Why you shouldn’t get excited about long range forecasts …

I ran across a weather blog yesterday (sadly, by someone with an AMS seal) playing up a possible hurricane hitting New Orleans next week, based on the GFS model forecast.  Here’s the forecast map in question, the 225 hour forecast from the 18z GFS/FV3 run on Tuesday, August 13th (the Tuesday Afternoon run).  Looks bad for the sweltering, drunken masses on Bourbon Street …

But, as a reader of this blog, I know that while the new models are better, global weather models still have a tendency to spin up vortexes, so I waited to see what the next run on Tuesday night showed before freaking out …

Oh, now it’s just a tropical depression or storm, and not a problem for the weekly NOLA Friday Night Bacchanalia.   But, what does that mean for my oil and cattle futures?  Lets look at the early morning (06z, Wed. 14 August) for the same time (03z Friday, August 23rd, now “only” 213 hours away) …

Hey, where’s my storm?  Now it’s just a blob of rain on the Alabama/Louisiana border?

Forecast tracks from the global models have improved a lot in recent years, once a storm spins up, and are better at forecasting formation in the short term (0-5 days).  But this example is why these long range models are not that useful for long range hurricane forecasts, and why the National Hurricane Center only does outlooks out five days.  These models just aren’t designed for it, and this far away, the uncertainty is so great you can get exhausted tracking every little vortex that, over the life of the model, will spin up, but don’t even exist in the “real” world (not to mention the systems that spin up in the real world).  So anybody talking about storms forming a week away is probably just phishing for clickbait.  Now, talking about those who talk about them, that’s a public service and perfectly ok …

NOAA’s Atlantic Hurricane Season Update

Last week the US National Oceanic and Atmospheric Administration (NOAA) released an updated seasonal forecast, and due to the waning El Nino has increased their forecast for the number of storms expected this year, now saying there is an increased chance for an “above average” season.  What does that mean to you, the huddled masses cowering in fear along the shoreline, waiting for your inevitable doom?

Exactly nothing (assuming you have a hurricane plan already, which you should no matter what the seasonal forecast says).

First, even if you knew *exactly* how many storms were going to form in a year, it tells you nothing about how bad the season will be.  There have been above average years in raw numbers with no hurricane landfalls.  1992 was a below average year – well, except for Hurricane Andrew.  So unless you know where they are going to go, even one hurricane can ruin your day, and 20 can be no big deal if they are all fish storms.

Second, the numbers used to compute the averages are becoming more and more suspect.  This year’s “hurricane” Barry more than likely would not have been classified as a hurricane in past years for a number of reasons (before anyone yelps, no, this isn’t part of the Vast Global Warming Conspiracy(tm), it’s because of better observation systems that can see small patches of possible hurricane force winds, and different classification criteria).

I really don’t like the hype around seasonal forecasts and their updates.  Dr. Mark Johnson of UCF and I used to do them (including something NOAA doesn’t do, landfall probabilities), but the media circus and subsequent fear mongering were just a bit too much.  We still generate them, and they have decent enough skill, but they aren’t really “actionable” except for narrow applications.  About the only thing they are good from a public safety standpoint is “awareness,” but there are other ways of doing that than shoveling out the statistical stables …

So if you haven’t put together a plan yet, slap yourself and go to visit the FEMA web site and get some checklists to think about, consult your local EMA for risk maps for your risk of flooding (which is by far the major threat to life; the golden rule is shelter from wind, evacuate from water), and put together a plan.  Then don’t worry about it.