Another questionable spotter report

[jdrenken]

Hopefully when the new MPAR comes into full scale deployment these types of questions won't be brought up because the local NWS will look at their system and say yes or no to a report like this.

 

[Mike Bates]

We had this issue about two months ago here in Colorado. NWS was swamped by spotter giving estimated rates per hour. Some weather stations can provide this information but it is where ever the station and the local spotters do not carry weather stations with them that could measure rain.

After discussion with the NWS Severe Weather Coordinator, we changed to reporting measured rain over a period of time 15, 30, or 60 minute intervals. This provided actual measurements and in some cases we reported at 10 minute intervals since there was lots of flooding in the area.

Rainfall rate per hour based on my experience is a very subjective number and there is no good way without instruments to provide good data...I guess I am saying in this case, estimates just to not work unless you have lots of experience reviewing lots of measured cases.

Mike - N7DQ

 

[Lanny Dean]

The 88D doesn't do rain rates either...Title fixed

???? I have noticed that you clearly avoided this and even changed your statement regard the rain rates, what gives???

 

[Steve Miller]

It's going to be funny when everyone on this board reaches the point that they don't want to report because they fear getting ripped apart by their "peers".

 

[Shane Adams]

It's going to be funny when everyone on this board reaches the point that they don't want to report because they fear getting ripped apart by their "peers".

And when it does happen, they can replace the "reports" forum with "how to be a money chaser while pretending it's about the storms".

 

[rdale]

I have noticed that you clearly avoided this and even changed your statement regard the rain rates, what gives???

I haven't avoided anything, nor have I changed my statement. You were wrong when you said the 88D gives out rain rate data. I said that, and Chris backed it up. I'm not sure what you want me to change?

Rain rates are USELESS. This issue has been around for 20+ years, and thankfully there are people that care about the quality of spotter reports and want to do something about it. Look at the SN review section. It's all about quality and making spotter reports the best they can be.

If you don't care about the quality of Skywarn info, that's your right.

But don't get all in a tizzy because there are people who say spotter reports can be improved.

 

[rdale]

It's going to be funny when everyone on this board reaches the point that they don't want to report because they fear getting ripped apart by their "peers".

That would be funny.

 

[Lanny Dean]

I haven't avoided anything, nor have I changed my statement. You were wrong when you said the 88D gives out rain rate data. I said that, and Chris backed it up. I'm not sure what you want me to change?

Rain rates are USELESS. This issue has been around for 20+ years, and thankfully there are people that care about the quality of spotter reports and want to do something about it. Look at the SN review section. It's all about quality and making spotter reports the best they can be.

If you don't care about the quality of Skywarn info, that's your right.

But don't get all in a tizzy because there are people who say spotter reports can be improved.

I am not getting "tizzy" at all, rdale, I was just trying to point out that I do not understand your statement and that IMO you are incorrect regarding the 88D's ability to calculate rainfall rates.
As far as what Chris said:

The 88D precip algorithms do calculate rain/snow rates, but these are used in producing the accumulation products and in external applications, such as the Flash Flood Monitoring Program (FFMP).

That says it all.

Again, I will direct you to a wonderful read that might help?
http://www.srh.noaa.gov/mrx/research/precip/precip.php

If you don't care about the quality of Skywarn info, that's your right.

Where is this coming from? I did not at all mention not caring about Skywarn info. If anything, I believe the request I made for you to change your original post should have been understood as such.

My mother used to tell me that I would run into people who would argue with a fence post.....

 

[rdale]

you are incorrect regarding the 88D's ability to calculate rainfall rates.

You say tomato - I say tomato.

There is no 88D product that shows rainfall rates.
Spotters should not report rainfall rates, as it is useless without other parameters (i.e. timeframe) and it is impossible to estimate.

 

[Patrick Marsh]

The current 88D networks do not measure rainfall rate. The 88D's measure the reflectivity factor and radial velocity. From the radial velocity, spectrum width can be computed as well.

From the reflectivity factor it is possible to "back out" an instantaneous rainfall rate using one of several different formulas depending on the environment. Again, this is not observed by the 88D; it is a post processed field. From the derived rainfall rates it is possible to then to a time integration to generate an estimated rainfall product.

As for rainfall rates, the smaller the time measurement, the more useful the information. Examples:

2" per hour could be composed of:

1. 0.01" per minute for 10 minutes (0.1" total), 0" per minute for 30 minutes (0" total), then 0.095" per minute for 20 minutes (1.9" total); or
2. 0.033" per minute for 60 minutes (2" total); or
3. 0.066" per minute for 30 minutes (2" total, then 0" per minute for 30 minutes (0" total)

All three of those are equivalent to 2" per hour, however at any given moment the rain rate was different. By decreasing the time component of the rate, you give a higher quality report containing more information about current rainfall intensity. However, without including how long that rate continued, it's impossible to know how much rain fell.

With that said, the best report would be to do one of the following:

1. Rain rate of 0.1" per minute for 10 minutes; or
2. Total rainfall of 1" over the last 10 minutes

Both of these reports are equivalent (1" in 10 minutes) and allows the NWS to compute the missing information (total rain in [1] and rain rate in [2]).

 

[Chance Metz]

Here in amhonng county we got about 2 inches from a strom that went through about a hour ago. radar esiamted an inch a hour so I guess this proves that estiamtes are not worth a grain of salt. By the way they storm lasted less then a hour.

 

[Matt Gingery]

Is this about misreports again?? First its Scud Fingers from 20 miles away, now its destruction junkies going overboard on rain totals. Where will it end?? These spotters really need to check themselves before they wreck themselves.

 

[Chance Metz]

I am waiting for a report of 20 inch a hour rainfall rates. Wen that happen I know someone belongs in the nuthouse.

 

[Chris Carter]

Spotters should not report rainfall rates, as it is useless without other parameters (i.e. timeframe) and it is impossible to estimate.

As there is no way of knowing if the rainfaill fluctuated during the storm. So much harder to measure rainfall rates than snow. Anytime i see rainfall rates, i usually see it as a radar indicated rate.

 

[jdrenken]

You say tomato - I say tomato.

There is no 88D product that shows rainfall rates.
Spotters should not report rainfall rates, as it is useless without other parameters (i.e. timeframe) and it is impossible to estimate.

What's this and how does the NWS issues Flash Flood Warnings quoting 88D rainfall rates?