ams 22 nd conference on weather analysis and forecasting/18 th conference on numerical weather...

AMS 22nd Conference on Weather Analysis and Forecasting/18th Conference on Numerical Weather Prediction - 2007 – Park City, Utah

1June 26, 2007

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


2June 26, 2007

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


3June 26, 2007

Flights into a numberof smaller airportsin addition to the 3 main hubs

And at lower altitudes (generallyto 20 kft or so)

Typical TAMDAR coverage (shown here 1000 UTC/18 Oct – 0400 UTC/19 Oct 06)


4June 26, 2007

Verification areas.Objective scoring isdone on both areas,for this study we will show some scoresfor the inner (blue) box .


5June 26, 2007

Still one of the most dramatic cases...4-5 Oct2005: heavy precip in the Upper Midwest.

Flooding reported inMinnesota to northernWisconsin.

Case 1: 4 October 2005 – 2100 UTC Surface analyses and reflectivity


6June 26, 2007

Very sharp cut off to theprecip in WIand a huge gradient witha 2-3” max.

NPVU estimated precipitation for 6-h ending 0000 UTC 5 October 2005


7June 26, 2007

Both runs forecast too much precip in southern half of Wisconsin, but the RUC run withTAMDAR correctly forecasts more precip (small spots of >1.00”) across the northern half of the state.

RUC forecasts from the 4 October 2005 1800 UTC runs 6-h total precipitation ending 0000 UTC 5 October


8June 26, 2007

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.


9June 26, 2007

Same comparison but for Peoria, Illinois. The RUC run with TAMDAR is closer to the RAOB especially at and below 700 mb.


10June 26, 2007

Heavy precip continuesin the same areas

Case 1/part 2: 5 October 2005 – 0300 UTC Surface analyses and reflectivity


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NPVU estimated precipitation for 6-h ending 0600 UTC 5 October 2005


12June 26, 2007

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 heavyprecip.

RUC forecasts from the 5 October 2005 0000 UTC runs 6-h total precipitation ending 0600 UTC 5 October

No TAMDAR With TAMDAR


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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


15June 26, 2007

About 5” of snow at O'Hare Airport in Chicago, but a foot just to the northwest.

Observed snowfall ending ~1200 UTC 21 January 2006


16June 26, 2007

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.


17June 26, 2007

Sounding comparison as before: RUC 6-h forecasts with (labeled dev2) and without (labeled dev, in black) TAMDAR, compared to the RAOB for GreenBay (green) at 0000 UTC 21 Jan 06. dev2 is closer to the observed sounding.


18June 26, 2007

Similar comparison for Peoria, Illinois. Not much difference in these forecasts


19June 26, 2007

Precipitation comparison. NPVU estimated precipitation for 6-h ending 0600 UTC 21 January 2006


20June 26, 2007

The RUC run with TAMDAR did a better job of forecasting more precipitation in centralIllinois.

RUC forecasts from the 21 January 2006 0000 UTC runs 6-h total precipitation ending 0600 UTC 21 January


21June 26, 2007

Case 3: 13 February 2007 – 1800 UTC Surface analyses and reflectivity


22June 26, 2007

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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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.

RUC forecasts from the 13 February 2007 1800 UTC runs 6-h total precipitation ending 0000 UTC 14 February


24June 26, 2007

NPVU estimated precipitation for 6-h ending 0000 UTC 14 February 2007


25June 26, 2007

TAMDAR coverage for the period 1500to 1800 UTC on 13 February 2007

Why the similar forecasts in the snow area? Maybe a lack of TAMDARbecause of flights canceled by the storm!

TAMDAR coverage for the period 1500to 1800 UTC on 15 February 2007 when conditions were dry in the region.


26June 26, 2007

Note the similar forecast soundings for Pittsburgh (6-h forecasts endingat 0000 UTC 14 February with the RAOB).


27June 26, 2007

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


28June 26, 2007

Perplexing comparison for Detroit, however, where there was abundantTAMDAR for this day.


29June 26, 2007

Case 4: 22 March 2007 – 0000 UTC Surface analyses and reflectivity Strong spring storm with lots of severe weather


30June 26, 2007

22 March 2007 – 0300 UTC Surface analyses and reflectivity


31June 26, 2007

SPC severe reports for 24-h ending 1200 UTC/22 March 2007


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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.

RUC forecasts from the 22 March 2007 0000 UTC runs 6-h total precipitation ending 0600 UTC 22 March



33June 26, 2007

NPVU estimated precipitation for 6-h ending 0600 UTC 22 March 2007


34June 26, 2007

The statistics agree with the subjective assessment favoring the RUC run that uses the TAMDAR data.

Objective scores for the two RUC forecasts for the small verification areaand for the 6-h period ending at 0600 UTC/22 March 2007


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Case 5: 21 June 2007 – 2100 UTC Surface analyses and reflectivity Strong convection with many reports of severe weather


36June 26, 2007

22 June 2007 – 0000 UTC Surface analyses and reflectivity


37June 26, 2007

SPC severe reports for 24-h ending 1200 UTC/22 June 2007


38June 26, 2007

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.

RUC forecasts from the 21 June 2007 1800 UTC runs 6-h total precipitation ending 0000 UTC 22 June



39June 26, 2007

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


40June 26, 2007

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


41June 26, 2007

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 TAMDARThreshold #obs # forecast #hits EQTS Bias #forecast #hits EQTS Bias 0.01 45924 72109 32735 0.310 1.570 72715 32839 0.309 1.5830.10 12385 17175 7218 0.305 1.387 16695 7033 0.301 1.3480.25 4901 4962 2055 0.257 1.012 4852 2078 0.265 0.9900.50 1596 1140 367 0.153 0.714 1111 391 0.167 0.6961.00 240 80 35 0.123 0.333 77 40 0.144 0.3211.50 72 8 4 0.053 0.111 11 3 0.037 0.1532.00 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 1.6440.10 15730 23262 8249 0.246 1.479 23217 8122 0.241 1.4760.25 6716 7499 2371 0.192 1.117 7458 2378 0.193 1.1100.50 2505 1586 536 0.148 0.633 1632 542 0.148 0.6511.00 531 115 57 0.097 0.217 130 66 0.111 0.2451.50 126 17 5 0.036 0.135 16 5 0.036 0.1272.00 34 4 0 0.000 0.118 5 0 0.000 0.147


42June 26, 2007

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

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