TheTrials Posted February 28, 2012 Share Posted February 28, 2012 EC isn't colder than the GFS where it counts... the BL. Its essentially identical as the GFS from 925 mb down to the surface. I can't show the sounding on AmericanWx so you'll just have to take my word for it. The EC is colder at 850 but it doesn't really matter. Here's the UKMET... its a lot like the EC sounding actually. Notice its still got a toasty BL. But there is clearly room to wet bulb and where there is intense precip rates this will help with anythign to accumulate away from the areas where it doesnt stick unless its in the 20's. Point is, its winter weather, and the first three hours could be fun around the area. Link to comment Share on other sites More sharing options...
famartin Posted February 28, 2012 Share Posted February 28, 2012 Look at the wet bulb potential at 24 hours on the 18z NAM. Here's a bigger version. What wet-bulb potential are you talking about, the possibility of the temp dropping to 36? Link to comment Share on other sites More sharing options...
famartin Posted February 28, 2012 Share Posted February 28, 2012 But there is clearly room to wet bulb and where there is intense precip rates this will help with anythign to accumulate away from the areas where it doesnt stick unless its in the 20's. Point is, its winter weather, and the first three hours could be fun around the area. Do you realize what kind of wet-bulb potential actually exists when the Dewpoint is above freezing? Link to comment Share on other sites More sharing options...
supermeh Posted February 28, 2012 Share Posted February 28, 2012 Looks like its all frozen in some form from just after 21 hours to just before 27 hours on the NAM for the city. Still below 0 at 850 for areas just to the n and w and ne but a there is a warm tick at 800 so probably just turning to pingers I think once you get into Yonkers this will be mostly frozen. Probably a 2-4 inch event switching to sleet about 2/3 of the way through. Link to comment Share on other sites More sharing options...
TheTrials Posted February 28, 2012 Share Posted February 28, 2012 Do you realize what kind of wet-bulb potential actually exists when the Dewpoint is above freezing? Here's a bigger version. What wet-bulb potential are you talking about, the possibility of the temp dropping to 36? I could easily see it getting to 34 ish in and around the city, the ukmet soundings always come in too warm at the surface based on watching them for a few years on Plymouth. I have no horse in this race, I am north of the city so I will see snow to start, but I don't think the city is just snow/sleet for 10 minutes and then rain. I still say there will be a prolonged period of frozen precip to start. Link to comment Share on other sites More sharing options...
eduggs Posted February 28, 2012 Share Posted February 28, 2012 EC isn't colder than the GFS where it counts... the BL. Its essentially identical as the GFS from 925 mb down to the surface. I can't show the sounding on AmericanWx so you'll just have to take my word for it. The EC is colder at 850 but it doesn't really matter. Here's the UKMET... its a lot like the EC sounding actually. Notice its still got a toasty BL. I don't think the UKMET graphical sounding is useful. I know I've made this exact comment before, but I've noticed for the past 10 years that it is not accurate (almost always too warm in the BL). Notice the plot has a lot of long, straight lines, which suggests that the graphical software is interpolating between a few data points. I don't know if there is better text data or if the UK soundings have improved over the years, but until I see reason to change my mind, I won't even look at it. Link to comment Share on other sites More sharing options...
Snow_Miser Posted February 28, 2012 Share Posted February 28, 2012 Look at the wet bulb potential at 24 hours on the 18z NAM. Yeah, could really get some nice cooling if precipitation falls hard enough like the Hi-Res models show. Link to comment Share on other sites More sharing options...
famartin Posted February 28, 2012 Share Posted February 28, 2012 I could easily see it getting to 34 ish in and around the city, the ukmet soundings always come in too warm at the surface based on watching them for a few years on Plymouth. I have no horse in this race, I am north of the city so I will see snow to start, but I don't think the city is just snow/sleet for 10 minutes and then rain. I still say there will be a prolonged period of frozen precip to start. Well if you think an hour or two is prolonged, then yeah I guess you are right. This is looking more and more as if only pure intensity (i.e., heat released from melting snow) are the only thing that will get an accumulation into the city. And that *might* happen, but again, I'd bet on a quick snow to sleet switch with perhaps a coating of sleet. Link to comment Share on other sites More sharing options...
jm1220 Posted February 28, 2012 Share Posted February 28, 2012 what part of my post says "BIG DEAL"? Where did I say that there would be big impact? I am sorry you live on the beach and need a HECS to feel satisfied, but in a winter like this, getting any kind of winter weather is a win. Stop projecting. The city could easily see 3 hours of frozen precip with some slushy accumulations to start, especially away from the beaches and mid-town. Seriously, chill out. It has nothing to do with where I live, and I'll have to work during whatever wintry precip falls anyway. Hopefully you're right and we do get more. I just hope people aren't setting up for disappointment when it more than likely doesn't happen. As Ray posted, look at the boundary layer soundings, across the board. Link to comment Share on other sites More sharing options...
famartin Posted February 28, 2012 Share Posted February 28, 2012 I don't think the UKMET graphical sounding is useful. I know I've made this exact comment before, but I've noticed for the past 10 years that it is not accurate (almost always too warm in the BL). Notice the plot has a lot of long, straight lines, which suggests that the graphical software is interpolating between a few data points. I don't know if there is better text data or if the UK soundings have improved over the years, but until I see reason to change my mind, I won't even look at it. Well, he wanted a sounding, I gave him one. I guess I'm just not seeing why no one is buying the warm BL when EVERY model I've seen shows it. Hell, a cold front went through yesterday and its 48 in the park right now. In February. After a cold front. Link to comment Share on other sites More sharing options...
Brian5671 Posted February 28, 2012 Share Posted February 28, 2012 Well, he wanted a sounding, I gave him one. I guess I'm just not seeing why no one is buying the warm BL when EVERY model I've seen shows it. Hell, a cold front went through yesterday and its 48 in the park right now. In February. After a cold front. EXACTLY Link to comment Share on other sites More sharing options...
Isotherm Posted February 28, 2012 Share Posted February 28, 2012 Well, he wanted a sounding, I gave him one. I guess I'm just not seeing why no one is buying the warm BL when EVERY model I've seen shows it. Hell, a cold front went through yesterday and its 48 in the park right now. In February. After a cold front. Agreed. IMO NYC may see wet flakes briefly but 99% of the event is a cold rain; I don't see surface temps getting any lower than 36 in Central Park during precip. 850's barely even fall sub 0c tonight, prior to the event, and we've got strong warm air advection starting by tomorrow afternoon. It'll be the type of thing where wet bulbing will allow some brief sleet or flakes but then it's raining 30 minutes later. Link to comment Share on other sites More sharing options...
TheTrials Posted February 28, 2012 Share Posted February 28, 2012 I don't think the UKMET graphical sounding is useful. I know I've made this exact comment before, but I've noticed for the past 10 years that it is not accurate (almost always too warm in the BL). Notice the plot has a lot of long, straight lines, which suggests that the graphical software is interpolating between a few data points. I don't know if there is better text data or if the UK soundings have improved over the years, but until I see reason to change my mind, I won't even look at it. i agree, they run warm. But ray is right, the wet bulb effect wont get below 36 on that and even the NAM right now, but just to the north they are much colder. He also points out the intensity factor and I could see that helping to cool the column, especially if the SPC WRF precip rates verify. Link to comment Share on other sites More sharing options...
TheTrials Posted February 28, 2012 Share Posted February 28, 2012 EXACTLY You saw 2-4 inches the other day with an even WORSE antecedent airmass and lift. But you only discuss bad busts , not good. And you live N and E of the City where the soundings look a lot better than the ones Ray posted. Link to comment Share on other sites More sharing options...
supermeh Posted February 28, 2012 Share Posted February 28, 2012 Does anyone have the 15z ETA? Link to comment Share on other sites More sharing options...
ag3 Posted February 28, 2012 Share Posted February 28, 2012 Well, he wanted a sounding, I gave him one. I guess I'm just not seeing why no one is buying the warm BL when EVERY model I've seen shows it. Hell, a cold front went through yesterday and its 48 in the park right now. In February. After a cold front. Thank you for the soundings. I think the big differences of the models are the timing and initial precip rates. Even at 36-37 degrees, if the NMM is correct, and the City sees .50" of precip in only 3 hours, while 850's are below zero, there will be accumulations on non-paved surfaces. Thats heavy dose of precip at big rates. The SCP-WRF and the MM5 are also pretty similar, with the intensity of the initial precip. Link to comment Share on other sites More sharing options...
TheTrials Posted February 28, 2012 Share Posted February 28, 2012 Brian5671's sounding at 27 hours on the NAM, all snow and up to this point .25 has fallen. Link to comment Share on other sites More sharing options...
TheTrials Posted February 28, 2012 Share Posted February 28, 2012 Brian5671's sounding at 27 hours on the NAM, all snow and up to this point .25 has fallen. he probably gets another hour of snow after this and then he pings. Link to comment Share on other sites More sharing options...
ag3 Posted February 28, 2012 Share Posted February 28, 2012 18z NAM has caught on to the heavy precip idea right at the onset. Just from hours 24-27, over .35" of precip falls. And the NAM is still a couple hours delayed compared to some other models. Link to comment Share on other sites More sharing options...
supermeh Posted February 28, 2012 Share Posted February 28, 2012 http://www.meteo.psu.edu/~gadomski/ETAEAST_18z/etaloop.html Colder than the NAM. Link to comment Share on other sites More sharing options...
TheTrials Posted February 28, 2012 Share Posted February 28, 2012 http://www.meteo.psu...8z/etaloop.html Colder than the NAM. It's been very steady with this idea, too bad its the old eta, but still, it really hasn't waivered. Link to comment Share on other sites More sharing options...
eduggs Posted February 28, 2012 Share Posted February 28, 2012 Thermodynamically, the atmosphere tends to settle right around 32F in marginal precipitation scenarios. Any warmer and melting/evaporation takes some energy from the air and cools it slightly. Any colder and freezing warms is slightly. This is partly why this temperature gradient (esp visible on hi-res models) is weakest between about 30 and 34F. Above and below there the temp gradient is much greater. At the thermometer, this is often realized as 33F and snow, in anything but heavy precip and full saturation. So I expect to see a lot of 33F snow obs tomorrow. Where this won't work out is in places that experience some surface advection off the ocean. I expect the dividing line between decent snow and crappy mix to be right around rockland and northern westchester, where an easterly wind is mostly off land. To get good snows into the metro, I think we need the models to be underestimating the temp or dp temp and/or resolving surface wind direction incorrectly. Link to comment Share on other sites More sharing options...
TheTrials Posted February 28, 2012 Share Posted February 28, 2012 Thermodynamically, the atmosphere tends to settle right around 32F in marginal precipitation scenarios. Any warmer and melting/evaporation takes some energy from the air and cools it slightly. Any colder and freezing warms is slightly. This is partly why this temperature gradient (esp visible on hi-res models) is weakest between about 30 and 34F. Above and below there the temp gradient is much greater. At the thermometer, this is often realized as 33F and snow, in anything but heavy precip and full saturation. So I expect to see a lot of 33F snow obs tomorrow. Where this won't work out is in places that experience some surface advection off the ocean. I expect the dividing line between decent snow and crappy mix to be right around rockland and northern westchester, where an easterly wind is mostly off land. To get good snows into the metro, I think we need the models to be underestimating the temp or dp temp and/or resolving surface wind direction incorrectly. Agree with all of this but I do expect a lot of the NYC posters off the beach to be somewhat surprised if this things comes in heavy right of the bat. Link to comment Share on other sites More sharing options...
eduggs Posted February 28, 2012 Share Posted February 28, 2012 Well, he wanted a sounding, I gave him one. I guess I'm just not seeing why no one is buying the warm BL when EVERY model I've seen shows it. Hell, a cold front went through yesterday and its 48 in the park right now. In February. After a cold front. I buy a warm BL. For snow I'd want to be well to the north and elevated. Maybe the Litchfield Hills. 50F after a cold frontal passage doesn't surprise me. DPs did come way down. We have full sunshine, no snowpack, and minimal snowpack where our cold air should be sourced from. Even so, I expect snowflakes to fall tomorrow somewhere in the NYC metro area (though probably non-accumulating). Link to comment Share on other sites More sharing options...
sn0w Posted February 28, 2012 Share Posted February 28, 2012 I think the most recent trends, mainly the NAM, aren't necessarily colder but may be signalling a little more snow, especially/mostly North and East of the City. Hour 30 of the 18z NAM http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?prevPage=Model&MainPage=indexℑ=&page=Param&cycle=02%2F28%2F2012+18UTC&rname=SFC-LAYER+PARMS&pname=850_temp_mslp_precip&pdesc=&model=NAM&area=NAMER&cat=MODEL+GUIDANCE&fcast=030&areaDesc=North+America+-+US+Canada+and+northern+Mexico&prevArea=NAMER&currKey=model&returnToModel=&imageSize=M .50"+ of precip has already fallen and the 850's are still South of parts of SE NY. While this may not be any colder at this hour as past model runs, it's definitely wetter earlier while temps are still cold. Link to comment Share on other sites More sharing options...
eduggs Posted February 28, 2012 Share Posted February 28, 2012 Agree with all of this but I do expect a lot of the NYC posters off the beach to be somewhat surprised if this things comes in heavy right of the bat. I'm hoping too. It's happened tons of times when precip comes in heavy, it's below freezig above 925mb, and the surface dynamically cools to near freezing. This scenario is a candidate for something like that to happen for a few hours. But that has to be considered unlikely based on today's data. Link to comment Share on other sites More sharing options...
ag3 Posted February 28, 2012 Share Posted February 28, 2012 I'm hoping too. It's happened tons of times when precip comes in heavy, it's below freezig above 925mb, and the surface dynamically cools to near freezing. This scenario is a candidate for something like that to happen for a few hours. But that has to be considered unlikely based on today's data. Even at 35-36 degrees, snow will stick to non-paved surfaces if it comes in heavy right off the bat. Link to comment Share on other sites More sharing options...
NEG NAO Posted February 28, 2012 Author Share Posted February 28, 2012 No mention of any mix in NYC ZONE FORECAST PRODUCT NATIONAL WEATHER SERVICE NEW YORK NY 346 PM EST TUE FEB 28 2012 NYZ072-291000- NEW YORK (MANHATTAN)- 346 PM EST TUE FEB 28 2012 TONIGHT...PARTLY CLOUDY THIS EVENING THEN BECOMING MOSTLY CLOUDY. LOWS IN THE MID 30S. NORTH WINDS 5 TO 10 MPH...BECOMING NORTHEAST AFTER MIDNIGHT. WEDNESDAY...RAIN MAINLY IN THE AFTERNOON Link to comment Share on other sites More sharing options...
tornadojay Posted February 28, 2012 Share Posted February 28, 2012 Upton replaced a lot of watches with advisories now Link to comment Share on other sites More sharing options...
Brian5671 Posted February 28, 2012 Share Posted February 28, 2012 Upton replaced a lot of watches with advisories now they are going all rain except inland SE NY and inland CT Link to comment Share on other sites More sharing options...
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