wkd Posted January 9, 2015 Share Posted January 9, 2015 Correct me if I'm wrong but I was told that the cause of the latent heat release was due to friction. Energy is used changing ice to water. That energy is released when water changes back to ice. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 9, 2015 Share Posted January 9, 2015 Sounds same as GFS... It's a touch warmer than the GFS at the surface and therefore the potential area for icing is little narrower. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 9, 2015 Share Posted January 9, 2015 Energy is used changing ice to water. That energy is released when water changes back to ice. Got it thanks, learn something new everyday Link to comment Share on other sites More sharing options...
SnoSki14 Posted January 9, 2015 Share Posted January 9, 2015 The main problem here is that we aren't getting a -AO to coincide with the -EPO like we did last January. The strong +AO pulse leaves just enough of a SE Ridge in place to favor the interior for frozen potential. Which is why people shouldn't get there hopes up. I don't expect anything more than minor snow events until the AO changes. I do believe we'll get a negative period next month offering the best odds for a storm based on Cohen's theory. Still some time to sort things through before making definitive statements about this storm as some icing is still on the table. Link to comment Share on other sites More sharing options...
Zir0b Posted January 9, 2015 Share Posted January 9, 2015 The 12z ECMWF starts the coast as rain and the far interior as snow with a narrow band of ice/sleet in between. Then the surface cools some but the mid-levels stay fairly warm. It would be a rain to ZR/IP for the immediate coast and just inland and mostly snow for the Poconos, NW NJ and most of the LHV with a battleground extending from about the DE Water Gap up through NE NJ and perhaps even the city. rain to ZR? Don't recall anything like that ever happening in this area. Would probably not be a big deal with temps close to freezing. N&W a different story as always in these situations. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 9, 2015 Share Posted January 9, 2015 rain to ZR? Don't recall anything like that ever happening in this area. Would probably not be a big deal with temps close to freezing. N&W a different story as always in these situations. You have some weak coastal development so you get some cooling as winds flip around but it's not enough to sufficently cool all layers. Link to comment Share on other sites More sharing options...
NEG NAO Posted January 9, 2015 Share Posted January 9, 2015 rain to ZR? Don't recall anything like that ever happening in this area. Would probably not be a big deal with temps close to freezing. N&W a different story as always in these situations. its not going to be a big deal on the treated roads and sidewalks - power lines and trees are the main concern with freezing rain situations even north and west...........as of right now it is impossible to accurately forecast who is going to get what but of course the further north and inland you go the chances of frozen increase.......... Link to comment Share on other sites More sharing options...
Rjay Posted January 9, 2015 Share Posted January 9, 2015 Which is why people shouldn't get there hopes up. I don't expect anything more than minor snow events until the AO changes. I do believe we'll get a negative period next month offering the best odds for a storm based on Cohen's theory. Still some time to sort things through before making definitive statements about this storm as some icing is still on the table. Yea Cohen is having a great year.....eek Link to comment Share on other sites More sharing options...
bluewave Posted January 9, 2015 Share Posted January 9, 2015 Which is why people shouldn't get there hopes up. I don't expect anything more than minor snow events until the AO changes. I do believe we'll get a negative period next month offering the best odds for a storm based on Cohen's theory. Still some time to sort things through before making definitive statements about this storm as some icing is still on the table. If the front end arrives fast enough it could start as frozen at coast but go over to rain and then back to frozen again to end. Link to comment Share on other sites More sharing options...
PB GFI Posted January 9, 2015 Share Posted January 9, 2015 This could be 2 to 4 or 3 to 6 just N of NYC This is a good set up just N of 80 . The worst KNYC gets is st hr 84. Plus 1 and 32 with .3 falling on the 12z euro so that's prob sleet and rain and between 78 and 80 it could get dicey. South of the Driscoll and out on to the island temps go to 34 so they go over. The N shore may frozen longer and flip back quicker if the euro is right. Link to comment Share on other sites More sharing options...
nyblizz44 Posted January 9, 2015 Share Posted January 9, 2015 It should go , without saying especially in a winter such as this one, nothing is set in stone here, 72 hours out and models will shift. How radically will determine precp. type and intensity, a more off shore track and we are looking at more frozen. If the SW if stronger than progged then we are talking dynamic cooling and so on. Wait and see is the best approach IMHO. Link to comment Share on other sites More sharing options...
SnowGoose69 Posted January 9, 2015 Share Posted January 9, 2015 It's a touch warmer than the GFS at the surface and therefore the potential area for icing is little narrower. The Euro tends to usually run too warm on its surface temps so thats not a surprise,,,the hardest part of this event will be our temps to start off, we don't see WSW flow here too much during winter weather events, my experience is usually it does not help moderate things much outside of eastern LI since its a land component. Link to comment Share on other sites More sharing options...
RU848789 Posted January 9, 2015 Share Posted January 9, 2015 Correct me if I'm wrong but I was told that the cause of the latent heat release was due to friction. Energy is used changing ice to water. That energy is released when water changes back to ice. Heat, from the surrounding atmosphere, is required to melt ice or to vaporize water, which is why the air column will cool when falling rain evaporates (or if falling snow/ice melts). The reverse occurs when falling rain freezes on cold surfaces, i.e., heat energy is released to the atmosphere, or when water vapor condenses into water droplets (or directly to snow/ice). Some people not familiar with the 2nd law of thermodynamics think that the freezing rain or condensation scenarios violate the 2nd law, since the entropy (the measure of disorder of the molecules: water vapor has far more disorder than liquid water, which is a little bit more disordered than ice) of the water phase is decreasing when it freezes. However, one has to consider the entire system, which includes the surrounding atmosphere - the heat energy released to the atmosphere raises the air temperature, which creates more entropy/disorder, since the air molecules move faster and more randomly when heated. The overall entropy has to increase in this situation, but the "subsystem" of just the water turning to ice can have a decrease in entropy. Anyway, from a meteorological perspective, it's not necessarily true that heavy rain falling into subfreezing conditions/surfaces is "better" than light rain. One has to factor in several things, such as the water droplet temp (are the falling drops above freezing or supercooled to below freezing?), the surface temperature (and soil/paved surfaces are often warmer than trees/power lines) and the intensity of the precip to determine the most important parameter, which is the rate of ice accumulation for a given surface. The best ice accumulation occurs when surface temps are well below 32F, with supercooled rain droplets falling onto those surfaces at a rate which does not warm the air above 32F - so it's possible for heavy freezing rain to accumulate well, although it's not as likely as light rain intensity if all the other conditions are the same, since less heat of fusion/freezing is released to the atmosphere. But even in situations which aren't optimal for ice accumulation, heavy rain will still result in more ice accumulation - sure, the efficiency of conversion of water to ice is much less, but all that really matters is the rate of ice accumulation, which will be at least equal to or greater for the heavier rainfall. For example, if the rainfall rate is falling at 1" per hour and only 0.4"/hr of that is freezing, that's still worse than if there is 0.3" per hour rainfall rate of which 0.2"/hr is freezing, i.e., 0.4" per hour of freezing rain accumulation is still worse than 0.2"/hr ice accumulation. Jeff Haby has a decent explanation of freezing rain and the variables that affect ice accretion - see the link. http://www.theweatherprediction.com/habyhints/210/ Link to comment Share on other sites More sharing options...
NEXtreme Posted January 9, 2015 Share Posted January 9, 2015 The Euro tends to usually run too warm on its surface temps so thats not a surprise,,,the hardest part of this event will be our temps to start off, we don't see WSW flow here too much during winter weather events, my experience is usually it does not help moderate things much outside of eastern LI since its a land component. Since winds will be light from the SW, won't some of snow cover, especially down around south Jersey and DC, Baltimore area have in impact on temps? Link to comment Share on other sites More sharing options...
Zelocita Weather Posted January 9, 2015 Author Share Posted January 9, 2015 NAM is turning this more into an organized coastal storm (with some initial overrunning), very close to a good snowstorm for all of N NJ. As is now good snowstorm for Rt.80 north, with the rest of the northern NJ in one heck of a wintry mix. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 9, 2015 Share Posted January 9, 2015 The 18z NAM is a nasty ice storm for northern sections of this area. Link to comment Share on other sites More sharing options...
PB GFI Posted January 9, 2015 Share Posted January 9, 2015 The 18z NAM is a nasty ice storm for northern sections of this area. KNYC soundings are mostly sleet on the 18z nam Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 9, 2015 Share Posted January 9, 2015 Yea Cohen is having a great year.....eek Cohen's SAI can still recover, but the longer the AO stays positive, the more difficult a December-February negative average will become. To illustrate this, below is a table that shows the required February AO average just for a December-February average figure of 0.0 based on a variety of January scenarios. This average takes into consideration the December 2014 figure of +0.413. I provide the percentage of February cases that met or exceeded the required February AO average for a winter figure of 0.0. Link to comment Share on other sites More sharing options...
MJO812 Posted January 9, 2015 Share Posted January 9, 2015 KNYC soundings are mostly sleet on the 18z nam With the cold air not far away, we have to watch to see if the cold air sinks further south. Link to comment Share on other sites More sharing options...
SnowGoose69 Posted January 9, 2015 Share Posted January 9, 2015 With the cold air not far away, we have to watch to see if the cold air sinks further south. With SW flow at 850 the models probably are not warm enough yet in the mid layers, this probably will be mostly a PL or FZRA event even in places that now look somewhat snowy. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 9, 2015 Share Posted January 9, 2015 KNYC soundings are mostly sleet on the 18z namHence why I said northern sections. Link to comment Share on other sites More sharing options...
jm1220 Posted January 9, 2015 Share Posted January 9, 2015 Correct me if I'm wrong but I was told that the cause of the latent heat release was due to friction. No, when water freezes, the latent heat from the liquid water transitioning into a solid is released into the air. It's the same mechanism that powers hurricanes-warm ocean water transitioning into a gas. Link to comment Share on other sites More sharing options...
packbacker Posted January 9, 2015 Share Posted January 9, 2015 Cohen's SAI can still recover, but the longer the AO stays positive, the more difficult a December-February negative average will become. To illustrate this, below is a table that shows the required February AO average just for a December-February average figure of 0.0 based on a variety of January scenarios. This average takes into consideration the December 2014 figure of +0.413. I provide the percentage of February cases that met or exceeded the required February AO average for a winter figure of 0.0. Looks bleak Don. The first half of Jan looks to be atleast +1.5, probably closer to +2 and the GEFS and EPS keep the AO around +1 until atleast the 20th. To get a DJF avg of -1.0, the AO for Feb would have to avg roughly -2.5 to -3.0, which hasn't happen but a couple of times in the past 40 years...yikes. Link to comment Share on other sites More sharing options...
jm1220 Posted January 9, 2015 Share Posted January 9, 2015 Models are notorious for being too cold in the mid levels during overrunning events at this stage, so I'd be very wary about predicting much snow for anyone besides maybe a narrow strip around I-84. I can't even count how many systems appeared to be colder at 850 and above 72 hours out just to warm up like crazy at the end in those levels when they caught onto the stronger WAA. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 9, 2015 Share Posted January 9, 2015 Looks bleak Don. The first half of Jan looks to be atleast +1.5, probably closer to +2 and the GEFS and EPS keep the AO around +1 until atleast the 20th. To get a DJF avg of -1.0, the AO for Feb would have to avg roughly -2.5 to -3.0, which hasn't happen but a couple of times in the past 40 years...yikes. I doubt that we'll see a winter average of -1 or below. Since 1950, the only years that saw February have an AO average of -2.5 or below were: 1969 -3.114 1978 -3.014 1986 -2.904 2010 -4.266 A negative or strongly negative AO in February can help produce a snowy end to winter, but barring a dramatic drop beginning not too far into the future, the SAI forecast for winter 2014-15 could fail very badly. If it does, and I hope it doesn't given the implications involved, that could be a strong indication that forecasting the predominant state of the AO remains a low confidence exercise. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 9, 2015 Share Posted January 9, 2015 More ice problems for interior sections of this area on the 18z GFS. Link to comment Share on other sites More sharing options...
SnoSki14 Posted January 9, 2015 Share Posted January 9, 2015 Indeed Don if it fails then there's a lot more research to be done unless this year is an anomaly regarding the SAI disconnection. The highly negative QBO likely played a role. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 9, 2015 Share Posted January 9, 2015 Indeed Don if it fails then there's a lot more research to be done unless this year is an anomaly regarding the SAI disconnection. The highly negative QBO likely played a role. Last winter it didn't do all that great either, though not as bas as could be the outcome this time around. I worry that consecutive winters of underperformance are more likely an indication that the correlation between trends in October Eurasian snowcover and the winter AO is weaker than the outcome is a matter of coincidence. It will be interesting to see what happens. Link to comment Share on other sites More sharing options...
easternsnowman Posted January 9, 2015 Share Posted January 9, 2015 More ice problems for interior sections of this area on the 18z GFS. Better than plain rain! Link to comment Share on other sites More sharing options...
easternsnowman Posted January 9, 2015 Share Posted January 9, 2015 On GFS if you're north of 80 around rt 84 and 81 it should be mostly snow Link to comment Share on other sites More sharing options...
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