24 May 2018

2018 likely to be 4th consecutive year with pre-season named storm: Alberto

The tropical system I mentioned in last Friday's update is indeed getting better organized in the western Caribbean.  Many models have been showing this for at least the past 10 days, so it comes as no surprise. As of Thursday afternoon, the system is centered inland over the eastern Yucatan peninsula and is tracking toward the north.

If this earns a name this weekend, which seems likely, it will be the unprecedented *4th* consecutive year with a pre-season named storm!  The first name on this year's list is Alberto.  (and coincidentally, the last time Alberto appeared in 2012 it was also a pre-season storm!)

Models have come into rough agreement on the track and timing of this potential tropical cyclone, but they still have differing opinions on the intensification.  Invest 90L, or "pre-Alberto", will head north through the central-to-eastern Gulf of Mexico this weekend. Water temperatures ahead of it are in the 27-28°C ballpark (80.5-82.5°F), which is plenty warm to fuel a tropical storm or a hurricane.

The system is embedded in a very moist envelope, so dry air wrapping into to the circulation shouldn't be an inhibitor. The biggest obstacle facing this nascent cyclone is vertical wind shear.  But even that may not be enough to stop it from intensifying by Saturday.  As of now, models agree on a Monday morning landfall as a strong tropical storm or possibly even a hurricane... somewhere between eastern Louisiana and the eastern Florida panhandle. The exact location doesn't matter though, as impacts extend far from the center.

Unfortunately, it's hard to trust the intensity details too much yet since it's currently not even a Depression. But as time goes on (and it escapes the influence of land), confidence in the model guidance will increase.

By far, the biggest concern associated with this is flooding caused by heavy rainfall.  Not only is very heavy rain expected in the northern Gulf coast region near the landfall location, but also over south Florida and up into Georgia and South Carolina in the coming week.

Depending on just how much this strengthens, the second-order concern will be storm surge along the west Florida coast and northeastern Gulf coast, so stay tuned!

On the topic of another pre-season named storm, I plotted up the formation date of the first named storm from the past 40 years.  A very obvious trend appears!  There may be a few reasons for this, but it's certainly interesting.

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