Wednesday, September 4, 2019

My After Action Review on Dorian

The storm missed us by a wide margin, turning north farther east than originally expected and staying well offshore.  The local NWS said we got 0.76" of rain yesterday and 0.37" today.  Let's assume it was all from Dorian, and say we got 1.13".  The highest wind measured at the airport in two days was 38mph and the highest gust was 51.  We were under hurricane warnings through early morning today, which means conditions of sustained 75 mph or greater winds were expected.  The last forecast graphic I have for our area predicted winds from 75 to 110 mph.

As a result, it's hard to assess an After Action Review because there really was no action.  Yes, we took down antennas, put up shutters, made sure batteries were charged and ice was on hand, but that's routine prep stuff.  We never needed the flashlights, batteries or the ice.  Our generator never came on.  It was just a quiet day here. 

On the other hand, it's very easy to get cocky over hurricanes and warnings when they're consistently alarmist and, frankly, wrong in critical predictions.  That could lead to people not paying attention when they need to and with this storm, we needed to pay attention.  As Dorian closed in on the Bahamas, it became one of the strongest hurricanes ever recorded in the Atlantic.  Winds were 185 mph sustained with gusts to 200.  The storm moved at an incredibly slow 1mph over Abaco and then stalled over Grand Bahama Island; DiveMedic at Confessions of a Street Pharmacist posts a pair of  commercial satellite photos of the destruction on Grand Bahama, and they are mind-boggling.  I combined those two images into this one.  It looks like Grand Bahama has been reduced to about 1/3 the amount of dry land it used to be. 

Everything that's outlined in yellow in upper portion of the bottom picture is land that's no longer there.  All of those light lines in the upper right of the bottom view represent streets and residential areas that don't exist.  I know the official death toll has been announced at 20, it's just hard to imagine that only 20 people would have been lost in that kind of devastation. 

Since then, I've found a larger scale image on NPR that overlays the two views at identical scales - these views are slightly different scales.

Government at all levels seems to say "when in doubt, evacuate", but that assumes there's no cost to evacuating which is never true.  I'm talking not just about the cost of gas, and hotel rooms, but also disruption to work.  What if the people don't have a car they could trust to drive long distances?  What if they don't own a car at all?  In this storm, it was possible for people on the east coast to evacuate to the west coast, but there aren't many routes across the state; just more routes than going north out of the state.  The worst thing that could happen might be getting stuck in your broken down car as the storm builds around you. 

The same atmospheric changes that pushed Dorian away from us are what caused it to stall and wipe out Grand Bahama (explained in great detail here).  It's unfortunately usually true with these storms that any change that's better for one location is worse for another.  The stall caused the storm to stir up the water underneath it so that a cold water upwelling occurred, which started sapping the storm's strength and the winds started dying down.  Essentially there were two competing weather systems, one wanting to steer it north and one trying to push it south.  The steering winds canceled each other out causing it to stall.  An approaching upper level low pushed the system on the west side south allowing the northward motion to start, and the ULL is now pushing Dorian near the Carolinas. 


  1. YOW! Looks like a good portion of the island is just.....gone.

    As you say, good for one location, bad for another.

    Good to hear you got through it OK.

  2. Living on an island is fun... until it's not. There's a price to play in Paradise.

    For example, having lived on an island for 3 years at a young age, I remember when the tidal wave sirens went off, loudly. Then, about 10 minutes later, the stand down. Said tidal wave passed by our coral atoll, not having anything to generate a wave with (slowly rising shoreline, nope, we had brutally vertical undersea cliffs) and went and ate Japan. Weird times.

    Dorian was a good dress rehearsal for the State of Florida. Including FLNatGuard prepositioning (my nephew went to Camp Blanding) and an interesting test of Florida's anti-price gouging laws (of which I am in some disagreement with, as if you haven't prepped yet, price gouging gives you an incentive to move to where price gouging isn't and then prep for next time once you get home.) Weird storm, all hype, very little wind or rain. Bad for stupid people next time as they won't have prepped and won't take the warnings seriously, and big egg on face of all the weather doomsayers.

    Gee, if they can't predict pretty precisely where a hurricane is going to be in 3 days, how can we trust these same people with forecasting the future climate change?

    1. and an interesting test of Florida's anti-price gouging laws (of which I am in some disagreement with

      Similarly, legislators should set the value of pi to be 3, because it's entirely a made-up number which man can set to any value he wants. When the rain is coming down at 1"/hour and the 40 MPH wind is blowing your car around, you should continue driving at 65 MPH. Both prices and safe speeds have no connection to local conditions.

      Now consider what would have happened if a gas station owner had sold gas at $5/gallon, then shot and killed the official commie central planning price enforcers when they showed up. What percentage of Americans would approve of that?

  3. I don't think that upwelling was the cause there. The water under where the eye was trapped is only about 20 to 30 feet deep. (Grand Bahama Bank) There isn't any cold, deep water to upwell. I think what happened was more that the hurricane simply used up all of the available heat content. I know it seems like a nitpick, but these sorts of things are fascinating from a physics standpoint.

  4. You might want to examine the arguments made by James McCanney on the electrical nature of Hurricanes--why they decrease in strength over land. Suggest you start here:
    His web page is a total mishmash so one must persevere to find what you want. The key is his book: PRINCIPIA METEOROLOGIA: Physics of Sun Earth Weather listed in his ordering page.
    Dan Kurt

  5. Glad you're OK, but holy cow the picture of Grand Bahama is a tragedy

    1. A friend of mine said something this morning that really nails the situation: it has gone from Grand Bahama Island to Grand Bahama Shoal.

      Shoal: a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises close enough to the surface of a body of water to be a hazard to navigation.