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Post by nei on Jan 4, 2019 0:28:44 GMT -5
I've mentioned in New England in the winter, precipitation happens more often when it's warmer; so even if the averages are well below freezing, a majority of precipitation is in the form of rain. A lot of the time precipitation comes when moist, mild from the south arrives. Places like the mountain west are the opposite: gets lots of snow even when the averages are above freezing. Made some graphs of temperature frequency in winter and summer; graphing over all hours, hours it rains and hours it heavily rains (> 2 mm / hr or 0.08 in / hr). Each bin of the histogram of 2Β°F. Y-axis is hours the temperature occurs per year on average. Blue color represents all colors. Green hours it rains, yellow it rains heavily. Rain obviously occurs much less often so I used a different scale so the plots look nicer; the y-axis number on the right are for the rainy hours graphs [green & yellow], left all temperatures [blue]. First Hartford in New England. You can see there's a lot of just above freezing rain  Rochester, similar latitude but further west doesn't have as much of a "cold rain" peak  even Whitefield, NH has a bit of a frequency peak at above freezing temperatures but the temperatures are much colder than the other two stations so the bulk of winter precipitation is in snow. Really cold temperatures there are dry because most cold is from radiational cooling.  The temperatures are by hour, so measured [or interpolated] at the end of each hour. And precipitation the amount over one hour (3-4 PM, 4-5 PM); if it rains from 3:59 to 4:01 it's counted as raining over two separate hours, with its temperatures graphed at 4 pm and 5 pm. |
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Post by AJ1013 on Jan 4, 2019 0:35:21 GMT -5
nei Awesome job. Rain is generally cool in Tucson and warm in Miami. Would be cool to see plots if you have time.
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Post by nei on Jan 4, 2019 0:38:22 GMT -5
nei Awesome job. Rain is generally cool in Tucson and warm in Miami. Would be cool to see plots if you have time. won't be hard to make more plots at all, just need to download the data. Think I've already downloaded Miami and Tucson; I'll post them tomorrow. Would like to do Denver as well and a few other western mountain stations, but harder to find ones with complete hourly data |
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Post by ππΏMΓΆrΓΆnππΏ on Jan 4, 2019 0:39:30 GMT -5
Here, the same principle should hold true as well. The only exception would be in the summer since warmer temps in the summer here equals dry weather usually.
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Post by Steelernation on Jan 4, 2019 15:07:10 GMT -5
Nice job nei. Thanks for doing one do Rochester. The plots are confusing though? The green extends down to like 4 f but it obviously canβt rain then...Maybe youβre counting snow? Tbe graphs do clearly show that it usually rains on warm winter days and that cold days are more likely to be dry than warm days. Very annoying feature of our climate. In summer, it looks like cool days are more likely to be rainy, warm days more likely to be dry, makes senseβitβs hard to get like a 70/50 summer day without it being wet. |
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Post by Deleted on Jan 4, 2019 15:29:14 GMT -5
Rain comes with warmer temps in winter, and cooler temps in summer here.
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Post by Crunch41 on Jan 5, 2019 12:14:08 GMT -5
Wisconsin stations will have the same general pattern. Warm days are wetter in winter, drier in summer. A western station would be interesting since their winter pattern is different. So would a place that gets lake effect snow, since that only appears when it's cold. Hancock, Michigan is probably the snowiest ASOS station for lake effect.
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Post by nei on Jan 6, 2019 16:54:43 GMT -5
Nice job nei. Thanks for doing one do Rochester. I remember from living there upstate NY got less cold rain than New England at similar temperatures + you can see often in winter on maps warm air comes up the coast with storms green/yellow color are for all precipitation, should have been more clear. I suppose I could separate by precipitation type; give a separate color for when an hour of precipitation has snow vs not snow. Thought it wasn't worth it since it would change at almost exactly 32Β°F but would be interesting to see how much there is above freezing snow and below freezing rain. Wouldn't be able to separate hours that have both rain and snow; I'd just classify them as "snow". Oh, I don't have snow data in the files I downloaded, would need to redownload, so another time The temperatures are graphed by hour not by day. Those cold temperatures in the graph are almost all morning temperatures. |
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Post by Steelernation on Jan 6, 2019 17:03:58 GMT -5
I remember from living there upstate NY got less cold rain than New England at similar temperatures + you can see often in winter on maps warm air comes up the coast with storms The temperatures are graphed by hour not by day. Those cold temperatures in the graph are almost all morning temperatures. That first part makes sense, no coastal storms here. The east coast gets a lot more precipitation than we do, although we get more rain days so it seems it would be more frequent here...havenβt lived on the east coast so canβt compare like you can. If the cold temps are in the morning, then would it show that precipitation is more likely in the morning than the afternoon or evening? That seems weird for summer, usually it rains in the afternoon or evening. It does cool down when it storms in summer so thatβs probably why rain is less frequent for the hotter temps which would be in the afternoon. |
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Post by nei on Jan 6, 2019 17:14:32 GMT -5
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Post by nei on Jan 6, 2019 17:28:30 GMT -5
If the cold temps are in the morning, then would it show that precipitation is more likely in the morning than the afternoon or evening? That seems weird for summer, usually it rains in the afternoon or evening. It does cool down when it storms in summer so thatβs probably why rain is less frequent for the hotter temps which would be in the afternoon. It's hard to tell since I'm not separating by time of day; just assumed the coldest temperatures are from morning. But rainy summer afternoons are often cold. In the Rochester graphs, looks like precipitation is uncommon at the coldest temperature, but then common warmer than that. |
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Post by knot on Dec 28, 2019 22:50:39 GMT -5
In winter here, the vast majority of precipitation falls as a result of polar frontsβi.e. cold weather.
That's why the 7Β° C average highs here are cold enough to allow regular falls of snow; oftent heavy snow. Even Khancoban, averaging 11Β° C in mid-winter maxima and 340 m AMSL, receives light snow and/or sleet occasionally (a few times per year).
Contrarywise, in summer, the vast majority falls with thunderstorm activityβi.e. warm weather.
Generally, the higher the precip rate, the faster the temp drop.
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Post by srfoskey on Dec 29, 2019 20:50:19 GMT -5
Brian Brettschneider made maps similar to what you're talking about. I wonder what place has the greatest percentage of precipitation with above normal temperatures in winter.  |
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Post by nei on Nov 23, 2020 22:45:33 GMT -5
Wisconsin stations will have the same general pattern. Warm days are wetter in winter, drier in summer. A western station would be interesting since their winter pattern is different. So would a place that gets lake effect snow, since that only appears when it's cold. Hancock, Michigan is probably the snowiest ASOS station for lake effect.
here's some more. looks like Hancock doesn't have an obvious "lake effect pattern" but does seem like precipitation = warmth in winter as is normal further east. Hard to get precipitation at the very coldest temperatures; as they're from radiational cooling on clear nights  Madison has a peak just around freezing  |
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Post by nei on Nov 23, 2020 22:47:36 GMT -5
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Post by Crunch41 on Nov 23, 2020 23:12:29 GMT -5
Brian Brettschneider made maps similar to what you're talking about. I wonder what place has the greatest percentage of precipitation with above normal temperatures in winter. A small area south of me, on the border between Indiana and Illinois is red in all four seasons.
Nowhere has the dark blue in all seasons, but a few areas have three, including Denver and Phoenix. More blue = more epic climate?
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Post by Crunch41 on Nov 23, 2020 23:26:16 GMT -5
nei thank you for these plots. Hartford definitely has a big cold rain peak, wonder why? Moisture from the ocean maybe? For Madison the most common temperature is just above freezing, and it does seem to be the most common temperature to get "stuck" if there are a few days in a row around the same temperature. Raleigh might have the largest jump between below and above freezing, up there with Hartford. Madison has the same pattern but not as drastic. Denver's winter graph is the opposite, almost no precipitation above freezing. I expected more skew in the temperatures, but it looks about even. San Francisco - I knew it had chilly summers, but didn't realize how little time it actually spends with warm weather. The most common temperature is 56-58 which is lower than every other place except for Stampede Pass. Fall is warmer than summer there, but still not warm.
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Post by segfault1361 on Nov 23, 2020 23:31:07 GMT -5
In Toronto, summer rain is cool (but often very humid/muggy), late fall / winter rain is warm and associated with moist low pressure systems from the south.
Early fall rain is neither warm nor cool.
Spring is the most interesting. We get moisture from the south all the time, but it's a cold rain if the low doesn't advance low enough north for the warm sector. It can instead be very chilly (and 3-5C cooler than northern suburbs) with an east wind off Lake Ontario. If it does advance far enough north it can get pretty warm. It can jump 10C in two hours if the cold east wind off Lake Ontario suddenly switches to southwest wind with the arrival of the warm sector.
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Post by srfoskey on Nov 24, 2020 0:46:52 GMT -5
Brian Brettschneider made maps similar to what you're talking about. I wonder what place has the greatest percentage of precipitation with above normal temperatures in winter. A small area south of me, on the border between Indiana and Illinois is red in all four seasons.
Nowhere has the dark blue in all seasons, but a few areas have three, including Denver and Phoenix. More blue = more epic climate?
One thing about the map tho is that the dark blue is above 75%, whereas the dark red is only below 35%. Another color for below 25% would make it balanced. |
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Post by knot on Nov 24, 2020 0:51:12 GMT -5
Not only does heavy rain decrease max temps here, but also min temps. In fact, the coldest temps here are only ever reached via evaporative cooling events (> 20 mm/hr rain rates, especially if there's snow on the ground).
That's why frost is borderline non-existent here, yet snow is very frequent.
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