hazwoper Posted February 2, 2011 Share Posted February 2, 2011 Shoot, I think I should stop using my outdoor therm. To give temp readings. If the sensor is no shielded and is being pelted by rain, I assume that will give me high readings? Can anyone confirm this? I ask as I see DYL still reporting 25 Link to comment Share on other sites More sharing options...
NortheastPAWx Posted February 2, 2011 Share Posted February 2, 2011 Up to 23 degrees now. Link to comment Share on other sites More sharing options...
Dosh Posted February 2, 2011 Share Posted February 2, 2011 Everything is iced over! Quite amazing out there. just went sliding down my street with no problem Link to comment Share on other sites More sharing options...
famartin Posted February 2, 2011 Author Share Posted February 2, 2011 Keep in mind the intial quick temp rise is expected as pcpn intensity increases from light-mod-heavy due to latent heat release at the surface. After this, NELY winds should cause temps to flat-line just below 32, probably holding 30-32 for most overnight. However, the warmer rain falling into the surface layer will also cause temps to rise somewhat as the warm air flowing in aloft transfers heat to the raindrops, which transfer it to the surface layer. The net effect will be a rise in temps unless there is a really impressive cold flow. Link to comment Share on other sites More sharing options...
Dosh Posted February 2, 2011 Share Posted February 2, 2011 Wind has picked up here and shifted to more ENE/E rather than the NE direction weve had all night. Link to comment Share on other sites More sharing options...
WeatherQ Posted February 2, 2011 Share Posted February 2, 2011 This storm is going gang busters to the sea. Look at that back edge already in VA....Possible for precip to be out by 0600? Link to comment Share on other sites More sharing options...
gibson16 Posted February 2, 2011 Share Posted February 2, 2011 However, the warmer rain falling into the surface layer will also cause temps to rise somewhat as the warm air flowing in aloft transfers heat to the raindrops, which transfer it to the surface layer. The net effect will be a rise in temps unless there is a really impressive cold flow. Thats what I thought I have a 45- 50 dbz heading for me should bring temps up a little Link to comment Share on other sites More sharing options...
johnc Posted February 2, 2011 Share Posted February 2, 2011 Shoot, I think I should stop using my outdoor therm. To give temp readings. If the sensor is no shielded and is being pelted by rain, I assume that will give me high readings? Can anyone confirm this? I ask as I see DYL still reporting 25 Most definitely. This storm is going gang busters to the sea. Look at that back edge already in VA....Possible for precip to be out by 0600? Probably in some areas. At least the steady stuff anyway. It's moving fast and has kinda "detached" from the snows in the midwest. Evergreens are getting a little droopy here, but roads look puddled up. I think all the salt plus marginal temps will keep sidewalks and roads down here mostly okay. Link to comment Share on other sites More sharing options...
NortheastBravest Posted February 2, 2011 Share Posted February 2, 2011 State of Emergency now in affect....http://nc911.org/Feb_1_2011_Adverse_Weather_Ice_Event_SitRep_3_1.pdf Link to comment Share on other sites More sharing options...
CoolHandMike Posted February 2, 2011 Share Posted February 2, 2011 While I wouldn't say that it was a downpour, the rain intensity definitely picked up for a few minutes outside just now as that band of yellow passed over West Chester. There is still an icy coating on the parking lot but I think the rate of rainfall should mitigate the glaze buildup, unless it gets colder through the night. Points north of here are in for a bad ice storm I think. Temp is up another degree in the past hour to 31F, and it's getting breezy (though it's hard to tell direction in the middle of my apartment complex). Link to comment Share on other sites More sharing options...
greg ralls Posted February 2, 2011 Share Posted February 2, 2011 Moderate ZR here now. Link to comment Share on other sites More sharing options...
greg ralls Posted February 2, 2011 Share Posted February 2, 2011 State of Emergency now in affect....http://nc911.org/Feb..._SitRep_3_1.pdf Is that only for Northampton County? Link to comment Share on other sites More sharing options...
SeNJWx Posted February 2, 2011 Share Posted February 2, 2011 Just hit 30.0 in Plainsboro/Cranbury.. its a sheet of ice out there. Zr has ranged mostly from light to moderate, though it was coming down heavy for a time. Temp has been on a slow but steady rise since earlier when it was 26.9. Link to comment Share on other sites More sharing options...
green tube Posted February 2, 2011 Share Posted February 2, 2011 the snow has an 1/8" layer of ice on it. car is encased in ice. friggin lights are blinking a bit. ugly. up to 29F although the rutgers wx station a few miles from here still 28 F... where it's been for a couple of hours. Link to comment Share on other sites More sharing options...
johnc Posted February 2, 2011 Share Posted February 2, 2011 Is that only for Northampton County? The document seemed to imply that it was for the entire state... but I haven't found any other confirmation on the Interwebs, or what that really means for morning travel. We're in that yellow 35 dbz goodies now and it's coming down moderate to heavy. Still hanging at 30.2 with ENE winds. Link to comment Share on other sites More sharing options...
RU848789 Posted February 2, 2011 Share Posted February 2, 2011 However, the warmer rain falling into the surface layer will also cause temps to rise somewhat as the warm air flowing in aloft transfers heat to the raindrops, which transfer it to the surface layer. The net effect will be a rise in temps unless there is a really impressive cold flow. Ray - I imagine that only occurs as the raindrops a few thousand feet up start falling through the sub-freezing layer and warm the top of that layer via the sensible cooling of the raindrops from whatever temp they reached (35-40F) in the warm layer. I would think these raindrops would then still easily become supercooled on the way down through the sub-freezing layer, such that the only heat imparted to the actual surface (or presumably the 2m temps) would come from the enthalpy of fusion from the phase change of the water to the lower energy state of ice. Link to comment Share on other sites More sharing options...
greg ralls Posted February 2, 2011 Share Posted February 2, 2011 The document seemed to imply that it was for the entire state... but I haven't found any other confirmation on the Interwebs, or what that really means for morning travel. We're in that yellow 35 dbz goodies now and it's coming down moderate to heavy. Still hanging at 30.2 with ENE winds. That's kind of what I got out of it as well, but I also couldn't figure out what it means for travel. Link to comment Share on other sites More sharing options...
famartin Posted February 2, 2011 Author Share Posted February 2, 2011 Ray - I imagine that only occurs as the raindrops a few thousand feet up start falling through the sub-freezing layer and warm the top of that layer via the sensible cooling of the raindrops from whatever temp they reached (35-40F) in the warm layer. I would think these raindrops would then still easily become supercooled on the way down through the sub-freezing layer, such that the only heat imparted to the actual surface (or presumably the 2m temps) would come from the enthalpy of fusion from the phase change of the water to the lower energy state of ice. I would imagine that the raindrops don't immediately cool to the ambient temperature, and as the temperatures typically fall from the warm layer down to near the surface, the raindrops would generally be warmer than the surrounding air at all levels and thus transfer heat to the air. Link to comment Share on other sites More sharing options...
wcu eoc Posted February 2, 2011 Share Posted February 2, 2011 To those asking if Pennsylvania is under a State of Emergency, the answer is no, not technically. It is, on the other hand, staged for counties that request it. That is what the Proclamation of Emergency entails. The document that was linked is specific to Northampton County. For those that are not familliar with emergency management procedures, it looks as if they have activated their emergency operations center and are currently applying Incident Command to the situation. The county will write up a situation report for every operational briefing. Next one should come out at 0800 hrs. I would assume many, many counties, if not all counties, have activated their EOC's for the event. Hope that helped. Link to comment Share on other sites More sharing options...
johnc Posted February 2, 2011 Share Posted February 2, 2011 Looks like South Jersey will be getting into a half-hour or so of lighter precip soon... theoretically that should be better for icing. I mean... for those who want that kind of thing. Link to comment Share on other sites More sharing options...
famartin Posted February 2, 2011 Author Share Posted February 2, 2011 Temps as of 2AM and 1-hour change MGJ 18 -1 FWN 20 0 12N 21 0 MPO 22 0 HPN 24 0 FRG 26 +1 ABE 27 +1 DYL 27 +1 CDW 27 +1 MMU 27 0 UKT 27 0 TEB 27 0 AVP 27 0 NYC 27 0 SMQ 28 +1 MUI 28 +1 BLM 28 0 JFK 28 0 NXX 29 +1 LGA 29 +1 XLL 30 +2 LNS 30 +1 PTW 30 +1 PNE 30 0 EWR 30 0 RDG 31 +2 LOM 31 +1 TTN 31 +1 WRI 31 +1 NEL 31 +1 VAY 31 +1 ILG 31 +1 MJX 32 +2 MQS 32 +2 PHL 32 +1 MIV 33 +1 DOV 33 0 W29 34 0 ACY 36 +2 WWD 37 +1 GED 38 +1 Link to comment Share on other sites More sharing options...
RU848789 Posted February 2, 2011 Share Posted February 2, 2011 I would imagine that the raindrops don't immediately cool to the ambient temperature, and as the temperatures typically fall from the warm layer down to near the surface, the raindrops would generally be warmer than the surrounding air at all levels and thus transfer heat to the air. Ray - you're already implying that the raindrops (which would have been snowflakes up above the warm layer and then melted at 32F in the warm layer) picked up some heat from the warm layer in the first place, so why wouldn't those same "warm" raindrops then transfer their heat to the cooler, subfreezing layer when they fall through it? I'm not saying it happens immediately, but continuously, during the entire descent (which sounds like what you said above and I agree - during the entire descent the raindrop will always be warmer than the cold layer, but the "delta" will get smaller and smaller until it's probably negligible as it nears the surface), until the raindrops at least come close to the ambient temp of the cold layer, hence becoming subcooled. Link to comment Share on other sites More sharing options...
famartin Posted February 2, 2011 Author Share Posted February 2, 2011 Ray - you're already implying that the raindrops (which would have been snowflakes up above the warm layer and then melted at 32F in the warm layer) picked up some heat from the warm layer in the first place, so why wouldn't those same "warm" raindrops then transfer their heat to the cooler, subfreezing layer when they fall through it? I'm not saying it happens immediately, but continuously, during the entire descent (which sounds like what you said above and I agree - during the entire descent the raindrop will always be warmer than the cold layer, but the "delta" will get smaller and smaller until it's probably negligible as it nears the surface), until the raindrops at least come close to the ambient temp of the cold layer, hence becoming subcooled. The bold above is exactly what I'm saying. The only difference regarding what I'm saying is that I tend to think the raindrops never match the ambient temperature since typically the temperature falls continuously from the warm layer down to the surface, so the raindrops are continuously cooling and thus continuously transferring warmth to the surrounding air all the way down to the ground. Link to comment Share on other sites More sharing options...
Parsley Posted February 2, 2011 Share Posted February 2, 2011 30 degrees here just north of Collegeville, PA at 3am......just woke up and figured I'd try to snap a picture or two while its still below freezing. Not the best quality shots, but it was pouring and I'm half asleep.... Maybe 2 or 3 tenths of an inch? Link to comment Share on other sites More sharing options...
RU848789 Posted February 2, 2011 Share Posted February 2, 2011 The bold above is exactly what I'm saying. The only difference regarding what I'm saying is that I tend to think the raindrops never match the ambient temperature since typically the temperature falls continuously from the warm layer down to the surface, so the raindrops are continuously cooling and thus continuously transferring warmth to the surrounding air all the way down to the ground. Okay, then we largely agree. In your first post, I thought you were implying the raindrop might be 35F when it hit the 26F ground, which is not what I think you're saying now. For example, I would think that if the drop warmed up to 35F it would then cool most of the way down to 26F during its descent through the cold layer, perhaps hitting the ground at 27-28F - still supercooled, but not quite as cold as the surface, such that it would slightly warm the surface, from sensible heat along with the heat of fusion. The interesting difference with evaporational cooling (due to phase change from water or ice to vapor) to saturate the column vs. heating from freezing raindrops, is that evaporational cooling is limited by the fact that the process stops as one nears 100% RH, whereas the heaating from freezing has no "limit" per se and should simply be a function of rainfall/freezing rates. As I was just out walking around, I noticed that there is a fair amount of the rain that is not freezing immediately and is running off or ponding, so a certain % of the QPF that's falling is not accruing. FWIW, I just measured the thickness of the ice crust on the snow as being 1/4", while the thickness of the ice on our street is about 1/8"; presumably the difference is due to the fact that the ZR didn't accumulate on the road during the day, while the ZR did accumulate on the snow during the day. Either way, if we don't get above 32F before about 6 am (we'll need an hour or two to melt the ice at 33-34F, I would think), the morning commute is going to be a complete mess. Link to comment Share on other sites More sharing options...
famartin Posted February 2, 2011 Author Share Posted February 2, 2011 Temps as of 3AM and 1-hour change MGJ 18 0 SWF 19 ? FWN 20 0 12N 21 0 MPO 23 +1 HPN 24 0 CDW 26 -1 FRG 27 +1 MMU 27 0 TEB 27 0 NYC 27 0 DYL 28 +1 UKT 28 +1 ABE 29 +2 AVP 29 +2 JFK 29 +1 LGA 29 0 SMQ 30 +2 BLM 30 +2 NXX 30 +1 LNS 30 0 XLL 31 +1 PTW 31 +1 PNE 31 +1 EWR 31 +1 RDG 31 0 TTN 31 0 LOM 32 +1 WRI 32 +1 NEL 32 +1 VAY 32 +1 ILG 32 +1 MJX 32 0 MQS 32 0 PHL 32 0 MIV 34 +1 DOV 34 +1 W29 34 0 ACY 38 +2 WWD 39 +2 GED 39 +1 Link to comment Share on other sites More sharing options...
famartin Posted February 2, 2011 Author Share Posted February 2, 2011 Wow this thing is hauling... backedge of the steady precip is already up to Harrisburg and is starting to show up on DIX... that might limit the damage in places that are getting freezing rain to death... Link to comment Share on other sites More sharing options...
mattinpa Posted February 2, 2011 Share Posted February 2, 2011 Wow this thing is hauling... backedge of the steady precip is already up to Harrisburg and is starting to show up on DIX... that might limit the damage in places that are getting freezing rain to death... It's now reading 32 at PTW - the fast movement means most of the event will be frozen, but it will be good for reducing the severity of the icing. Link to comment Share on other sites More sharing options...
RutgersWx92 Posted February 2, 2011 Share Posted February 2, 2011 It's now reading 32 at PTW - the fast movement means most of the event will be frozen, but it will be good for reducing the severity of the icing. The faster movement probably doesn't make too much of a difference (around here at least) since a slower movement would've probably just meant a lot more plain rain (which I'm doubtful we see any of at this point with the rate this storm is moving). Link to comment Share on other sites More sharing options...
famartin Posted February 2, 2011 Author Share Posted February 2, 2011 It's now reading 32 at PTW - the fast movement means most of the event will be frozen, but it will be good for reducing the severity of the icing. How much ice do you have there? PTW is reporting 0.42" liquid equivalent so far... I'm curious as to how that's translating to ice accretion. Link to comment Share on other sites More sharing options...
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