Ian Posted September 16, 2015 Share Posted September 16, 2015 Dulles was warmer than DCA today. This time of year is a tricky one to assess much because we tend to see stuff like this where there's not much range. For people who have lived here a long time it's peculiar they won't at least even admit to that fact. Link to comment Share on other sites More sharing options...
mattie g Posted September 17, 2015 Share Posted September 17, 2015 We should nominate people. Congrats on your new position. Keep your head down! Link to comment Share on other sites More sharing options...
mattie g Posted September 17, 2015 Share Posted September 17, 2015 Link to comment Share on other sites More sharing options...
Deck Pic Posted September 17, 2015 Share Posted September 17, 2015 68 at DCA currently and 56 and IAD....curious to see what the lows are......DCA's 68 consistent with surrounding OBS, but perhaps a surrounding OB 20 feet away on a tarp would be 58.... Link to comment Share on other sites More sharing options...
famartin Posted September 17, 2015 Share Posted September 17, 2015 68 at DCA currently and 56 and IAD....curious to see what the lows are......DCA's 68 consistent with surrounding OBS, but perhaps a surrounding OB 20 feet away on a tarp would be 58.... Link to comment Share on other sites More sharing options...
MN Transplant Posted September 17, 2015 Share Posted September 17, 2015 You realize that he is agreeing with you and ragging on Tenman's argument, right? Tenman wouldn't get getting quite the pushback on this issue if he hadn't been running with the same incorrect idea for, evidently, decades. Three interrelated issues: 1) Is DCA representative of the region? No, of course not. Everyone agrees on this point. It is stuck on a spit of land in a river without any elevation in a dense urban area. It does not represent much (especially for lows) outside of a small area of DC and urban Arlington. However, it is not a bad match for the prior reporting location which was very much in the downtown core. 2) Are DCA's temperatures accurate? This is where the split happens. Tenman believes that DCA, again especially for lows, has been incorrectly reporting the temperature for decades. Pretty much everyone else believes that DCA is accurate for that dense urban core area, based upon comparisons with other stations (weatherbug, PWSs, other city or federal locations). 3) Did something happen with DCA's temperature sensor at the start of 2014 that caused it to diverge from IAD? That is our current unknown. We can compare against other sites, but only know of two point measurements to test the sensor. The comparisons are further complicated by the change in sensible weather recently which should have naturally reduced the difference between IAD/DCA. Link to comment Share on other sites More sharing options...
Ellinwood Posted September 17, 2015 Share Posted September 17, 2015 The comparisons are further complicated by the change in sensible weather recently which should have naturally reduced the difference between IAD/DCA. Which is why it is dumb for anyone to claim a definitive victory one way or the other at this point. 1-2 summer/summer-like months is not a complete enough dataset. Link to comment Share on other sites More sharing options...
Ian Posted September 17, 2015 Share Posted September 17, 2015 Yes to MN an Ellinwood. Many yes. Link to comment Share on other sites More sharing options...
CAPE Posted September 17, 2015 Share Posted September 17, 2015 Let me rephrase then. The sensor was a piece of crap. You don't need to know the physics of the measuring device to determine this - you just need to know statistics. The difference between IAD and DCA highs have ranged from 0 to 2 degrees (as famartin's stats support). Suddenly we had 19 consecutive months where the difference in airport highs exceeded what was typically observed. The chance of this happening by simple random variation is statistically impossible. Either something significant changed in the surrounding environment at either IAD or DCA, or one of the sensors had a warm bias. Flash forward to five weeks ago. The sensor at DCA was replaced. Voila, immediately the difference between airports reverted to within its historical range (1.6 degrees thus far). The verdict: the sensor at DCA was a piece of crap. The difference between old sensor (~4 degree difference) and new sensor (1.6 degrees) is 2.4 degrees - that's a significant difference. That supports my assertion that the old sensor was reading 2-3 degrees too high. I'm aware of other possible contributing factors such as the nature of certain weather patterns, wet/dry soils, etc; but sometimes the simplest explanation is the best one: the sensor at DCA was crap. I don't know why there are so many DCA apologists here - even posting this topic immediately triggered pushback and nonstop chanting of "UHI" (which, by the way, was never something I argued about). I think there should at least be acknowledgement that there is strong evidence that the DCA highs in 2014 and most of this year were, to put it in football terms, inflated. This is why you DO need to understand the technology(physics). Because you know nothing about temperature measurement techniques, or acceptable methods for testing sensors, it makes it easy for you to blame the "problem" on the sensor out of ignorance. IF this "warm bias" was even possible (and Platinum RTDs do not behave this way), this offset, of say +3, would not only be evident during the day when its warmer, but also at night. Not seeing the same "corrected" difference in nightime lows with the new sensor. There are other factors at play here that sensor replacement does not explain away. Of course part of the problem is there is simply not enough data available since the sensor was replaced to draw any meaningful conclusions, and climo has been shifting (in both locations) as we head into fall. Using comparisons of temperature differences between two disparate locations is itself an improper and flawed method of verifying the existence of a "problem" (at DCA), and whether or not it has been corrected. So claiming victory at this juncture, stating that all is resolved based on replacement of a "piece of crap" sensor, is simply ignorant, faulty logic, and a premature conclusion to make. Link to comment Share on other sites More sharing options...
Ellinwood Posted September 18, 2015 Share Posted September 18, 2015 Ditto what I said about Tenman to Inverted. Link to comment Share on other sites More sharing options...
Deck Pic Posted September 18, 2015 Share Posted September 18, 2015 currently 71 at DCA and 65 and Andrews Link to comment Share on other sites More sharing options...
Deck Pic Posted September 18, 2015 Share Posted September 18, 2015 overnight lows DCA: 65 Andrews: 57 BWI: 56 IAD: 55 Link to comment Share on other sites More sharing options...
MN Transplant Posted September 18, 2015 Share Posted September 18, 2015 overnight lows DCA: 65 Andrews: 57 BWI: 56 IAD: 55 PWSs in downtown DC and nearby Arlington were 63-65 and the nearby buoy was 67. So, DCA was basically dead-on despite being 10 degrees warmer than IAD. Link to comment Share on other sites More sharing options...
WEATHER53 Posted September 22, 2015 Share Posted September 22, 2015 Small minds cannot admit their errors even when media, state climatologists and mets interceded to try and bring an out of line station into line and then do so. First baby steps have been taken with more to come and then some will totally lose their grip Link to comment Share on other sites More sharing options...
Ian Posted September 23, 2015 Share Posted September 23, 2015 OK then. Link to comment Share on other sites More sharing options...
AvantHiatus Posted September 23, 2015 Share Posted September 23, 2015 OK then. Tenman is giving a run for my money. Link to comment Share on other sites More sharing options...
Ian Posted September 23, 2015 Share Posted September 23, 2015 Tenman is giving a run for my money. Peculiar as he seems to be about the only truly closed minded one on this subject yet he keeps acting like it's everyone else. Link to comment Share on other sites More sharing options...
CAPE Posted September 23, 2015 Share Posted September 23, 2015 Peculiar as he seems to be about the only truly closed minded one on this subject yet he keeps acting like it's everyone else. I would love to have the old sensor so I could test it under controlled conditions. Unless there was signifcant corrosion at the point of connection to the circuit board, I dont see how it could have developed an (apparently non linear) "additional" resistance. Link to comment Share on other sites More sharing options...
RodneyS Posted December 9, 2015 Share Posted December 9, 2015 FYI: During each of the first seven months of 2014, DCA's official average monthly temperature exceeded IAD's by a range of 4.3-5.6 degrees, with an average of just over 5 degrees. The picture for the first seven months of 2015 was quite similar, with DCA's official average monthly temperature exceeding IAD's by a range of 4.3-5.9 degrees, with an average -- again -- of just over 5 degrees. The first nine days of August 2015 showed DCA's average monthly temperature exceeding IAD's by 6.3 degrees, a little higher than the August 2014 differential of 5.9 degrees. Then on August 10, 2015, the DCA temperature sensor was replaced, and for the rest of August 2015, the differential fell to 4.1 degrees. Since then, there have been the following 2015 DCA/IAD monthly differentials vs the comparable 2014 monthly differentials: September 2015: 3.9 vs 6.4 in September 2014 October 2015: 3.7 vs 6.1 in October 2014 (Corrected from 5.9) November 2015: 3.4 vs 6.2 in November 2014 December 2015: 4.0 vs 5.4 in December 2014 (Dec 2015 through the 8th) Link to comment Share on other sites More sharing options...
MN Transplant Posted December 9, 2015 Share Posted December 9, 2015 FYI: During each of the first seven months of 2014, DCA's official average monthly temperature exceeded IAD's by a range of 4.3-5.6 degrees, with an average of just over 5 degrees. The picture for the first seven months of 2015 was quite similar, with DCA's official average monthly temperature exceeding IAD's by a range of 4.3-5.9 degrees, with an average -- again -- of just over 5 degrees. The first nine days of August 2015 showed DCA's average monthly temperature exceeding IAD's by 6.3 degrees, a little higher than the August 2014 differential of 5.9 degrees. Then on August 10, 2015, the DCA temperature sensor was replaced, and for the rest of August 2015, the differential fell to 4.1 degrees. Since then, there have been the following 2015 DCA/IAD monthly differentials vs the comparable 2014 monthly differentials: September 2015: 3.9 vs 6.4 in September 2014 October 2015: 3.7 vs 5.9 in October 2014 November 2015: 3.4 vs 6.2 in November 2014 December 2015: 4.0 vs 5.4 in December 2014 (Dec 2015 through the 8th) I'd be curious of the breakdown between highs and lows. Link to comment Share on other sites More sharing options...
RodneyS Posted December 9, 2015 Share Posted December 9, 2015 I'd be curious of the breakdown between highs and lows. I don't have every month at my fingertips, but here are the final four months of each year, with the DCA/IAD maximum differential listed first and the DCA/IAD minimum differential listed second: September 2015: 1.4/6.2 vs 4.5/8.2 in September 2014 October 2015: 0.8/6.6 vs 4.0/8.2 in October 2014 November 2015: 0.8/5.8 vs 4.2/8.0 in November 2014 December 2015: 1.6/6.4 vs 4.2/6.6 in December 2014 (Dec 2015 through the 8th) Link to comment Share on other sites More sharing options...
MN Transplant Posted December 9, 2015 Share Posted December 9, 2015 I don't have every month at my fingertips, but here are the final four months of each year, with the DCA/IAD maximum differential listed first and the DCA/IAD minimum differential listed second: September 2015: 1.4/6.2 vs 4.5/8.2 in September 2014 October 2015: 0.8/6.6 vs 4.0/8.2 in October 2014 November 2015: 0.8/5.8 vs 4.2/8.0 in November 2014 December 2015: 1.6/6.4 vs 4.2/6.6 in December 2014 (Dec 2015 through the 8th) The highs are definitely a more compelling story. Very interesting. Link to comment Share on other sites More sharing options...
GramaxRefugee Posted December 14, 2015 Share Posted December 14, 2015 hmmm...has The Mighty Tenman seen this post? proof, pudding , and all that. (Or perhaps I've looked too hastily) Link to comment Share on other sites More sharing options...
RodneyS Posted August 9, 2016 Share Posted August 9, 2016 On 12/9/2015 at 11:37 AM, RodneyS said: FYI: During each of the first seven months of 2014, DCA's official average monthly temperature exceeded IAD's by a range of 4.3-5.6 degrees, with an average of just over 5 degrees. The picture for the first seven months of 2015 was quite similar, with DCA's official average monthly temperature exceeding IAD's by a range of 4.3-5.9 degrees, with an average -- again -- of just over 5 degrees. The first nine days of August 2015 showed DCA's average monthly temperature exceeding IAD's by 6.3 degrees, a little higher than the August 2014 differential of 5.9 degrees. Then on August 10, 2015, the DCA temperature sensor was replaced, and for the rest of August 2015, the differential fell to 4.1 degrees. Since then, there have been the following 2015 DCA/IAD monthly differentials vs the comparable 2014 monthly differentials: September 2015: 3.9 vs 6.4 in September 2014 October 2015: 3.7 vs 6.1 in October 2014 (Corrected from 5.9) November 2015: 3.4 vs 6.2 in November 2014 December 2015: 4.0 vs 5.4 in December 2014 (Dec 2015 through the 8th) As today marks the end of a year since the new temperature sensor was installed at DCA, here is an update comparing how many degrees (F) higher the temperature averaged at DCA than at IAD during the same calendar month (fractions of a month for August) immediately before and after installation of the new sensor: Before After August 10-31, 2014: 6.0 August 10-31, 2015: 4.1 September 2014: 6.4 September 2015: 3.9 October 2014: 6.1 October 2015: 3.7 November 2014: 6.2 November 2015: 3.4 December 2014: 5.4 December 2015: 2.5 January 2015: 5.9 January 2016: 3.4 February 2015: 4.9 February 2016: 2.9 March 2015: 5.1 March 2016: 2.9 April 2015: 4.7 April 2016: 2.8 May 2015: 4.3 May 2016: 2.0 June 2015: 4.7 June 2016: 3.1 July 2015: 5.5 July 2016: 3.2 August 1-9, 2015: 6.3 August 1-9, 2016: 4.1 Overall, for the year ended August 9, 2015, DCA averaged 5.4 degrees higher than IAD, whereas for the year ended August 9, 2016, DCA averaged 3.2 degrees higher than IAD. Breaking these averages into maximum and minimum differentials, for the year ended August 9, 2015, DCA's average maximum was 3.7 degrees higher than IAD's and its average minimum was 7.2 degrees higher. In contrast, for the year ended August 9, 2016, DCA's average maximum was 1.1 degrees higher than IAD's and its average minimum was 5.2 degrees higher. While the above comparisons are not absolute proof that the DCA sensor was reading too high for a long period of time prior to its August 10, 2015 replacement, I think any other explanation is pretty implausible. Of particular interest in this regard may be the fact that the DCA May 2015 average temperature of 73.2 degrees set a record high for that month. However, that temperature barely broke the previous DC May record of 73.0 established in 1991. Had the DCA sensor been replaced on May 1, 2015, I think it's safe to say that the 1991 record would still stand. Link to comment Share on other sites More sharing options...
Inverted_Trough Posted August 10, 2016 Author Share Posted August 10, 2016 4 hours ago, RodneyS said: As today marks the end of a year since the new temperature sensor was installed at DCA, here is an update comparing how many degrees (F) higher the temperature averaged at DCA than at IAD during the same calendar month (fractions of a month for August) immediately before and after installation of the new sensor: Before After August 10-31, 2014: 6.0 August 10-31, 2015: 4.1 September 2014: 6.4 September 2015: 3.9 October 2014: 6.1 October 2015: 3.7 November 2014: 6.2 November 2015: 3.4 December 2014: 5.4 December 2015: 2.5 January 2015: 5.9 January 2016: 3.4 February 2015: 4.9 February 2016: 2.9 March 2015: 5.1 March 2016: 2.9 April 2015: 4.7 April 2016: 2.8 May 2015: 4.3 May 2016: 2.0 June 2015: 4.7 June 2016: 3.1 July 2015: 5.5 July 2016: 3.2 August 1-9, 2015: 6.3 August 1-9, 2016: 4.1 Overall, for the year ended August 9, 2015, DCA averaged 5.4 degrees higher than IAD, whereas for the year ended August 9, 2016, DCA averaged 3.2 degrees higher than IAD. Breaking these averages into maximum and minimum differentials, for the year ended August 9, 2015, DCA's average maximum was 3.7 degrees higher than IAD's and its average minimum was 7.2 degrees higher. In contrast, for the year ended August 9, 2016, DCA's average maximum was 1.1 degrees higher than IAD's and its average minimum was 5.2 degrees higher. While the above comparisons are not absolute proof that the DCA sensor was reading too high for a long period of time prior to its August 10, 2015 replacement, I think any other explanation is pretty implausible. Of particular interest in this regard may be the fact that the DCA May 2015 average temperature of 73.2 degrees set a record high for that month. However, that temperature barely broke the previous DC May record of 73.0 established in 1991. Had the DCA sensor been replaced on May 1, 2015, I think it's safe to say that the 1991 record would still stand. Thanks for this analysis, RodneyS. I said from the beginning that the sensor at DCA was a piece-of-crap. I got so much push-back from the usual suspects about how the "sensible weather has changed at both locations" and that "we need more data to make a conclusion" well, we have a year of data, and this confirms that, for 14 months, DCA's temperatures were too high, by about 2-3 degrees. That's fourteen months of the historical record that's significantly tainted. What's frustrating about it is the mentality of NWS with issues like this, where they acknowledge the historical record is flawed, but since they don't know what the "true" measurement should have been, the records stay. The same thing happened with the snowfall measurement in January: they knew the snowfall measurement was very flawed, but kept it anyway since they couldn't determine what the "true" measure should have been. Link to comment Share on other sites More sharing options...
WEATHER53 Posted August 10, 2016 Share Posted August 10, 2016 6 hours ago, RodneyS said: As today marks the end of a year since the new temperature sensor was installed at DCA, here is an update comparing how many degrees (F) higher the temperature averaged at DCA than at IAD during the same calendar month (fractions of a month for August) immediately before and after installation of the new sensor: Before After August 10-31, 2014: 6.0 August 10-31, 2015: 4.1 September 2014: 6.4 September 2015: 3.9 October 2014: 6.1 October 2015: 3.7 November 2014: 6.2 November 2015: 3.4 December 2014: 5.4 December 2015: 2.5 January 2015: 5.9 January 2016: 3.4 February 2015: 4.9 February 2016: 2.9 March 2015: 5.1 March 2016: 2.9 April 2015: 4.7 April 2016: 2.8 May 2015: 4.3 May 2016: 2.0 June 2015: 4.7 June 2016: 3.1 July 2015: 5.5 July 2016: 3.2 August 1-9, 2015: 6.3 August 1-9, 2016: 4.1 Overall, for the year ended August 9, 2015, DCA averaged 5.4 degrees higher than IAD, whereas for the year ended August 9, 2016, DCA averaged 3.2 degrees higher than IAD. Breaking these averages into maximum and minimum differentials, for the year ended August 9, 2015, DCA's average maximum was 3.7 degrees higher than IAD's and its average minimum was 7.2 degrees higher. In contrast, for the year ended August 9, 2016, DCA's average maximum was 1.1 degrees higher than IAD's and its average minimum was 5.2 degrees higher. While the above comparisons are not absolute proof that the DCA sensor was reading too high for a long period of time prior to its August 10, 2015 replacement, I think any other explanation is pretty implausible. Of particular interest in this regard may be the fact that the DCA May 2015 average temperature of 73.2 degrees set a record high for that month. However, that temperature barely broke the previous DC May record of 73.0 established in 1991. Had the DCA sensor been replaced on May 1, 2015, I think it's safe to say that the 1991 record would still stand. My goodness. The more this plays out the more I have been right for many years. I will be gracious about it unlike my detractors . Link to comment Share on other sites More sharing options...
WEATHER53 Posted August 10, 2016 Share Posted August 10, 2016 On 9/17/2015 at 8:49 AM, MN Transplant said: You realize that he is agreeing with you and ragging on Tenman's argument, right? Tenman wouldn't get getting quite the pushback on this issue if he hadn't been running with the same incorrect idea for, evidently, decades. Three interrelated issues: 1) Is DCA representative of the region? No, of course not. Everyone agrees on this point. It is stuck on a spit of land in a river without any elevation in a dense urban area. It does not represent much (especially for lows) outside of a small area of DC and urban Arlington. However, it is not a bad match for the prior reporting location which was very much in the downtown core. 2) Are DCA's temperatures accurate? This is where the split happens. Tenman believes that DCA, again especially for lows, has been incorrectly reporting the temperature for decades. Pretty much everyone else believes that DCA is accurate for that dense urban core area, based upon comparisons with other stations (weatherbug, PWSs, other city or federal locations). 3) Did something happen with DCA's temperature sensor at the start of 2014 that caused it to diverge from IAD? That is our current unknown. We can compare against other sites, but only know of two point measurements to test the sensor. The comparisons are further complicated by the change in sensible weather recently which should have naturally reduced the difference between IAD/DCA. And I was right and CWG new station will be interesting to follow also. Link to comment Share on other sites More sharing options...
GramaxRefugee Posted August 10, 2016 Share Posted August 10, 2016 11 hours ago, Tenman Johnson said: ...I will be gracious about it unlike my detractors . Well, in my book, there's "gracious" and then there's "Tenman gracious". The former is for when one feels especially charitable. The latter is for when you want to actually get something accomplished. Nice work Tenman. Link to comment Share on other sites More sharing options...
MN Transplant Posted August 10, 2016 Share Posted August 10, 2016 On 8/11/2015 at 1:16 PM, Tenman Johnson said: At least the heads are out of the sand and the FAA versus NWS stuff got put aside long enough to replace the sensors with the bent fins. It's probably a tip of the iceberg and really the daytime maxes have been off 2-4 and the nights 5-10+ for a long time so even the acknowledgment of the 2-2.5 during the daytime calibration comparisions is a step in the right direction. Link to comment Share on other sites More sharing options...
MN Transplant Posted August 10, 2016 Share Posted August 10, 2016 Here is the long-term chart of DCA vs IAD temps. Link to comment Share on other sites More sharing options...
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