CoastalWx Posted July 10, 2015 Share Posted July 10, 2015 If you toss out almost the entire state of Mass..especially north of the pike..then sure it was meh..lol ...franklin county... shutesbury 1.91 815 AM 7/10 ham radio 2 SE orange 1.18 703 AM 7/10 asos greenfield 1.14 734 AM 7/10 co-op observer ...hampshire county... williamsburg 1.55 834 AM 7/10 ham radio belchertown 1.53 839 AM 7/10 ham radio easthampton 1.48 838 AM 7/10 ham radio south hadley 1.45 840 AM 7/10 ham radio goshen 1.44 835 AM 7/10 ham radio amherst 1.32 735 AM 7/10 co-op observer worthington center 1.21 733 AM 7/10 co-op observer ...middlesex county... natick 2.50 829 AM 7/10 ham radio hopkinton 2.04 830 AM 7/10 ham radio weston 1.89 822 AM 7/10 ham radio framingham 1.83 831 AM 7/10 ham radio marlborough 1.48 824 AM 7/10 none wayland 1.48 832 AM 7/10 ham radio belmont 1.45 858 AM 7/10 ham radio watertown 1.44 857 AM 7/10 ham radio maynard 1.09 821 AM 7/10 none lexington 0.97 557 AM 7/10 general public 2 WSW bedford 0.86 711 AM 7/10 asos ...norfolk county... wellesley 2.21 825 AM 7/10 ham radio dedham 2.13 852 AM 7/10 ham radio milton 2.03 836 AM 7/10 blue hill observatory ...plymouth county... duxbury 1.77 800 AM 7/10 none ...suffolk county... boston 1.89 854 AM 7/10 ham radio 1 N east boston 1.27 702 AM 7/10 asos ...worcester county... boylston 2.59 819 AM 7/10 ham radio milford 2.53 844 AM 7/10 ham radio northboro 2.10 841 AM 7/10 ham radio auburn 1.88 843 AM 7/10 ham radio shrewsbury 1.84 846 AM 7/10 ham radio barre 1.84 817 AM 7/10 ham radio grafton 1.80 850 AM 7/10 ham radio north grafton 1.47 848 AM 7/10 ham radio holden 1.45 821 AM 7/10 ham radio 4 SE fitchburg 0.74 710 AM 7/10 asos Kevin here. I explained it. Less than .7 in most spots. Like I said, it shifted south by 30-40 miles as far as the def band goes. So much for wild tstms and 1-2" of rain for all. Nobody said no rain, but .5" of rain from what some of the comments earlier is rather mundane. That was the point. This little band did surprise me though. GFS actually hinted at it. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted July 10, 2015 Author Share Posted July 10, 2015 Really only south of BDL to 95 in CT got shafted..Everyone else got a good to great rainfall and in some cases wild amounts in short period of time And of course as is the case with every snow or rain event the last 2 years South Weymouth is the jackpot Link to comment Share on other sites More sharing options...
radarman Posted July 10, 2015 Share Posted July 10, 2015 Kevin here. I explained it. Less than .7 in most spots. Like I said, it shifted south by 30-40 miles as far as the def band goes. So much for wild tstms and 1-2" of rain for all. Nobody said no rain, but .5" of rain from what some of the comments earlier is rather mundane. That was the point. This little band did surprise me though. GFS actually hinted at it. RAD_KBOX_NTP.gif Pretty awful radar estimates for many. To some extent the error is a function of beamheight, but even fairly close by to the radar it's underreporting substantially. Link to comment Share on other sites More sharing options...
CoastalWx Posted July 10, 2015 Share Posted July 10, 2015 Really only south of BDL to 95 in CT got shafted..Everyone else got a good to great rainfall and in some cases wild amounts in short period of time And of course as is the case with every snow or rain event the last 2 years South Weymouth is the jackpot Shafted and getting some rain are different things. I thought the BOS-ORH-BOS-PVD triangle was the shaft. It was just south. So, I was off by a bit..but the idea of getting sort of meh amounts in between features was the whole point. However, the deformaton stuff really did better than I thought. Sometimes those are model fantasies like last weekend, but the GFS and even HRRR did a good job. I'll give it that. Link to comment Share on other sites More sharing options...
CoastalWx Posted July 10, 2015 Share Posted July 10, 2015 Pretty awful radar estimates for many. To some extent the error is a function of beamheight, but even fairly close by to the radar it's underreporting substantially. The dual polar stuff was much better. It's just to give an idea of axis placement. Link to comment Share on other sites More sharing options...
Ginx snewx Posted July 10, 2015 Share Posted July 10, 2015 The dual polar stuff was much better. It's just to give an idea of axis placement. Bet that dumb drought monitor site still has you in drought conditions next week Link to comment Share on other sites More sharing options...
Typhoon Tip Posted July 10, 2015 Share Posted July 10, 2015 Looks like a pretty warm to hot weekend. Mentioned this the other day that there was a low probability for a low-end heat wave (meaning of course 90+) No 'big heat' as the local vernacular says it, but official nonetheless. Or, could be 88 or 89 over steadily rising DPs from 58 to 70 come Monday, just the same, which would feel the same. Last night's way overly argued, insignificant blip along the transom of summer ... was what I like to call a "sensible" warm front. After it has ended the air mass behind it has a warmer feel, despite the however weak CAA is mathematically shown. But it was even stranger than that; the 500 mb thickness receded 4 or 5 DM, yet the 850s warm up. I would think perhaps better lapse rates result above that level - maybe. anyway, nice stripe of 1 to 1.5" of rain after all ... nearly collocated west to east with Massachusetts. Not sure how that result fits into the debate yesterday, but for all intents and purposes ..nice bit of a drink of water for the landscape. Link to comment Share on other sites More sharing options...
CoastalWx Posted July 10, 2015 Share Posted July 10, 2015 Bet that dumb drought monitor site still has you in drought conditions next week I wish I had a rain gauge, but I think 9.5" or so since end of May. Not exactly dry. Last year at this time, but lawn was dying. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted July 10, 2015 Share Posted July 10, 2015 Pretty awful radar estimates for many. To some extent the error is a function of beamheight, but even fairly close by to the radar it's underreporting substantially. Powderfreak and I were opining the public access (internet site's) estimates from KTAN earlier in the summer. It can be [apparently] off by as much as .5"! I wonder how you know it is "beamheight" per se... Probably, sure... The error doesn't appear to equally occur point to point across the displays. Link to comment Share on other sites More sharing options...
Baroclinic Zone Posted July 10, 2015 Share Posted July 10, 2015 Not bad. 1.5" over 2 days. Dry begat wet and soggy. Time to do the dew. Link to comment Share on other sites More sharing options...
moneypitmike Posted July 10, 2015 Share Posted July 10, 2015 Bet that dumb drought monitor site still has you in drought conditions next week LOL. That thing is pretty ridiculous. Link to comment Share on other sites More sharing options...
Nate Posted July 10, 2015 Share Posted July 10, 2015 I measured 1.14" and was right on the sharp gradient. I should have moved my gauge, any wind from the North to the Southeast would have lowered my measured amounts due to trees and I usually move it if that direction is forecast, but didn't last night. APHS has me over 2" but I doubt it was that much or there would have been more water coming into my basement. With all that said, estimate 1.5ish in reality. Certainly better than last year with this regular rainfall. Nice wetting before the heat this weekend and after the surface was drying up a bit. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted July 10, 2015 Share Posted July 10, 2015 Not bad. 1.5" over 2 days. Dry begat wet and soggy. Time to do the dew. Definitely some truth here ... The gradient is weak and we are not advecting significantly enough; the soil water uptake will in part dry and be used of course, but a significant part will evaporate into a sun heating air mass that has a warm mixing depth - such that we'll put some theta-e in the bank locally on this. Link to comment Share on other sites More sharing options...
radarman Posted July 10, 2015 Share Posted July 10, 2015 Powderfreak and I were opining the public access (internet site's) estimates from KTAN earlier in the summer. It can be [apparently] off by as much as .5"! I wonder how you know it is "beamheight" per se... Probably, sure... The error doesn't appear to equally occur point to point across the displays. Out here we received 1.8" and that map suggests closer to .6"... huge error indeed. At a quick glance I thought the radar estimates appear to be marginally worse out here than further east which I am chalking up to beam height... attenuation can also increase error as a function of distance, but S band is not very prone to attenuation, particularly for lack of very strong convection. In any case, I didn't realize they were still running the old z-r based algorithm... maybe time to retire it with the new tech available. The coefficients may be set to some summer mode where in general low Z suggests lighter rains. I would imagine that KDP was quite high last night, with dense smaller droplets. Link to comment Share on other sites More sharing options...
HIPPYVALLEY Posted July 10, 2015 Share Posted July 10, 2015 I'm ready to dry out for a spell. Almost 10" here since June 1st. Done. Bring back May's hot and dry please. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted July 10, 2015 Share Posted July 10, 2015 Out here we received 1.8" and that map suggests closer to .6"... huge error indeed. At a quick glance I thought the radar estimates appear to be marginally worse out here than further east which I am chalking up to beam height... attenuation can also increase error as a function of distance, but S band is not very prone to attenuation, particularly for lack of very strong convection. In any case, I didn't realize they were still running the old z-r based algorithm... maybe time to retire it with the new tech available. The coefficients may be set to some summer mode where in general low Z suggests lighter rains. I would imagine that KDP was quite high last night, with dense smaller droplets. Mmm, it might be hard to demo the seasonal error-bias, I think. The winter storms that flip over to rain and strata pound would probably be the same. In other words temperature doesn't really reflectivity rates. Link to comment Share on other sites More sharing options...
radarman Posted July 10, 2015 Share Posted July 10, 2015 Mmm, it might be hard to demo the seasonal error-bias, I think. The winter storms that flip over to rain and strata pound would probably be the same. In other words temperature doesn't really reflectivity rates. The problem with Z-R is you are using a constant... I wasn't making a claim of seasonal error bias, because you can change (and should change) the constant based on climo. No matter what you pick you can get substantial errors... For example most of our precip in the summertime comes from convective systems. Convection tends to produce strong updrafts, which in turn leads to high ZDRs, given that the droplets take on oblate shapes as they increase in size (function of updraft strength) and then fall. Standard Reflectivity is horizontally polarized, so if the Z-R constant is tuned with expectation of convective rains, and you measure low Z, the logic behind the alg is that this means weak updrafts and likely light rains. Synoptic processes in combination with high PWATs can cause heavy rains with lower ZDRs... tropical storms are particularly known for this... but unless a radar op is tuning the constant on a case by case basis they will be misinterpreted... in this case underreporting substantially. Link to comment Share on other sites More sharing options...
Ginx snewx Posted July 10, 2015 Share Posted July 10, 2015 Out here we received 1.8" and that map suggests closer to .6"... huge error indeed. At a quick glance I thought the radar estimates appear to be marginally worse out here than further east which I am chalking up to beam height... attenuation can also increase error as a function of distance, but S band is not very prone to attenuation, particularly for lack of very strong convection. In any case, I didn't realize they were still running the old z-r based algorithm... maybe time to retire it with the new tech available. The coefficients may be set to some summer mode where in general low Z suggests lighter rains. I would imagine that KDP was quite high last night, with dense smaller droplets. best to use digital arrays when looking at Radar totals Link to comment Share on other sites More sharing options...
radarman Posted July 10, 2015 Share Posted July 10, 2015 best to use digital arrays when looking at Radar totals No doubt, I'm surprised they're even still putting out Z-R totals. We have demonstrated substantial accuracy improvements with KDP based QPE estimates at X band over S band in Texas this spring, though attenuation is a much bigger problem meaning you absolutely need to have a dense network to do it well. In certain portions of the metro we had enough overlapping coverage to fill in the attenuation gaps, but in the outlying single radar areas we incorporated Nexrad data into the processing to assist. Link to comment Share on other sites More sharing options...
CoastalWx Posted July 10, 2015 Share Posted July 10, 2015 That's why he is Radarman. Nice lesson there. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted July 10, 2015 Share Posted July 10, 2015 Jeez. Close to 2" of rain here overnight? Barely heard it other than a little thunder AC white noise ftw Link to comment Share on other sites More sharing options...
Typhoon Tip Posted July 10, 2015 Share Posted July 10, 2015 The problem with Z-R is you are using a constant... I wasn't making a claim of seasonal error bias, because you can change (and should change) the constant based on climo. No matter what you pick you can get substantial errors... For example most of our precip in the summertime comes from convective systems. Convection tends to produce strong updrafts, which in turn leads to high ZDRs, given that the droplets take on oblate shapes as they increase in size (function of updraft strength) and then fall. Standard Reflectivity is horizontally polarized, so if the Z-R constant is tuned with expectation of convective rains, and you measure low Z, the logic behind the alg is that this means weak updrafts and likely light rains. Synoptic processes in combination with high PWATs can cause heavy rains with lower ZDRs... tropical storms are particularly known for this... but unless a radar op is tuning the constant on a case by case basis they will be misinterpreted... in this case underreporting substantially. Brings back memories ... of Radar class while as an undergrad up at UML. Man, there are some formulas for radar that are pretty crazy with dangling ratios of variables and derivatives... Not sure if any of that has been normaized to easier algorithms since, just what we learned at the time ..circa the mid to late 1990's. But yea, not sure how NWS KTAN is calibrated but there is no doubt in my mind that whatever it is, they're rad provisions to that internet site are junk. Particulate shape/density can be disparate reflectors; that's one thing we learned, and there were formulas that were derived by engineers that tried to explain. Hail -vs- hail water coated ...same for wet versus dry snow aggegration (sometimes refer to "bright-banding" ,, all phenomenon that certain rad modes are better or worse for. That all said, being under by a minimum error of .25" and sometimes as much as an inch makes the product pretty useless in my op - Link to comment Share on other sites More sharing options...
Damage In Tolland Posted July 10, 2015 Author Share Posted July 10, 2015 BDL 90 tomorrow and BDL /BOS 92 Sunday Link to comment Share on other sites More sharing options...
radarman Posted July 10, 2015 Share Posted July 10, 2015 That all said, being under by a minimum error of .25" and sometimes as much as an inch makes the product pretty useless in my op - In densely populated regions such as this one cocorahs data, or even a compilation of off the shelf wx station tipping buckets (which have their own well known issues), are a lot more useful for storm totals, particularly for synoptic type precip events which have a more even distribution. On occasion you might get some popcorn style showers/thunderstorms that could miss the gauges... for that radar estimates are pretty useful... or if you are looking at flash flood threats for which instantaneous rainfall rates (along with hydrologic factors) are necessary to warn in advance. Z-R was better than nothing, especially for ag out in the plains, but the dual pol upgrade has made a huge difference for radar QPE no question. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted July 10, 2015 Author Share Posted July 10, 2015 Tuesday still has a tornadic look Link to comment Share on other sites More sharing options...
Ginx snewx Posted July 10, 2015 Share Posted July 10, 2015 BDL 90 tomorrow and BDL /BOS 92 Sunday no one lives there, 84-86 where people live Sat 86-88 Sunday Link to comment Share on other sites More sharing options...
Damage In Tolland Posted July 10, 2015 Author Share Posted July 10, 2015 no one lives there, 84-86 where people live Sat 86-88 Sunday Noone lives in Boston? Link to comment Share on other sites More sharing options...
tamarack Posted July 10, 2015 Share Posted July 10, 2015 Flood watches never should have been issued in the first place. 1-2 inches of rain doesn't cause flooding Not in July (unless it all comes in 20 minutes.) March or April, not so sure, depending on snowmelt conditions. Link to comment Share on other sites More sharing options...
HIPPYVALLEY Posted July 10, 2015 Share Posted July 10, 2015 BDL 90 tomorrow and BDL /BOS 92 Sunday Sounds like mid-July. Link to comment Share on other sites More sharing options...
Chrisrotary12 Posted July 10, 2015 Share Posted July 10, 2015 It's been forever since I've had an overnight t-storm. It seemed they happened with regularity 20-30 years ago Some of my favorite memories as a kid were laying in bed and watching the flashes out my window. Even 10-15 years ago now it seemed like we used to get them a couple times a summer. Now.....nothing. Link to comment Share on other sites More sharing options...
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