Joe’s Weather Blog: The rarity of what Florence MAY become (MON-9/10)

Good morning…no rain or significant weather is expected around our region for at least a week or so…there is a cold front that may make it to the area sometime on Sunday…maybe a few showers? Overall though we’re mild to warm with pleasant nights and a bit more humidity later in the week.

This blog will talk about the tropics which is what every newscast and most weathercasts in the country will be talking about all week long.



Forecast:

Today: Sunny and pleasant with highs well into the 70s

Tonight: Fair and seasonable with lows in the 50s

Tuesday: Sunny and mild with highs in the lower 80s

Wednesday: Sunny with highs 80-85°



Discussion:

Florence continued to strengthen overnight and is forecast to intensify as the day and tomorrow move alonog. This is going to be a bad>devastating storm unless somehow it can remain more offshore of the Carolinas. Sadly that chance seemingly dwindles by the day as the new data, while vacillating on a landfall point…continues to show a direct hit somewhere in the Carolinas area.

There will be wide ranging effects inland as well with devastating flooding and perhaps record rain amounts for some states. Records that have stood for decades.

There are actually 3 hurricanes ongoing in the Atlantic Basin + another area eing watched towards the western Caribbean. Isaac may eventually be a big ticket item for those islands…and potentially will affect some of the same islands that were devastated by the hurricanes last year.

It’s a small (in size) hurricane at this point. Here is Isaac…

Helene is farther west towards Africa but will harmlessly curve out to sea.

Then there is Florence which is the main concern. Residents appear to be taking this seriously and are buying supplies to prepare for the storm. That’s a good thing…unfortunately the storm continues on it’s path and is getting stronger.

As of this writing…Florence is a category 2 hurricane. On the edge of becoming a category 3 (major) hurricane. The next advisory may well bring it to “major” status. You will be hearing a lot about category numbers over the next 4 days or so as Florence churns closer and closer to the coast. What do those category numbers represent?

The higher the storm category the more the damage. Damage can come from several things…wind…surge (big ones) and flooding (more widespread big one).

Once the surge and wind (mostly near coastal effects) diminish then the focus is flooding and that will be a BIG issue with this soon to be slow moving hurricane. The steering currents will be collapsing and that means the nudge to the storm will gradually diminish and a fading hurricane without steering push…is bad news for the folks there.

When I was at a conference a few weeks ago there were many presentations about how Texas and the Houston area handled Harvey which brought 60+” to parts of Texas.  Some of the state officials pretty much were doubling all the forecasts that were being issued for rain totals…when the forecast was for up to 15″ they were preparing for up to 30″ and so on…

Well the forecast from the WPC for this storm is shaping up like this (right now)…and much like what happened with Harvey…this is sort of an opening salvo. Odds favor these numbers are going up over the next few days.

So as the above graphic shows…up to 14″ is possible…I think doubling that number would be a potential upside…especially in some of the higher terrain areas of VA/NC. Our EURO model

Why?

Orographic lift. This was a huge issue for Lane in Hawaii…when it cranked out close to 50″ of rain.

It may be a big issue with Florence since it will slow to a crawl.

This graphic sort of explains it well.

Fast moving air from the circulation of Florence runs up the mountainside and creates more lift on the windward side of the mountain…this enhances and adds to the rain totals, potentially in a very substantial way.

This is where the eventual track of the hurricane inland plays a huge role…on the other side of the hurricane the wir would actually be coming down the mountains and reducing the rains. So that issue will have to be worked out.

The coastal area, while not dealing with orographic lift…will be dealing with storm surge and wind issues (obviously). Storm surge is another term you’re going to hear a lot about this week. The higher the surge the more of a push inland the seas can travel. Surge also pushes up rivers/bay waters that dump into the Ocean and, in a sense, can back up those waters and push farther inland.

Surge is caused by a buildup of water out in the Ocean, which is created by strong winds circulating around the hurricane. As the hurricane comes ashore, in a sense it’s bring this water with it. So in addition to the wave action with the devastating winds…this “pile” of water rushes in and can cause widespread destruction. For this part of the country…many houses are built on stilts to prop them up above sea-level.

IF Florence comes in at high tide…it adds to the levels of high water that are possible.

There are going to be track changes up until about 6 hours or so before the storm actually hits land…so the precise landfall remains to be seen…but,a s an example…here is the tidal chart for Wilmington, NC.

High tides on THU are around 1:25 PM and 1:40 AM Friday AM…note the close to 5 FEET of difference between the 2 tides…that’s why IF Florence could hit during the lower part of the tidal cycle that would be a good thing.

As the landfall location potential changes we’ll keep an eye on the tides.

Data overnight did show a somewhat south shift, perhaps bring more of upstate SC in play…at this point though anyone from coastal Charleston, SC to Cape Hatteras, NC are truly under the gun for surge and wind issues…then inland from there for wind and flood issues.

Interestingly enough…you may think that the wind is the biggest killer when it comes to hurricanes…it seems the media’s focus is always on the wind and category number…well in reality it’s NOT the wind that is the main killer in hurricanes…and it’s not even close.

Oh and there may be some tornadoes as well somewhere on the eastern and northeastern side of the hurricane from the outer bands of the storm.

As I mentioned for the last few days…the current position of Florence and it’s forecast future (as a combination) is a rare thing…

In and of itself it doesn’t mean much but by the same token records go back to the 1850s although perhaps reliable records only go back to the satellite tracking era…still though very interesting to me.

Is there a way to prevent the worst from happening, mainly along the coastal areas…well yes and now. There are some indications that the storm, as it approaches the coastline, over the final 24 hours out in the Ocean…may start moving into a more hostile environment for strengthening. This will be a tricky thing but there are indications that some wind shear may come into play…which IF it happens…COULD weaken the storm somewhat as it spins towards landfall.

It’s an important thing to watch for on Wednesday into Thursday…because the satellite pictures this morning are pretty impressive. Shear weakened the storm last week from cat 4 status to tropical storm status in about 24 hours…so wind shear, that rips the best convection away from the storms core…could be something that helps the cause in weakening the storm as it gets closer to land. A LOT of ifs with that but 25-35 MPH wind shear isn’t something to disregard.

There you have it…everything you wanted to know about Florence and then some…if it was up to me I’d spend 10 minutes talking about all this on the news tonight…alas I don’t think that would fly with the folks upstairs. That’s the great thing about my blog though!

The People of Cowtown got out to Grinter Farms last week…spectacular shot!

Joe

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s