ChescoWx

Just an FYI for those that may be interested. I have added a few additional stations to join the few we already have included that are while not in Chester county are close to the Chester County border and meets our area description. Some are only historical like NWS COOP locations for Pottstown which has precipitation and snow only while New Holland NWS COOP in Lancaster County is temperatures, precipitation and snow. Below are all stations not in Chester County - some are as close as 400 feet at Octoraro Lake , but New Holland are within 2 miles of the Chester County border. Also attached is a map with all current and historical stations included for reference.

Just an FYI for those that may be interested. I have added a few additional stations to join the few we already have included that are while not in Chester county are close to the Chester County border and meets our area description. Some are only historical like NWS COOP locations for Pottstown which has precipitation and snow only while New Holland NWS COOP in Lancaster County is temperatures, precipitation and snow. Below are all stations not in Chester County - some are as close as 400 feet at Octoraro Lake , but New Holland are within 2 miles of the Chester County border. Also attached is a map with all current and historical stations included for reference.

Some showers are around this morning and will likely increase in coverage later in the day into this evening. We should see some sun returning tomorrow but still a chance of additional showers. Total rain amounts look to be from 0.50" to 1.00" with the higher amounts likely over Western Chester County and into Lancaster County. Tuesday and Wednesday look like great weather with sunny skies and low humidity with temperatures slightly below normal for the middle of August.

Some showers are around this morning and will likely increase in coverage later in the day into this evening. We should see some sun returning tomorrow but still a chance of additional showers. Total rain amounts look to be from 0.50" to 1.00" with the higher amounts likely over Western Chester County and into Lancaster County. Tuesday and Wednesday look like great weather with sunny skies and low humidity with temperatures slightly below normal for the middle of August.

Great weather today with comfortable humidity and temperatures not too far from normal for mid-August. We turn wetter and a little stormy by later tomorrow into tomorrow night some spots could see upwards of an inch or so of rain. We turn sunny any by Monday with pleasant weather returning and lasting through mid-week.

Great weather today with comfortable humidity and temperatures not too far from normal for mid-August. We turn wetter and a little stormy by later tomorrow into tomorrow night some spots could see upwards of an inch or so of rain. We turn sunny any by Monday with pleasant weather returning and lasting through mid-week.

So let's address Charlie @chubbs post above Charlie, of course no dispute that Phoenixville stepped down at the 1948 move. But you've written the very objection into your own post: "Not surprising because the bias adjustments are calculated from the raw data." Charlie, your test is pairwise comparison of a target against raw neighbors across a break date. But so is the PHA! You've actually hand-implemented the method NCEI automates. Agreement demonstrates reproducibility, but of clearly not correctness as you are simpling showing us the same method, same data. It's the same issue as Berkeley and NCEI agreeing being offered as independent confirmation - they are of course not! On your "bullet proof" claim - the four available estimates of this one documented move: Berkeley -1.23 F / yours vs Coatesville -1.49 F NOAA -1.88 F / yours vs West Chester -2.03 F Four pairwise estimates of the same event spanning 0.80 F; the largest is 65% bigger than the smallest. Same sign and rough scale but the real question here as always has been the magnitude is what's in dispute here, and that spread isn't what bullet proof looks like!!. Also, your 2 references disagree by 0.54 F. If both were stable through 1947-50 they should agree on that Phoenixville's step. They don't, so they moved relative to each other in your window - and you date West Chester to 1970 and Coatesville to 1946, before your "before" period even opens. So you also say "all of the major county COOP stations moved in the same direction and roughly the same magnitude after the war". If so, doesn't that actually represent a real problem for the method, not support for it??. Pairwise comparison sees only RELATIVE change - a shift common to the whole network differences out and is invisible by construction. The more synchronised those moves were, the less your test and the PHA can detect, in exactly the era carrying the county's largest adjustments. So Charlie while none of this says your step estimate wrong. It means the method you are using is simply being validated against itself, the spread across implementations exceeds the confidence claimed, and the scenario you offer as clinching is the one the method handles worst.!! Paul

That is a great answer Mike! that transformer efficiency improving over time means declining waste heat, which puts spurious cooling into the raw record, which needs the later data warmed. That's the sign NCEI applied. It's a coherent mechanism and it's the first one offered in this thread that resolves the direction problem. Thank you for it. However....I think it may cost you a bit more than you think this buys you! A few posts ago your position was "100% documented evidence of microsite impacts" and "Coatesville's breakpoints are fully documented at this point." Now the site is "literally a thermal zoo" and the complexity "obviates all the musings about what caused a precise shift at time X and magnitude Y." Those are different arguments. The first says the causes are documented and therefore the corrections are validated. The second says the causes can't be pinned down and therefore we have to trust the detector. I don't think both can be true of the same station, and the second is a much weaker claim than the one you started with. It also runs into my actual objection rather than around it. If the microsite is too complex to attribute a given shift to a given cause, then it is also too complex to verify that the correction applied was the right size. You're offering unverifiability as a reason for confidence. Unverifiability is the thing I've been objecting to. And your mechanism argues against the correction's shape. Transformer technology improving across decades is gradual. A cooling pool installed at one point and removed after 2005 is two events. Steadily declining waste heat produces a ramp, not a staircase. The PHA fits steps. By your own account the physical signal is the wrong shape for the correction being applied to it - and that's your description of the site, not mine. There's a specific case I'd like your read on. The 1946-01 changepoint is +0.79 C, warming everything from 1946 forward. That's the move TO Newlinville. If the station relocated onto a substation with massive transformers and high loads, the raw record should have jumped warm at that moment and needed a cooling correction. NCEI warmed it instead. That only works if Newlinville was cooler than the water plant site it came from - which is your earlier "hot location to progressively cooler ones" account, and I don't see how it sits alongside "massive heat sources" at the same site in the same year. Last thing, If Coatesville 1SW spent 36 years in a thermal zoo with industrial heat sources that moved, changed technology, and gained and lost a cooling pool, there's a conclusion available that neither of us has put on the table: that this record can't be salvaged for trend estimation and shouldn't be used for it. "Automated detection is the only way to salvage this data" assumes it can be salvaged. What's the basis for that, given everything you've just described? And is it a kind of a funny coincidence that the station carrying the county's largest adjustments is the one you're describing this way? Paul

Mike, I'll take your four questions in order Q1 - yes. Raw records could potentially carry non-climatic biases that don't cancel but not always! Q3 - yes. Williams 2012, Venema 2012 and Killick 2022 are real, adversarial, and they show homogenisation reduces error if a station has proven data issues, I accept that and I'm not going to pretend the literature says otherwise. Q2 - one correction. You say breakpoint detection is "even unstable run-to-run (shown in this thread's own evidence)." It wasn't shown. I went looking for it: two pulls of the West Chester QCF taken a few years apart were identical across all 119 complete years, unadjusted series identical too. NCEI told me the output can change daily; I tested it and found none over that interval. That concession isn't mine to accept. Q4 is where we really differ, and it's about scope. My claim is narrower: the specific magnitudes applied to specific Chester County stations haven't been independently verified, and showing an event occurred doesn't verify the size of the correction attached to it. The benchmarks measure whether homogenisation moves a NETWORK closer to truth on average - the right quantity for a national series, and a different question from whether one station in one decade got the right number. Venema's own write-up notes it modelled small European networks at high station density without network-wide trend biases; Williams found improvement in the presence of widespread systematic errors. Both are aggregate statements under stated conditions. The conditions matter here. Before 1951 this county has three continuous stations. Menne and Williams say it themselves in the 2009 paper: false alarms at neighbouring stations reduce the number of homogeneous neighbours and thereby prevent the estimation of adjustments. That's the sparse-network failure mode described by the algorithm's own authors, in the era carrying the largest adjustments. On cherry-picking - you introduced Coatesville as the exemplar and called it two resounding yeses. If it's representative enough to validate, it's representative enough to examine. You asked for a case. Here's the beginning of one, and it's a magnitude test rather than an occurrence test. So I built a regional reference for Coatesville from the raw, unadjusted Chester County records only - leaving Coatesville 1SW out so that it never contributes to its own comparator, and no homogenised product anywhere in the calculation. Measured drift of Coatesville against those raw neighbours over 1895-1982 is -0.190 F/decade using every available station, or -0.113 F/decade using a fixed panel that can't change membership. The applied NCEI adjustment runs +0.303 F/decade, which implies a drift of -0.303. That value falls outside the 95% confidence interval of the measured drift under both reference constructions. The adjustment also tracks the drift year to year - r = -0.74 - so it's aimed at something real. It's the size I'm questioning, not the existence. What this is so far in all of my multiple years of review which has been my analytic goal of this process of reviewing the adjustment of raw data at one targeted station Coatesville 1SW is that the correction appears larger than the divergence it corrects, measured without using any homogenised data. If that's wrong I'd like to know how?? Paul

Mike, those aerials are genuinely useful and I'm glad to have them. They establish something I'd have had a hard time establishing myself: that the site was disturbed, repeatedly, across that whole period. I'm not disputing that. But again they just don't get you to either of the two claims you're making. Documenting that something happened at a site is not the same as documenting how much it changed the temperature, or in which direction. The aerials show construction. They don't measure its thermal effect. Every step magnitude in the NCEI record was sized by neighbor comparison, not by anything visible in a photograph, and that is the number that has to be right for the correction to be right. And there's a direction problem I raised earlier that I have not heard you answer or reconcile. An electrical substation with megawatts running through it, accumulating buildings and hard surfacing from 1946 through 1982, that is clearly a warming influence on the raw record. Correcting a progressive warming bias means pushing the later data down or cooler relative to the earlier. NCEI's correction goes the other way - the two NOAA changepoints in that window are +0.45 F at 1959 and +0.95 F at 1971, net +0.40 F, raising the later data, and the overall adjustment lifts the modern era relative to the early one. You do offer a second mechanism - that the station itself may have moved as office space changed. If it moved away from the heat sources, that would produce cooling steps needing a warming correction, and the sign would work. But that's the opposite mechanism from the one the aerials show, and it's offered as a possibility rather than as something documented. Both can't be driving the same window. Which one do you think it is, and in which years? The other thing that doesn't sit right: if construction were producing stepwise changes throughout 1952-1982, I'd expect the detectors to be finding them. NOAA places two changepoints in that window. Berkeley places five, and by your own figure they come to about -0.10 F net across seventeen years. That's a lot of documented disturbance producing very little net correction. So where I see us in reality standing on this analysis is on validity: showing that an event occurred does of course not validate the size of the correction applied to it. That would take an independent measure of the effect, and I don't think you have so far produced one yet - yours truly also! Of clear necessity: demonstrating that the adjustment is essential requires showing the uncorrected data gives the wrong climate answer, which requires knowing the right answer independently. Neither of those has been establish here. I'm not claiming the adjustments are wrong. I'm saying "documented" and "validated" are different words, and the work so far has established the first, not the second. If you have something that speaks to magnitude rather than occurrence, I'd genuinely like to see it. But again we are far away from any proof you claim to see!

What remains genuinely open regarding Coatesville 1SW remains the magnitudes have never been independently checked. A documented 0.3-mile move does not actually tell us the offset should be +0.86 °C. That number comes from neighbor comparison, not from the site. Nobody in this thread has tested whether the applied steps match what the physical changes would produce. Also of note about a third of the adjustment trend attaches to no listed changepoint at all. +0.123 reconstructed against +0.184 actual. No station history can validate a component that no documented event is claimed to explain, and NCEI hasn't yet answered that from my earlier email. Lastly, and what can't be overlooked is that the raw cooling doesn't behave the way the artifact explanation predicts. Fitting the breaks actually deepens it rather than dissolving it!!

Not so fast Mike!! We are not close yet to what think is being answered! The deep dive above clearly has not yet answer these two questions for Coatesville! First the refit I promised with some very important findings!! and then where I think you and I are answering different questions. At the end I will address your Phoenixville box above. I said I wouldn't quote that 1952-82 trend until I'd refit it against the full break set, because if there are several real discontinuities in the window then a single-step model is under-specified and the number is worthless. I've now done it, and the result is quite surprising!! The mechanism first, because it's the interesting part. A step term and a trend term compete for the same variance in a regression. If Coatesville's apparent cooling were really just the station stepping down at a few dates, fitting those steps should soak up the drop and leave the residual slope flattened toward zero. That is exactly the test. But what actually happened is the complete reverse. Every fitted step comes out positive - the model wants the later years lifted, not lowered - and lifting the later years forces the underlying line to fall more steeply to still pass through the data. Coatesville 1952-1982, annual, trend and steps estimated jointly in one model rather than subtracting steps first: no steps -0.594 F/decade p = 0.0001 1973 only (my attributed break) -0.735 F/decade p = 0.0048 NOAA's two (1959, 1971) -0.959 F/decade p = 0.0272 Berkeley's five (1959/68/71/73/76) -1.657 F/decade p = 0.0188 Significant in all four. Fitted steps +0.45, +0.46, +0.89, +0.91, +0.81 F, every one positive. So the more of your documented breaks I grant, the more raw cooling is left over needing some other explanation. The weaknesses, because I'd rather flag them myself. Not one of those steps is individually significant - best p is 0.17, standard errors 0.6 to 0.7 F against steps of 0.45 to 0.91. So this isn't proof the steps are positive. It's that the data, asked where steps would sit if they exist, puts them in the direction that deepens the cooling. Suggestive, not conclusive, and it neither confirms nor refutes your documentation, because at annual resolution this series can't resolve steps that size. AIC prefers the no-steps model over every step set, though with those SEs that's weak too. And the five-break fit is badly under-powered: seven parameters on 31 values at 0.75 F residual SD detects a genuinely present trend only about 14% of the time in simulation. It found one anyway, which is why I'm reporting it rather than quietly setting it aside - it's the most favourable number to me and the one I trust least. So what I'll stand behind is a range: -0.59 to -1.66 F/decade over 1952-1982 depending on the break set assumed, significant in all four specifications. Now, on validity and necessity. I think we're answering different questions. Your work establishes that events occurred at those dates, and I've conceded that without reservation. Validity is a further step: it requires the magnitude applied at each date to be right. The PHA sizes each step from neighbour comparison, not from the site. A 0.3 mile move is a documented fact. The +0.86 C attached to it is an estimate. Nothing in the 530-1s, the deeds or the aerials tests that estimate, and that's the question I keep coming back to - it isn't answered by more documentation, however good the documentation is. Necessity is different again. If the raw cooling at Coatesville were an artifact of the station changes, fitting those changes should dissolve it. It doesn't. It deepens it!!!!. Whatever else that shows, it isn't what "the adjustment is essential to get the right answer" predicts. And about a third of Coatesville's adjustment trend isn't attached to any listed changepoint at all. NCEI's twelve cumulate to +0.123 C/decade against an actual adjusted-minus-raw trend of +0.184. Station history can't validate a component that no documented event is claimed to explain. I've asked NCEI what accounts for it rather than guessing, and I'll post their answer either way. On Phoenixville I'd want to look at your figure properly before saying much, and I'll say up front that my own analysis can't support a claim about that station in either direction. When I tested its 1952-82 trend against a step placed at every possible date, 14 of 21 rendered it non-significant. That series is too short and too noisy to separate a step from a trend, so I'm not going to argue it either way. I'd also note that if the microsite is changing continuously - your reading of the aerials is roughly every ten years from 1927 forward - then the disturbance is gradual, and a step function is an odd model for gradual drift. On the two hours: fair enough, and I've said as much. Though the changepoint list I've been working from came from NCEI directly on request, and isn't online anywhere. The offer stands on your 530-1 and deed compilation. Your dates are better than the ones I read off your figure, and the magnitude question needs them. Now regarding the last Phoenixville block - that block does not say what your post said. Your comment claims the adjustments are "valid and absolutely necessary," but the header states ten breaks now carry a documented physical cause and seven smaller breaks remain unexplained, plus one marked UNRESOLVED at 1966 and a merged box labelled "UNDOCUMENTED — 7 BREAKS." That's 10 of 18, not a resounding yes!!!! Thanks for posting it — it's a more careful figure than the summary suggests. What strikes me most is that the two sources diverge here in a way they don't at Coatesville. At 1940 — the largest documented move in the record, 2.1 miles — BEST flags +0.75 F and NOAA flags nothing at all. At 1942 it's the reverse. At 1985 you note the NOAA break is a single-station calibration artifact. If two implementations of neighbour-based detection disagree about whether the biggest documented move in the record produced a break, that seems worth more attention than either of us has given it. The 1920 entry is the strongest piece of documentary work in either of your figures, incidentally — coords changing then reverting a year later while the offset doesn't is a real finding and I'd not have got there. My own analysis cannot support the claim that Phoenixville cools — which matters because Phoenixville has been used as a comparator throughout this thread. Charlie dismissed my Coatesville–Phoenixville comparison over a 1948 break, and I cited Phoenixville's raw trend earlier in the exchange. Testing its 1952-82 trend against a step at every possible date, 14 of 21 rendered it non-significant. Too short and too noisy to separate a step from a trend, so to date we cannot find total support for these NCEI adjustments to Coatesville 1SW Paul

Kevin I can't wait for less humidity I am over it while not our hottest summer It sure feels like one of our most humid!!

Mike, this is in my view the most useful thing anyone has put in this thread, and it changes my position on several points. Thank you for doing the archival work rather than just asserting it. Taking your points in order. You're right that "undocumented" in the algorithm's metadata linkage is not the same as "no documentation exists." I was treating the two as equivalent and that was a wee bit sloppy. Your figure shows some actual events behind most of the Coatesville breaks, and the burden argument is fair — I shouldn't claim an absence of records without going through the 530-1s, the deeds and the aerials first. I hadn't. You had - thanks!. You're also right that a high rate of undocumented detections is expected from a detector built to catch undocumented changes, so the 86% figure doesn't carry the weight I was giving it. I'd already dropped that argument after NCEI sent me their changepoint list for this station — it shows 4 of 12 linked to documented events, not zero, so the Berkeley code counts were never a good proxy for what the PHA is doing. On the ramp point: Mike - you're right - many small stacked breaks produce a ramp-shaped cumulative. I proved your point without meaning to — cumulating NCEI's twelve discrete changepoints gives a series that fits a straight line at r-squared 0.495. That's a stack of steps looking smooth, exactly as you say. Zero-adjustment stations and the diurnal range point are both fair points also. A detector leaving clean stations alone is working, and DTR divergence is a studied phenomenon rather than a contradiction. And I accept that a handful of stations in one county is a noisy sample by nature. Now a couple things I will push back on a little, not on it's substance but on how firmly you state it. Your own figure marks 1920 unresolved. And I'd read the 1959-1976 group differently to the header on it. The box says five breaks, but NOAA only has two in that window — 1959 and 1971. The other three are BEST-only. And BEST's five nearly cancel: -0.50, +0.37, +0.02, +0.72, -0.71 comes to -0.10 F net across seventeen years, which isn't doing much work. NOAA's two come to +0.40 F, and that's the direction you'd correct for spurious cooling, not for a station warming under encroaching infrastructure. Which brings me to the part I can't pull together. The station moves to progressively cooler sites implies the raw acquires spurious cooling and needs the later data warmed — which matches what NOAA applied. Infrastructure growing up around the site implies the opposite. Both are in your account of this window. Which one do you think is actually driving it? For what it's worth, your 1959 and 1971 values match NCEI's changepoint list for this station exactly once converted — -0.54 and +0.94 F against -0.28 and +0.53 C. So we're working from the same PHA output, which is worth knowing! Thanks again Mike!! That window also stops something I was about to post. I ran a segmented breakpoint analysis on the raw daily data and it attributed only one concordant discontinuity to Coatesville, January 1973. I then fitted the 1952-82 trend with that single step in the model. If there are more real breaks in that window, my model is under-specified and the number isn't worth quoting. I'm going to refit it against the full break set before I use it. If it doesn't survive, I'll say so here. Stay tuned for that later! The one thing still open is narrower and comes out of NCEI's own files rather than the station history. Cumulating their twelve changepoints reproduces +0.123 C/decade of adjustment trend. The actual adjusted-minus-unadjusted trend for the same station and years is +0.184. About a third isn't in any listed changepoint. It isn't rounding, and it isn't run-to-run variation — I compared two pulls of the adjusted series two days apart and they were identical across all 119 years at West Chester. I've asked NCEI what accounts for it rather than guessing, and I'll post their answer either way. I sent the email this morning to my contact there...stay tuned for more of that later! Now my ask - would you be willing to share your compiled 530-1 and deed work for Coatesville, and whatever you have for West Chester? I'd rather build on it than duplicate it badly, and I'll take your point about the 1978, 1982 and 1988 West Chester breaks — the Daily Local should have left a trail worth chasing. Charlie, I think most of the above answers you as well. You were right that a 35-year regression is not a breakpoint test, and running it properly is what led here. On 1945-49 specifically, NCEI's list has a documented move at 1946-01 with a +0.79 C step, so something documented did happen there. I still can't test that window myself — only three Chester County stations cover 1930-1975 with continuity and attribution needs four — so at this point we can't claim it either way. Paul

Today will be our last day with higher humidity. We should cooler weather both tomorrow and especially on Saturday. However, we turn more humid and wetter again by later Sunday into Monday. Drier and near normal temperatures arrive by next Tuesday.