Dorian Update for Thursday Morning, 29 August 2019

Dorian is now well past Puerto Rico and the Virgin Islands. Fortunately damage seems fairly light, mostly power outages, scattered roof damage, and some trees down.  Here’s a farewell radar scan from the San Juan International Airport …

Dorian didn’t intensify much overnight, but is entering an area where conditions are more favorable.  The primary track and intensity models are in agreement for landfall somewhere on the Florida coastline between Miami and Jacksonville.  I’ve heard some snarky comments about that, but it is an amazing improvement in our ability to forecast hurricanes that the band is that narrow four or five days out.  In this dynamic situation, even 10 or 15 years ago the uncertainty band would have been from Miami to New Jersey.  Here’s the scary confusing “spaghetti model map” …

… honestly, these kinds of maps are pretty useless like this so let’s peel back the layers and see what is really going on. If you are in a hurry you can skip down to “The Bottom Line” below.  Many of these lines are what are known as ensemble members, secondary models, or model runs based on older data.  Here are just the current/recent “primary” track models:

Not so bad, is it?  The brown line taking off to the north is the “CLIPER” model.  It is a purely statistical model that shows us where historical storms that were near where Dorian is now, and moving about the same direction, ended up going.  It doesn’t know anything about the weather now, but is a good indicator that in about a day or so Dorian is expected to do something “unusual.”  The faint gray line, XTRP, is what would happen if the storm just kept going in a straight line.  So what about the GFS (the dodger blue line), which has been causing some FUD (Fear, Uncertainty, and Doubt) in Georgia.  Let’s look at just the GFS family of model runs.  Again, the blue line is the primary run, the cloud of thin gray lines are twenty (20) “ensemble members” – simulations that started in slightly different positions, and with slightly different initial conditions.  The brown line is the average of these scenarios.   Note that is right back in the central/south Florida area where the other models are showing landfall …

The Bottom Line

So what should you do?  Well, if you are not a tropical cyclone expert there is only one line you need to care about, the National Hurricane Center official forecast track.  They go through the above exercise every six hours, using their years of experience to blend all the model data along with real time observations and aircraft data to create a forecast. Here is the current (5am ET Thursday) forecast track, along with the estimated impacts based on my Haetta/TC model using their track and intensity …

The storm track forecast has slowed down a little.  People in the northern Bahamas need to start preparing for a major hurricane.  It’s maybe three days out from the initial impacts, and it looks to be bad.  For the Florida coastline from West Palm to Jacksonville, and inland areas in the post-landfall path, it’s time to start getting serious.  Given the holiday weekend, expect evacuation guidance and other plans to kick in to high gear a bit early, potentially later today or tomorrow.  Remember the key life saving mantra: evacuate from water, shelter from wind.

If you had plans to go to Florida for labor day, I hate to say this but better luck next year.  Airlines are already realigning their flights.  Best to stay away.

For Georgia, it’s still watch and wait.  For now it looks like the bad impacts will be south of us, although the far south Georgia (Brunswick and St. Marys) need to be more ready for the fringe impacts and, if things go squirrely, take action.  I’m hearing that SCAD is recommending “voluntary evacuation” Saturday.  That’s not helpful.  At this time it looks like impacts to the Savannah Georgia area will be minimal.

On an unrelated but related note, there are some concerns about coastal flooding along the Georgia/SC coast because of high astronomical tides.  The forecast at Fort Pulaski was already close to major flood levels (which means US 80 closed), and we will likely see that tonight at the 8pm high tide and the overnight tides on Saturday, Sunday, and Monday.  You can see the tide forecast here.  People who live on the Georgia Coast and it floods with spring tides can expect that.  I wouldn’t expect Matthew or Irma kinds of flooding, as Dorian is a small storm, but we could well have a couple days of onshore winds so that with the high astronomical tides means at least a foot or two above the normal higher high tide levels.

8 thoughts on “Dorian Update for Thursday Morning, 29 August 2019

  1. Traveling through Jacksonville tomorrow to get to I 10 in route to Pensacola ( not for vacation) Please advise as to when you think it will hit Jacksonville?

    • Tomorrow (Friday) should be a nice day. It will be Sunday/Monday/Tuesday that are rough. But beware that if evacuations start travel in Georgia/FL/Alabama will get bad fast …

  2. CW – thank you so much for your rational descriptions and reader-friendly (and humorous) possibilities. Every year I share your blog with new employees who begin to panic 10 days out and start searching for spaghetti models and contemplate ‘other scenarios.’ I’d hate to rely on local TV and NHC – so please maintain this site.

    • Sorry, I don’t have a specific app (I don’t get paid or make any money off this; in fact it actually costs me time/money/etc). You can subscribe to email notifications, and the posts are sent to both facebook and twitter (although I understand not wanting them in your life!_.

  3. I’d love to see an example of a forecast for a similar storm at the same relative point 10 to 15 years ago to see the progress in forecasting, any good examples come to mind?

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