# Presentation: 515472

## 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

## 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/](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

## 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)

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

## Verification areas.

- Objective scoring is
- done on both areas,
- for this study we will
- show some scores
- for the inner (blue) box .

## 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.

## 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.

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

## RUC forecasts from the 4 October 2005 1800 UTC runs

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

-    6-h total precipitation ending 0000 UTC 5 October

## 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.

## Same comparison but for Peoria, Illinois.  The RUC run with TAMDAR 

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

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

- Heavy precip continues
- in the same areas

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

## RUC forecasts from the 5 October 2005 0000 UTC runs

- 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.

-    6-h total precipitation ending 0600 UTC 5 October

**No TAMDAR**

**With TAMDAR**

## Case 2: 20 January 2006 – 2100 UTC Surface analyses and reflectivity

##              This event impacted an extensive area with winter precipitation

-              This event impacted an extensive area with winter precipitation
-   Power outages from portions of Iowa to Illinois where snow became freezing rain

## Observed snowfall ending 

- 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

## Most of the snow fell in the 12-h period ending at 0600 UTC, so can 

- 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.

## Sounding comparison as before: RUC 6-h forecasts with (labeled dev2) and 

- 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.

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

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

## Precipitation comparison.  NPVU estimated precipitation for 6-h ending 

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

##     RUC forecasts from the 21 January 2006 0000 UTC runs

- The RUC run with TAMDAR did a better job of forecasting more precipitation in central
- Illinois.

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

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

## Case 3: This was a high-impact event with huge area of winter weather 

- 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

##     RUC forecasts from the 13 February 2007 1800 UTC runs

- 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

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

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

## Why the similar forecasts in the snow area?  Maybe a lack of TAMDAR

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

- 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.

## Note the similar forecast soundings for Pittsburgh (6-h forecasts ending

- at 0000 UTC 14 February with the RAOB).

## 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

## Perplexing comparison for Detroit, however, where there was abundant

- TAMDAR for this day.

## Case 4: 22 March 2007 – 0000 UTC Surface analyses and reflectivity

-                Strong spring storm with lots of severe weather

## 22 March 2007 – 0300 UTC Surface analyses and reflectivity

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

##      RUC forecasts from the 22 March 2007 0000 UTC runs

- 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

**No TAMDAR**

**With TAMDAR**

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

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

## Objective scores for the two RUC forecasts for the small verification area

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

- and for the 6-h period ending at 0600 UTC/22 March 2007

## Case 5: 21 June 2007 – 2100 UTC Surface analyses and reflectivity

-                Strong convection with many reports of severe weather

## 22 June 2007 – 0000 UTC Surface analyses and reflectivity

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

##      RUC forecasts from the 21 June 2007 1800 UTC runs

- 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

**No TAMDAR**

**With TAMDAR**

## Sounding comparison for 6-h forecasts for RUC with TAMDAR (dev2) vs RUC without 

- 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

## Sounding comparison for 6-h forecasts for RUC with TAMDAR (dev2) vs RUC without 

- 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

## 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

## Summary

-  W**hen 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**