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January Forecast Discussion


REDMK6GLI

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The only thing that I can say about the +AO in December and January is that the AO has been more

positive since the record March 2013 drop. April 2013 to September 2014 featured the longest streak

of monthly averages where AO failed to drop below -1.000 in over a decade.

 

Longest monthly streaks with the AO failing to drop below -1.000 since 2000:

 

4/13-9/14.........18 months

9/11-9/12.........13 months

6/08-5/09.........12 months

3/07-4/08.........14 months

3/04-1/05.........11 months

1/03-12/03.......12 months

4/99-10/00.......19 months

 

With every positive AO reading, the prospect of  negative winter AO average as per the SAI and OPI is decreasing. After today's +1.689 figure, the remainder of the December-February period would need an average AO of -1,840 to achieve a winter average of -0.500 and a mean figure of -2.818 to have a winter average of -1.000. Yesterday, those respective averages were -1.765 and -2.722.

 

Through today, 45% of the days this winter have seen the AO at +1.000 or above, while 7% of days saw it at -1.000 or below. In addition, the lowest AO figure this winter has been -1.280. In contrast, 36% of days have seen the AO average above +1.280.

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Go thru past 4 runs on navgem...clearly a trend to bring precip into south jersey. This is all philly forum talk anyway so I will head back on over there.

IMO, there's probably enough model support to keep open the possibility of a period of accumulating snow in a portion of southern New Jersey e.g., the Cape May area. The NAM is probably overdone, but a scenario where a few inches accumulates probably should not be dismissed outright.

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And the 12z NAM is well south of previous runs. Doesn't get much into SNJ. These inverted troughs are nearly impossible to nail down.

Yeah alot of dry air to start. Delaware does ok this run. I wouldn't say the precip was "well south" though. Still close to being a nuisance during tomorrow morning rush hour in those areas (extreme south jersey and delaware).
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Models all beginning to agree, with the GFS leading the charge, on a favorable MJO progression as we head into late month, with the PV displaced (possibly from the SSWE that just occurred last week). The thaw appears to be canceled and cold may very well prevail. Not much to cherry pick today. We may only have a two weeks window, but a setup appears to be on the horizon that is very favoriable for east coast snow. Let's see how things progress over the next couple of days. 

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Euro has a shot of artic air Friday and cancels Sunday's warm up....we get rain from a coastal storm Sunday night and then arctic air rushes in Monday..

How is that rain? The 850mb freezing line is east of the city by hour 132. I agree that it may start as rain on the coast but even they flip to snow before ending.

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How is that rain? The 850mb freezing line is east of the city by hour 132. I agree that it may start as rain on the coast but even they flip to snow before ending.

The surface is in the great lakes...Might end as some light snow. It's 100% rain for us verbatiam...take the snow goggles off. It's not all about that blue line!

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The surface is in the great lakes...Might end as some light snow. It's 100% rain for us verbatiam...take the snow goggles off. It's not all about that blue line!

700mb is pretty cold and 850's are below freezing at the height of the event West of the city. The only warm layer is 925mb to the surface so it's a snow/rain mix profile or non accumulating snow profile, but you have some room for dynmaic cooling in there if you can get robust enough precip.

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