Dorian Update, Friday 30 August (And a rant on models. Again.)

Bottom Line: Hurricane Dorian has started the expected turn to the west, and has the potential to strengthen before hitting The Bahamas.  As noted in the NHC Key Messages product, there is a hurricane watch up for the northern Islands, and people there should be executing their hurricane plans. People on the Central and South Florida should be getting ready for watches, warnings, and evacuation directions.  Georgia may see some effects of the decaying or remnant storm in 6-7 days, but it is way too early to say much on that.  More details at the end of this post.

The big picture hasn’t really changed all that much since yesterday, but the details have, and those can have a big impact on potential damage.  NHC has shifted the track a bit further south, and again the forecast speed has slowed down.   The forecast environment isn’t quite so favorable as was thought a couple of days ago, but Dorian will still likely be a major hurricane, it may even reach Cat 4 (130mph) before landfall. It be a dangerous, powerful storm.  Here’s the scary model track map …

(begin rant)
Once again, for planning purposes, all you need to concentrate on is the red line of the official forecast track.  All the talk about models is just stressful and confusing.  I was watching CNN last night, and like many outlets they made a big deal about  “The American Model” vs  “The European Model.”  Guess what: there is no such thing in either case. There are multiple models, and operating modes. used by the US National Centers for Environmental Prediction, NHC, US Navy,  and so forth.  Likewise, the European Center for Medium range Weather Forecasting (ECMWF) has multiple operating modes for their Integrated Forecast System, including hurricane specific modes.  And the UK Met Office has a modeling suite (and they are I suppose European until Halloween at least!).  Not to mention the Canadian Meteorological Center.  What CNN and other members of the professional and amateur chattering classes are showing you are the graphics from the main forecasting runs of the GFS (the “American” model) and the ECMWF IFS (the “European Model”).  It especially irks me that IFS is touted as being so much better than any of the US models.  Yes, IFS is good, especially in some circumstances.  But last year the “consensus” models that blend multiple models (including GFS and IFS), such as the TCVA, or the Florida State Super Ensemble (FSSE) were better.

So which “model” was the best overall? Here’s the report from last year.  THE NATIONAL HURRICANE CENTER OFFICIAL FORECAST TRACK.  So just stop it already!  If you want to use a model to illustrate some point, fine, but showing them because the graphics are prettier and animated, or to set up some artificial horse race competition, is just scare mongering.
(end rant)

As for impacts, The Bahamas and Florida look to be hit hard.  Here is the forecast impact map based on the 5am NHC Forecast …

As noted above, the northern islands of The Bahamas needs to be getting ready.  Dorian will be Andrew-like in damage to those areas.  Abaco and Grand Bahama (Freeport) are likely to be hit hard.  Currently the forecast landfall location is just north of West Palm Beach, putting the worst of the storm North of the WPB-Fort Lauderdale-Miami corridor.  Even on this track it’s a $38 Billion dollar storm. But shift the track a mere 50 miles south and it becomes well over $100 Billion dollars in direct damages.  Woah.  When you throw in economic impacts of the Labor Day weekend, if Dorian makes landfall at the expected intensity it will easily be in the top 10, and is on track to perhaps be the most expensive hurricane in US History …

In Florida the Lake Okeechobee area is often overlooked, but is also at great risk for flooding and ruptured flood control works, especially if as forecast the storm stalls.  People in that area should be especially aware of their flood zones.

Florida evacuations are going to be a goat rope. Follow the advice of your local EMA’s where possible.  Keep in mind the mantra: evacuate from water, shelter from wind.  Don’t get caught out on the road if things jam up, evacuating from wind if you live in a sturdy structure above the flood zone may actually be more dangerous than staying put.  It may not be pleasant, but better than in your car! This is an especially problematic storm in that it will put much of south and central Florida in storm conditions, with those spreading up towards the north, so to get completely out of the track would mean a journey to Alabama or North Georgia.  If in a flood zone or mobile home just get out.

What happens after day 5?  The NHC track ends at 120 hours for a reason: the uncertainties are just too great.  The global models  take the storm (or remnants thereof) across Georgia then either out to sea or up the east coast.  A warning here: there is at least one popular web site that has been showing the 850mb maps from GFS and/or IFS.  These look scary for Georgia, but the SURFACE winds were only 20 or 25 mph.  I suppose I’ll have to rant about that later.  So the bottom line in Georgia is what it was the last two or three days: we’re still more than 5 days from seeing anything from the storm, so best to just watch and keep out of the way of folks who need to move.

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