[Ncep.list.idp.mrms.users] [awips2dev] MRMS

Fri Jun 22 14:54:59 UTC 2018

Jeffery, I'll definitely agree with you that for where the most precip
fell, MRMS was on the hot side (mrms-radar-only.PNG). The gauge-adjusted
product doesn't seem to have really changed much of that
(mrms-gauge-adj.PNG), though looking at the diagnostic provided by MRMS
(the *Gauge Influence Index*, viewable on MRMS Op Product Viewer site)
there doesn't appear to be *any *gauge correction going on anywhere right
now or in the past 24 hours for any precip accumulation timeframe. (*I
think the issue of no gauge adjustment happening is an actual problem with
MRMS, so I'm looping the MRMS Users email list on this thread*.)

Compared to the RLX radar (STA, STA-hires, and STP images), the MRMS data
certainly has a broader area of 3"+ and a fairly broad area of 4"+ compared
to the legacy and dual-pol estimates. So even compared to other precip
estimates, MRMS seems on the high side. Why the MRMS estimates are running
too hot? As I said in my first message, it is probably a case of
mis-classification of the type of rainfall occurring - maybe using the
tropical algorithm when it should be using a standard convection one.
Looking through the Reflectivity Cube (see the Op Product Viewer), during
the most intense parts of the rain yesterday MRMS certainly seems to have
ingested your radar and surrounding radars correctly with no gross errors
obvious to me. The MRMS Ops folks on the Users listserv may be able to
diagnose what's going on in this case better than I can.

We can't expect MRMS to be perfect, just like we know the radar-based
legacy and dual-pol estimates are going to have errors for various reasons.
For what it's worth, on our recent heavy rainfall event last weekend MRMS
absolutely *nailed *the precip estimation with no strong high or low bias -
it got the maximum amounts just about as spot-on as you can expect... and
that was with our primary radar down! (MPX's radar provided sufficient
radar data to help fill in the gap to our radar being down, but at a higher
elevation than DLH would have been scanning if it were up.)

If there is a noticeable problem with MRMS data, this should be reported to
the MRMS/NCEP folks so they can investigate (I think
*ncep.list.idp.mrms.users at noaa.gov
<ncep.list.idp.mrms.users at noaa.gov>* is the best choice but someone else
chime in there's a better option!)

-Joe

MRMS Op Product Viewer: https://mrms.nssl.noaa.gov/qvs/product_viewer.php
WRH Wx and Hazard Viewer: https://www.wrh.noaa.gov/map/

On Fri, Jun 22, 2018 at 9:19 AM, Timothy Humphrey - NOAA Federal <
timothy.humphrey at noaa.gov> wrote:

> Over the past several days here at the Lake Charles office, we also
> noticed that the MRMS-QPE Radar only was running quite hot compared to our
> individual radars' estimates and surface observations. Comparing this
> morning's 12Z 72 hour MRMS estimates to a variety of observation sites
> including ASOS/ALERT/COOP confirmed this with a few comparisons listed
> below:
>
> JYDT2: 7.91"  MRMS: 10.33"
> JYET2: 7.76"  MRMS: 13.18"
> JYGT2: 6.38"  MRMS: 7.48"
> KBPT:  5.79"  MRMS: 8.11"
> ORNT2: 4.91" MRMS: 6.06"
>
> Based on our experience, the QPE-Radar Only seemed that it was running
> much hotter compared to previous events and we were also curious what might
> have been causing such a large difference. Our concern is that these large
> differences could result in derived FLASH products being less reliable for
> warning decision making.
>
> On Fri, Jun 22, 2018 at 8:54 AM, Jeffrey Hovis - NOAA Federal <
> jeffrey.hovis at noaa.gov> wrote:
>
>> Jack,
>>
>> It was approximately 10 miles from the area of heaviest rainfall to the
>> radar site (RLX) .  As you indicated, COOPS are not included in the MRMS
>> data.
>>
>> I just wanted to see what might have caused the large difference in
>> rainfall amounts.
>>
>> We issued a Flash Flood Warning based on the MRMS data.  It was a good
>> warning as we did have lots of flash flooding reports.
>>
>> Jeff
>>
>> On Fri, Jun 22, 2018 at 9:42 AM, Jack Settelmaier - NOAA Federal <
>> jack.settelmaier at noaa.gov> wrote:
>>
>>> I may be mistaken, but I'm guessing MRMS does not use COOP data in its
>>> algorithms, as it's more real-time (not QCd too much) and mostly just uses
>>> radar data.  How far from the nearest radar was the site?
>>>
>>> https://training.weather.gov/wdtd/courses/MRMS/index.php
>>>
>>> On Fri, Jun 22, 2018 at 8:10 AM, Jeffrey Hovis - NOAA Federal <
>>> jeffrey.hovis at noaa.gov> wrote:
>>>
>>>> All,
>>>>
>>>> I just wanted to give you an update.  When I came into the office this
>>>> morning, I checked the MRMS 24 hour QPE amount against our COOPs,  We had a
>>>> COOP that was located in the area of heavy rain.  MRMS indicated that
>>>> rainfall amounts between 3.54 and 5.11 inches near the location of our
>>>> COOP.  Our COOP actually reported 2.20 inches of rain.
>>>> This is a very big difference.
>>>>
>>>> There was Flash Flooding in the area.  However if the MRMS data had
>>>> verified, the flooding would likely have been much worse.
>>>>
>>>> Jeff
>>>>
>>>>
>>>> On Thu, Jun 21, 2018 at 3:23 PM, Jeffrey S. Hovis <
>>>> jeffrey.hovis at noaa.gov> wrote:
>>>>
>>>>> All,
>>>>>
>>>>> We are currently experiencing an area of heavy rain north of our
>>>>> office.  The MRMS QPE-Radar Only product is indicating as much as 3.42
>>>>> inches of rain had fallen over a location in the past 3 hours.  However,
>>>>> none of the surrounding radars are indicating that much rain has fallen.
>>>>> In fact, the highest 3 hour rainfall amount based on radar that I have
>>>>> found is closer to 2.5 inches.
>>>>>
>>>>> What could be causing this difference between these two products?
>>>>>
>>>>> Jeffrey Hovis
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Jack Settelmaier
>>> Digital Techniques Meteorologist
>>> NOAA/NWS, Southern Region HQ
>>> Fort Worth, TX
>>> Work: 682 703 3685
>>>
>>
>>
>
>
> --
> Tim Humphrey
>
> Meteorologist
> National Weather Service
> Lake Charles, Louisiana
> 337.477.5285
>
> Follow us on Facebook <http://www.facebook.com/NWSLakeCharles>, Twitter
> <http://www.twitter.com/NWSLakeCharles> and Youtube
> <http://www.youtube.com/user/NWSLakeCharles>
>
>

-- 
*Joseph J. Moore*
Meteorologist | WFO Duluth Social Media & IDSS Program Leader | Open Source
GIS Evangelist
NOAA/National Weather Service Duluth, MN
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