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January 2012

The tropics, a possible polar low, and North American winter musings

   Posted by Levi at 12:47am on January 10, 2012

The global tropics are fairly quiet overall, with the only activity confined to the southern Indian Ocean, where the remnants of Tropical Cyclone Chanda are beginning to exit Madagascar, leaving much of the island drenched in over a foot of rain in some places. These remnants may get stuck north of a subtropical ridge and try to regenerate later, but for now they will cease to be an immediate threat after leaving Madagascar. An invest off of northwestern Australia may become a weak tropical storm over the next few days as it moves southwards towards the west Australian coastline, bringing rain to that area, but no models strengthen it beyond manageable intensity for now.

The video shows an interesting vertically-stacked low pressure area in the Sea of Okhotsk, which may become a polar low during the next 48-72 hours as it sits nearly stationary and strengthens, in part due to warm-core processes.

Back in North America, the forecast battle for the rest of the winter continues. Blocking is due to develop up through Alaska, Siberia, and over the north pole this week, sending the arctic oscillation negative and providing a tempting look to the pattern for snowlovers in the eastern United States. However, the arctic vortex over northern Baffin Bay is remaining strong, and the blocking over the pole will do little to it except squeeze it slightly more southward and allow the northern tier states of the U.S. to get in on some seasonal cold at times during the next 10 days or so. The southeast and central part of the country will get a day or two of cold as a trough rolls through in about 96 hours, but then normal temperatures will return in its wake.

The thing about the Alaskan blocking is that such blocks loves to build up and then cut-off into blocking highs that retrograde westward into northern Russia as they weaken. Heights then crash in their wake, and the arctic vortex loves to redevelop farther west into the void left by the exiting block. All of the ensemble sets are starting to see this in the 10-15 day forecast, and I show those in the video. This would make sense also because the troughing loves to be in western Canada when the PDO is negative and cold water exists along western North America, helping heights to lower. With the arctic vortex remaining intact and shifting westward during the next two weeks, it is going to be very hard to shut off the strong zonal flow over the U.S. and get true long-lasting cold air into the eastern half of the country. As the cold builds in western Canada, some may get into the northwest U.S. and midwest as time goes on, which is only natural in this kind of a winter, but for the east and southeast, don’t expect a big pattern flip going into the end of January.

We shall see what happens!




  • TzuMom says:

    Excellent analysis, Levi, thank you. These forecasters who proclaim a freezing February here in the US are not looking at ALL the factors that determine weather, as you do. I’m not a betting person, but if I was, my money would be on you!

  • Ken says:

    Thanks Levi:
    Whenever you “Shine the Light” on the N.E. Pac. I watch. To be honest I watch anything you put up.

  • StormW says:

    Great job Levi! I remember when you first started on that other site. I must certainly say…you have excelled tremendously in your analysis and forecasting skills!!

  • John says:

    Great video and glad to see SPRING around the corner for the Mid Atlantic.

  • TomTaylor says:

    Great analysis as always. Latest GFS Ensembles from today show exactly what you said. Retrograding cut off high into Siberia…trough moves into Alaska…exactly what the doctor (you) ordered lol

  • TomTaylor says:

    Two other things,

    Firstly, I honestly haven’t gotten the impression that you are being a blowhard at all. You do your analysis and call it as you see it. Although, I would like to add that I am glad you are taking a minute to reflect on this, because I honestly wouldn’t like to see you become one. I know Joe B has long been one of your idols, and I also think he’s a great forecaster and knows a lot about weather, but personality-wise he comes off too strong sometimes, and it just gets obnoxious and arrogant. Not to mention he’s gotten way to wrapped up in the Global Warming debate.

    Secondly, is there a way to get a profile picture for this site?

    • Levi says:

      I’ve been meaning to put up some info on avatars.

      Go to the Gravatar signup page and enter the email that you use on this site. You will then be able to pick an avatar that will show up within a few minutes. Folks that are already wordpress users should have their avatars automatically transferred to this site.

  • KevinZ says:

    Great video and writeup but I have one issue with a statement you made. You said “because the troughing loves to be in western Canada when the PDO is negative and cold water exists along western North America, helping heights to lower.”

    It sounds like you are saying that when the PDO is cold for it run of 10 – 20 + years that the PV loves to be where it has been for the most part this winter. If that is the case you would expect milder winters across the Eastern US. But that is not the case. Joe Bastardi tweeted something about 2 weeks ago with an anomaly chart. It showed that during the last PDO (he used 1956 – 1981) that the Eastern US was significantly colder. Then it went to warm when the PDO turned warm 1982 – 2007. The latest chart shows the cold anomalies returning 2008 – 2011 as the PDO goes cold again.

    • Levi says:

      That’s not the same thing. The period 1956-1981 was generally colder everywhere, not just North America, and the PDO was not negative every single one of those years, just most of the time.

      Here is the correlation between the PDO and Dec-Feb 500mb heights. The correlation map will show high positive values when the PDO is positive, but I have reversed the colors so that you can see what it looks like when the PDO is negative (blue is low heights, red is high heights). The troughing is in western Canada, and the ridging in the southeastern U.S. makes it warm there.

      • KevinZ says:

        So I would say you are disagreeing with Joe Bastardi? He said the cold across most of the USA (1956 – 1981) was caused by cold PDO.

        His exact tweets: (I wish I could post the pics but I can’t figure out how to paste them here)

        “PDO turned cold in 50s, amo in 60s. Similar cycle starting now. Look at last time it did this..50s thru 70s”

        “Not cyclical? You have to be blind.30-55 warm, pdo 56-81 cold, 82-07 warm, then last 3 winters as pdo turns cold”

        Sounds like he is basing a lot of the cold cycles in the US around a cold PDO. He also mentions in the one tweet that the AMO also was cold in the 1960s so that likely had an effect on how cold it was in the USA and world. He also alludes to that he thinks the AMO is also going to flip to its cold phase soon and expects a 20 year period or so of colder than average in the USA and world as happened in the 60’s and 70’s.

        • Levi says:

          Well he is playing around a bit with the periods he mentioned. The PDO was negative from the mid-1940s through 1976. Taking that period, here’s what we get for U.S. temperatures (can only go back as far as 1949 due to NCAR reanalysis only going back that far):

          Notice the warmth in the south and east as we should expect. Now the PDO went positive in 1977 through 2007. Here are the temperatures for that period:

          Guess what, it’s pretty darn cold. JB’s periods overlap the PDO cycles by 5 years or so, and that may have an effect. While the AMO was cold, the U.S. was colder, and the period 1977-1995 shows this:

          But when the AMO flipped warm in 1995, it got substantially warmer overall:

          So leaving out the 4-year period between 1977 and 1981 apparently was enough to weight 1981-2007 to slightly above normal, but barely, because the cold AMO/PDO combination was so cold. He’s right on that point, but the trends for U.S. temperature with the PDO are very clear. Again, here is a correlation map between U.S. temps and the PDO. The colors here show what happens when the PDO is positive, and you have to mentally reverse them to see the temperatures when the PDO is negative.

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