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Snow & Convective Reports Feb 2nd-8th 2009

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Author Topic: Snow & Convective Reports Feb 2nd-8th 2009  (Read 1467 times)
Roman White
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« Reply #15 on: February 04, 2009, 12:42:10 pm »

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?!   Shocked

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.  Roll Eyes
http://astrophotoweather.smfforfree4.com/index.php/topic,1002.msg6579.html#msg6579

But 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...
« Last Edit: February 04, 2009, 12:51:42 pm by Roman White » Report Spam   Logged

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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 »

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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« Reply #18 on: February 04, 2009, 05:57:08 pm »

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 »

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...  Huh

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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« 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.

Quote
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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