Flight Reaches 801 Mph as a Furious Jet Stream Packs Record-breaking Speeds

["Dave Farber" <farber () gmail com>]

Begin forwarded message:

> The jet stream, the high-altitude air current along which storms travel, is
> furious. The river of air was clocked at more than 230 mph over Long Island on
> Monday. That measure comes from the 250 millibar pressure level, meaning it
> was at a height above 75 percent of the atmosphere's mass. It sets the record
> for the fastest 250 millibar wind speed ever recorded over New York and,
> probably, the country.
>
> The 250 millibar level generally tends toward 30,000 feet to 35,000 feet.
> That's about the same height at which commercial planes fly. Unsurprisingly,
> the jet stream can have big implications on how quickly aircraft reach their
> destination.
>
> With a speed max currently over central Pennsylvania, airplanes flying through
> the jet will either be sped up or slowed down big time, depending on their
> direction of travel. It's like the moving walkway at the airport. You have
> your own forward speed, but if you continue this velocity in an environment
> that is itself moving, it can propel you at an impressive rate.
>
> A Virgin Atlantic flight from Los Angeles to London peaked at a whopping 801
> mph Monday evening 35,000 feet over Pennsylvania. "[N]ever ever seen this kind
> of tailwind in my life as a commercial pilot," tweeted Peter James, a jet
> captain.
>
> It appears that's a record for the Boeing 787-9 twin jet, which in the past
> has flown at speeds up to 776 mph. The ordinary cruising speed of a Dreamliner
> is 561 mph, with a maximum propulsion of 587 mph. Any speed gained on top of
> that is thanks to Mother Nature's helpful boost.
>
> Although the plane didn't remain in the "jet streak" — the zone of maximum
> wind embedded within the jet stream — for long, it still arrived 48 minutes
> early. And you might notice something suspect about the 801 mph reading — it's
> above the speed of sound (767 mph). Commercial aircraft ordinarily can't break
> the sound barrier, because they're not designed to handle the sudden increase
> in drag and other aerodynamic effects associated with those speeds. Despite a
> ground speed that high, the plane didn't come close to reaching that threshold
> because it was embedded in the swiftly moving air.
>
> An LAX-JFK Delta flight overnight hit 678 mph at 39,000 feet over the Ohio
> Valley, while a 737 from Chicago to New York passed 700 mph at 8:43 Eastern
> this morning. Chicago to New York/Boston routes will be shortened to 1 hour,
> 24 minutes tomorrow instead of the usual nearly two-hour flight time.
>
> Likewise, flight times from Dallas to Boston dipped below three hours, with an
> Embraer ERJ-190 twin jet achieving 739 mph in the jet streak.
>
> Odds are that if you're flying west, you won't find the jet stream helpful.
> Departing flights out of New England and the New York area will probably incur
> 20 or 30 extra minutes of travel time, either slowed by the jet streak or
> forced to divert around it. But if you're traveling east , you might find
> yourself on the ground a bit sooner than normal.
>
> For the jet stream to get cranking this much, there must be a big storm
> brewing somewhere, right? Surprisingly, it's the opposite (the closest
> developing storminess is in the western Gulf of Mexico on Tuesday). Storms
> cause the jet stream to bend, cresting and dipping into waves that ride across
> the Lower 48. Just like kinking a garden hose, it causes the flow speed to
> decline. In the absence of large-scale weather systems, a zonal west-to-east
> jet is free to gather considerable speed, much like how we reach our fastest
> highway speeds on straightaways.
>
> The jet stream can usually get to speeds this high only in the winter because
> temperature differences between the north and south are maximized.
> Temperatures on Tuesday hovered around minus-10 to minus-20 in eastern Canada
> while soaring well into the 80s over Florida. Such large differences in
> temperature (and pressure) power the wind.
>
> Click Here to see the story as it appeared an the Washington Post website.
>
> Copyright 2019 The Washington Post
>
> -0- Feb/19/2019 18:20 GMT


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