Monday, October 28, 2013

Halloween Storm

We have got a lot to discuss here as we end October on the stormy side.  First of all, remember the post a couple weeks ago where I looked at the fall so far in terms of temperature?  At that point, October was almost 3 degrees ABOVE average.  After all the cool weather lately, we're now .7 degrees BELOW average.  With that said, temperatures are going to really warm up until we get this storm system out of here on Halloween so there's a good chance we will end this month slightly above.

The one thing I really want to hit hard on this post is the fact we're in our secondary severe weather season and this concerns me.  At this point, the system coming in on Wednesday and Thursday doesn't look like a big severe weather producer, however, that can change.  Many don't realize how dangerous this time of the year can be.  I'll take you back 4 years ago tomorrow (Tuesday).  On October 29th, 2009, several tornadoes tore through south Arkansas.  Leading up to the event, if I remember correctly, the models were advertising this as a high shear, low CAPE environment.  This means there wasn't much instability, but there was plenty of spin available in the atmosphere to create tornadoes if storms were able to tap into it.  But without instability, that can be tough to do.

On the day of the storms, the instability sky rocketed.  The models were incorrect and there was plenty of fuel for these storms to build and spin.  As a result, there were 9 tornadoes that day including one in East Camden which damaged the Fire Training Academy.  You can read more about that day by CLICKING HERE.

I want to make if clear, as of today, I'm not calling for a severe weather outbreak.  Can that change?  Yes.  I just want everyone to be weather aware just in case.  Right now, it looks more like a heavy rain producer.  The timing of this system just isn't all that favorable for severe weather.  The worst of it will come in at night and into the early morning when instability levels are usually at their lowest.  That doesn't mean there can't be severe weather, so let's all watch this carefully.  

As I mentioned, heavy rain will be a real threat and I would not be surprised to see at least 2-3 inches or more in some locations.  As of today, I still think there's a very good chance most of the rain will exit by sunset on Halloween (6:16 PM).  The bulk of the rainfall is scheduled to arrive Wednesday night and Thursday morning.

Remember previous posts where I pointed out the differences between the GFS and the Euro.  I sided with the Euro and I'm glad I did.  When all is said and done, the Euro will have presented a picture that was most realistic.  It's not perfect, but it's doing better than the GFS which is playing catch up with the system.

Below are a few maps explaining what to expect. 

THE MODEL MAPS BELOW ARE FROM A WONDERFUL SITE CALLED WEATHERBELL.COM.  It's a fantastic site and if you're a weather geek, you should check it out.

I'm going to show you a series of maps from the 12Z GFS.  The green blobs show you how much rain has accumulated over the previous 6 hours.  So these maps aren't showing you where it's raining at the time, just how much has already fallen.  You can clearly see the surface low over the OK panhandle.  The black lines are isobars, lines of equal barometric pressure.  Remember,  the flow is counterclockwise into the low.  The tighter the spacing between the black lines, the windier it is.  This is showing you a strong south wind around 1AM Thursday with almost 1'' of rain over the previous 6 hours over western AR and SE OK.
Over the next 6 hours ,1AM to 7AM Thursday, that axis of heavy rain shifts to the east.  The surface low is moving into SE KS.
From 7AM to 1PM Thursday, rain and storms are scooting through the state.  It's a rainy start Thursday.
From 1PM to 7PM Thursday, notice the heaviest of the rain has shifted away.  There's only lingering light showers as the front is in eastern Arkansas here.
From 7PM Thursday to 1AM Friday, it's dry ACCORDING TO THIS MODEL.  This would make Trick-Or-Treaters very happy!!!!
How much rainfall total?  We'll the GFS shows at least 3 inches over western Arkansas and maybe more from southwestern areas of the state into north TX where 6-8 inches could fall there!WOW!  Just a model.
The Storm Prediction Center has placed much of OK and north TX into far western AR in a slight risk for severe weather Wednesday.  The prime time is when instability is the highest.  As the system pushes to the east into the overnight, instability will not be as great.   Remember, this can still change and I'll keep you updated.  The main threat at this time appears to be heavy rain, but strong to severe storms can't be ruled out at this time.

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