ace0927 Posted January 31, 2011 Share Posted January 31, 2011 I posted that 8 posts ago. So the .50"-.75" that falls thru hour 42 is not significant icing? I still dont understand your point. point- there will be no ice accretion on anything other than trees and cars with temps "around" freezing. Just my opinion...you need temps to be in the low 20 to mid 20's to get a real dangerous ZR situation...especially in the city Link to comment Share on other sites More sharing options...
jm1220 Posted January 31, 2011 Share Posted January 31, 2011 yeah- you have no idea how many times i tried to get closer! either way, if the NAM is right we are going to have serious flooding issues...unfortunately our snowpack is going to take a very large hit I think if it's only 1" or less of liquid rain, the snow should eat most of it up unless temps really surge past 40. If it stays 35 or so, not much snow will melt, even with the rain. It just soaks it all in and then freezes solid when the cold air rushes back in. We need to watch that on future model runs, because there will certainly be a coastal front zone likely where the wind shifts direction to more E or ESE. It could go from 35 to 45 very easily if that front passes. That's when real flooding problems become likely. Link to comment Share on other sites More sharing options...
Stormlover74 Posted January 31, 2011 Share Posted January 31, 2011 They are much more likely to issue warnings with serious icing than even a 3 to 6" snowfall. Even with the NAM there is a lot of precip falling with surface temps at or below freezing. I also don't think they should base a forecast on one run of the NAM which has been wildly inconsistent all winter. I dont think they took into consideration the NAM before their disco. I think they are going bullish so people dont get caught off guard and more for the ice than anything else. I think its unlikely that Central Jersey gets the 2-4 they are forecasting. There should be some sort of special ice advisory I think that makes more sense in situations like this Link to comment Share on other sites More sharing options...
LocoAko Posted January 31, 2011 Share Posted January 31, 2011 Intensity of the precipitation combined with the temperature of the rain thats falling. if the air is +5C (41F) 3-5,000 feet above the ground, it may only cool one or two degrees before it hits the surface, not giving it enough time on cooled surfaces such as trees and powerlines to freeze before it runs off. If the warm layer were thinner or cooler, we would see much more accretion, but the strength of the warm air advection is just too strong. You don't think a cold layer of that depth (and significance - look at how cold the air is just above the surface on earthlight's sounding) would be enough to supercool a drop? Don't forget all the thermal energy goes into melting a snowflake - only once it is completely melted will the temperature of the raindrop begin to rise. I just don't think it'd be that much of an issue... I doubt the raindrop is going to warm to a full 40F or something. I assume it will be near freezing to begin with. Link to comment Share on other sites More sharing options...
jm1220 Posted January 31, 2011 Share Posted January 31, 2011 point- there will be no ice accretion on anything other than trees and cars with temps "around" freezing. Just my opinion...you need temps to be in the low 20 to mid 20's to get a real dangerous ZR situation...especially in the city We already have some significant tree damage in spots in Long Beach because of the 16" of very wet snow sticking to everything. If we tack on ice and sleet, I see power outages becoming a real concern along with more tree damage, even if we go to rain. Again, if it only rises to 35 or so, not much will melt. Link to comment Share on other sites More sharing options...
ag3 Posted January 31, 2011 Share Posted January 31, 2011 point- there will be no ice accretion on anything other than trees and cars with temps "around" freezing. Just my opinion...you need temps to be in the low 20 to mid 20's to get a real dangerous ZR situation...especially in the city Temps are 26-29 for the .50"-.75" of liquid. Link to comment Share on other sites More sharing options...
EasternLI Posted January 31, 2011 Share Posted January 31, 2011 I have to disagree with the whole rain in the 20's idea, it may not instantly freeze when its falling....but it WILL freeze. I would tend to think especially with the ground being as cold as it is. I could see this point if temps were borderline like 31-32, but not 20's. Link to comment Share on other sites More sharing options...
jm1220 Posted January 31, 2011 Share Posted January 31, 2011 This may be the first time we see warnings for northern Nassau/Suffolk and advisories for southern Nassau/Suffolk, lol. Link to comment Share on other sites More sharing options...
Zir0b Posted January 31, 2011 Share Posted January 31, 2011 point- there will be no ice accretion on anything other than trees and cars with temps "around" freezing. Just my opinion...you need temps to be in the low 20 to mid 20's to get a real dangerous ZR situation...especially in the city well i agree with this. I don't expect much ice accretion on blacktops...but it will be an issue on trees and powerlines especially in the suburbs. Link to comment Share on other sites More sharing options...
KEITH L.I Posted January 31, 2011 Share Posted January 31, 2011 it's plain and simple..if it raining and it is below 32 degrees..it is freezing rain, or am I missing something? Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 31, 2011 Share Posted January 31, 2011 I dont think they took into consideration the NAM before their disco. I think they are going bullish so people dont get caught off guard and more for the ice than anything else. I think its unlikely that Central Jersey gets the 2-4 they are forecasting. There should be some sort of special ice advisory I think that makes more sense in situations like this that's for the lower portion of the warning where criteria is only 0.25". Up here in Morris County where criteria is 0.50" they still went with a WSW. I suspect, that sometime on Tuesday night the WSW will be replaced by Ice Storm Warnings. Link to comment Share on other sites More sharing options...
Zir0b Posted January 31, 2011 Share Posted January 31, 2011 Yeah ag, up until sunrise it will be accreting on most surfaces... but as the temperature gets closer to freezing during the daytime i expect conditions to improve on sidewalks/roads Link to comment Share on other sites More sharing options...
earthlight Posted January 31, 2011 Share Posted January 31, 2011 Wow, Upton is going pretty bullish down to the immediate burbs. Link to comment Share on other sites More sharing options...
Sundog Posted January 31, 2011 Share Posted January 31, 2011 You don't think a cold layer of that depth (and significance - look at how cold the air is just above the surface on earthlight's sounding) would be enough to supercool a drop? Don't forget all the thermal energy goes into melting a snowflake - only once it is completely melted will the temperature of the raindrop begin to rise. I just don't think it'd be that much of an issue... I doubt the raindrop is going to warm to a full 40F or something. I assume it will be near freezing to begin with. Good post. Just because the air temperature reaches a certain level does not mean the object passing through that warm layer has that temperature as well. Link to comment Share on other sites More sharing options...
Sundog Posted January 31, 2011 Share Posted January 31, 2011 Wow, Upton is going pretty bullish down to the immediate burbs. Either they expect the thermal profiles to be colder for round 2 or they think the precip shield for round 1 will be farther south than depicted in the latest runs. Link to comment Share on other sites More sharing options...
Stormlover74 Posted January 31, 2011 Share Posted January 31, 2011 Generally speaking yes but the ground can be colder than the air temperature or like in cases in urban areas, warmer. I think thats why you rarely see freezing rain events in Manhattan. I think it would have to be raining below 27 or 28 to get severe icing in the city it's plain and simple..if it raining and it is below 32 degrees..it is freezing rain, or am I missing something? Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 31, 2011 Share Posted January 31, 2011 Wow, Upton is going pretty bullish down to the immediate burbs. pretty good indication their, Upton will go with warnings for NJ, Upstate NY and CT and WWA for the city and east. Link to comment Share on other sites More sharing options...
earthlight Posted January 31, 2011 Share Posted January 31, 2011 Good post. Just because the air temperature reaches a certain level does not mean the object passing through that warm layer has that temperature as well. Sure, but it becomes more difficult to cool the rain droplets as the warm layer becomes deeper. It may not be 40 F, but it's probably warm enough to avoid significant icing especially in the city where temperatures rise above freezing for a good period on the NAM, even during the heavy precipitation. Also, it's important to keep in mind the NAM is the coldest amongst guidance...and has a tendency to be too cold in these types of events. Link to comment Share on other sites More sharing options...
Shades Posted January 31, 2011 Share Posted January 31, 2011 Wow, Upton is going pretty bullish down to the immediate burbs. Actually stating that eastern Long Island will have more icing than western LI (although not by much .10-15, but notable nonetheless), which is a bit bizarre, unless they are taking into account the urban effect of roads/sidewalks being treated. Link to comment Share on other sites More sharing options...
SomeguyfromTakomaPark Posted January 31, 2011 Share Posted January 31, 2011 If that Upton map verefies the Northern half of Westchester county would suffer some very significant disruptions. When was the last time you saw 10 inches of snow AND almost a half inch of ice from the same event? Link to comment Share on other sites More sharing options...
SnowDemon Posted January 31, 2011 Share Posted January 31, 2011 A half inch of ice atop 10 inches of snow would be disastrous for LoHud. Link to comment Share on other sites More sharing options...
Chris L Posted January 31, 2011 Share Posted January 31, 2011 An additonal 4-5 inches of snow ontop of the snow we have now, and .25 of ice is going to make it very heavy.... Link to comment Share on other sites More sharing options...
EasternLI Posted January 31, 2011 Share Posted January 31, 2011 pretty good indication their, Upton will go with warnings for NJ, Upstate NY and CT and WWA for the city and east. That Upton map has me around .3 of ice....that would warrent more than a WWA, which we all know nobody takes seriously. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 31, 2011 Share Posted January 31, 2011 That Upton map has me around .3 of ice....that would warrent more than a WWA, which we all know nobody takes seriously. sorry but warning criteria ice for LI is 0.5". With that being said, I've seen warnings before where they went with a warning for the combo of ice and snow. The ice is still 24 hrs away though, and it looks like LI doesn't get much snow so I would say WWA is the way to go now with a possible upgrade tomorrow. Link to comment Share on other sites More sharing options...
jasonli18t Posted January 31, 2011 Share Posted January 31, 2011 Actually stating that eastern Long Island will have more icing than western LI (although not by much .10-15, but notable nonetheless), which is a bit bizarre, unless they are taking into account the urban effect of roads/sidewalks being treated. The same thing happened in VD07. The winds will remain more northerly in nature the further east you go for a longer period of time in a setup like this. Link to comment Share on other sites More sharing options...
Sundog Posted January 31, 2011 Share Posted January 31, 2011 Sure, but it becomes more difficult to cool the rain droplets as the warm layer becomes deeper. It may not be 40 F, but it's probably warm enough to avoid significant icing especially in the city where temperatures rise above freezing for a good period on the NAM, even during the heavy precipitation. Also, it's important to keep in mind the NAM is the coldest amongst guidance...and has a tendency to be too cold in these types of events. I also agree that with a deep enough warm layer the droplets will require more time to solidify and/or recool to freezing. And, with temps being near 32 degrees, not much ice accretion will occur on roadways and other "warmer" surfaces. However, prior to that warm frame you posted, temperatures are quite cold at the surface and the warm layer is not as large. Couple that with the fact that the ground has an enormous snowpack, and you wind you with decent ice accretion, at least for a while. Some anecdotal evidence: last week when the temperatures were holding in the mid to upper 30's in the evening, puddles that had formed during the day were already freezing solid, especially those that were right around snow The key here is is that it wasn't a radiational cooling night either. I doubt areas in Manhattan will get accumulating freezing rain, but then again Manhattan is the last place I would go to for winter weather. Link to comment Share on other sites More sharing options...
LocoAko Posted January 31, 2011 Share Posted January 31, 2011 it's plain and simple..if it raining and it is below 32 degrees..it is freezing rain, or am I missing something? Overall yes, but there are certain things that can cause the rain to not freeze. If the temperatures are only marginally below 32F, the latent heat released from the raindrop freezing can warm up the surrounding air and reduce further freezing (a sort of negative feedback). Plus blacktops can be warmer than the air temperature, etc. Plus as was being discussed/debated, the raindrop may not have time to supercool between the warm layer and the surface. If that were the case the raindrop would remain liquid and roll off of surfaces and freeze the normal way instead of directly freezing upon contact. Link to comment Share on other sites More sharing options...
winterwarlock Posted January 31, 2011 Share Posted January 31, 2011 wow Upton is really really bullish with that snowmap maybe they should clarify it as sleet Link to comment Share on other sites More sharing options...
EasternLI Posted January 31, 2011 Share Posted January 31, 2011 sorry but warning criteria ice for LI is 0.5". With that being said, I've seen warnings before where they went with a warning for the combo of ice and snow. The ice is still 24 hrs away though, and it looks like LI doesn't get much snow so I would say WWA is the way to go now with a possible upgrade tomorrow. 0.5 ice is quite a lot, if that were to ever happen.....forget about warnings,THAT would be disaterous.... Link to comment Share on other sites More sharing options...
jm1220 Posted January 31, 2011 Share Posted January 31, 2011 Overall yes, but there are certain things that can cause the rain to not freeze. If the temperatures are only marginally below 32F, the latent heat released from the raindrop freezing can warm up the surrounding air and reduce further freezing (a sort of negative feedback). Plus blacktops can be warmer than the air temperature, etc. Plus as was being discussed/debated, the raindrop may not have time to supercool between the warm layer and the surface. If that were the case the raindrop would remain liquid and roll off of surfaces and freeze the normal way instead of directly freezing upon contact. In State College it often took temps of 30 or lower to really start freezing rain because of the blacktop and heated sidewalks on campus. The higher uphill you went, the more ice always accreted. Wednesday though looks like it could be a major icestorm there. I saw tons of sleet there but only a couple of major freezing rain events. Link to comment Share on other sites More sharing options...
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