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Thursday Wintry Threat II


Baroclinic Zone

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The surface winds are northerly even down into se mass. Not much in the way of strong ne flow..it's just northerly flow and cold air drainage....but the problem is that "cold" this time around is mostly mid 30s, with a mild atmosphere aloft until the last minute.

I have a basic understanding of ageostrophic flow. But what are you looking at to know if it is occuring? 10 m winds?

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I have a basic understanding of ageostrophic flow. But what are you looking at to know if it is occuring? 10 m winds?

You look at the flow relative to the isobars...if its distinctly left of the isobars then its a good sign of strong ageostrophic flow.

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I have a basic understanding of ageostrophic flow. But what are you looking at to know if it is occuring? 10 m winds?

Like Will said, if they are left of the isobars. For instance the isobars may be aligned sw-ne, but the actual wind vector is from the north.

What I meant earlier, was that I was surprised to see winds modeled more nrly even down into the south shore. It could be because the whole system is slowly sagging southeast, even as the low develops. You also don't have a big high to the ne to keep winds more onshore along the coast. The winds instead will respond to the low intensifying..which may be causing it to be more nrly.

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Like Will said, if they are left of the isobars. For instance the isobars may be aligned sw-ne, but the actual wind vector is from the north.

What I meant earlier, was that I was surprised to see winds modeled more nrly even down into the south shore. It could be because the whole system is slowly sagging southeast, even as the low develops. You also don't have a big high to the ne to keep winds more onshore along the coast. The winds instead will respond to the low intensifying..which may be causing it to be more nrly.

can you tell if there's ageostrophic flow by a lack of bending in wind direction due to coriolis?

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Yeah NAM crushes you know who.

Hi

Yeah it's awfully toasty. MRG cashes in while the rest of us drip and go to slush.

I can't imagine that ever happening.

Do we bang on Pete's door at 9PM Wednesday evening?

Most of you would be welcome. Drinking until the wee hours and then a big buttermilk pancake breakfast with bacon, eggs and freshly ground french roast coffee before digging out and heading to the Berkshire Snow Basin. Skiing and sledding for the intrepid. Unfortunately, I think this is a NW charger and the jackpot could easily slip NW. I know how to get to Rick's area though.

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can you tell if there's ageostrophic flow by a lack of bending in wind direction due to coriolis?

Well there is always ageostrophic flow to some extent when a low approaches. If there wasn't..winds would always be parallel to the isobars. When lows deepen, the winds tend to act more like they are expected to if they only went by the pressure gradient force...i.e blowing from high pressure to low pressure.

In the winter, cold high pressure to the north can also act to keep the flow more northerly, just by exerting its own force.

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Well there is always ageostrophic flow to some extent when a low approaches. If there wasn't..winds would always be parallel to the isobars. When lows deepen, the winds tend to act more like they are expected to if they only went by the pressure gradient force...i.e blowing from high pressure to low pressure.

In the winter, cold high pressure to the north can also act to keep the flow more northerly, just by exerting its own force.

Well I'm out for good now. Have fun with the GFS and euro.

Thanks again for the help tonight, as always!

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The 00Z NAM looks like a mini 10/29 for Berks and Monads. As this is a weakening wave, it will lack the classic CCB comma head that 10/29 had. As such, it will be a quick hitting front ender. Deformation and meso band signature looks good. It could really go to town here for several hours in the predawn hours Thursday if the NAM verifies verbatim. Airmass is very marginal, but it should be cold enough to do the trick above 1K.

Edit: It should change to SN even at sea level for a while near the end, but areas with some elevation in Berks, Monads, and N ORH hills are much more likely to cash in and get some solid accumulations.

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What about when you have a system like Boxing Day last year. Where you have an extremely strong low? I was in Brockton for that one and correct me is I am wrong but was it ageostrophic flow that saved me from flipping over?

Yes there was enough ageostrophic flow for BOS in that one...it wasn't as obvious as it is over the interior with a weak low and strong high setup, but it was there enough to push the CF down to the south shore.

Ageostrophic flow is also strongest over the interior due to land friction.

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Yes there was enough ageostrophic flow for BOS in that one...it wasn't as obvious as it is over the interior with a weak low and strong high setup, but it was there enough to push the CF down to the south shore.

Ageostrophic flow is also strongest over the interior due to land friction.

Thanks. I cashed in quite a few times because of the CF. Was my friend for many years down on the south shore.

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It's a race before the cold and precip. Unfortunately, low areas east of ORH will drip for a while. So close to something more substantial. Kind of frustrating. I haven't seen appreciable snows since 1/21 of last season (yes, I'm excluding the 4" of glop from Oct that lasted all of 12 hours)

You saw good snow on 1/27 and 2/1-2

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