Tuesday January 2, 2007

Meterological question: The Gulf Stream only happens in some years. It’s happening right now, and which is why the hurricane season was so uneventful. But is that also why the winter so far has been so warm? Update: I completely bungled this question — I got my El Niño confused with my Gulf Stream. See comments for more information, and the answer.

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  1. Paul305    Tue Jan 2, 05:39 PM #  

    While the strength of the Gulf Stream varies from year to year, it must “happen” to some extant every year and every day as a matter of physics. The amount of energy required to start up a system of this size is so large that it cannot just start or stop in a few years but rather in hundreds or thousands of years. On the other hand, El Nino, which is basically defined as a positive temperature anomaly of greater than 0.5 degrees Celsius in the Eastern Pacific, can start and stop very quickly. This year an unexpected El Nino system was the main reason for our inactive hurricane season. This may seem counterintuitive to those who have been told that warmer ocean water means more hurricanes but just keep in mind that El Nino is a condition of the Pacific Ocean and not the Atlantic where warm ocean water is known to increase hurricane frequency and intensity.

    According to Wiki, the other reason why the 2006 hurricane season was so benign was the “pervasive presence of the Saharan Air Layer” or SAL. The SAL is basically a dry, dusty and (most importantly) hot layer of air which floats above the humid ocean air of the Atlantic. Since warm air rises and cool air sinks, the SAL prevents the rise of humid ocean air to altitudes necessary to start a tropical cyclone.

    As for the unseasonably warm winter, all I can say is that the Gulf Stream is at least part of the reason why this winter and the rest of our winters are always warm. It is also the reason why Miami Beach is usually warmer than West Kendall during the winter. However, I would attribute this abnormally warm winter mostly to Miami’s low latitude and most of all to chance.



  2. Robert    Tue Jan 2, 05:59 PM #  

    The Gulf Stream is always there. It has a lot more to do with the Jet Stream, which is the air current at 35,000 feet which steers weather systems. This winter, the jet stream has been taking a southward dip out west, keeping the southward plunges of cold air out there instead of in the East.

    It’s not just Miami that’s been warm this winter so far. All of Florida has been quite mild, and the major cities of the Northeast have barely seen a snowflake. There’s even stories I’ve heard of green grass in parts of New England!

    There’s still plenty of time for a few outbreaks of chilly air like what we had over Thanksgiving.



  3. alesh    Tue Jan 2, 06:47 PM #  

    I completely bungled this question — I got my El Niño confused with my Gulf Stream. Duh.

    Thanks for clearing me up, and for the explanation(s).



  4. Robert    Tue Jan 2, 07:51 PM #  

    Don’t worry Alesh, happens to me all the time.

    ;)



  5. Manola Blablablanik    Tue Jan 2, 09:03 PM #  

    I remember my sailing friends telling me that you always have to travel southward when going east crossing the stream because when you are crossing it, the current pulls you northward and you have to compensate.

    Robert, doesn’t the stream shift slightly? Also I’ve heard that it’s because of the stream that Ireland is called the Emerald Isle. Don’t know if that’s anecdotal or what.



  6. alesh    Tue Jan 2, 09:24 PM #  

    There’s a very interesting section in An Inconvenient Truth about the Gulf Stream. Basically, it keeps Europe much warmer then it would otherwise be. Wait a second, I’m getting confused again — that’s talking about ocean currents, not air currents.

    Go, go, Gadget brain!



  7. Rick    Wed Jan 3, 07:17 AM #  

    A really nasty comment about “sticking with things you know about” seems highly appropriate here, but, really…why state the obvious?

    .



  8. alesh    Wed Jan 3, 07:26 AM #  

    Yes. There’s also the possibility of a comment about the virtues of admitting when you’re wrong. Of course that would never occur to you, Rick, since you never are.



  9. Rick    Wed Jan 3, 08:08 AM #  

    I’m wrong a lot, Alesh. Not as much as you think I am, but still, quite a bit.

    BTW, keep up the great work. Meteorology is a slippery slope and something only the #1 blog in Miami is brave enough to take on. Bravo.

    PS: Can you tell me why Denver is getting so much snow this year? Thanks a bunch.

    .



  10. alesh    Wed Jan 3, 09:48 AM #  

    Whatever, Rick. I’m sure if I push you hard enough you’ll be able to cite an example of where you corrected yourself. But I have better things to do.

    Also, I think you’re suffering from a bit of semantic confusion around the word “question.”



  11. mkh    Wed Jan 3, 10:45 AM #  

    Okay, boys, don’t make me stop the car, because I will. Rick, quit touching Alesh. Alesh, if you keep making that face it will freeze like that!

    I mean it, stop it. Daddy’s all out of patience and Valium and that’s a bad combination.



  12. alesh    Wed Jan 3, 11:15 AM #  

    Um, he started it. :)



  13. Bloggers Gone Wild    Wed Jan 3, 11:27 AM #  

    Mud wrestling! We want mud wrestling!



  14. Robert    Wed Jan 3, 12:09 PM #  

    To answer Manola’s question…

    The Gulf Stream does shift slightly, sometimes the edge of it can be only 2 or 3 miles offshore, other times it can be up to 10 miles offshore. It’s a big deal, not only because of the northward moving current, but because the waves can be much higher in the stream if you have a north or northeast wind opposing it.

    As Alesh mentioned, the stream does go all the way to off Northern Europe, and that’s why the British Isles and even parts of Scandinavia are much milder than other locations with the same latitude such as Siberia and Canada.



  15. Bryan Norcross    Wed Jan 3, 01:57 PM #  

    Show off.