In his final novel "Back to Blood," Tom Wolfe described the Florida sun as “an unnatural brilliance… [a] hellish heat lamp, which was the entire sky,” and even one of Wolfe’s impeccable, bespoke white suits would be no match for the sun on the summer solstice on Friday, June 20.

With our friendly neighborhood star no more than 7 degrees from the sky’s zenith at midday across the Gulf Coast, 12 will describe both the UV index and the number of minutes it takes for every squamous cell in your epidermis to go dysplastic without proper sun protection. Wear sunscreen, like Baz Luhrmann said.

That will be particularly true in the Southeast over the next week, as a strong ridge of high pressure developing over the U.S. East Coast keeps thunderstorm activity in check and lets the sun do its McDonald’s fry lamp thing.

High pressure, low tropical threats

In addition to unrelenting heat and humidity with high temperatures mostly in the mid 90s for the next 7 days, this ridge is contributing to an inconducive pattern for tropical development in the Gulf, Caribbean, and western Atlantic. Flexing high pressure means stronger than average east-to-west low-level trade winds across the Tropical Atlantic, which lards up the Main Development Region with Saharan dust, cools surface waters, and generally prevents tropical disturbances from getting better organized.

Brisk trade winds aren’t the Atlantic’s only issue today: vertical wind shear, the differential between low-level and upper-level winds, is also through the roof because of strong westerly winds aloft over the Gulf and Caribbean. The combined 30 to 60 knots of vertical wind shear is far too much for hurricanes to form on the Atlantic side of Central America, and with little change expected for at least the next week to 10 days, don’t look for any U.S. tropical threats through early July.

Not so in the Eastern Pacific, where Hurricane Erick rapidly intensified on Wednesday, and has since moved onshore in southern Mexico to the east of Acapulco at near-Category 4 intensity. One or two additional storms is a solid bet over the next few weeks in the E-Pac.

Call the cops when you see E-Pac (cyclogenesis), because it is stealing Atlantic tropical activity; in fact, what happens in the Pacific matters very much to tropical activity worldwide. In the short term, outflow from Erick is streaming east over the Caribbean, enhancing and reinforcing the high wind shear regime there.

WeatherTiger El Nino /La Nina Model Output for 2025.

Understanding Pacific patterns

In the longer term, understanding the Pacific is always crucial to predicting Atlantic storm activity. Seasonal hurricane forecasts like WeatherTiger’s are based on recurring, persistent patterns in the ocean and atmosphere that exercise a predictable influence on global weather, and there is no more important climate pacemaker than El Niño and La Niña.

El Nino, first recognized by South American fishermen in the 1600s and later rediscovered by Chris Farley in the early 1990s, is scientifically defined as a long-lasting period of ocean temperatures at least 0.5°C warmer in a specific region of the Central Pacific Ocean along the Equator, south of Hawaii and east of the International Date Line. La Nina, conversely, is when the average ocean temperature in this same region of the Pacific is 0.5°C or more cooler than average.

An El Nino or La Nina event isn’t always happening: each is only active about one-third of the time. However, once an event gets going (usually triggered by semi-random variations in trade winds between March and June), it tends to lock in for one to two years.

The entire irregular sequence of El Nino to neutral to La Nina and back again in the Pacific can take anywhere from three to seven years. Collectively, these influential cold and warm phases are known as El Niño-Southern Oscillation (ENSO).

Florida hurricane landfalls by fall La Nina/El Nino.

Heartbeat of circulation cycles

Why do forecasters like me care so much about cycles of water temperatures in a small, seemingly random patch of ocean? Because just like a heartbeat, the whole circulation of the atmosphere turns out to be driven by those cycles.

When the waters of the Equatorial Pacific are warmer than average, the weak temperature contrast between the eastern and western Pacific slackens east-to-west trade winds. Not only do weaker trade winds cause additional ocean warming that sustains the El Nino, the resulting eastward shift in Tropical Pacific thunderstorm activity induces a particular worldwide pattern to where air rises and sinks.

In a La Nina, stronger trade winds form a feedback loop with cooler waters in the East-central Pacific, shifting Pacific convection west and favoring the opposite patterns of rising and sinking air globally.

These rising and sinking circulations influence the location of the mid-latitude jet stream responsible for dividing warm, moist tropical airmasses from cooler, drier polar airmasses, with distinctive jet stream signatures for El Nino versus La Nina regimes.

Therefore, knowing what the Eastern and Central Pacific will be doing for the next six to 12 months allows forecasters to make an educated guess as to whether particular regions of the globe are more likely to be wetter, drier, warmer, or cooler than average for the upcoming year.

La Nina pattern

Influence on Atlantic hurricane season

ENSO also plays a major role in determining whether an Atlantic hurricane season is impactful or not. When the Pacific is cooler than average, fewer tropical storms develop there, and vertical wind shear is usually weaker than normal over the portions of the Atlantic Basin closest to the continental U.S. around and after the September peak of hurricane season. During an El Nino, the tendency for stronger shear close to the U.S. coast results in fewer, weaker landfalls, on average.

In fact, historical U.S. landfall rates during stronger La Ninas are about three times higher than in stronger El Ninos. Of course, like a fast food drive-thru order, those odds are subject to an (un)healthy uncertainty; for instance, the last El Nino event in 2023 was accompanied by a rare U.S. major hurricane landfall, Idalia. Climate is what you expect, but weather is what is actually in the bag.

El Nino pattern

Staying on neutral ground

In 2025, I continue to expect that the season will take place in the neutral ground between El Nino and La Nina, which is where we are this summer, and partially accounts for the Atlantic’s slow start. There remains some chance that a weak La Nina may re-emerge through fall, which all else equal might prolong the Atlantic hurricane season.

However, WeatherTiger’s hot-off-the-press June ENSO guidance shows lower odds of that than previous model runs, which is another indicator that the 2025 season should be more reasonable than 2024, or at least not quite as deranged.

Finally, for those looking for more information on El Nino and La Nina, NOAA has a terrific ENSO blog packed with useful forecast updates and easy-to-read explainers.

You need to hurry, though: the NOAA scientists who write that blog have been fired, and it is unknown if the articles will remain beyond July 1, which is a real shame. Unfortunately, when watching the skies and learning about El Nino-Southern Oscillation is outlawed, only outlaws will learn about El Nino-Southern Oscillation and keep watching the skies.

Dr. Ryan Truchelut is chief meteorologist at WeatherTiger, a Tallahassee company providing forensic meteorology expert witness services and agricultural and hurricane forecasting subscriptions. Visit weathertiger.com to discover how to put our expertise to work for you and access our real-time 2025 seasonal hurricane forecast model data.