Monday, August 27, 2012

All Arkansas Eyes On Isaac

For very frequent updates, you will get even more information on facebook and twitter.


7AM Tuesday Update... I will update the blog a little later this AM with more in depth information.  A quick glance continues to thankfully show Isaac is struggling and not reaching hurricane status.  However, I do think it will achieve that before landfall.  The current forecast track takes him right through central Arkansas early Friday morning.  This puts eastern Arkansas in line for the worst weather.  Western areas will still likely to get rain, but it's eastern areas which could see several inches.  I still think there is a good chance it's out of here by game day!!  More later and check out the video below.

9:55 PM Monday Update.... It was almost 5 years ago I had the privilege of flying with the Air Force Hurricane Hunters through Hurricane Ike.  These men and women work extra long hours to stay on top of developing tropical systems with flights around the clock.  They play a vital role in helping us forecast.  Right now, they're working non stop flying through Isaac.

Here's a story about the trip which aired shortly after I got back.

2:20 PM Monday Update... Isaac is strengthening slower than anyone expected.  With that said, I still think this will become a hurricane and make landfall as a cat 1... maybe a cat 2.  The central pressure this Monday afternoon is down to about 984 mb and it's just a matter of time before the NHC increases the sustained wind speed and officially makes this a hurricane.

How about the impact on Arkansas?  In terms of wind energy, the weaker this is at landfall, the better for us.  The wind energy will dissipate and this will become a depression faster.  This means heavy rainfall will be the primary concern.  There's also the risk for isolated tornadoes for any location east of center.  The exact track of the center is NOT set in stone.

Yes, we need rain and this COULD put a huge dent in the drought.  However, I want to caution you, too much at one time isn't a good thing either.   Here are the latest computer models.  Scroll down further to find more in depth info from this AM.

The Monday morning run of the European shows the center of low pressure in far SE Arkansas.  This would bring the heaviest rain to far eastern areas into Mississippi.
The Canadian is similar and with a weakened area of low pressure bringing the worst to areas east of Arkansas.
This is the GFS early Friday morning.  The center of the low is over western Arkansas.  This would bring areas of heavy rain for much of the state.  Isolated tornadoes would also be possible.

As of Monday morning, Isaac is maintaining its strength as a formidable tropical storm with sustained winds around 65 mph.  At this time, many models and meteorologists with the Hurricane Center thought this would be a hurricane.  While the chances are still likely this will become a hurricane, the forecast intensity has come down some.  That's one of the hardest things about forecasting tropical systems... the intensity and Isaac is proving that to be true.  Nevertheless, it may become a category 1 or 2 at landfall and hopefully nothing higher.

Have you noticed that with each update from the Hurricane Center, the track shifts to the west?  Just a few days ago, this was forecast to hit Tampa and now it's going to be nowhere close!  With landfall only a couple days away, I can't help but ask, how much to the west will the corrections continue?

With that said, we need to look at the computer model guidance to help with that answer.  But before I do that, let's talk about the center of the circulation and what we're watching at Channel 7 as he comes ashore.  First, remnant tropical systems are no stranger to Arkansas and no 2 storms are alike!  In 2005, we had Rita and Katrina.  Rita brought tornadoes and some flooding.  Katrina went east of Arkansas, but did manage to spiral a few rain bands into the state.  in 2008, Gustav hit Arkansas with flooding rainfall, but no tornadoes.  Shortly after, Ike hit Arkansas with high winds, flooding, and tornadoes.

The tornadoes in a tropical system are NOT like the typical ones we experience, but are still a threat to life and property.  They are usually on the lower end of the EF scale and are short lived.  They also move very, very rapidly.

The worst weather from a tropical system can be found on what's called the "right front quadrant."  The area east of the center of circulation usually experiences heavy rainfall bands and storms embedded within those bands can rotate and spin up those tornadoes.  West of the circulation, rainfall still occurs, but it's usually not as heavy and the threat for severe weather is lower.  So as we watch the adjustment to the track further to the west, that's what raises alarm bells.  If this tracks up through the ArkLaTex and into eastern OK or western AR, that can bring problems as mentioned above.

Here are the latest computer models.

The Canadian model has the center of low pressure Friday morning over northeast Arkansas.  This would spare much of the state from the worst weather, but NE Arkansas would deal with heavy rainfall and some severe weather.  At this point, Isaac would barely even be a tropical depression.  It's very weak here.
The European model valid late Thursday shows the center over central MS.  This model eventually takes Isaac into far eastern and northeastern Arkansas.  This would spare most of the state from the worst weather, but once again, Eastern areas would be more susceptible to heavy rain and severe weather.
THIS IS WHAT WORRIES ME!  The Global Forecasting System, also known as the GFS, brings the remnants of Isaac into eastern Oklahoma.  This places all of the state in the right front quadrant.  This would allow for heavy rain bands and embedded severe weather to move across the state.  This is model has been very consistent lately with this solution and must be watched.
The UKMET valid late Wednesday shows the storm near the MS/AL border.  This falls into the "eastern solution" camp and would have minimal impact on Arkansas.
This shows the forecast rain amounts from the HPC and really illistrates
The Storm Prediction Center shows where the severe weather would be expected with the current forecast track.   The area in yellow has a slight risk for severe weather after landfall.  The main threat would be tornadoes.    Once again, any adjustment to the west will put AR in this and any adjustment to the east takes it away.

1 comment:

Anonymous said...

It annoys me a bit when individuals continually state "Sure we need rain, but too much isn't good either!", as well as worrying about it raining during a silly football game. Wake up and get in touch with the real world.

We are in the middle of an extremely devastating drought. Our farm and rangelands have dried up to the point that in some areas it looks like West Texas or New Mexico. Creeks and ponds are going dry. We desperately need several inches of rain to get those water levels up and to initiate the growth of green grass before the fall frosts come. Ranchers are already feeding hay and grain due to the grass shortage. If we can get some heavy rains, the grass will start growing and they can get a reprieve for a couple of months before they have to start winter feeding.

Do we want tornados? No. Do we want flooding? No. However, when we need things and ask for them, we should be thankful and take the good with the bad. Things are not always naded to us exactly the way we think they should be.

Don't worry, there will be plenty of other football games for you hog fanatics, there may not be another opportunity like this to put a real ding in the ravages of the drought.

NOAA Winter Guidance