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HURRICANE FLORENCE MSG #6

Scott Sherrill - Wednesday, September 12, 2018

Pls see below re; a msg from Rudi, our Shore Protection Officer.  He has a very good grasp on the interaction of storms and the island, and as you’ll see below is tied in with UNC-IMS on storm surge.

Also: pls don’t let this morning’s news on the track fool you.  We remain in as dangerous as situation as many have seen since Hazel.  This is a deadly storm.   All should on the road off the island by now.

VR Brian

Dear Beach Commission et al.,

Hope everyone is well into storm preparation by now and just wanted to pass along a few notes regarding Florence and potential impacts.

(1) Track Change – As you are probably waking up to by now, there has been a steady shift in the model guidance that is stalling, then pushing Florence almost due west once she hits land near Wilmington OR possibly just miss Wilmington and Cape Fear altogether (see 5 AM NHC advisory below).  Nonetheless, we will exposed to the northeast side for a very prolonged amount of time and across multiple high tides.  In terms of the actual storm surge (the water being pushed along the northeast quadrant of the eye wall like a bulldozer blade), we seem to be in a “better” situation (very relatively speaking) beach wise as the center of the storm continues to drift the storm west of us per the models.   The prolonged east winds however from Florence will really pile up the water Down East and other locations, which indirectly leads us to the next bullet.

cone graphic

(2) Water Level Estimates and ADCIRC – I’m sure you have seen predicted maximum water levels via the National Hurricane Center (NHC) and/or parlayed on television.   Honestly, they are coarse and difficult to read/interpret.  However, immediately below is the web address for the ADCIRC model pioneered by our own Dr. Rich Luettich at UNC-IMS.  This is an interactive site and predicts water levels generated by storm surge, wind forcing, etc. based on the NHC’s track/intensity of the storm – it is not predicting where the storm is going, just the impacts if you will.  It will update just a couple/few hours after each of the NHC Major advisories at the “5s” and “11s”.   Below are a few screen grabs – in the first one below, notice the red circles that indicate what NHC Advisory it is modeling, the color-coded maximum water level legend, AND the little graph looking icon on the left side of the page.   If you click your cursor on this icon and left click on an area --- it will provide a water level graph at the cursor’s location.  See the second image below.   The zoom and other features are very good.

https://cera.coastalrisk.live/

(3) More on Water Levels – The United States Geological Survey (USGS) has been busy installing temporary water level gauges across the State.   This will provide actual measurements and can help calibrate models for better performance in the future.    They also have a good interactive website - https://stn.wim.usgs.gov/FEV/.  Click your cursor inside the “select event” drop box and it will provide event options for Florence and past storms. 

(4) Pre-storm pictures – Were taken Monday and are available at http://www.carteretcountync.gov/gallery.aspx?AID=59.   When the storm finally passes, we will take post storm pictures as discussed earlier.

(5) Post-storm Survey – Again has been activated and we have been in constant communication with Geodynamics concerning access to the island and other logistics.