Joe’s Weather Blog: Florence’s rain is the biggest issue (THU-9/13)

Good afternoon…lots of clouds in the region this afternoon is actually helping keep our temperatures in check today. KCI is running in the upper 70s as of the 1PM hour…Downtown in the lower 80s. You may also have noticed the dew points coming up…they’re higher today compared to the the last 5+ days…so it is a bit more muggy out there and will continue to be muggy into next week.

Meanwhile the continued weather story is Florence which continues to churn towards the coastline very slowly. The storm is already generating 70+ MPH winds along the coast and off shore. Details on Florence will be in the discussion.



Forecast:

Tonight: Variable clouds and milder with lows in the 60s

Tomorrow: Mixed clouds and sunshine with highs well into the 80s

This weekend: Mostly sunny and light breezes with highs 85-90°



Discussion:

Once again there is little local weather to speak of…and that beat goes on through the middle of next week. Temperatures will become the larger story locally heading into the final weekend of summer (according to the calendar). Highs will be running about 10° above average over the weekend and for several days next week. I’m not real excited about rain prospects for at least a week, if not longer.

Onto Florence…

This storm is indeed, as I mentioned yesterday, throwing us some curveballs…some expected some not. Yesterday I wrote about the shear that the storm would encounter as it approached landfall. What happened last night though wasn’t really expected…essentially the southern part of the hurricane got ripped to shreds.

Hurricanes typically hate at least 3 things…frictional effects of land…colder waters and wind shear ripping at the circulation. Last night #3 was the big item. Believed to be winds between 30,000-40,000 feet up…the bottom part of the hurricane got all messed up. Another aspect that it’s apparently fighting today is some dry air being circulated into the core of the hurricane.

Over the past 6 hours…the storm has moved towards and into the really warm Gulf Stream waters…this started to help the core I think try and reorganize a bit but alas it’s still “struggling”.

Here is a look at radar…

and a look at what will become the major story starting this weekend especially…the rain totals according to doppler radar.

As far as the latest information goes…

Storm surge and related flooding is already happening along the Outer Banks of NC.

There is actually a camera off the coast of NC…about 34 miles in the Ocean…called Frying Pan Shoals that is sending back live images.

There is still a question about where exactly it comes ashore…it’s possible that it skirts the coastline and moves towards the SW(!) which is something that I don’t ever remember seeing before in that part of the country.

So storm surge…and that aspect of a slow moving hurricane going through multiple tidal fluctuations will be most felt on the coastline…this will rip away at the barrier islands for many…many hours. It will rearrange the sandy soil and cut new inlets into the barrier region off the coast.

Then there is the matter of the winds…and while the hurricane may or may not come ashore later tonight or early Friday…the eye wall may well scrape the coastline and that means the coastline should see the higher gusts. The hi-res NAM model shows winds gusting to near 100 MPH…which is about right I think…80-110 MPH in gusts seem most likely assuming the eye scraps the coastline or even comes ashore.

Then the EURO model, at least…drags it DOWN the coast (VERY WEIRD) as a result of a collapse of steering currents and then it makes another (potentially last) landfall near Charleston, SC on Saturday evening. Wow! The GFS has this near Wilmington, NC and then takes it inland from there keeping the worst of the winds totally confined to NC. Here is some buoy data from off shore the Wrightville Beach area.

and a little farther towards the NE of there.

Regardless of all this…the rain will be the bigger and more widespread disaster out of this…including prolonged and dangerous flooding that will engulf the Carolinas and their floods down’t easily drain and go away.

Can 40″+ of rain come from Florence…yup. Here are a couple of model forecasts then the “official” forecast.

GFS…

Euro…

Official from WPC…

The point though is flooding will encompass WAY more square mileage than the storm surge…than the significant wind damage, than the whatever tornado damage may occur…it’s almost always been about the flooding with Florence and THAT hasn’t changed despite the “weakening winds”.

Another note about the storm surge aspect of this…note this animation of the Topsail Beach area…look at all the houses…

A fast perusal of the Outer Banks indicate that the highest elevations are only around 10-20 above sea level…add in the storm surge plus the waves and you can see why there is so much concern. Many of the structures there are built above the beach on stilts…to allow the water to pass underneath them…we’ll see how well they fare.

Here is a PDF file containing a briefing done by the NWS in Morehead City.

and from the NWS in Wilmington, NC

and finally some links from the NWS in Charleston, SC

Joe

 

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