Author Topic: High rain rate  (Read 418 times)

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Offline WxLover16

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High rain rate
« on: July 21, 2018, 04:32:55 PM »
After coming home from work today I noticed my VP2 had recorded a 20.57"/hr rain rate. At work, (the same general conditions that occured at my house), it almost looked like a hurricane coming through with lots of incredibly heavy rain, small hail and high winds. My question, has anyone else ever measured a rain rate that high? When I saw that value, I was shocked.
Davis Wireless VP2 SHT31 24hr 24CFM FARS

Offline SLOweather

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Re: High rain rate
« Reply #1 on: July 21, 2018, 05:07:11 PM »
Reducing that down, that would equal 2 tips of the rain bucket in 1.75 seconds. That's certainly not out of the question, although rare. There also could have been a momentary plug in the rain cone.
 
FWIW, the fastest my VP2 will tip is 1 every 0.4 seconds or so, which would be a theoretical rain rate of about 90"/hour.

Offline ocala

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Re: High rain rate
« Reply #2 on: July 21, 2018, 06:08:07 PM »
One time. Not sure if it was accurate though but that's what the software recorded.
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« Last Edit: July 21, 2018, 06:10:33 PM by ocala »

Online Mattk

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Re: High rain rate
« Reply #3 on: July 21, 2018, 06:39:07 PM »
That is possible and may have occurred for a very short period within the rain event as the rain rate is a computed tipping value over time.

Offline SnowHiker

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Re: High rain rate
« Reply #4 on: July 21, 2018, 08:36:23 PM »
The rate at which, and when, the hail melted may have skewed the reading.  The small hail could also have temporarily plugged the bucket so that all the rain came through at once when it melted.

Offline Dj1225

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Re: High rain rate
« Reply #5 on: July 21, 2018, 10:09:09 PM »
During Hurricane Isaac in 2012 my VP2 recorded a rain rate over 20" I attributed that to the high wind speeds, but now I'm wondering maybe it wasn't.

Offline StretchCT

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Re: High rain rate
« Reply #6 on: August 08, 2018, 09:07:08 PM »
I was going to ask what the maximum rate was. We had rate of 8.23 this evening which is the highest this year. Made me wonder what the highest rate possible to measure is for the Davis VP2. Im going with 25 per OTMs post. But if anyone knows of a higher rate, please chime in. 
First Torn. warn May 15. 5 confirmed in WCT/HV
First STW:  May 3rd (no T-storm imby)
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First 80+ day: May 2, 89.2
First 70+ day:  Feb 22, 77
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Seasonal snow - normal 44"

2017-2018 74.5"
2016-17: 58"
2015-16:  33.5"
2014-2015 57"
2013-2014 58.25"
2012-2013 64.5"
2011-2012  30.5"
2010-2011 79"
2009-2010  49"

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Offline SLOweather

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Re: High rain rate
« Reply #7 on: August 09, 2018, 01:59:28 PM »
I just set up an experiment with a cabled VP2 and ISS, and dumped a quart of water into the rain cone.

The highest rain rate I saw was 82.29"/hour, which is close to my calculation of 90"/hour in the second post of this thread. Manually flipping the tipper faster doesn't generate a higher rain rate, so that limit is probably fixed in the firmware, either in the ISS or the console. That's probable an error-catching thing, since my 90"/hour calculation was based on timing tips with a surplus of water in the cone. The diameter of the rain cone orifice and the head of water in the cone would seem to be the physical limiting factors.

I was going to ask what the maximum rate was. We had rate of 8.23 this evening which is the highest this year. Made me wonder what the highest rate possible to measure is for the Davis VP2. Im going with 25 per OTMs post. But if anyone knows of a higher rate, please chime in.

Offline dendrite

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Re: High rain rate
« Reply #8 on: August 09, 2018, 02:37:11 PM »
I just set up an experiment with a cabled VP2 and ISS, and dumped a quart of water into the rain cone.

The highest rain rate I saw was 82.29"/hour, which is close to my calculation of 90"/hour in the second post of this thread. Manually flipping the tipper faster doesn't generate a higher rain rate, so that limit is probably fixed in the firmware, either in the ISS or the console. That's probable an error-catching thing, since my 90"/hour calculation was based on timing tips with a surplus of water in the cone. The diameter of the rain cone orifice and the head of water in the cone would seem to be the physical limiting factors.

I was going to ask what the maximum rate was. We had rate of 8.23” this evening which is the highest this year. Made me wonder what the highest rate possible to measure is for the Davis VP2. I’m going with 25” per OTMs post. But if anyone knows of a higher rate, please chime in.
(82.29"/hr)/60min = 1.37"/min

Looks like Davis has themselves covered considering the record 1 minute precipitation is 1.00" at Unionville, MD (although I question that observation).

I think my best 1 minute rainfall is 0.16" and I had back-to-back minutes of that. I want to say it resulted in a rate of a little under 14"/hr. It looked like the sky was falling as it was. I can't imagine what 1" in a minute would look like.

 

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