Sunday, January 19, 2014

Early February 2014 Forecast

This post will address the predicted weather pattern for the first half of February.

January 23-24 500mb height anomaly forecast
As we enter February, expect the pattern to be on the warm-up, as ridging over Japan on January 23rd and 24th means ridging over the US from a January 29th to February 3rd period. Because the ridge in Japan is rather progressive, I wouldn't doubt we see the same result here in the United States when the ridge comes along for early February. By the time we reach February 5-7, it appears we will see another shot of Arctic air.

This image shows an analysis (not a forecast) of the 500mb height anomalies over the Pacific, as of 6 PM Central Time last night. We can see the deep negative height anomalies over the Bering Sea, and the identifier of the Bering Sea Rule, Joe Renken, sees this as a signal that the February 7-12 period will see significant cold weather. I agree with this idea, and it does look like the first 10 or so days of February will be characterized by an up-and-down weather pattern.

GEFS 500mb height anomaly forecast for January 31

I expect we see tentative settling-down of the pattern by the middle of the month, as persistent high pressure just south of the Bering Sea at the end of January indicates we could see a zonal flow situation not unlike we saw earlier this winter, where high pressure dominated the Southeast and stormy weather affected the West Coast. Because of this Southeast ridge returning, I expect we see the late January East Coast snow zone retreating back into the Midwest and Plains. Unfortunately for those in the East, this winter does look to be confined more to the Central US as opposed to coastal regions.

To sum up:

•February 1-7: Warming up in the Central/East US before a cool-down at the end of the period.
•February 8-14: Potentially intense cold in the beginning and middle of the period before a relaxation into more moderate temperatures, especially in the South and East.



Eric (weather advance) said...

Nice post Andrew, and I may add that looking at the LRC, I'm a bit surprised you didn't take a stab @ the storm systems that came up out of the southern plains & TN/OH valleys into the northeastern US in the early stages of December. Looks like beyond this (based on LRC, among other things) time a new series of clippers will keep a trough in the east for a while before the trough starts to kick into the western US, partially in response to decreasing jet strength & wavelengths. And if you recall the rather severe arctic outbreak we observed in early January, the LRC implies this would come back to haunt us near the beginning of March (guess the old saying, "March comes in like a lion & out like a lamb") may be quite applicable this year. Looks like I will be paying a lot more attention to OPI researchers who had warned well in advance of these relatively periodic cold shots into eastern North America which would be most prominent when jet amplitude maximized. Although we are a very long way from the start of the hurricane season & thinking about preliminary ideas, this persistent north Pacific ridge certainly has my attention as I've noted it's behavior in the late winter has connections to the following hurricane season. I've seemed to note that when comparing the amount of hurricane landfalls in above normal hurricane ACE years in the Atlantic (this of course does assume next hurricane season is generally more active than normal), that the difference in the years with one or fewer hurricane landfalls vs years with several hurricanes striking the US coast lies in the strength of the north Pacific ridge & associated -PDO. In years with more hurricane landfalls, the north Pacific ridge is much stronger & extends much further east towards North America as opposed to years with fewer landfalls that have a relatively "wimpier" north Pacific ridge. This makes sense given that the stronger & more eastward extended north Pacific ridge in late winter allows the Aleutian trough in the summer to also become displaced east towards north America. This eastward displacement of the Aleutian trough into the Gulf of Alaska enables the jet downstream near eastern North America to lift into a ridge axis in the general vicinity of SE Canada, which forces any tropical cyclones that make their way into western Atlantic to get forced into N America. Now, considering that the TNH pattern is generally a product of the the strength of the anomalies of the north Pacific SST that help modulate the intensity of the north Pacific jet along w/ ENSO (& on smaller timescales, convectively coupled equatorial waves, especially the Kelvin Wave), given that we saw an all-time record set for strongest +TNH in the month of Dec (broke the previous record set in 1972) I though it would be sufficient that if I wanted to try & get an idea on the strength of the north Pacific ridge in the late winter period, I would extrapolate years with a similarly strong +TNH into the Feb-Mar period & interestingly, this is what I found (link) a considerably strong & extended north Pacific ridge, reminiscent of the preceding late winter patterns in high ACE atlantic hurricane seasons with several hurricane landfalls on the US coast. You should also note in the extrapolated +TNH patterns, a defined -NAO signature develops, which in turn would slow the northeasterly trade winds in the deep tropical Atlantic, allowing waters to warm significantly, that would generally favor a more amplified warm Atlantic tripole signature going into spring. Of course, plenty of caution must be used given last year's hurricane season forecast bust, but as long as the thermohaline circulation doesn't suddenly pull a fast one on us & crash like it did last spring, we'll certainly have to look to other factors to limit the 2014 hurricane season.

Eric (weather advance) said...

Here's the link to the picture of the extrapolated strong +TNH patterns in December to late winter that may have implications going into the 2014 hurricane season.

Anonymous said...

Dear Andrew,
Since that you are forecasting temperatures to moderate in the south and eastern US, will Chicago see a major winter storm or just any winter storm in this period?

Anonymous said...

how about here in kansas
when do you think we will get a real good snow
i would even take a blizzard
its been a cold dry winter here
need moisture
please tell your thoughts on this