We're at the peak of Atlantic hurricane season. What's next?

September 10 is the climatological peak of hurricane season in the Atlantic Ocean. This is the day with the greatest odds of having at least one named storm somewhere in the Atlantic basin—and, true to form, we've got a hurricane brewing in the Gulf of Mexico.

It's clear that this year isn't going to live up to expectations of a hyperactive hurricane season. But that doesn't mean we should let our guard down. Here's what we could expect from the second half of hurricane season ahead.

All signs pointed toward a bustling basin

The field's leading experts almost unanimously called for an extremely active hurricane season this year.

An average Atlantic hurricane season would see 14 named storms, seven of which would strengthen into hurricanes, and three of those turning into major hurricanes. NOAA called for 17-25 named storms this season, while the good folks over at Colorado State University expected about 23 named storms this year. 

Why so bullish? Everything seemed to be aligning just right. We're in between El Niño and La Niña right now. An active monsoon season across sub-Saharan Africa should've led to more disturbances that could seed the development of tropical systems.

On top of all that, sea surface temperatures across the Atlantic have been near historic highs for over a year now. Those sultry ocean waters helped power an above-normal hurricane season last year despite the odds against it. 

Things haven't panned out as expected

The atmosphere is complicated. Meteorology, for all its incredible advances over the years, is still an inexact science. There's plenty that even the leading minds in the field are still working to understand about the intricate links between every aspect of our skies above.

Despite all the ingredients seemingly coming together for a blockbuster hurricane season, it's been...well, not that. Hurricane Beryl showed us what those hot sea surface temperatures are capable of when it roared into a category five storm in early July. Since then, though, we've only seen a smattering of named storms.

Francine, which is gathering strength in the Gulf as of this post, is only the season's sixth named storm. If projections remained on track, we should've seen twice as many storms form by the peak of the season.

Lots of factors contributed to this unexpected lull in hurricane activity. I wrote a bit about it for The Weather Network a couple of weeks ago:

[...] You can’t bake a sweet cake with just flour. Water temperatures are just one part of the equation that plays into the formation of a vigorous tropical cyclone. This precise mix of ingredients includes moist air, calm wind shear, and vigorous thunderstorms that serve as the seed from which a hurricane grows.

Those ingredients have been a little bit out of step this season. Monsoon rains in sub-Saharan Africa have been travelling farther north than usual—bringing rare rains to the desert while missing key windows to seed tropical disturbances over the Atlantic. We've also seen intrusions of dry, dusty air puffing off the desert itself, as well as a general lack of instability over the tropical Atlantic.

The dangers of a "quiet" season

If you follow any meteorologists on social media, you've probably seen a lot of this introspective chatter over the past week. But Francine highlights the danger of banging away at this being a supposedly quiet season: it only takes one storm to make a mess.

An example I frequently use is the 1992 hurricane season. That was a below-normal hurricane season that didn't produce its first named storm until the end of August. That storm was Hurricane Andrew. That's not to say we're going to see anything close to a repeat. But this season has already proven what it's capable of in Hurricane Beryl's rapid intensification over the Caribbean.

Storms toward the latter half of hurricane season tend to form closer to land, reducing the amount of time residents have to react and prepare for a storm's arrival. Look at Francine in the Gulf—if anyone in Louisiana tuned out the weather over the weekend, they were probably shocked by the hurricane warning that hit their phone last night.

Folks throughout the southern and eastern United States need to remain prepared for dangerous storms well into November. Even though this season isn't going as expected, we've got a long way to go before the basin shuts down for the winter. September and October have a long history of nasty storms swirling ashore. 

Make plans to deal with dangerous weather, including potential evacuations, flooding from heavy rainfall, and even tornadoes as storms push inland. Make sure you've got an emergency kit ready for power outages that could last days—even far inland from where a storm might make landfall.

[Satellite image of Beryl courtesy of RAMMB/CIRA]

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Francine expected to hit the northern Gulf Coast as a hurricane Wednesday

A dangerous storm developing in the southwestern Gulf of Mexico will make landfall as a hurricane Wednesday along the Louisiana coast.

Tropical Storm Francine spent Monday rapidly getting its act together off the eastern shores of Mexico.

The latest advisory from the National Hurricane Center (NHC) says that Francine has maximum sustained winds of 65 mph. The storm even appears to be developing an eye based on satellite and radar imagery, which is a sign the storm could soon close in on hurricane intensity.

Sea surface temperatures are a few degrees warmer than normal across the western Gulf, partially a result of having next to no storm activity over the region so far this year. (Tropical systems churn up cooler waters from below, even if briefly.)

Given the warm ocean temperatures and favorable environmental conditions around the storm, forecasters expect Francine to strengthen into a hurricane before making landfall on the central Louisiana coast during the day Wednesday.

Wind and Storm Surge

The NHC expects Francine to be near peak strength by the time it makes landfall in Louisiana on Wednesday. 

Widespread tree damage and long-lasting power outages are possible where Francine's eyewall makes landfall. Hopefully the worst winds remain over the relatively unpopulated bayous, but Lafayette—home to more than 100,000 people—could find itself in or close to the eyewall based on the current projected track.

Damaging winds are possible as far east as New Orleans and as far west as Beaumont, Texas. The outer edges of the storm could bring winds high enough to cause some downed trees and sporadic power outages.

A life-threatening storm surge is likely along the coast where Francine makes landfall. The latest advisory calls for a storm surge of 5-10 feet where the eye crosses the coastline if landfall coincides with high tide. This is some of the most surge-vulnerable land in the United States. Storm surge flooding can extend many miles inland across southern Louisiana's flat, marshy terrain. 

Any eastward jog in the storm could bring more dangerous wind and storm surge closer to New Orleans.

Heavy Rainfall

Tropical downpours are a certainty along Francine's track inland. The majority of deaths associated with landfalling tropical storms are the result of flash flooding from heavy rainfall. 

The Weather Prediction Center calls for 5-7+ inches of rain along Francine's track inland, which will pretty closely follow the Mississippi River north of Baton Rouge. Several inches of rain could fall as far west as Little Rock and as far east as Birmingham through the end of the week.

It's also worth noting that little bullseye over upstate South Carolina and adjacent areas. Southerly winds and enhanced moisture associated with Francine flowing up the foothills could produce 3-5 inches of rain over the region, leading to a localized flash flood threat. 

Almost all flash flood injuries and deaths are preventable. Never drive across a flooded roadway. It's impossible to tell how deep the water is until you're in it, and the road itself could be washed out beneath the water. It's not worth the risk to your life or those who have to rescue you or recover your body.

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Hot and humid nights drove another summer of record heat across the U.S.

This was one of the hottest summers—if not the hottest summer—ever recorded for large portions of the United States, another data point on the undeniable trend toward warmer days and even warmer nights as our climate steadily changes.

Meteorological summer began on June 1 and ended on August 31. This clean division of months more closely tracks temperatures than dividing the year up based on astronomical solstices and equinoxes.

The overall pattern we saw this summer featured persistent ridges of high pressure over the western and eastern ends of the U.S., with troughing in the center of the country.

Ridges foster sinking air, which warms up as it compresses on descent toward the ground. Troughs force air to rise, leading to unsettled weather and generally below-seasonal temperatures.

Source: IEM

We can see this divide in a map showing how much average daily temperatures departed from normal. A day's average temperature is the daytime high and nighttime low averaged together. Troughing in the center of the country led to somewhat seasonable temperatures, while folks west of the Rockies and east of the Appalachians dealt with warmer-than-normal conditions.

What really stands out is the desert southwest.

Folks in Phoenix, Arizona, just lived through their hottest summer on record. The daily average temperature there was a whopping 98.9°F this summer, which beat the previous record (set last year!) by nearly two degrees.

This summer's daytime highs in Phoenix were absolutely blazing hot—as of this post, the city is in the midst of a 100-day streak of daytime highs at 100°F or hotter, exceeding the previous record 100-degree streak by nearly three weeks.

Source: IEM

But it was the nighttime lows that really stood out.

Every single day this summer saw a warmer-than-normal low temperature, with those departures often coming in 10 or more degrees above normal. That's no small thing when midsummer nights don't cool off much in the desert. The city's low temperature in July only dipped below 88°F five times, and it remained 90°F or warmer at night 19 days throughout the month.

Here are the Summer (Jun-Aug) 2024 A) temperature rank, B) temperature departure from normal, C) precipitation rank, and D) precipitation percentage of normal. pic.twitter.com/8lUdLBQ1j7

— Brian Brettschneider (@Climatologist49) September 2, 2024

While not as unbelievably hot, the story of nighttime lows driving near-record summertime temperatures is constant up and down the East Coast.

Take a look at interior New England, where Caribou, Maine, just saw its warmest summer since records began there back in 1939. Repeated intrusions of muggy air in late June, mid-July, and in early August made low temperatures above 65°F a common sight in this small community near the Canadian border. For reference, Caribou's average low on July 16—summer's midpoint—is about 57°F.

This summer's noteworthy heat and humidity follows the pattern you'd expect to see as the climate changes.

Source: Climate Central

As I wrote back in July: "Climate change sets a new baseline for extreme heat throughout the United States and around the world. As the entire frame of reference moves toward a hotter climate, warm temperature extremes are far more likely that cold temperature extremes. Excessive heat will come in hotter than what we grew used to just one or two generations ago."

A warmer atmosphere can also hold more moisture. This increase in humidity makes it harder for nights to cool off as much as they used to, which is a significant factor driving warmer-than-normal summer low temperatures.

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Yes, 'corn sweat' is real and it can enhance brutal Midwestern humidity

A dangerous heat wave gripping portions of the central United States made headlines this week for two words: corn sweat.

Yes, 'corn sweat' is a real thing that can have a real impact on the weather.

Daytime highs soaring into the middle to upper 90s is brutal any day, but throw in humidity and it's unbearable even for folks who are acclimated to hot temperatures. That's what we're seeing across the Midwest this week. As of about 2:30 p.m. on Tuesday, the temperature at Chicago O'Hare was a record 98°F with a heat index of 114°F. 

That's hot! A major factor driving this excessive heat is the excessive humidity strangling the area like a wet blanket. The best measure of moisture in the air is the dew point, which is a good proxy for how much moisture is present in the air at any given time.

Relative humidity—"the humidity is 95%!"—is really only useful for forecasting fog and wildfires. If you want to measure comfort, dew point is the way to go. 

Any dew point below 50°F is generally dry and comfortable. Things get noticeably humid when the dew point climbs above 60°F. It's downright muggy when the dew point reaches 65°F, and you're in tropical territory when the dew point hits 70°F or higher.

Dew points climbed above 80°F throughout Iowa, Illinois, Minnesota, and Wisconsin during the day Monday. That's an atrocious, strangling level of humidity, especially when combined with high temperatures. 

It's uncommon to see dew points climb toward 80°F outside of tropical rainforests and the U.S. Midwest roughly for the same reason: evapotranspiration, or the infamous "corn sweat."

Plants consume a tremendous amount of water in order to survive and thrive. Excess water evaporates out of the plants into the atmosphere, raising moisture levels to heights rarely seen outside of areas blanketed by lush vegetation.

Why is corn sweat such a big deal and not, say, "kudzu sweat" from those invasive leafy vines that blanket the southern states? Corn gives off a ton of water. "An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day," according to the USGS. And we have vast swaths of the Midwest carpeted with cornfields churning out that much water vapor every day.

[Top image courtesy of Unsplash]

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Dangerous rip currents expected along U.S. East Coast as Ernesto passes by

Hurricane Ernesto will come dangerously close to Bermuda this weekend as it passes through the western Atlantic Ocean. While the storm itself won't hit the United States, the storm's rough surf will reach the East Coast and bring a threat for dangerous rip currents from Florida to Maine.

Ernesto is strengthening on approach to the tiny island of Bermuda, which sits about 650 miles east of South Carolina. 

Forecasters expect the storm to come close to major hurricane status before brushing just west of Bermuda Friday night into Saturday, putting the island in a vulnerable position for damaging winds and storm surge flooding.

The storm will continue heading north-northeast through the western Atlantic and eventually threaten Newfoundland with high winds and heavy rain by early next week. 

Even though the storm is going to miss the United States, folks along the coast will experience some dangerous impacts from this storm. Hurricanes generate high waves that can travel hundreds and even thousands of miles away from the storm. These waves bring with them a risk for rip currents beginning tonight and lasting through the weekend.

Rip currents are strong channels of water that pull away from the beach and directly out to sea. They don't pull you under like in the movies—they drag you away from safe shores in a hurry. People can quickly exhaust themselves fighting against the current, and that's when they run the risk of drowning.

Just about every beach from Florida to Maine has a risk for rip currents this weekend, especially in places like North Carolina, Virginia, and the Delmarva Peninsula.

Source: NOAA

Please stay out of the water if told to do so by local officials. They're not kidding when they say it's unsafe to swim. Lifeguards on a single beach can conduct dozens of water rescues every day as a result of people failing to heed red flag warnings for rip currents.

Rip currents look like calm patches of water amid otherwise rough surf. This apparent serenity lulls swimmers into a false sense of complacency, luring them into the ocean only to find themselves caught in a rip current.

If you're ever caught in a rip current, don't panic. Calmly signal for help. If you're a capable swimmer, swim parallel to the shore until the current stops dragging you out, then swim straight back to the beach. If you can't swim, tread water until help arrives. Don't struggle directly against the current. It's too strong for even the strongest swimmer to conquer.

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Major flood threat to develop this week as tropical storm stalls over southeast

A major flood threat will develop this week as a brewing tropical storm is expected to stall-out over the southeastern United States.

Forecasters expect Tropical Storm Debby to rapidly get its act together in the eastern Gulf of Mexico through the weekend, making landfall in Florida's Big Bend region as a strong tropical storm early Monday.

After landfall, the storm will slowly track into Georgia through Tuesday before emerging off the coast into the western Atlantic Ocean by late Tuesday night or early Wednesday morning.

From there, though, this system isn't going to go anywhere in a hurry.

SOURCE: Tropical Tidbits

Two large ridges of high pressure will essentially pin the storm in place after landfall. One ridge over the western Atlantic and another over the south-central U.S. will act like barriers that the storm won't easily squeeze through.

As a result, Debby will meander off the southeastern coast for several days before an opening allows the storm to finally begin pulling north later in the week.

A stalled tropical system dumping copious amounts of rain over the same areas is a story we've seen time and time again in recent years. This won't be any exception. The Weather Prediction Center calls for a large swath of 5-10 inches of rain across northern Florida, eastern Georgia, and the eastern Carolinas. More than 10 inches of rain is possible along the storm's path proper.

This much rain falling in a relatively short period of time is a recipe for flash flooding. Most deaths from landfalling tropical systems are the result of motorists drowning in flash floods. If you're in the area, please don't try to drive across a flooded roadway. It's impossible to tell how deep the water is until it's too late.

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A flash drought turns to flash floods across parts of the southeast

It's been quite the summer across the southeast and Mid-Atlantic as bouts of intense and prolonged heat roasted the region. Hot temperatures, bright sunshine, and scant rainfall forced the region to fall into a flash drought over the course of a single month.

The United States Drought Monitor at the beginning of June showed no drought anywhere across the southeast. The only region that was starting to slip behind in the rainfall department was central Virginia, which was abnormally dry as of the June 11 update of the USDM.

Fast forward a month and change and it's a completely different story. A significant swath of the region had fallen into a severe or extreme drought. This is a short-term drought—the kind that affects crops and lawns instead of reservoirs and wells.

Things changed in a hurry last week as the pattern flipped from hot and dry to...well, hot and wet.

Source: Tropical Tidbits

For the past few days, we've seen troughing off to the west with a strong ridge of high pressure over the Atlantic to the east. This new regime broke the ridging that brought record-breaking temperatures to the region, including the all-time hottest temperature ever recorded at Raleigh-Durham International Airport and a string of 100-degree days in Washington and Baltimore.

A constant flow of humid air pumping in from the Gulf of Mexico juiced the atmosphere and primed the region for daily bouts of thunderstorms.

As a result, some areas in North Carolina and Virginia have completely reversed their rainfall deficits in recent days. Precipitation totals over the past 60 days are showing above-normal values across portions of eastern North Carolina and southern Virginia that have dealt with constant storms and repeated rounds of flash flooding.

It's been hit-or-miss, though, given the pop-up nature of the storms. One town gets a deluge while folks down the street look on in envy (or relief). 

Source: CPC

The latest outlook from the Climate Prediction Center shows that this pattern of warmer temperatures with routine thunderstorms is likely going to continue heading into the month of August. Of course, seeing above-normal precipitation throughout the southeast moving into the peak of what's expected to be an active hurricane season is a bit of an eyebrow-raiser...but for now, at least, there's nothing to worry about on the horizon.

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Another round of dangerous heat arrives during a dangerously hot summer

An excessively hot summer across the U.S. rolls on this week as another stretch of dangerously hot temperatures spreads from I-5 to I-95.

Temperatures could easily crest the century mark for many locations over the next couple of days as broad ridges of high pressure rule the roost to start the week.

Tuesday will feature the worst temperatures, with 100-degree readings expected in Oklahoma City, Nashville, Washington, and Philadelphia. The high heat will stretch all the way into New England, where daytime highs in the 90s will reach into Maine.

Humidity will make the heat exceptionally dangerous in many of these locations, with heat indices exceeding 105 for many communities. 

The National Weather Service's new HeatRisk product shows widespread "major" to "extreme" impacts from this latest bout of high heat.

Folks living with chronic health conditions, working outside, or living without air conditioning will feel the greatest impacts from this latest heat wave. Heat exhaustion or heat stroke can develop in under an hour with these conditions.

Very warm and humid nights won't provide much relief from the blazing daytime temperatures. The compounding effects of hot days and steamy nights will make this especially tough for folks without adequate cooling at home. Fans alone won't be enough to combat this heat.

This is the latest volley of blistering temperatures during an already-hot summer across almost all of the United States.

Source: IEM

Data collected by the Iowa Environmental Mesonet shows that just about everyone save for the northern Plains and Upper Midwest has dealt with above-average temperatures so far this season. Much of the excessive heat has been driven by warmer-than-normal nighttime low temperatures, a side effect of the increased humidity we've seen this season.

Source: IEM

Folks across the Southwest have taken the brunt of the extreme heat this year, with week after week of brutally hot temperatures roasting the region. Phoenix has seen above-average temperatures on 163 of the 195 days we've trudged through so far in 2024. The last time they saw a below-average day was at the beginning of May.

Source: IEM

It's not just the Southwest dealing with the heat. It's a similar story back east. Washington, D.C., has seen above-average temperatures for 78 percent of the year through Saturday, July 13, and we're about to add another week of excessive heat to those grim statistics.

The relentless heat we've seen so far this year is exactly what you'd expect to see in a changing climate. Temperatures have steadily risen each decade across just about the entire United States—and we're even outpacing the new climate standards that run from 1991 to 2020. 

Source: Climate Central

Climate change sets a new baseline for extreme heat throughout the United States and around the world. As the entire frame of reference moves toward a hotter climate, warm temperature extremes are far more likely that cold temperature extremes. Excessive heat will come in hotter than what we grew used to just one or two generations ago.

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