Thursday, September 1, 2011

Nasty Looking Labor Day Weekend

The tropical disturbance in the Gulf -- 'Invest 93L' -- still isn't terribly well organized this morning. However, take note of just how large the system is, with shower and t-storm activity covering just about the entire eastern half of the Gulf.

The National Hurricane Center has increased chances of development to 70% as of its latest update at 7 a.m. this morning. However, regardless of development, the bigger concerns for this weekend appear to be heavy rainfall and coastal flooding.  Most of our guidance still points toward low pressure being centered off the Louisiana coast by tomorrow and then has it meandering through the weekend, and in some cases, even longer. We often refer to these composites of computer models as 'spaghetti plots' and I think you can see where the 'spaghetti' term comes from in this case!

The Hurricane Hunters are scheduled to investigate the mess in the Gulf this afternoon to see if Tropical Depression #13 may be forming. While it does look quite likely that we'll get Tropical Depression #13 and/or Tropical Storm Lee out of this over the next day or two, the primary concern for the next few days will be heavy rainfall because of the slow movement.  The National Weather Service has already posted a Flash Flood Watch for areas generally south of I-10. I hesitate to show you this next graphic, but since it is a possibility, it's worth a look. The Hydrometeorological Prediction Center (HPC; a branch of the NWS) is painting a scary picture in terms of potential rainfall over the next 5 days.  Note the bullseye along the coast topping 18"! Now, this is far from a certainty, but the potential for BIG rain totals is a serious concern.

Strong westerly winds continue in the upper levels of the atmosphere across the northern Gulf of Mexico this morning, resulting in some shear impacting 93L. While the shear may let up a bit in the next day or so, it doesn't appear as though it will totally go away over the weekend. That's why at this point we're thinking the intensity of the system may not be a huge issue, at least for the next few days. However, if it does manage to linger in the Gulf long enough, conditions could become more favorable and allow it to intensity by late in the weekend or early next week.

Even if the winds aren't terribly strong, a persistent flow out of the east and southeast would likely mean coastal flooding concerns this weekend. That is something we'll certainly have to watch.

The possibility of a looping/meandering storm certainly brings back memories of a couple others. We have to be careful about making comparisons since each system is unique, but 2001's Allison and 1985's Juan do come to mind. Most of you likely remember the historic flooding from Allison; Juan actually made 3 separate landfalls along the Louisiana coast as it completed a couple of loops.

Let's hope that our current system does NOT resemble these in the coming days, but there is a real potential for this disturbance to be pestering us well into next week.

A final note...lost in all of this mess is that fact that today marks the 3rd anniversary of Gustav's landfall in Louisiana (Sept. 1, 2008; Labor Day). As we went days -- and in some cases weeks -- without power  3 years ago, I felt our struggles were lost on the national media. Since the storm didn't devastate New Orleans, there was little attention paid to the rest of us. Today, I still think Gustav is a forgotten hurricane.  How many times did you hear Ike referenced during the Irene coverage last week? But did you hear anyone mention Gustav?

Gustav's peak winds easily surpassed that of what we saw with Andrew in 1992 and essentially matched those of Betsy in 1965.  Here's a quick comparison for Baton Rouge:

Storm          Peak Sustained Wind          Peak Wind Gust
Betsy                     58 mph                           92 mph
Andrew                 46 mph                           70 mph
Gustav                   61 mph                           91 mph

Here are a couple of radar snapshots of Gustav.  The first is the hurricane making landfall near Cocodrie around 10 a.m. Note how the heaviest storms are located in the western eyewall at this point. It looked like metro Baton Rouge would miss out on the worst. However, those same storms rotated completely around the eye and did hit Baton Rouge shortly after 1 p.m., producing the 91 mph wind gust.

Radar image of Hurricane Gustav at landfall near Cocodrie on Sept. 1, 2008 around 10 a.m.

Radar image of Hurricane Gustav taken at 1:10 p.m. on Sept. 1, 2008.  The eyewall was impacting metro Baton Rouge at this point, producing a wind gust to 91 mph at BTR Metro Airport.


  1. Great work as usual Steve!

  2. Thank you for the mention of the power of Gustav. Having lived in Louisiana most of my life, I did indeed realize this was one of the strongest to hit us just from experience. It's hard to explain this to people who don't live through it!