CROSS POLAR FLOW —OR, HOW TO MESS UP COMPUTER MODELS—

I am very ignorant concerning computers, and I only mention this as a ignorant soul telling a Rembrandt his shoelace is untied.

The models amaze me with their accuracy five days into the future, most of the time. I have a hard time forecasting tomorrow. Therefore I rely on models, and notice when they are not amazing, five days into the future. Recently they have been spectacularly wrong, especially as you get up into northern latitudes.

I’ve been wondering if they think in a circular manner. They might see weather patterns going around and around the earth.  It might throw a wrench in the works, and be over-the-top, so to speak, when rather than around and around, cross-polar-flow brings things over the top.

The recent cold that clobbered Europe was unseen by models, even three days ahead of time. I think it may be because the models are based on a nice, “zonal” flow, and have trouble when the Pole is afflicted by what some (me) call a “loopy” flow, and others call “meridianal.”

The best model at handling such cross-polar-flow seems to be the Canadian “JEM” model, likely because Canada gets clobbered by cross-polar-flow more than most other nations. Perhaps the JEM model does not do as well with round-and-round the earth patterns, for it is not the best model overall, however when it does score a “coup” it seems it is because it added over-the-top cold to the mix. (Of course, the JEM model has a habit of creating over-the-normal super-storms, but no one is perfect.)

I thought it might be interesting to see what the JEM model produced, and what follows gives you an idea of the wrenches the Pole can throw into the works of any model that accepts a zonal flow as a basic premise.

(These maps are produced by a Rembrandt of the weather-map-world called Dr. Ryan Maue, of the Weatherbell site, however these maps are blemished by a bit of digital graffiti down the left sides. Likely Dr. Maue was operating on two hours of sleep when he wrote the code for this map, or perhaps the Canadian computers produced the glitch and the graffiti  is beyond Dr. Maue’s control. In any case, it is an untied shoelace, and I hope you will ignore it and enjoy the great art.)

All these maps can be clicked, or opened to a new tab, to enlarge them. Then they can be clicked a second time to enlarge them further.

The first, “initial” map shows a Pacific invasion has nearly reached the Pole, but a tremendously cold airmass in Siberia, (the hottest pink is -70°), is rushing north behind the invasion, cutting it off. (The clash between the the milder and frigid air is creating a decent polar storm.) This northward rush of Siberian air is what I called “the snout of Igor” last year, and makes me worry, though I am off the map and on the far side of the planet.

CPF1 cmc_t2m_arctic_1

The next map shows that a day later the Siberian air has charged right across the Pole. The Pacific invasion is cut off, but an Atlantic invasion is starting north west of Norway. (Notice the cold air has been driven from northern Scandinavia.) Things look bad for Canada, with that thrust of Siberian air charging their way.

CPF2 cmc_t2m_arctic_5

The next map, 48 hours later, makes one say, “But what is this?” A new invasion of Pacific air is attacking the cross-polar-flow from one side, as the Atlantic invasion proceeds from the other. Will the flow be strangled?

CPF3 cmc_t2m_arctic_9

After 72 hours the Pacific invasion seems to be overpowering the Atlantic invasion, and rather than the cross-polar-flow being nipped in the bud, it is developing a curve, or a sort of saddle. Warmth has pushed east of Finland into Russia.

CPF4 cmc_t2m_arctic_13

After 96 hours the curve in the cross-polar flow has become such an oxbow that the air is starting to aim not towards Canada initially, but west towards Scandinavia. Notice that west of Finland, the cold is no longer retreating east in Russia, but starting to advance west.

(I think this is where some models start to lose it.)

CPF5 cmc_t2m_arctic_17

After 120 hours the original cross-polar-flow has collapsed into a surge of cold back towards Scandinavia. However a new cross-polar-flow is starting, and the most-recent Pacific invasion is again being cut off. Northern Scandinavia is much colder.

CPF6 cmc_t2m_arctic_21

Lastly at 144 hours, (which is starting to enter la-la land, for models), we see some bizarre feature north of Greenland throwing mild air up towards the Pole.  (“I’ll believe it when I see it.”)  However what seems a little more reliable is, first of all,  that the new cross-polar-flow has hooked up with Canada, and the air in northern Canada is nearly as cold as Siberia’s.  Secondly, the old cross-polar-flow has sent really cold air crashing into Scandinavia.

(It is sort of like the cross-polar-flow was a meandering river, and cut off an oxbow, but in the atmosphere an oxbow does not just sit stagnant, as an oxbow lake, but is a mobile thing, as Scandinavia may see first hand, 144 hours from the time of the first map.)

CPF7 cmc_t2m_arctic_25

Please remember all of the above is occurring in the virtual world of computer models. It is theory, not reality.  However what is so fascinating to me is how different weather patterns look, when you view the globe from the top, rather than always from one side or another.

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