Welcome to May! We are now two-thirds of the way through spring, and right on schedule, the atmosphere has a mini heat wave in the forecast for most of us east of the Rockies. On top of that, models are trying to spin up some sort of a tropical cyclone-ish thing off the East Coast next week.

Meteorological Spring

We really are two-thirds of the way through spring, even though it doesn’t quite feel like it for many of you. Instead of using astronomical seasons, we follow meteorological seasons when talking about the weather. Meteorological spring, for example, begins on March 1 and ends on May 31, while meteorological summer starts on June 1 and stretches through August 31. As I explained in-depth last September, meteorological seasons are cleaner, easier, and tend to follow temperature/precipitation profiles better than using astronomical seasons.

Why is that important? It helps keep it in perspective when I say that some people many of you will have to tick on your air conditioners next week. Spring and fall serve as transitions between hot and cold—the first half of spring trends cold, while the latter half gradually heats up to uncomfortable levels before schools let out and the droning sound of bugs looking for mates in the heat of the afternoon sun. We’re approaching the latter.

Mild Heat Wave

Wavy jet streams are what provide us exciting weather. Troughs in the jet bring us turbulent weather, while ridges tend to foster calm, warm conditions. Beginning next week, much of the eastern half of the United States will be under the influence of quite the ridge in the jet stream, allowing warmer weather to take hold.

Combine the ridge in the jet stream with southerly winds pumping warm air from the tropics, and it’s a recipe for the first major influx of heat this year. The animation above shows the jet stream (contours and wind arrows) superimposed on a map of model-forecast surface temperatures, illustrating the steep ridge across the eastern part of the country, with temperatures in the low- to mid-80s climbing relatively far north.

It’s going to get pretty toasty in some spots. As shown above, the GFS model predicts temperatures approaching (or even hitting) 90°F as far north as Greensboro, North Carolina.

There will be a sharp cutoff between warm and mild, though—it’s along these boundaries where showers and thunderstorms are most likely next week.

Tropical Thing

Hurricane season doesn’t begin in the Atlantic Ocean until June 1, but nature doesn’t always follow our boundaries (wouldn’t it be great, though?). We’ve seen tropical and subtropical storms develop in April, so one in May, while uncommon, wouldn’t be unprecedented.

Both the GFS and European models are hinting at the possibility of what would likely be a subtropical depression or subtropical storm developing off the southeast coast next week. A subtropical cyclone is a hybrid between a tropical cyclone and an extratropical cyclone—it has characteristics of both. Things can and will change over the next few days, but if you live along the East Coast, it’s something worth keeping an eye on.

If it strengthens into a sub/tropical storm, its name would be Ana. If it continues to appear on models next week, the National Hurricane Center will handle forecasts and advisories on the system before and during its existence.

There are only 30 days until (meteorological) summer.

[Images: GREarth, WeatherBELL, Tropical Tidbits]

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