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As we waited agonizingly for convection to initiate in our Central Oklahoma Domain (and as of this writing, we are still without storms), we were paid a visit by Don Berchoff, Director of the NWS OS&T.
Our discussion with Mr. Berchoff included:
the need to continue improvements in Convective Initiation (both sensor and model based)
using multi-sensor blending for more holistic storm interrogation
his thoughts on the coming of AWIPS2 and the utility for extensibility
the need for improved analysis and visualization tools in light of the 12 fold increase in data flow
“Fortunately” the weather “cooperated” with us and everyone in the room was able to engage in the discussion.
We had Kevin D. Jessica and Bill forecast our area and issue an AFD. We have decided for the sake if getting “clean” CI and OUN WRF activities, we are focusing on the OUN area.
2355Z Update: Although OUN-WRF continues to generate well defined supercells east of dryline across central Oklahoma, confidence very low due to cooling boundary layer. Dryline is just beginning a shift westward so will need to watch it for just a little while longer. 19/0100Z.
OUN-WRF, since 18z run, has consistently shown signal for convective development just west of OKC metro. Embedded supercells, with southern flank 2-5km updraft helicities 200+ m2/s2 and deviant motions. 20-21z runs want to bring supercell through Norman 23-2330z with southern flank of this storm shifting south and turning right toward Ada. Model has been too eager to develop convection, but depiction of central Oklahoma impacts continues.
Brief convective element over western Major county and weak echoes across southwest Oklahoma from wildfire. Will continue to monitor CI products and trends of ounwrf. kbrown 2215z
Morning surface analysis shows surface low pressure over the northern TX panhandle, with a warm front extending ESE across northern OK and multiple drylines…one over western TX with dewpoints in the 20s behind it, another over western OK separating air with dewpoints in the 40s to the west and lower 60s to the east. Aloft, the 12Z NAM indicates mid level energy ejecting from the western closed low, with a mid level shortwave moving into southeast CO and southwest KS late in the day, with a weaker southern extension moving into western OK…while the northern TX low intensifes and retrogrades into northeast NM. NAM forecast soundings also show an 800 hPa capping inversion eroding late this afternoon over western OK.
With the eastern dryline already into western OK and a little farther east than the NAM forecast, think best chance for convective initiation will be over a narrow corridor in west central OK, beginning about 21Z-22Z, especially where low level convergence will be maximized near the intersection of the dryline and warm front just northwest of OKC. This plus strong veering wind profiles and SBCAPE values up to 2500 J/kg support idea of isolated surface-rooted supercells capable of producing large hail and tornadoes during this time, becoming elevated later this evening as they move east of OKC where the cap should hold. The 14Z HRRR and 12Z SPC WRF also lend support to this idea.
A much more conditional severe threat exists farther northwest into southeast CO and southwest KS north of the warm front, where lift will be better but instability more elevated in nature as the cap holds. Farther east across eastern OK, models (especially the OUN/SPC WRF) generate waa-induced showers along and north of the warm front, but instability is meager and do not expect CI algorithms to perform as well in this area.
Taking a look at high resolution simulated reflectivity, the RUC HRRR has been consistent in its past few runs of a lone supercell initiating and then propagating east. The NSSL WRF is similiar in this idea, though generates several training supercells. Both are in agreement for an area North and west of Norman. The 15Z OUN WRF was consistent with the 0z SPC 4 km WRF in not generating convective activity…and keeping things confined to weak echoes east of OKC. Now, a look at the 16z OUN WRF is now suggesting supercellular convective initiation similiar to the NSSL WRF. It indicates, Max column hail values in excess of 40 kg/m2, Updraft helicity in the 2-5 km layer indicates in excess of 300 m2/s2, and we are now seeing convective initiation from OUN WRF reflectivity. Timing of convective initation looks to be in the 21-23z time frame. The image below is the 16z OUN WRF model simulated reflectivity forecast at 23z, the first run to initiate convection over NW Oklahoma. Note also the model places updraft helicity in the correct conceptual model location, with the max hail slightly removed. Max column hail (integrated graupel) values greater than 40 kg/m2 and Updraft helicity in the 2-5 km layer in excess of 200 m2/s2 are indicative of strong mesocyclones, with is consistent with the high CAPE and strong low and mid level shear environment.
OUN WRF 7 hr forecast of Simulated Reflectivity (img), Max Column Hail (black), and Updraft Helicity (red)
Therefore, it looks at this time with the plethora of data around OUN that this will be our area of focus this after to test the convective initiation products and to monitor the progresssion of the OUN WRF and other hi-res models, despite additional convective activity possible in SE Colorado.
Ongoing thunderstorms in the Mid Atlantic may serve as a possible alternative location in addition to SE Colorado, should convective activity fail to materialize in the southern plains. MUCAPE 500-1000 J/kg, effective bulk shear 30-40 kt there, and cold pool aloft with 500 hPa temperatures -18C to -20C are supportive of locally severe storms from the Delmarva northwest into southwest PA and WV…with the main threat large hail. Low LCL’s and localized/marginal 0-1km SREH of 100 m^2/s^2 also suggest brief tornado potential in new storms via stretching of rotating updrafts.
Around 2330z we switched from the LWX area to BOU where storms have developed and become severe. There have been reports of a ‘landspout’ tornado near 00z.
Bill and Jessica have mentioned the utility of the updraft field (Merged W Composite) as being an interesting tool for landspout-type environments.
It should be noted that compared to the updraft field looked quite “off” (incorrect) with the storms in the DC domain, but look much better in the Floater (BOU) domain. Perhaps the 3DVAR we are using is better “tuned” for a supercell environment and the sub-severe storms in the DC area provided a bit more of a challenge.
We will operate for another hour or so and then begin surveys.
Today we are focusing on the Sterling/Roanoke WFOs as per our morning AFD and the SPC Day 1. We are keeping an eye in Eastern CO as a secondary target per the coordination with the EFP CI Desk:
As the day continues, we have dropped the Roanoke CWA and have everyone on LWX:
Widespread cumulus fields forming across central eastern VA and UAHCI products capturing this much better than CIMMS in this case, which is a very moist, weakly unstable, but uncapped environment (almost tropical). While most new CI IDs are very scattered to isold in nature, now beginning to see some banding or clustering, which actually matches very well with at least one 4km WRF (12Z run for SPC…see second image above), and will be watching to see if the IDing of this banding of CI zones within otherwise wideapread cu field helps to identify where stronger storms could soon be forming in this kind of environment.
Convection ongoing across Carolinas into Virginia this morning, and convection is expected to continue and intensify this afternoon given some clearing in warm sector and minimal cap. Nearly saturated environment, low-cape/moderate shear environment will result in strong and possibly severe storms. Although damaging wind gusts will be primary concern, low-lcl environment will keep threat of brief/weak tornadoes with initial development of convection primarily over eastern Virginia into eastern North Carolina where low-level cape/stretching potential will exist. Warm front extending sw-ne across northern portions of Virginia will need to be monitored as well with conentrated low-level shear. CI satellite detection possible early in the event before cirrus canopy becomes an issue. Hi-res models forecast banded convection near cold core and initiation of bands with CI detection may prove useful where higher impact areas will evolve. Already some more obvious clusters of CI detection using UAH product are highlighting areas in srn VA/nrn NC where new 12Z SPC 4km WRF is fcstg clusters of convection near short wave to develop early afternoon. CI products may continue to be useful to help identify where these potential severe clusters/bands may develop within the wider scattered shallower convection expected to develop. Value of 3dvar may prove useful as well where low-level vort and updraft fields can help warning forecasters concentrate on regions where low-level cape/shear are maximized. Good opportunity to experiment with utility of many 3DVAR products with shallower convection. Same with MRMS products. In addition, some of the nearcast differential theta-e/PW products indicating severe potential through mid to late afternoon over central VA shifting NW into northwestern VA…consistent with local WRFs and SPC WRF ideas.
High plains convection will be possible near developing dryline across eastern Colorado/western Kansas. CI detection will be useful late this afternoon and early this evening as it may take a while for CI once cu develops. Although shear will be increasing through the day, moisture availability will be a concern for more than LP type supercells, especially as storm move off of higher terrain.
Warning ops – our feeling is that initial warning ops, perhaps through at least 21z, should be centered on mid-atlantic region with the option of shifting west to Colorado eastern plains and western Kansas after 21z for possible initiation of isolated/scattered supercells. Greatest value of satellite CI detection and 3dvar fields may be most useful over eastern ops area, although CI detection along with OUN WRF output could be utilized out west. Expecting mainly a hail threat with the LP-type storms in the Plains, and evaluation of some of the MRMS products would be helpful as well.
Forecasters are finishing their surveys on the DRT case. When they are done, we will spend some time discussing their first look at the products and have some Q&A. Comments folow…
Thoughts on training vs DRT case:
Steve – Would like to have more background but also have the chance for an in-depth look, but given the time time constraints this worked. Essentially, would like more time for background AND data analysis.
Kevin D – will now look back at the handbook after having some idea of the usable values.
Kevin B. – procedures preset would have been very helpful to jump into the analysis more quickly.
Bill – more of a chance to see relationship between base data and experimental.
Jessica – would like to have seen something other than a slam dunk case.
Initial thoughts on using experimental data for the first time:
Kevin B – “misplaced” downdraft max to SE of storm E of Henessey (2216 Z). Illustrates confusion of the max/min composite W can have to operational forecaster. If we were able to browse levels, this might be a bit easier to use/grasp. We may try using WDSSII a bit more to illustrate this.
We have completed the orientation briefings for the day and each of the participants is working through the DRT Case (19 May 2010). This is the first taste that the forecasters are getting with the data. We have encouraged the forecasters to explore ways to blend the data that they have available to them.
Jessica has captured a screenshot of using a 4-panel display which several forecasters have migrated to:
