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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First named storm of the season could be brewing in the Gulf of Mexico

This is now my 31st year writing these updates on tropical Atlantic activity.  During that time, I have written approximately 1470 posts spanning 488 tropical cyclones including 228 hurricanes, 107 major hurricanes, and 57 retired storm names. 

I began writing these posts in the summer of 1996 (prior to starting my junior year of college), and the internet and data availability looked very different then. We were still at least a decade away from social media. I was honored to be asked to write blog posts for the New York Times from 2007-2010 and then the Washington Post's Capital Weather Gang from 2012-2019.

I plan to continue this blog into 2026, but that also seems like a good milestone to wrap it up. I know some of you reading this have been following along the entire time, but whether you've been reading these posts for 1 year or 30 years, I truly appreciate your interest!

Now, on to the tropics. Over the past week or so, a poorly-organized disturbance has been festering over Central America, then crossed the Yucatan Peninsula, then oozed across the Bay of Campeche, and is now located inland over southern Texas.

It has been tagged as Potential Tropical Cyclone One, which is a fancy way of saying it's still just an area of interest, but could develop soon and tropical storm watches and warnings have been issued for parts of coastal Texas and Louisiana. If it becomes a subtropical or tropical storm, the first name on this year's list is Arthur.

Although it will only have a brief window to exist as a tropical cyclone over water on Wednesday, the primary threat from this system is not wind, it's water. Extended periods of heavy rain from Texas into Georgia and surrounding areas will result in widespread flooding through the rest of this week.

If this does became a named storm, 2026 will be the fifth consecutive year with the first named storm forming in June... prior to that the first named storm formed before June 1 for seven consecutive years.

I'll take the rest of this post to look at a bigger picture.  A much-anticipated El Niño has just begun, and model forecasts indicate it will become a strong one in the coming months. In general, that will act to suppress Atlantic hurricane activity, especially in the deep tropics where its influence on vertical wind shear is the greatest.

Unlike in 2023 when there was an El Niño and record-warm water temperatures across the Atlantic producing competing nudges on hurricane season, this season is beginning with near-to-below-average water temperatures across the deep tropical Atlantic as we look ahead to a very strong El Niño.

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

As such, the seasonal outlooks are generally indicating below-average activity this season. The average season has 14 named storms, 7 hurricanes, and 3 major hurricanes, so a slightly below-average season could still have 11 named storms, 5 hurricanes, and 2 major hurricanes (from the Colorado State University forecast released on June 10).  It is just as important to stay vigilant and prepare for hurricane season this year as in any other year.

If you missed my first two posts earlier this year, they are available here...

March 4: 100th Storm Name Retired After 2025 Hurricane Season

March 16: 2026 "Cone of Uncertainty" Update & Refresher

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2026 "Cone of Uncertainty" Update & Refresher

Anyone who lives on or near a hurricane-prone coast is undoubtedly familiar with the track forecast cone or "cone of uncertainty" which has been produced by the National Hurricane Center since 2002.  It begins as a point at the current position of a tropical cyclone and expands to show the potential position of the storm's center in the next five days. It is often called the "cone of uncertainty" because the further out in time you go, the more uncertain the forecast becomes... and it tends to look like a cone!

(By the way, "tropical cyclone" is a blanket term that refers to tropical depressions, tropical storms, and hurricanes.)

A "cone of uncertainty" for Hurricane Irma (left) and Hurricane Harvey (right). Both cones are from 2017 and are therefore identical to each other in their construction. 

The size of the cone is fixed for every forecast of every storm during an entire hurricane season, but the size slowly evolves from year to year. If the storm is moving quickly, the cone will appear more elongated and if the storm is moving slowly, the cone will appear more compact... but it's the exact same cone.  The examples shown above are from Irma (left) and Harvey (right); both storms occurred in 2017, so both cones are identical in their construction.

The cone is updated each year prior to the start of hurricane season, and it usually shrinks each year.  Overall, hurricane track forecasts are gradually improving, meaning that in general, there is less uncertainty where a storm will track now than there was a couple decades ago.

The map below shows a sample satellite image with the new 2026 cone overlaid on the 2015 and 2004 cones for comparison.  In 2026, the cone is the smallest it has ever been at days 2-4 and then tied for the smallest at 1 and 5 days! The largest improvement over last year's cone is at the 2-day lead time, with a 7.4% reduction in size.

So just how is the size updated each year?  The National Hurricane Center uses its own track forecast errors over the previous five years to calculate a circle at each "lead time" (1 day, 2 days, ... 5 days).  The size of that circle is designed to enclose the position of the storm's center with 2/3 probability, meaning that there's historically a 1/3 chance the storm will track outside the circle at that time.  Lines connecting the various circles complete the shape of the cone. [Note that the 2026 cone size is thus determined from track errors during the 2021-2025 seasons.]

This next chart shows the evolution of the cone's size at each forecast day -- it's clear that progress is slowing and perhaps has reached a limit at some forecast lead times.

Improvements are getting increasingly challenging to achieve because there can never be a perfect forecast of a chaotic system like the atmosphere. We call this a "limit of predictability", and there will come a time when we reach it and meaningful improvements can no longer be made.  Some would argue we are very close to that limit.  It's critical to understand that forecasts evolve and there is always some amount of uncertainty in them.

Since the cone is so widely used yet sometimes misunderstood, here are some key refreshers:

• The cone does not tell you anything about where impacts will be experienced.  It is NOT a "cone of concern"! Even for a perfect down-the-middle track forecast, impacts such as strong wind, heavy rain, storm surge, and tornadoes will extend beyond the cone. Cone graphics on the NHC website include some of the relevant watches and warnings, as shown in the examples at the top of the post.  Given its positive reception during the past couple of years, tropical storm and hurricane watches and warnings will be displayed inland too, not just on the coast (see this example from Milton 2024). 

• The cone does not tell you anything about the size of the storm.  Regardless of how strong they are, hurricanes come in a wide range of sizes.  Back in 2017, NHC added the latest observed size of the wind field to its cone graphics to help illustrate this (see the Irma and Harvey examples above... the orange and red shading indicates the extent of tropical storm and hurricane-force winds at the time the forecast was issued).

• The cone does not tell you anything about the actual uncertainty associated with the forecast. Since the size of the cone is fixed, it cannot become more narrow or broad to accommodate a more or less predictable environment.

• Nothing magically happens at the edge of the cone. If a hurricane is approaching and you are scrutinizing each new forecast to see if you are inside the cone or not, you are missing the point of it.  It is arbitrarily chosen to be the 67% historical probability threshold... a 75% probability cone would be larger, and a 50% probability cone would be smaller.  Again, it is NOT a "cone of concern"... there is no such thing.

• If you use the cone graphics from NHC, there is some information about intensity provided. At each forecast point, there is a letter written inside the black dot corresponding to a general intensity range: D (tropical depression), S (tropical storm), H (hurricane (Category 1-2)), and M (major hurricane (Category 3+)).  But keep in mind that there is uncertainty associated with the intensity forecasts too!

So, let's imagine what a cone of uncertainty for intensity might look like. Consider this: averaged over the past five years (2021-2025), the mean error in a 1-day forecast is +/- 8.3 mph, the error in a 3-day forecast is +/- 13.7 mph, and the error in a 5-day forecast is +/- 18.2 mph.  But there is also a wide range of values that go into those averages, meaning that there is a small probability of a very large error and a small probability of very small error.

To create the next figure, I simply averaged five years of intensity errors together such that the values listed for 2026 are based on the NHC's intensity errors during the 2021-2025 seasons (and 2025 used 2020-2024, and so on).  This five-year averaging helps to mimic the smooth trends of the track forecast cone, but it is not a 2/3 probability like the track cone. Although not quite as convincing as track, one could make the case that we are nearing the limit of predictability for intensity at several lead times too. 

Next, using a made-up five-day intensity forecast and the average error values for 2026, I created the following chart.  This is what an intensity forecast cone could look like; a hypothetical intensity forecast is shown with the red line and the "cone of uncertainty" is the light red shading surrounding the forecast.