Roman White
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« Reply #15 on: February 04, 2009, 12:42:10 pm » |
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Something is going on with the weather right now. The pressure is quickly falling: 762mmHg (max) yesterday, 760mmHg at midnight, 749mmHg right now. My barometer is going mad, blinking with all possible downward arrows. I can observe as it falls another 0.1mm each several minutes. I will post the graph later. The temperature was min -5C at night, now it is almost stable around -1C. If the forecast is correct, it will be max +5C on Thu-Fri and max +8...+14C on weekend. Is it spring or what?! The most interesting - precipitation. Nothing at night, then gentle snow started to fall at 12PM, very soon it became moderate. By that moment I was outside trying to capture some snow crystals in macro. http://astrophotoweather.smfforfree4.com/index.php/topic,1002.msg6579.html#msg6579But soon (at 2PM) the precipitation became hard to describe. The snow changed into insuficient hail (or maybe it wasn't hail) - tiny transparent grains 0.5-2mm in diameter. Next it became more like sleet ... when I went home I saw a definite hail (dense, with grains ~5mm in dia.) through my window. But now it is more like rain...
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« Last Edit: February 04, 2009, 12:51:42 pm by Roman White »
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brianb
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« Reply #16 on: February 04, 2009, 01:39:31 pm » |
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The snow changed into insuficient hail (or maybe it wasn't hail) - tiny transparent grains 0.5-2mm in diameter. "Soft hail" or "graupel" - either is much more common than proper snow here! The difference is that soft hail starts as snow that partially melts as it falls through a warm layer on the way down, graupel is rain that falls into a cold air layer & freezes solid. Neither tends to last very long as the precipitation changes the active air layer.
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Roman White
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« Reply #17 on: February 04, 2009, 02:34:17 pm » |
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The difference is that soft hail starts as snow that partially melts as it falls through a warm layer on the way down (...)
...It was melting, but... graupel is rain that falls into a cold air layer & freezes solid.
...possibly more like this - I was wondered to see very transparent grains (they usually less transparent in summer, and usually white in winter,// I mean hail). Now I think it was a rain that freezed somewhere higher but it was again close to melting at the ground level. A hour ago we had here freezing rain (the first one which I saw this winter) - it was very short and not powerful, but a thin layer of ice is present on the both vertical & horizontal (clear of snow) surfaces. Now there is no noticeable precipitation, but the pressure is falling.
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martinastro
Martin Mc Kenna
Global Moderator
Hero Member
Posts: 5182
Maghera, N. Ireland
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« Reply #18 on: February 04, 2009, 05:57:08 pm » |
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Do you get any rime Roman? Brian, I have annotated the anvil image to describe in more detail the various forms I seen at the time. Looks like more snow this evening and tonight.
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Roman White
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« Reply #19 on: February 05, 2009, 07:58:32 am » |
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Do you get any rime Roman?
Absolutely no. Yesterday the temperature went above zero, and now in the morning (8-10AM) there is dense fog (visibility ~200m). Here is the pressure graph for last 7 days... looks like a significant drop... but no stormy weather here, even no serious precipitation (yesterday's total 4mm). I need to consult with meteorologists... Looks like more snow this evening and tonight.
Hmm, it is going now vice versa: the UK gets a bit of winter with snow & frosts and here the winter seems to go away (maybe just for a while) - high temperatures (up to +10C) are forecasted, along with powerful rain on Sun-Mon.
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SkyWatcher 130/900mm EQ3, Bresser 76/700mm, 20x90 bino. and other, Olympus SP-550UZ Eclipse & comet chaser, occultation & meteor observer Poltava Astronomy Portal
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brianb
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« Reply #20 on: February 05, 2009, 08:36:09 am » |
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Brian, I have annotated the anvil image to describe in more detail the various forms I seen at the time. Thanks, very useful. Looks like more snow this evening and tonight. Hmmm, I did think twice before driving down to Belfast for the IAA meeting, but needn't have worried much. A couple of millimetres of very slushy snow between Antrim & Ballymoney (at 2200-2245) which was not settling on the (gritted) road at all. Here at Portballintrae, just drizzle.
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