As a meteorologist, I continue to monitor Potential Tropical Cyclone 2. The storm continues to meander in the northern Gulf of Mexico as a broad circulation. The most recent satellite imagery shows a large area of thunderstorm activity and some hints at better organization. As of the morning of July 11th, I have noticed some interesting trends and changes in the models even since yesterday. It is useful to try and decipher the good news and bad news in the current situation. There is also a very big concern that lingers with this storm as it slowly develops.
Following my usual procedure, here is a summary provided by the National Hurricane Center in its 4:00 am forecast discussion and 8:00 am advisory:
- Potential Tropical Cyclone 2 is expected to become a tropical depression at some point on Thursday, July 11th.
- The storm (as of 8:00 am on July 11th) is located 115 miles Southeast of the Mississippi Delta with winds of 35 mph.
- A Hurricane Watch has already been issued for most of the Louisiana coast, and additional watches and warnings may be issued.
- Models are still projecting the storm to make landfall as a hurricane within the next 48 to 72 hours.
I want to start with the “good” news first, and this is only relatively good news. There is nothing that I say here that should cause anyone to let their guard down. I noticed this morning that most of the major models have trended toward a track that is further east than previous runs. IBM and Weather Company tropical meteorology expert Michael Ventrice tweeted some perspective, “This shift in predicted track will likely result in less time over water, meaning the chances for a stronger tropical cyclone have reduced.” National Hurricane Center meteorologist Lixon Avila writes in the morning discussion:
The NHC track forecast continues to be located on the western edge of the guidance envelope, and it has
been adjusted slightly eastward….It should be noted that track errors are typically larger for potential tropical cyclones than more mature systems. In addition, the run-to-run consistency in the track models has been poor, so confidence in the details of the forecast is not high at the moment.
The last statements are important. Typically, track forecasts are pretty good within 2 to 3 days of expected landfall, but this storm has not fully developed yet so it makes model initialization (and resulting forecasts) less certain. As the storm organizes, the models will gain a better handle on the situation. I should at least mention that one model called the H-WRF continues to resolve a stronger storm at landfall. While somewhat of an outlier, it did the same for Hurricane Michael in 2018, and we know what happened with that storm. A good meteorologist never plants a flag with one model but should consume guidance from them all.
It is now time for the bad news. The consensus storm tracks have shifted closer to New Orleans. Storm surge is often more dangerous on the right side of the storm. The eastward track shift means that more storm surge would affect the Mississippi River delta region and New Orleans, Louisiana. Some river forecasts have suggested that the Mississippi River near New Orleans could crest at 20 feet this weekend. Most levees in the city are effective to 20 feet, and NBC meteorologist Bill Karins tweeted the graphic below from the Army Corp of Engineers that illustrates places where the levees are vulnerable below 20 feet of water.
My big concern is that New Orleans is a “bowl.” Water literally has to be pumped out of the city as we saw on Wednesday when the city experienced tremendous flash flooding before the main storm even developed.The rainfall potential from this storm, irrespective of name or category, is tremendous. The National Weather Service has issued a rare 3-day outlook “high risk” warning for excessive rainfall in the area. I recall this happening for Hurricane Harvey and Hurricane Florence, respectively. Both of these storms were life-altering events because of flooding. This storm easily has the potential of producing over a foot of rainfall in some places and perhaps locally even more. A foot of rainfall, a dangerous storm surge, and a low-lying urbanized region are a toxic combination. On top of that, the city of New Orleans is playing host to many tourists and conventions like the Delta Sigma Theta national sorority convention. Many of these people are not familiar with the unique threats this situation may present. That is my wife’s sorority. I am glad she didn’t go.
I will close with the following reminder: Focus on impacts not category or name. If you are tempted to say “It’s only a tropical storm or a category 1,” talk to someone that experienced the latter stages of Harvey, Florence, or Allison.”