Hurricane Michael update for mid-day, Monday 8 October 2018

First here’s the obligatory pretty satellite image.  Michael continues to organize but still doesn’t have the “classic” presentation with an eye …

As for the where it’s going part of the analysis, NHC has been trying to avoid a common problem with weaker storms that are likely to intensify rapidly (which Michael is showing signs of doing, it’s now a hurricane).  That problem is known in the business as the “windshield wiper effect.”  Track models will swing wildly from left to right depending on the initial position (and knowing the center of a storm to within 100 miles is hard in the early stages of a storm), and the evolution of the storm has a strong interactive impact with the track forecasts.  This is a huge problem in the Gulf, since storms that form in the western Caribbean tend to be weak until they clear the Yucatan straights, but can spin up very rapidly. Yesterday things were trending east, but this morning are trending west even though the storm initial position has been trending east.  Here’s some of the latest track forecast models, along with the key thing to monitor, where the official watch and warning areas are.  Note that the NHC official 5am forecast track is now on right hand edge of the models available as forecast time …

Bottom line on “where”: if you are in western Cuba, or the gulf coast of Florida, take the storm seriously and prepare.  So how bad when it gets where it’s going?  The “best guess” is the storm will hit a peak of near category three, but shear and interaction with land may drop the landfall intensity to Category two. Plan of a three to be safe if you are in the pink (Hurricane Watch) area of the above map.  Here’s the possible impacts, and the new NHC official track as of 11am …

Depending on exactly where the eyewall crosses and how strong, Michael could cause anywhere from $2 (exact track shown) to $5 Billion (left wobble putting eyewall over Panama City) in damage.  Inland, as typical for a storm like this, you will see trees down, weaker structures damaged, and the inevitable power outages.  Michael should be a fast moving storm, so unlike Harvey or Florence catastrophic flooding isn’t too likely, but it could still drop lots of rain into already wet areas, so flash flooding and more misery for SC/NC are unfortunately in the cards.  Otherwise, for the Atlantic coast, rip currents and coastal flooding are possible from Georgia up through Virginia on this track, along with some trees down and power outages, but nothing catastrophic.  That doesn’t mean you shouldn’t prepare, especially for those impacts, and especially in flood prone areas, but for perspective it’s not like the Gulf Coast is facing, or that NC and northern NC experienced (actually, are still experiencing) with Florence.  Here’s the WPC Rain swath map.  Not the 30″ catastrophe of Florence, peaks a bit over 10″ with 7″ inland across Georgia, maybe 4-5″ in SC/NC, but even a few inches in a short time can certainly cause flash flooding.  If in a flood prone area, beware …

3 thoughts on “Hurricane Michael update for mid-day, Monday 8 October 2018

    • Because the storm is inland and we are to the right of track, the winds will be blowing onshore, causing higher than normal water levels. Because we are within a few weeks of the equinox (21 Sept), tides are running a bit above normal anyway because the sun and moon are “lined up” and working together. The “Mean higher high water” (MHHW, the multi-year average of the highest of the two tides each day) for the Fort Pulaski gauge is 7.5 feet. With no wind we would expect the tide Wednesday evening to be 8.02 feet, and Thursday morning to be 8.42ft, so 0.5 to one foot above normal. If Michael follows the forecast track it should add at least another foot to that total, maybe as much as two feet. We start to get problems like US 80 flooding at around 9.4 feet, and at 10 feet parts of Tybee start to have problems, so the higher than average tide due to the time of year plus the onshore winds adding to that means some areas could have problems. The gauge data and a forecast is here … https://water.weather.gov/ahps2/hydrograph.php?wfo=chs&gage=fpkg1

      • Thanks. I get it. That is probably also why the tides along the Savannah coast were so very high for last year’s Hurricane Irma.

        Is there a source of historic tide information so that I could look up just how high the tides were then?

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