Test Case from AWT-2011 domain: 2 August runs

• Goal: trying to see why all the ensemble runs kill all the convection midway through the 6-h forecast cycle• Real-time runs examined

• 12z EWP3 and STMAS_CI runs out to 6-h

• EWP3 run• The “box of doom” with omega is shown

• But alone this would not explain the end of the reflectivity by ~3-h into the forecast• The temperature forecast shows warming through the entire atmosphere but

highest near 500 mb.• Increases with time but begins only 15-min into the forecast• Would certainly be sufficient to cap the atmosphere

• For most of the atmosphere it looks like drying also occurs

• So warming and some drying appears to cap the atmosphere, but why does the warming occur?

• STMAS_CI run• Looks reasonable, does a decent job with the echoes.

Comparison of 500 mb temperatures at 12z on 2 August 2011

RUC analysis of 500 mb temperatures

The analyses of 500 mb temperature are similar and compare well to the RUC analysis and observations.

EWP3 analysis

STMAS_CI analysis STMAS_CI_CYC analysis

Comparison of 500 mb temperatures at 16z on 2 August 2011

RUC analysis of 500 mb temperatures

The 4-h forecasts of 500 mb temperature from the STMAS runs are similar and compare well to the RUC analysis, while EWP3 is way too warm.

EWP3 4-h forecast

STMAS_CI 4-h forecast STMAS_CI_CYC 4-h forecast

Closer look at the EWP3 500 mb temperature forecasts from the 12z on 2 August run

EWP3 analysis of 500 mb temperatures

The erroneous 500 mb temperature warming in the EWP3 run gradually moves across the domain.

EWP3 1-h forecast

EWP3 2-h forecast EWP3 4-h forecast

EWP3 wind omega forecasts from the 12z on 2 August run

EWP3 analysis of omega

The erroneous 500 mb omega in the EWP3 run appears to move in from the boundaries and emanate from convection over WI.

EWP3 1-h forecast

EWP3 2-h forecast EWP3 4-h forecast

Closer look the omega forecasts- Cross-section location is shown below

EWP3 wind omega forecasts from the 12z on 2 August run – 15 min interval output for first hour

EWP3 analysis of omega

The erroneous omega seems to

grow fairly gradually.

EWP3 15-min forecast

EWP3 30-min forecast EWP3 45-min forecast

EWP3 wind omega forecasts from the 12z on 2 August run – 1-h interval output for hours 1 to 4

EWP3 1-h forecast

There is a dramatic increase in vertical

velocity (sinking largely in this cross-

section) between hours 1 and 2, then the scale seems to break down into

smaller horizontal scales but still large values (more waves

if you will, sort of get this same

interpretation from the horizontal

omega plots at 500 mb shown earlier).

EWP3 2-h forecast

EWP3 3-h forecast EWP3 4-h forecast

STMAS wind omega forecasts from the 12z on 2 August run – 1-h interval output for hours 0 to 3

Analysis

The vertical velocity from the STMAS_CI

run looks reasonable.

1-h forecast

2-h forecast 3-h forecast

EWP3/STMAS_CI wind omega forecast comparison for hours 4 and 6 from the 12z forecast run

STMAS_CI 4-h forecast

There is a tendency perhaps for the

erroneous vertical velocities in EWP3 to weaken by 6-h. The STMAS_CI run looks

reasonable and is shown to compare to the EWP3 run.

STMAS_CI 6-h forecast

EWP3 4-h forecast EWP3 6-h forecast

EWP3/STMAS_CI sounding comparison for hours 0 to 6 from the 12z forecast runanalysis The two runs are compared. The

white arrows point to the STMAS_CI run (fatter arrow with

wider head points to the temperature, the other white arrow to the dew point curve

(dotted line, harder to see). The yellow arrows do the same for

the EWP3 run.

The soundings are very close at the analysis time. By 1-h into the

forecast the EWP3 run is considerably warmer, with the

greatest warming at 500 mb, but really spread through pretty

much the entire atmosphere. Note how the spread in

temperature between the two runs grows with time. It appears that the EWP3 run (white arrows)

is consistently more moist (at least at this point (grid point

25/25).

1-h forecast

4-h forecast 6-h forecast

EWP3 sounding comparison for the first hour from the 12z forecast runanalysis

In this sequence we look at the sounding at point 25/25 from the

EWP3 run only, at 15-min intervals for the first hour. The

fatter yellow arrow points to the temperature profile and the

thinner yellow arrow points to the dewpoint curve. The off-

white vertical arrow is held at the 400 mb temperature from the

analysis for reference. Using this point as a reference shows the

gradual warming that begins at 15-min into the run.

15-min forecast

30-mon forecast 45-min forecast

EWP3/STMAS_CI cross-section temperature forecast comparison from the 12z forecast run

EWP3 analysis

Here is another look at the temperature forecasts using the same cross-section as earlier. For reference the horizontal white line is at 500

mb, and the yellow line at 700 mb in each figure. You can see that the temperature at these two

levels does not change much at all in the STMAS_CI run, but warms in the EWP3 run.

The initial temperatures (analysis) are close but not identical, particularly in the lowest 100-200

mb or so.

EWP3 4-h forecast EWP3 6-h forecast

STMAS_CI 6-h forecastSTMAS_CI analysis

EWP3

Analysis

The warming shown in the previous slides would explain why the echoes disappear in EWP3, eventually the domain is severely capped. STMAS looks good.

1-h forecast 2-h forecastST

MAS

_CI

NO

WRA

D

1200 UTC 1300 UTC 1400 UTC

EWP3

3-h forecast

The echoes are pretty much gone by 3-h into the EWP3 forecast. General forecast from STMAS_CI looks good, misses the New England cells.

4-h forecast 6-h forecastST

MAS

_CI

NO

WRA

D

1500 UTC 1600 UTC 1800 UTC