31 May: Late developing storms western TX

1. 31 May: Late developing storms western TX General upslope across Southern Plains produces storms far western TX after 21z with some severe weather Mostly within a small area of Slight Risk Storms were severe with a number of severe hail reports, max = baseball hail HWT focus area was more centered on MI where a Moderate Risk was in place, and these forecasts are not discussed here. Runs examined 1800 UTC: LAPS, STMAS and HRRR. No echoes develop until 2200 UTC in far western TX/eastern NM LAPS and STMAS do not have any echoes forecast (under-forecast), while HRRR has too much 2200 UTC: LAPS and HRRR only. Gradual strengthening of echoes in western TX/eastern NM in general upslope area The HRRR has a pretty good forecast, while LAPS is way under-forecast 0000 UTC: LAPS, STMAS and HRRR. Lots of severe hail reports this period, activity gradually weakens by 0600 UTC. LAPS continues to be way under-forecasting the activity, while STMAS and HRRR are much more active but different, with an edge to the HRRR.

2. 31 May: Reports and Convective Outlook Moderate Risk in MI, separate Slight Risk over western TX (see below) HWT focus area (for 00z runs) is centered on MI Strong cold front associated with the Moderate Risk Slight Risk area in western TX just a general upslope area Opportunity to compare runs beginning at 18z/31 May Forecast comparison (no initial storms) for LAPS/STMAS, then later storms in progress Storm Prediction Center (SPC) Day 1 Outlook issued at 1601z on 31 May SPC severe weather reports for 31 May

3. Tuesday 31 May 2011 - overview 1800 UTC 31 May – Visible/radar image with observations 2100 UTC 31 May – Visible/radar image with obs. 0000 UTC 1 June – Visible image with radar and obs. 0600 UTC 1 June – radar and observations

4. 1800 UTC 31 May 2011 runs – Analysis comparisons (composite reflectivity) HRRR 1800 UTC 31 May – Visible image combined with radar and obs(cold front in blue) Not much going on at 1800 UTC, just some very weak echoes in MO ahead of the cold front. Note that the cold front is strongest north of MO. LAPS HW T2 STMAS

5. 1800 UTC 31 May 2011 runs – 1-h forecast valid 1900 UTC (composite reflectivity) HRRR 1900 UTC 31 May – Visible image combined with radar and obs(cold front in blue) It looks like STMAS is over-developing small cells that are really just cu/tcu. This is seen in another case as well. Not sure what is going on with that. The southern half of the cold front is really now just a quasi-stationary wind shift boundary that is slowly weakening. LAPS HW T2 STMAS

6. 1800 UTC 31 May 2011 runs – 2-h forecast valid 2000 UTC (composite reflectivity) HRRR 2000 UTC 31 May – Visible image combined with radar and obs(cold front in blue) Would have to look at this more closely to see how strong these tiny echoes are in STMAS; maybe they are quite weak? The HRRR is a little hot with too strong an echo just sw of STL. Otherwise, still nothing over the western TX High Plains. LAPS HW T2 STMAS

7. 1800 UTC 31 May 2011 runs – 3-h forecast valid 2100 UTC (composite reflectivity) HRRR 2100 UTC 31 May – Visible image combined with radar and obs(cold front in blue) STMAS and to a lesser extent LAPS have too much echo in far sw TX. The HRRR remains too active ahead of the cold front in MO, where no echoes have yet formed. Otherwise, dropped the southern end of the “cold front” since it is really washed out in the southern portion. LAPS HW T2 STMAS

8. 1800 UTC 31 May 2011 runs – 4-h forecast valid 2200 UTC (composite reflectivity) HRRR 2200 UTC 31 May – Visible image combined with radar and obs(cold front in blue) No echoes yet. LAPS and STMAS have nothing except for far sw TX. The HRRR remains too active with cells from MO to northern TX. LAPS HW T2 STMAS

9. 1800 UTC 31 May 2011 runs – 5-h forecast valid 2300 UTC (composite reflectivity) HRRR 2300 UTC 31 May – Visible image combined with radar and obs(cold front in blue) The only echoes are way back in sw TX & se NM. LAPS and STMAS have nothing except for far s TX in STMAS. The HRRR remains too active with cells from MO to northern TX but does have some cells in far sw TX. LAPS HW T2 STMAS

10. 1800 UTC 31 May 2011 runs – 6-h forecast valid 0000 UTC/1 June (composite reflectivity) HRRR 0000 UTC 1 June – Visible image combined with radar and obs(cold front in blue) The general theme of this forecast cycle continues, with the HRRR far more active than LAPS (with no echoes) and STMAS (with just one cell far southern TX, but also far more tiny weak echoes. LAPS HW T2 STMAS

11. Summary of 1800 UTC 31 May forecast cycle • Not a lot of development during this time frame except for far sw TX and ne NM along dry line. • Cold front overall weakens with time in domain (from STL south) with no real development on it. • The HRRR has too much development along the cold front and/or old frontal boundary where none occurs. LAPS & STMAS have nothing here. • But the HRRR does correctly develop storms in far sw TX/eastern NM whereas LAPS and STMAS have nothing here either. • STMAS has a lot of tiny echoes that are probably very weak; are these trying to represent tcu?

12. 2200 UTC 31 May forecast cycle • Only LAPS HWT2 and HRRR available for this cycle (no STMAS). • There is really no surface-based forcing feature • The cold front is pretty much washed out south of central MO • There is no real dryline, in fact more se upslope flow into western TX and eastern NM • Main action is storms gradually forming in western TX and eastern NM and these storms result in a number of large hail reports.

13. Tuesday 31 May 2011 – overview for 22z run cycle 2200 UTC 31 May – Visible/radar image with observations 0000 UTC 1 June – Visible/radar image with obs. 0200 UTC 1 June – radar and observations 0400 UTC 1 June – radar and observations

14. 2200 UTC 31 May 2011 runs – Analyses (composite reflectivity) HRRR 2200 UTC 31 May – Visible image combined with radar and obs. Nothing going on yet and nothing in the model analyses either. LAPS HW T2

15. 2200 UTC 31 May 2011 runs – 1-h forecast valid 2300 UTC/31 May (composite reflectivity) HRRR 2300 UTC 31 May – Visible image combined with radar and obs. Both models have an echo or 2 developing in far western TX and see this in the observations. Not sure what to make of the weak elongated echo at the western boundary of the LAPS regional run. LAPS HW T2

16. 2200 UTC 31 May 2011 runs – 2-h forecast valid 0000 UTC/1 June (composite reflectivity) HRRR 0000 UTC 1 June – Visible image combined with radar and obs. Both models have some development in far western TX and see this in the observations, but the HRRR has more and while not exactly where the echoes are forming, this is better than LAPS which does not have enough echoes in the forecast. LAPS HW T2

17. 2200 UTC 31 May 2011 runs – 3-h forecast valid 0100 UTC/1 June (composite reflectivity) HRRR 0100 UTC 1 June – Visible image combined with radar and obs. Similar to the last hour, the HRRR has a little too much development but LAPS does not have enough. LAPS HW T2

18. 2200 UTC 31 May 2011 runs – 4-h forecast valid 0200 UTC/1 June (composite reflectivity) HRRR 0200 UTC 1 June – Visible image combined with radar and obs. Now the differences between the forecasts are growing, with the HRRR actually having a pretty good forecast while LAPS hardly has any echoes at all. LAPS HW T2

19. 2200 UTC 31 May 2011 runs – 5-h forecast valid 0300 UTC/1 June (composite reflectivity) HRRR 0300 UTC 1 June – Visible image combined with radar and obs. The same differences between the forecasts seen at hour 4, with the HRRR having a good forecast while LAPS not predicting any echoes. LAPS HW T2

20. 2200 UTC 31 May 2011 runs – 6-h forecast valid 0400 UTC/1 June (composite reflectivity) HRRR 0400 UTC 1 June – Visible image combined with radar and obs. The same differences between the forecasts seen at hours 4 and 5, the HRRR has a good forecast while LAPS not predicting any echoes. LAPS HW T2

21. Summary of 2200 UTC 31 May forecast cycle • Slowly increasing development western TX/eastern NM • No real forcing feature, just easterly flow onto the High Plains • The HRRR has a pretty good forecast, while LAPS does not have anything in this area. • Overall summary: way under-forecast by LAPS, fairly good forecast by HRRR.

22. 0000 UTC 1 June forecast cycle • Compare LAPS HWT2 and HRRR for this cycle. • An interesting time, with echoes developing more by 02z (end of the LAPS forecast cycle). • Main forcing feature is the cold front moving across western NE/KS. • Also a dryline further south, but no echoes form here through 03z.

23. 1 June 2011 – overview for 00z run cycle 0000 UTC 1 June – Visible/radar image with observations 0200 UTC 1 June – Radarimage with observations 0400 UTC 1 June – Radarimage with observations 0600 UTC 1 June – radar and observations

24. 0000 UTC 1 June 2011 runs – Analysis comparisons (composite reflectivity) HRRR 0000 UTC 1 June – Visible image combined with radar and observations LAPS and STMAS have more detail in the analyses, but the HRRR has the area of cells pretty well analyzed also. These storms are already producing severe-sized hail. LAPS HW T2 STMAS

25. 0000 UTC 1 June 2011 runs – 1-h forecasts valid 0100 UTC (composite reflectivity) HRRR 0100 UTC 1 June – radar image and observations All 3 models are doing a good job at this point. Storms continue to produce severe-sized hail. LAPS HW T2 STMAS

26. 0000 UTC 1 June 2011 runs – 2-h forecasts valid 0200 UTC (composite reflectivity) HRRR 0200 UTC 1 June – radar image and observations Now the model forecasts begin to diverge. There are new storms in eastern NM (yellow arrow) and these are producing baseball-sized hail, with other severe reports in western TX. None of the models captures the NM storms. LAPS is losing the storms in far sw TX, but STMAS still has these. The HRRR is doing best with the storm moving eastward (white arrow), although it is too fast moving it eastward. LAPS HW T2 STMAS

27. 0000 UTC 1 June 2011 runs – 3-h forecasts valid 0300 UTC (composite reflectivity) HRRR 0300 UTC 1 June – radar image and observations There are more severe reports with the storms. The HRRR remains the only model capturing is the cells moving eastward (white arrow) but still remains too fast. LAPS continues to be way to weak, with STMAS better. Interestingly STMAS has only one cell in eastern NM and it is just where the HRRR has a cell, but all models really miss this activity. LAPS HW T2 STMAS

28. 0000 UTC 1 June 2011 runs – 4-h forecasts valid 0400 UTC (composite reflectivity) HRRR 0400 UTC 1 June – radar image and observations The spread in the forecasts is growing; LAPS is WAY too weak with nothing at this point, while STAMAS is quite different from the HRRR. STMAS is too organized with the TX Panhandle complex; in reality cells have collapsed here with growth of new cells to the west and north (not to the east as in STMAS). STMAS does have more cells in eastern NM than the HRRR at this time. LAPS HW T2 STMAS

29. 0000 UTC 1 June 2011 runs – 5-h forecasts valid 0500 UTC (composite reflectivity) HRRR 0500 UTC 1 June – radar image and observations Most of the severe hail is now from the New Mexico cells, and of the 3 models STMAS has more activity in eastern NM. STMAS still has too much organization with the TX system compared to what is going on, although there is some indication of a bit of an arc of convection in this area (yellow arrows). The HRRR remains best with the northern TX Panhandle storms though some flaws as well. LAPS HW T2 STMAS

30. 0000 UTC 1 June 2011 runs – 6-h forecasts valid 0600 UTC (composite reflectivity) HRRR 0600 UTC 1 June – radar image and observations Still a few severe hail reports, but cell strength overall is decreasing. Again, some indication of an arc of outflow moving to the se out of the TX Panhandle, with some resemblance to the arc seen in STMAS, although echoes are too strong in STMAS. The HRRR is weakening cells overall too much, but interestingly has the strongest cell pretty close to where it is seen (yellow arrow). LAPS HW T2 STMAS

31. Summary of 0000 UTC 1 June forecast cycle • This is a period of some pretty strong cells in western TX/far eastern NM. • A number of severe hail reports from these, including up to baseball sized hail. • The runs start out quite similar, capturing the activity, but then diverge. • LAPS loses all the cells by 4-h into the forecast. • STMAS tends to over-organize the convection in the TX Panhandle into an MCS-looking complex with an organized arc of outflow. Radar suggests such an arc may have formed but cells are much weaker than in the forecast. • STMAS does capture some of the cells in eastern NM. • The HRRR does best at capturing some of the cells at the northern end of the activity, and also has a little bit in eastern NM. • Overall summary: LAPS does the poorest job, STMAS is different from the HRRR and both have some issues, but probably would need to give an edge to the HRRR overall.