UPDATE ON TAMDAR IMPACT ON RUC FORECASTS

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UPDATE ON TAMDAR IMPACT ON RUC FORECASTS
RECENT TAMDAR/RAOB COMPARISONS
Ed Szoke, Brian Jamison, Bill Moninger, Stan
Benjamin, Randy Collander, and Tracy Smith
NOAA/ESRL Global Systems Division
Joint
collaboration with the Cooperative Institute for
Research in the Atmosphere, Colorado State
University, Fort Collins, CO
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Outline

• Using the high-resolution TAMDAR data available
  since 30 Mar 06...
• Examine impact on RUC forecasts
• Subjective evaluation concentrating on
  short-range precipitation forecasts
• Focus on 6-h accumulated precipitation forecasts
  ending at 0000 and 0600 UTC (but other fields
  also examined)
• For 1800 UTC runs compare forecast soundings with
  observed soundings
• Models used identical RUC-20 km runs with and
  without TAMDAR
• Compare TAMDAR sounding quality and detail
• TAMDAR soundings compared to each other
• TAMDAR soundings compared to nearby RAOBs
• Emphasis on the kinds of sharp structures that
  can be resolved with the higher resolution TAMDAR
  data

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30 Mar 2100 UTC Deepening storm with severe
weather ND snow
System is at north/west edge of TAMDAR to within
network (in WI/IL). In ND rain changing to
snow. Will examine precipitation fields and
CAPE and helicity.
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Display of the TAMDAR coverage from 2100 UTC 30
Mar to 0000 UTC 31 Mar
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TAMDAR/RAOB comparisons for 0000 UTC 31 Mar 06
Minneapolis
Good overall agreement with the sounding and
all TAMDARs nicely resolve the dry layer
centered at 800 mb
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TAMDAR/RAOB comparisons for 0000 UTC 31 Mar 06
Minneapolis
The most variability in this set is from the
flight heading off to the southeast.
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AMDAR/RAOB comparisons for 0000 UTC 31 Mar 06
Minneapolis
For comparison to TAMDAR, here are a few
AMDAR temperature profiles compared to the MSP
RAOB
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TAMDAR/RAOB comparisons for 0000 UTC 31 Mar 06
Peoria, Illinois
Here we do see a difference between the
ascent and descent soundings (that track in
pretty much the same location and not far off
in time), with a better match to the RAOB for
the TAMDAR ascent.
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7 April 0000 UTC Deepening storm with severe
weather R
High risk severe wx day NE to eastern KS. Also
heavy rains in band e-w across MSP. Will
examine precipitation fields and CAPE and
helicity.
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Comparison of 6-h RUC precipitation forecasts
with and without TAMDAR for runs initialized at
1800 UTC on 6 April 06.
Without TAMDAR
With TAMDAR
gt0.25
gt0.5
gt1.0
gt0.10
Two main differences are highlighted 1) In
MN/nrn IA with more precip in TAMDAR run 2)
More of a line of precip in eastern NE in the
TAMDAR run
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Observed 6h precipitation ending 0000 UTC 7 April
06
TAMDAR run looks better for having more precip
near MSP. Similarly, in eastern KS more
precip in the TAMDAR run is also better.
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Comparison of 6-h RUC CAPE and CIN forecasts with
and without TAMDAR for runs initialized at 1800
UTC on 6 April 06.
Without TAMDAR
With TAMDAR
Not a lot of differences in the CAPE fields
although more CIN across IL in the TAMDAR run.
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Analyzed CAPE from the NAM valid 0000 UTC 7 April
06
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Comparison of 6-h RUC Helicity forecasts with and
without TAMDAR for runs initialized at 1800 UTC
on 6 April 06.
Without TAMDAR
With TAMDAR
A few differences are seen (northern IA, eastern
KY). Analysis (next) perhaps favors TAMDAR
run slightly....
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Analyzed SREH from the NAM valid 0000 UTC 7 April
06
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6 April 1800 UTC Storm intensifying with severe
weather developing
Next we'll examine some TAMDAR/ RAOB
comparisons for 1200 UTC and for the special
soundings launched at 1800 UTC for MSP and LZK
(Little Rock, AR).
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TAMDAR/RAOB comparisons for 1200 UTC 6 April 06
Minneapolis
Good agreement between the two descent TAMDARs

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TAMDAR/RAOB comparisons for 1200 UTC 6 April 06
Minneapolis
Same with this set
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TAMDAR/RAOB comparisons for 1200 UTC 6 April 06
Minneapolis
Also good agreement with a descent/ascent pair.

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TAMDAR/RAOB comparisons for 1200 UTC 6 April 06
Minneapolis
The main disagreement is found for the 2
TAMDARs heading south, but note these are 80
min apart in time.
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TAMDAR/RAOB comparisons for Minneapolis time
series
Nice depiction of the effect of sustained lift
on the strong inversion centered near 850 mb.
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TAMDAR/RAOB comparisons for 1200 UTC 6 April 06
Little Rock/Nashville
Good overall agreement with the sounding and
all TAMDARs.
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TAMDAR/RAOB comparisons for 1800 UTC 6 April 06
Little Rock/Nashville
Note how well the sharp inversion is resolved
near 900 mb, and the very sharp dry layer above
this.
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TAMDAR/RAOB comparisons for 1200 UTC 6 April 06
Little Rock/Nashville
Similar good resolution with this set of
soundings a little while later.
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TAMDAR coverage for 1500-1800 UTC 6 April 06
Coverage doesn't go quite to Little Rock but is
close.
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The next day 7 April 2100 UTC - Severe weather
moves into eastern/southern part of TAMDAR network
Another high risk day, this time shifted east to
western TN/KY. By 2100 UTC 4 tornado watch
boxes were already in place.
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Southern TAMDAR coverage for 7 April 06
BNA
Little Rock
Jackson
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Comparison of 6-h RUC precipitation forecasts
with and without TAMDAR for runs initialized at
1800 UTC on 7 April 06.
With TAMDAR
Without TAMDAR
gt0.25
gt0.5
gt1.0
gt0.10
More precipitation is produced by the run with
TAMDAR across southern IN into OH. The run
without TAMDAR has more precip in nw AL.
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Observed 6h precipitation ending 0000 UTC 8 April
06
TAMDAR run looks better for having more precip
in IN/OH
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TAMDAR/RAOB comparisons for 1200 UTC 7 Apr 06
Jackson, MS
Sharp dry layer above the inversion is really
captured well.
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TAMDAR/RAOB comparisons for 1500-1800 UTC 7 Apr
06 Jackson, MS
Sharp moisture changes between 700 to 750 mb are
shown in special RAOBs and TAMDARs. Also, good
agreement with the moisture profile down low.
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TAMDAR time series for Memphis leading up to
initial tornadoes
Nice time series showing both the removal of the
early morning cap near 850 mb and then the
development of a much more moist and unstable
layer in the lowest 100 mb.
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Summary

• RUC forecasts with and without TAMDAR showed
  some differences
• Generally did not find cases as dramatic as
  those shown at AMS
• But the differences that were found usually
  favored the TAMDAR runs
• For other cases recently (not shown) differences
  were minor
• Sounding comparisons...
• Showed 3 different strong severe weather days
• Overall consistency between TAMDAR soundings is
  fairly good
• Higher resolution data is able to nicely capture
  very sharp moist/dry layers
• TAMDAR soundings continue to show value for
  forecast applications
• Nice Memphis time series leading up to the
  initial TN tornadoes last Friday