IMPACT OF TAMDAR DATA ON RUC SHORTRANGE FORECASTS

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IMPACT OF TAMDAR DATA ON RUC SHORT-RANGE
FORECASTS
Ed Szoke, Randy Collander, Brian Jamison,
Tracy Smith Stan Benjamin, Bill Moninger, Tom
Schlatter, and Barry Schwartz NOAA/Earth
Systems Research Laboratory Global Systems
Division
Joint collaboration with the
Cooperative Institute for Research in the
Atmosphere, Colorado State University, Fort
Collins, CO Cooperative Institute for Research
in Environmental Sciences (CIRES), Boulder,
Colorado
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Overview

• TAMDAR soundings have been shown to be useful
  for forecasting
• Talks at the last SLS Conference and previous
  Annual Meetings
• WFO Green Bay helps maintain the official NOAA
  TAMDAR web page at http//www.crh.noaa.gov/tamdar/
  
• In this talk we focus on the impact on NWP
• Evaluation of RUC precipitation forecasts for
  runs with and without TAMDAR for significant
  weather events
• Mostly a subjective evaluation, but objective
  scoring for 2007 cases
• Procedure
• RUC is run at 20-km horizontal grid resolution
• Identical runs made hourly to 6 h, and out to 24
  h every 3 h
• Here we will concentrate on shorter term (usually
  first 6 h to 12 h) forecasts initialized when
  TAMDAR data is most plentiful
• 1800 UTC and 0000 UTC initialization times
  generally used

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Typical TAMDAR coverage (shown here 1000 UTC/18
Oct 0400 UTC/19 Oct 06)
Flights into a number of smaller airports in
addition to the 3 main hubs And at lower
altitudes (generally to 20 kft or so)
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Verification areas. Objective scoring is done on
both areas, for this study we will show some
scores for the inner (blue) box .
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Case 1 4 October 2005 2100 UTC Surface
analyses and reflectivity
Still one of the most dramatic cases...4-5
Oct 2005 heavy precip in the Upper
Midwest. Flooding reported in Minnesota to
northern Wisconsin.
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NPVU estimated precipitation for 6-h ending 0000
UTC 5 October 2005
Very sharp cut off to the precip in WI and a
huge gradient with a 2-3 max.
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RUC forecasts from the 4 October 2005 1800 UTC
runs 6-h total precipitation ending 0000 UTC 5
October
Both runs forecast too much precip in southern
half of Wisconsin, but the RUC run with TAMDAR
correctly forecasts more precip (small spots of
gt1.00) across the northern half of the state.
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Sounding comparison RUC 6-h forecasts with
(labeled dev2) and without (labeled dev1, in
black) TAMDAR, compared to the RAOB for Detroit
(green) at 0000 UTC 5 Oct 05. Incorrect dry
layer in the dev1 forecast.
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Same comparison but for Peoria, Illinois. The
RUC run with TAMDAR is closer to the RAOB
especially at and below 700 mb.
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Case 1/part 2 5 October 2005 0300 UTC Surface
analyses and reflectivity
Heavy precip continues in the same areas
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NPVU estimated precipitation for 6-h ending 0600
UTC 5 October 2005
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RUC forecasts from the 5 October 2005 0000 UTC
runs 6-h total precipitation ending 0600 UTC 5
October
No TAMDAR
With TAMDAR
For this period the RUC run that used the TAMDAR
data is a much better forecast with a very sharp
cut off to the precipitation in Wisconsin and a
better location for the heavy precip.
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Case 2 20 January 2006 2100 UTC Surface
analyses and reflectivity
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This event impacted an extensive
area with winter precipitation Power outages
from portions of Iowa to Illinois where snow
became freezing rain
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Observed snowfall ending 1200 UTC 21 January
2006
About 5 of snow at O'Hare Airport in Chicago,
but a foot just to the northwest.
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Most of the snow fell in the 12-h period ending
at 0600 UTC, so can compare the amounts observed
to the RUC 12-h snowfall forecasts below.
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Sounding comparison as before RUC 6-h forecasts
with (labeled dev2) and without (labeled dev, in
black) TAMDAR, compared to the RAOB for Green Bay
(green) at 0000 UTC 21 Jan 06. dev2 is closer to
the observed sounding.
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Similar comparison for Peoria, Illinois. Not
much difference in these forecasts
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Precipitation comparison. NPVU estimated
precipitation for 6-h ending
0600 UTC 21 January 2006
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RUC forecasts from the 21 January 2006 0000
UTC runs 6-h total precipitation ending
0600 UTC 21 January
The RUC run with TAMDAR did a better job of
forecasting more precipitation in
central Illinois.
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Case 3 13 February 2007 1800 UTC Surface
analyses and reflectivity
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Case 3 This was a high-impact event with huge
area of winter weather watches and warnings and
even a blizzard warning, plus severe weather
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RUC forecasts from the 13 February 2007 1800
UTC runs 6-h total precipitation ending
0000 UTC 14 February
Forecasts are pretty close in the snow area (as
verified by the objective scoring), but there
are some differences farther to the south in the
convection ahead of the trailing cold front.
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NPVU estimated precipitation for 6-h ending 0000
UTC 14 February 2007
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Why the similar forecasts in the snow area?
Maybe a lack of TAMDAR because of flights
canceled by the storm!
TAMDAR coverage for the period 1500 to 1800 UTC
on 15 February 2007 when conditions were dry in
the region.
TAMDAR coverage for the period 1500 to 1800 UTC
on 13 February 2007
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Note the similar forecast soundings for
Pittsburgh (6-h forecasts ending at 0000 UTC 14
February with the RAOB).
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Not the case for this same sounding comparison at
Nashville, Tennessee. Overall, the sounding
from the run using TAMDAR (dev2) is closer to the
RAOB. The RUC run with TAMDAR had a better
forecast in the central Tennessee
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Perplexing comparison for Detroit, however, where
there was abundant TAMDAR for this day.
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Case 4 22 March 2007 0000 UTC Surface analyses
and reflectivity Strong spring
storm with lots of severe weather
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22 March 2007 0300 UTC Surface analyses and
reflectivity
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SPC severe reports for 24-h ending 1200 UTC/22
March 2007
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RUC forecasts from the 22 March 2007 0000
UTC runs 6-h total precipitation ending
0600 UTC 22 March
No TAMDAR
With TAMDAR
Some differences are seen these are outlined in
the forecasts The RUC forecast that uses TAMDAR
is generally better except within the orange
oval area, where no precipitation fell.
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NPVU estimated precipitation for 6-h ending 0600
UTC 22 March 2007
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Objective scores for the two RUC forecasts for
the small verification area and for the 6-h
period ending at 0600 UTC/22 March 2007
The statistics agree with the subjective
assessment favoring the RUC run that uses the
TAMDAR data.
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Case 5 21 June 2007 2100 UTC Surface analyses
and reflectivity Strong convection
with many reports of severe weather
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22 June 2007 0000 UTC Surface analyses and
reflectivity
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SPC severe reports for 24-h ending 1200 UTC/22
June 2007
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RUC forecasts from the 21 June 2007 1800 UTC
runs 6-h total precipitation ending 0000
UTC 22 June
No TAMDAR
With TAMDAR
Main difference is the precipitation in IL and IN
predicted by the RUC run without TAMDAR
compared to almost nothing in the run with
TAMDAR. Verification showed that no
precipitation fell in the IL/IN area.
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Sounding comparison for 6-h forecasts for RUC
with TAMDAR (dev2) vs RUC without TAMDAR (dev)
compared to the DVN RAOB at 0000 UTC 22 June 2007
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Sounding comparison for 6-h forecasts for RUC
with TAMDAR (dev2) vs RUC without TAMDAR (dev)
compared to the ILX RAOB at 0000 UTC 22 June 2007
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Precipitation scores for 2007 broken down by
season
Scores for 6-h forecasts from 1800 UTC
runs Winter season (1 Jan-31 Mar) (56 cases)
RUC run without TAMDAR RUC run
with TAMDAR Threshold obs forecast hits
EQTS Bias forecast hits EQTS Bias
0.01 45924 72109 32735 0.310
1.570 72715 32839 0.309 1.583 0.10
12385 17175 7218 0.305 1.387
16695 7033 0.301 1.348 0.25
4901 4962 2055 0.257 1.012
4852 2078 0.265 0.990 0.50 1596
1140 367 0.153 0.714 1111
391 0.167 0.696 1.00 240
80 35 0.123 0.333 77
40 0.144 0.321 1.50 72
8 4 0.053 0.111
11 3 0.037 0.153 2.00
26 0 0 0.000 0.000
0 0 0.000
0.000 Summer/convective season (1 Apr-20 June)
(62 cases) Threshold obs forecast hits
EQTS Bias forecast hits EQTS Bias
0.01 51102 82566 35944 0.293
1.616 84024 36110 0.289 1.644 0.10
15730 23262 8249 0.246 1.479
23217 8122 0.241 1.476 0.25
6716 7499 2371 0.192 1.117
7458 2378 0.193 1.110 0.50 2505
1586 536 0.148 0.633 1632
542 0.148 0.651 1.00 531
115 57 0.097 0.217 130
66 0.111 0.245 1.50 126
17 5 0.036 0.135
16 5 0.036 0.127 2.00
34 4 0 0.000 0.118
5 0 0.000 0.147
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Summary

• When we began to examine precipitation forecasts
  in late 2005 were impressed by the 4-5 October
  2005 case with significantly better forecasts by
  the RUC run that used TAMDAR
• But that remains our best case
• More typically, we see much smaller impacts
• These tend to favor the RUC run that uses TAMDAR,
  but not always
• And sometimes mixed...forecast better in some
  spots but not in others
• Objective scoring of the precipitation forecasts
  that began in 2007 agrees with our overall
  subjective impression
• Longer-term statistics show relatively small
  differences generally favoring the RUC run that
  uses TAMDAR
• But on a case by case basis can see greater
  differences in the scores