Stebo Posted September 14, 2013 Share Posted September 14, 2013 I'm not going to be too quick to discount the discrepency. The following is a post from IND's Facebook page At 6 AM. Their office is less than 2 miles west of the airport. It's only a 3 degree difference, not 5, but all of the runways, tarmacs, buildings, etc. can make some difference. "50 degrees at Indy Airport and 47 degrees at Indy NWS." Howell's airport is tiny compared to Indy's and 5 degrees within a mile, someone is off and I will side with the NWS maintained equipment. Link to comment Share on other sites More sharing options...
Stebo Posted September 14, 2013 Share Posted September 14, 2013 Frost doesn't form at 39 degrees. That's the beauty of PWSs in 2013, gives us a higher resolution view of local weather. I have frost on the top of the building here, and we are reading 44 at the surface and 50' in the air where I am 42 per our backup equipment. Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 Those weather underground observations are not accurate as they are just random personal weather stations, I am going by the ASOS sensor data from the airport that is about a mile west of him per his post from last night. Do what you want, it matters not. The two measurements PWS's suck at are humidity and wind direction.... Temp accuracy has been perfected on the cheapest home system for years. Siting can only skew temps high, rarely low. Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 I have frost on the top of the building here, and we are reading 44 at the surface and 50' in the air where I am 42 per our backup equipment. Pics? I have never seen frost above 40 degrees.... I don't buy it. Link to comment Share on other sites More sharing options...
weatherbo Posted September 14, 2013 Share Posted September 14, 2013 Those weather underground observations are not accurate as they are just random personal weather stations, I am going by the ASOS sensor data from the airport that is about a mile west of him per his post from last night.there's a cold spot less than 2 miles from here that is typically 3-5 degrees colder on radiational cooling nights.....I'd trust his particular station type too. Link to comment Share on other sites More sharing options...
Stebo Posted September 14, 2013 Share Posted September 14, 2013 Since you wanted a picture here is one Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 Doesn't look like frost to me... Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 I believe the NWS uses 36F as their threshold for frost, you might want to send that pic in and have them change that to 45 degrees. New criterion. Link to comment Share on other sites More sharing options...
Stebo Posted September 14, 2013 Share Posted September 14, 2013 Doesn't look like frost to me... I know what frost is, that is 100% frost whether or not you choose to believe it Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 I know what frost is, that is 100% frost whether or not you choose to believe it Ok, I believe you. I'll just have to move forward with the new knowledge that frost can form on black roofs at 45 degrees. That doesn't really do much for disproving my 34F. Link to comment Share on other sites More sharing options...
TugHillMatt Posted September 14, 2013 Share Posted September 14, 2013 there's a cold spot less than 2 miles from here that is typically 3-5 degrees colder on radiational cooling nights.....I'd trust his particular station type too. Agreed. Personal Weather Stations have helped to improve upon the science of microclimates. Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 Agreed. Personal Weather Stations have helped to improve upon the science of microclimates. Dr. Jeff Masters, who I generally get annoyed with, has created a new forecast system based on PWS's. http://www.wunderground.com/blog/WunderLainey/about-bestforecast ASOS are more accurate than a PWS.... Its the location of the PWS's that lead to most of the reading differences, not the equipment. Link to comment Share on other sites More sharing options...
Stebo Posted September 14, 2013 Share Posted September 14, 2013 Ok, I believe you. I'll just have to move forward with the new knowledge that frost can form on black roofs at 45 degrees. That doesn't really do much for disproving my 34F. I'm not disproving other than helping you insure you get an accurate reading, what height is your thermometer at outside? Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 Ok, I believe you. I'll just have to move forward with the new knowledge that frost can form on black roofs at 45 degrees. That doesn't really do much for disproving my 34F. I'm not disproving other than helping you insure you get an accurate reading, what height is your thermometer at outside? Its about 8 feet up. Link to comment Share on other sites More sharing options...
Stebo Posted September 14, 2013 Share Posted September 14, 2013 Its about 8 feet up. Ok well that isn't bad, probaby about a foot and a half too high though. I guess you probably are within range of error and must be in a valley compared to the airport to get that large of a departure. Link to comment Share on other sites More sharing options...
daddylonglegs Posted September 14, 2013 Author Share Posted September 14, 2013 45F here... Sparta is showing 30F... Black River Falls (north of Sparta) shows 28F. Central Wisconsin is just a big frost hollow. Link to comment Share on other sites More sharing options...
Brewers Posted September 14, 2013 Share Posted September 14, 2013 Dropped to 46 at RAC and MKE. BUU made it to a crisp 34. Link to comment Share on other sites More sharing options...
SpartyOn Posted September 14, 2013 Share Posted September 14, 2013 Frost can form above 32 degrees, but only by a few degrees. There are factors that come into play like surface temps and dew points. Link to comment Share on other sites More sharing options...
cyclone77 Posted September 14, 2013 Share Posted September 14, 2013 Made it down to 40 here, which was the coldest of the season so far. MLI tied the record at 39. This follows record highs of 98/97 on Mon/Tue. Very impressive turnaround. Link to comment Share on other sites More sharing options...
Jonger Posted September 14, 2013 Share Posted September 14, 2013 Frost can form above 32 degrees, but only by a few degrees. There are factors that come into play like surface temps and dew points. I think it has to do with the ground being the lowest point and possibly evaporational cooling on the objects themselves, that's just a theory. Link to comment Share on other sites More sharing options...
michsnowfreak Posted September 14, 2013 Share Posted September 14, 2013 Those pics clearly show light frost both on the grass in Howell and the right side of the rooftop at DTW. Looks like the official low at OZW was 37F and DTW was 42F. Bottomed out at 42F also at DET and Wyandotte (41.5F), and outside of areas right on the water (warm spot Port Hope at 44F) most everyone else looks to have been in the 30s. What did your thermometer bottom out at Jonger? I have seen frost on rooftops at 40F many times but not on grass til its in the 30s. The more we have been talking about UHI, concrete runways, rural fields, etc the last several days the more I get to thinking about how easily temps are influenced under certain conditions. I am out near DTW quite often, and I know that driving near DTW on those excellent radiational cooling nights....and its very rural near and just west of the airport (as Trent said one of the most rural areas of Wayne county)... my cars temperature gauge will drop like a rock (several degrees colder than DTW itself) and then rise several degrees as I get more solidly back into suburbia. So temperature differences over very short distances on nights with excellent radiational cooling (such as last night) happen all the time. In the 1960s, 70s, or even early 80s, on a morning when everything else is identical to the conditions of this morning, DTW is probably 34-35F and thus a new record low...today they are 42F and simply well below normal. DTX office in White Lake got down to 33F and posted this on their facebook page. Link to comment Share on other sites More sharing options...
cyclone77 Posted September 14, 2013 Share Posted September 14, 2013 Regarding weather stations. I've owned a variety of weather stations through the years and the one thing they all had in common was that they were all very accurate temperature wise. That is of course as long as you shelter/ventilate them properly from the sun. I've never seen a thermometer sensor error on the side of being too cold, only too warm due to solar/ventilation issues. Link to comment Share on other sites More sharing options...
michsnowfreak Posted September 14, 2013 Share Posted September 14, 2013 Interesting that it seems to have been colder on this side of Lake Michigan last night. Another thing to me that seems quite impressive last night its the duration of the chilly temps. DTW spent 11 hours in the 40s. Its now crystal clear and sunny. While hints of color are around, its weather like this that really kick starts the Fall-color process. Link to comment Share on other sites More sharing options...
wisconsinwx Posted September 14, 2013 Share Posted September 14, 2013 Looks like an A++ day ahead. I'm actually looking forward to some coolish stratiform rain, as it has been awhile since we've seen a soaking large scale rain event. Link to comment Share on other sites More sharing options...
wisconsinwx Posted September 14, 2013 Share Posted September 14, 2013 Interesting that it seems to have been colder on this side of Lake Michigan last night. Another thing to me that seems quite impressive last night its the duration of the chilly temps. DTW spent 11 hours in the 40s. Its now crystal clear and sunny. While hints of color are around, its weather like this that really kick starts the Fall-color process. Not really surprising, the heart of the trough was centered near Michigan, as has been anticipated for awhile. In fact, after May, which was a bit warmer on your side of Lake Michigan, Michigan has escaped the brunt of the heat compared to Wisconsin, Minnesota, Iowa, Illinois, etc. Link to comment Share on other sites More sharing options...
cyclone77 Posted September 14, 2013 Share Posted September 14, 2013 ...I'm actually looking forward to some coolish stratiform rain, as it has been awhile since we've seen a soaking large scale rain event. Yeah I'm looking forward to it too. Been quite awhile since we've seen a cool, all day rain event. Good day to stay inside and watch football. Been awhile since we've seen a point like this... Sunday Rain, mainly after 7am. High near 62. South wind 5 to 10 mph becoming north in the afternoon. Chance of precipitation is 90%. New precipitation amounts between a half and three quarters of an inch possible. Link to comment Share on other sites More sharing options...
Geos Posted September 14, 2013 Share Posted September 14, 2013 Down to 40° here this morning. Looks like frost in all those pictures on the last page. Average high/low now 72/54. Pretty crazy the low on Tuesday was 76°. 54° temperature spread this week! Link to comment Share on other sites More sharing options...
Hoosier Posted September 14, 2013 Share Posted September 14, 2013 Made it down to 41. Link to comment Share on other sites More sharing options...
Hoosier Posted September 14, 2013 Share Posted September 14, 2013 Indiana sub 40 degree roundup: La Porte: 36 Fort Wayne: 37 Goshen: 38 Muncie: 38 Zionsville: 39 Link to comment Share on other sites More sharing options...
WestCoaster Posted September 14, 2013 Share Posted September 14, 2013 Bottomed out at 42 F on a clear night with light winds. Lake Ontario is running a couple degrees above normal for this time of year anyway, so getting any cold night lows will be tough enough. Link to comment Share on other sites More sharing options...
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