Sunday, August 26, 2012

Isaac Hinting He Might Want To Visit Arkansas


I know we need rain, but this is usually not the way you want to come out of a drought.  Rain from a tropical system can take you from one extreme to another. Flash flooding causes death and property damage.  I would much rather come out of this drought gradually with periods of good soaking rains over the next few months.

There are still several computer models which bring Isaac to Arkansas, especially eastern areas.  I'll admit, I don't know much about farming, but after talking to Ryan Vaughan at KAIT in Jonesboro, rice farmers don't need this right now.

The official forecast track from the Tropical Prediction Center still takes Isaac east of Arkansas, but now much of the state is in their "cone of uncertainty."  They are taking into account the modeling which brings it further west.  If it goes too far west, then we're dealing with 2 problems: severe weather (tornadoes) and flooding.

If the storm center tracks west of your location, you are exposed to what is called the "right front quadrant".  Due to the counter clockwise circulation, this draws huge amounts of moisture off the Gulf of Mexico and it can dump flooding rainfall.  The amounts that falls is a function of the heavy rainfall bands location and the overall speed of the entire system.  It's possible to get good rainfall if the system has enough forward speed.

But this also opens the door to severe weather and tornadoes.  We have seen this numerous times in the past.  For example, Rita in September of 2005 and Ike in 2008.  Tornadoes produced by tropical systems are a bit different than the typical tornadoes in springtime.  They usually are on the lower end of the EF scale, rapidly form, and rapidly dissipate.   The formation of these short lived twisters are due to the tremendous amounts of spin associated with these remnant lows and their frictional effect with the ground.

Now let's pause for a second and take a deep breath!  The chance is still more likely the worst of this will be east of the state.  However, since there are still computer models which bring it to Arkansas, this is something I urge all of you to watch this week.

Below are various computer models from Sunday morning.  I'll keep you updated!

This is the European model late Thursday and it shows the center of Isaac over central Alabama.  If this solution verifies, there will be little if any impact on Arkansas weather.
This is the overnight run of the GFS.  This far west solution raises major concerns.  This map is valid at 10 AM next Friday and shows the center over SE Oklahoma.  This places all of Arkansas in the right front quadrant exposing us to the possibility of flooding and severe weather.
This is the Canadian model valid late next Thursday.  Notice the remnant low of Isaac is located near central Arkansas.  This would bring rain to the state with the most intense over eastern Arkansas.
The HPC forecast shows where they expect Isaac to track.  Notice the huge swath of rainfall which could amount to more than 1 foot over the southeast.  Imagine that in a short period of time.  That's what tropical systems can do.  Also, notice the western edge of the QPF field.  There is a very sharp gradient.  The track of the center is expected up that gradient and the heaviest rainfall in that right front quadrant I was talking about above.
And now the official track from the TPC.  While they expect the storm to stay east of Arkansas, much of central and eastern Arkansas is in the "cone of uncertainty".  They are taking into account the various computer models I have showed you above which brings the system further west.  By no means is this forecast set in stone.  Stay tuned and I'll keep you updated.


Anonymous said...

Hey Todd, What are the chances of Issac hitting New Orleans and if you had to make a guess as to how strong Issac will be when it makes landfall, wherever that may be, what would your guess be?

Jason H said...

They still have this storm to far East imo. Isaac will hit LA and will have plenty of warm gulf waters to become a cat 2 or higher storm. JasonBHampton

Jason H said...

Also with that being said there is NO reason this storm cant reach a Cat 4 or 5 with the very warm waters of the Gulf and it will travel a good distance over it. WATCH OUT NEW ORLEANS!

Anonymous said...

I can't help but wonder: if we do get rain from Isaac, would that mean that no dry ground means temperatures will generally stay lower?

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