Meteorologists listen to ensembles for help with long-range forecasts


Meteorology, whether your choose to believe it or not, has come a long way in the last few decades. However, there will always be ways to improve our inexact science.

Forecast models are tools we use to guide us in the right direction when predicting the weather, with experience and knowledge helping determine if those models are on to something. These models, generally speaking, do a poor job of handling exact details 5+ days out. To make a long story short, the computing power just isn't there yet.

That's exactly why you shouldn't take a hurricane forecast as gospel more than a few days away, and the same could be said with snowfall forecasts in the winter!

The meteorological community understands that it's 2017, and that the demand for information is very high. So, we try to stay ahead of the curve. But there's a way to do that without sounding so certain in a forecast that's 5+ days away.

That's where we have to start listening to the 'ensembles.' Two of the main forecast models we use are the GFS and the European. Their 'ensembles' can help us convey uncertainty in the forecast a little better.

Picture each of these models being a conductor, with each having a certain amount of members in its ensemble. If the members are playing the same piece, it should sound great. If each member is playing a different piece at the same time, it's a mess.

That's where the spaghetti plots come into play, and we'll use Hurricane Jose as an example.

The forecast for one day away shows each member of the GFS model in agreement, that Jose is going to begin curving around in the open Atlantic. The ensemble is sounding tight. There's certainty in the forecast.

When you go 5-7 days away, uh-oh! The members of the GFS ensemble start drifting apart, and the band starts to sound really bad. You have members taking this storm up the east coast, and you have members taking it out to all the fishies in the open sea. The forecast is highly uncertain.

Even with that being the case, you will see articles about 'the next storm' and how 'Jose is bearing down on the east coast.' We don't know that just yet. In fact, there's more wind shear working against Jose.

If we didn't learn that patience is a virtue from Hurricane Matthew's always-changing path in 2016, hopefully we learned it from Irma's these past two weeks.

You can watch how its forecast path changed a lot (especially as it moved through the Caribbean) below.

In fact, this is a large part as to why the National Hurricane Center's forecast path only goes out 5 days in advance. It's also why their forecast paths are shown in a 'cone of uncertainty.'

Yet, there were still meteorologists and non-meteorologists who would post about likely landfalls on the east coast when that was very much in question. They were then forced to retract that statement when the forecast path inevitably changed.

As my family who evacuated from Naples, Florida could tell you - that kind of back and forth puts you through an emotional rollercoaster.

So (for what it's worth) here's what I propose the meteorological community does. Be 100% transparent and honest. We strive to do that day in and day out on the StormTrack 5 weather team. If we don't know, we tell you that we don't know. And sometimes not knowing can show that you have a wealth of knowledge.

It's okay to say "Jose's spinning in the Atlantic, with a wide variety of options as to where it will wind up. There's no need to panic, but understand that we'll be keeping our eyes on it - should it become any concern." It's not okay to say "Here comes Jose!" and then a few days later go "Wait...nevermind. Sorry, y'all!"

Perhaps this blog post comes across as a rant. It isn't intended to be that way. It's more so intended to show you guys where we stand in meteorology, and why you shouldn't over-react to most high impact potential forecasts (snowfall, hurricanes, severe weather) 5+ days away. Pay attention, check back for updates, but don't freak out.

Know that we've got you covered on all things weather, and that we do our best to give you the most honest and accurate forecast every day.

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