Models

Spaghetti plots don’t necessarily tell the story.
Notice how for the next few days the models are in general agreement of where this storm might go.

However, from there, things go wildly awry. In fact the differences in paths goes from a few miles to hundreds of miles.

From southern Florida to New England is quite a bit of uncertainty. But as we’ve seen with this very storm, that uncertainty shifts significantly with each model run. Some take it farther west and others take it farther east, even avoiding a U.S. landfall all together. However, spaghetti plots take forecasting uncertainty to a whole new level.

Why Spaghetti Plots are Bad

For starters, spaghetti plots and ensemble forecasts are as wildly different as the different forecast paths themselves.

While an ensemble forecast plots all of the different possible forecast paths of a given model run, spaghetti plots throw all of the different models on one map.

Sounds good right? Not so fast.
Just to give you a quick idea of what is plotted here is a sample of just a couple plots.

  • NHC: The National Hurricane Center’s forecast.
  • CLP5: Not a model, simply where storms in this area go climatologically. No current weather is taken into account.
  • TABS/TABM/TABD: Statistically where this storm might go, also doesn’t factor in any current weather.

The list goes on and on. Some are forecast models, others are just a bunch of random lines that may or may not mean anything.
The behind-the-scenes team here at WeatherNation does a great job of pulling some of the wilder models out of the spaghetti plots, but for the most part– what you see on the internet isn’t telling the whole story.

A More Trustworthy Forecast

The best thing to do is to simply look at the National Hurricane Center’s forecast cone.

The yellow portion is just the first 48 hours of forecast. It’s the part of the cone forecasters are more certain on a storm track.

From there, the cone widens as the storm becomes more difficult to forecast.

As of press time, Irma is expected to make landfall in southern Florida Sunday afternoon.

The forecast is bound to change as a potential landfall nears, so be sure to check with the NHC and WeatherNation for the latest.


— Meteorologist Jeremy LaGoo

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