Bertha bringing unsettled weather to northern Gulf coast

Shortly after my previous post, Invest 91L was upgraded to Tropical Depression Two, then late Monday night, it was upgraded to Tropical Storm Bertha... the second named storm of the season.

It has barely moved since it formed but is gradually oozing westward just off the Gulf coast. That slow motion will continue over the next several days as it scrapes along the coastline.  Tropical storm watches and warnings are in effect for the coastal Florida panhandle over to western Louisiana.  On the cone graphic below, remember the cone does NOT show where impacts will be experienced, only the likely area where the center of the storm will track. [Cone refresher]

As you can see in the satellite animation at the top of the post, the storm is extremely sheared, with the surface center exposed and the thunderstorm activity displaced to the south.  That significant vertical wind shear will keep the storm from intensifying much.

The only relatively minor impact will be storm surge of 2-4 feet along Mississippi and eastern Louisiana... the rain should not be a big problem because the bulk of the messy part of the storm will remain over the Gulf of Mexico.  The stronger side of the storm in terms of wind is also more over the Gulf and less over land, but the graphic below shows the probability and most likely arrival time of tropical storm force winds. Most places over land are under a 50% chance of seeing such winds.

Bertha is still a name from the original set of rotating lists... first used in 1984 and every six years since.  So this is its 8th time in use and will be certainly be around for a 9th time in 2032. [Storm naming and retiring refresher]

 

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Watching northern Gulf of Mexico for tropical development

Over the past several days, a persistent blob of disturbed weather has been drifting westward across Florida and is now centered over the northeast Gulf of Mexico.  The National Hurricane Center has had this in their outlook since Wednesday morning. Now tagged as Invest 91L, this disturbance is likely to become Tropical Depression 2 soon, or perhaps Tropical Storm Bertha.

It is forecast to track generally westward across the Gulf over the next 5 or so days, sticking very close to the coastline.

The water temperature under and ahead of the disturbance is quite warm (almost record warm for the date), with anomalies up to 2°C at its current location.

https://bmcnoldy.earth.miami.edu/tropics/sectors/

This system does not have a lot water to work with, nor a lot of time over open water, so significant development is very unlikely, but that won't stop it from producing a lot of rain near and over the northern Gulf coast. This map shows the 5-day accumulated rainfall forecast, and although the heaviest totals are shown over water, it wouldn't take much of a nudge from this to place those higher values over land.

Climatologically, the second named storm forms on July 15, so if this manages to become Tropical Storm Bertha, it would be very close to average in the season.

Stay tuned to https://www.nhc.noaa.gov/ for updates and new watches and warnings.

Finally, thank you to all of the people who contacted me after my previous post announcing that this would be my final year of writing these posts... 1996-2026. I really appreciate the outpouring of kind words, especially from those who have been following for the whole three decades!

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Tropical Storm Arthur forms on Texas coast

The first named storm of the 2026 Atlantic hurricane season, Arthur, has formed and is centered just southwest of Galveston. The maximum sustained winds are 40 mph and it's crawling toward the northeast at 9 mph. Although it will dissipate soon once it's back over land, the flooding rainfall threat will exist for the next several days across the southeast U.S.

As is evident in the satellite image at the top of the post, the strong thunderstorm activity is all displaced to the south and east of the low-level center, so the heavy rainfall threat is already over for Texas, but a lot lies ahead for Louisiana and areas to the east... all the way into Georgia this weekend.

Over the past five decades, the median date of first named storm formation is June 18, so this is right on schedule. And although the trend is toward earlier in the year, the past five years are all above that trend line (later).

Although there's nothing else on the horizon now, the next couple of names on this year's list are Barry and Chantal.  Arthur, by the way, has been on the rotating list of names since it was first introduced in 1984, so this is its 8th time around (1984, 1990, 1996, ..., 2026).

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