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NYC CWA Feb 1-2 Storm Discussion


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Also, nobody has mentioned this, but there is a good potential for a long period of freezing drizzle Tuesday night during our "break". Freezing drizzle can cause massive problems in its own right.

OKX has a low temp in the lower 20's up here with 2-4 of snow near KSWF. If it is frz.drizzle it would be a mess. I would think you have more ice accums.with drizzle than a steady frz.rain.

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Ummmm.....you all do know that was just ONE model run right? Who's to say its even accurate? We've been discussing that area of HP in canada now for a while with regards to what ultimately happens here with this event. Doesn't anyone realize that the warmer solutions the HP is further north/weaker and colder solutions is further south or stronger. In fact, I've yet to see any consistency with what happens with that feature.

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And looking at the skew-T for our latitude/longitude, we're really only about +1C at the surface at 39 hours, and -1C at the surface at 36 hours. We probably still have another hour of freezing rain after that...we probably go over to plain rain at ~37 hours on the NAM, verbatim.

during the last ice event the freezing rain lasted 3 hours longer than the NAM had indicated in New Brunswick and vicinity

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OKX has a low temp in the lower 20's up here with 2-4 of snow near KSWF. If it is frz.drizzle it would be a mess. I would think you have more ice accums.with drizzle than a steady frz.rain.

A lot of times when you have a storm going on, and an "in-situ" break like this, you get freezing drizzle, because there's moisture at the sfc, but no support for anything else.

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I think somebody mentioned also that relatively lighter rainfall with the surface below freezing tends to cause more icing than heavier rainfall with a below freezing surface. I mean it's not like the droplets just magically freeze when they hit the surface, unless it's raining with surface temps in the teens or something.

They do if they're supercooled and the surface they land on is below freezing...

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Ummmm.....you all do know that was just ONE model run right? Who's to say its even accurate? We've been discussing that area of HP in canada now for a while with regards to what ultimately happens here with this event. Doesn't anyone realize that the warmer solutions the HP is further north/weaker and colder solutions is further south or stronger. In fact, I've yet to see any consistency with what happens with that feature.

Agree. The models are all over the place with High pressure.

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Ice events are very rare around here, actually the most ice I've seen was a couple of weeks ago in the morning. I think we had only a tenth or 2 tenths of an ice but it was a huge pain, it looked like a skating rink out there and I had to chip all of that ice from my car.

In most cases that deals with ice threats, we either have more sleet than freezing rain or the temperatures are around 31-33F and the rain was falling during the day and not freezing onto the surface.

Growing up in the early seventies around here, ice events were very common. More so than snow storms.

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I think you're missing the point. in Manhattan with temps just a hair below freezing it won't be that big a deal. It needs to be at least in the 24 to 28 range. 31 degrees and rain would yield some icing but nothing like it would in rural areas and on power lines/trees away from urban centers

thats the central thesis to my confusion as to why earthlight thinks this is rain with temps below freezing

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well I think one thing is for sure...this event will teach us a lot about how these kind of situations evolve. Last major one was VD 2007 and things def went differently than forecasted, and I believe that'll be similar with this one. Just who knows in what direction, even though we could probably guess in terms of climo

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I think you're missing the point. in Manhattan with temps just a hair below freezing it won't be that big a deal. It needs to be at least in the 24 to 28 range. 31 degrees and rain would yield some icing but nothing like it would in rural areas and on power lines/trees away from urban centers

I'm not missing the point. All of NYC isn't urban with buildings everywhere. There are many areas (obviously not necessarily within manhattan itself) that are more suburban than urban. Temps are also not forecast to be 31 and ZR until about hr 34 or 35 on the NAM. So for a period temps will be below 30 and likely in the mid and upper 20's, with precipitation falling

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0z Nam text soundings

At 36 hours, NYC has 0.61 QPF, which all of that is frozen. Temps are in the upper 20's. At 42 hours, it warms up to 34 degrees. That's the warmest that it gets.

http://68.226.77.253/text/NAM80km/NAM_Knyc.txt

tonight's gfs should be interesting, I think the gfs handles low level cold better than the NAM does.

I think the Nam handles it better.

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I am at the point of disregarding the NAM, RGEM is the way to go, although I haven't had the opportunity the last few hours to diagnose the ice situation. With clogged storm drains, flooding Wednesday is something that should be played up, in my opinion.

The RGEM for thermal profiles? Not sure the RGEM is a good model for this kind of situation.

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Well, BUFKIT is out, and it isn't pretty. Just loaded up the New Brunswick, NJ file - 0.60" of freezing rain. Unfortunately I'm on a Netbook and my resolution sucks so that I can't see the bottom timestamps (lol), but the first round is about an inch of snow followed by 0.17" of ZR. Then a break in the precip, then another 0.45" before going over to plain rain and getting 0.60" of that as well. Surface temperatures are in the 26-28F range at the start of the second event and slowly rise after that.

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Well, BUFKIT is out, and it isn't pretty. Just loaded up the New Brunswick, NJ file - 0.60" of freezing rain. Unfortunately I'm on a Netbook and my resolution sucks so that I can't see the bottom timestamps (lol), but the first round is about an inch of snow followed by 0.17" of ZR. Then a break in the precip, then another 0.45" before going over to plain rain and getting 0.60" of that as well. Surface temperatures are in the 26-28F range at the start of the second event and slowly rise after that.

Wow, thanks for the post. There is no sleet at all in the first wave? It just goes directly from snow to ZR?

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Wow, thanks for the post. There is no sleet at all in the first wave? It just goes directly from snow to ZR?

Looks that way. The depth of the freezing layer at the surface only appears to be 2K-2.5K feet thick. (It may be km... not having the bottom 1/3 of the screen is really hurting, lol). It has a built in precipitation type algorithm and it is solidly within the freezing rain area on the graph.

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As of his 4:05 update PT still has high confidence of significant frozen precip for tomorrow and Wednesday. Five asterisks for Tuesday and four for Wednesday. Don't see him on here now but hopefully he chimes in with some of his ideas on where things stand at this point.

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well areas SE of NYC isn't what you said...you included NYC...even southern areas I'd be surprised if there was any flooding. Out on LI its a diff story but if temps kiss 40 or more than obv you have to worry about snowmelt, but massive enough for flooding, I doubt.

Even if we get an inch of rain it won't do much to a snowpack that is 3-4" of liquid equivalent - it'll be mostly absorbed. And an inch of rain is generally no big flooding threat by itself - we'd need major melting to go along with it and that won't happen unless it gets much warmer than expected. The only flooding that is of concern is urban flooding from rain combined with blocked sewers.

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Even if we get an inch of rain it won't do much to a snowpack that is 3-4" of liquid equivalent - it'll be mostly absorbed. And an inch of rain is generally no big flooding threat by itself - we'd need major melting to go along with it and that won't happen unless it gets much warmer than expected. The only flooding that is of concern is urban flooding from rain combined with blocked sewers.

Won't it be fun when that freezes up Wed night? :whistle:

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Folks insisting there would be no flooding in this situation are not looking at the big picture. If the snowpack has a coating of ice on it and .60 to .72 of plain rain fails per the soundings, it won't be absorbed by the snowpack and therefore, there will definitely be flooding. There'd be no place for the rain to go. Ice is a problem but so is water in this case.

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