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Line of convection working through Omaha’s CWA. Initial CI hits 50-60% at the northern end of a line of cumulus at 1825Z.
At 1830Z CI probs increase to 80-90%. Weak reflectivity is evident at this point.
At 1855Z cumulus further south along the line shows CI at 60-70%. The northern portion of the line has developed into a strong shower/minimal thunderstorm.
At 1915Z the CI probs have verified – the line of developing cumulus is now a line of showers and thunderstorms.
Scott Rudge.
Models agree on low pressure lifting NE or NNE form eastern NE into MN through the afternoon. As of 19Z, all of IA was in the warm sector, with a cold front expected to cross form the west during the afternoon/early evening. the 12 Z NAM puts the front near DSM at 0Z; the 12Z GFS still has it just to the west.
Earlier convection is exiting stage right, and some clearing is taking place in western IA. We’re getting rapid scan GOES data today, so we’ll be monitoring the boundary structures that are evident on the imagery. Below is the CI product superimposed over the visible image…we’re seeing 67% probability of development of 35 dbz returns in the next hour or so along these boundaries.
As this activity develops and moves eastward, Nearcast forecast theta-e difference by 22Z would indicate pockets of instability (in an area of closer to neutral stability) moving in over the next few hours from the west. Will be interesting to see how this translates into storm coverage, or even storm mode, as the front moves in.
And in the time it’s taken me to work on the above…we’re seeing gradually developing convection marching to the NE/IA border in an area marked by the CI earlier. Only low to moderate hits on ProbSevere (45% or less by 1930Z).
Do have LAPS data today, but a late realignment of the domain has the model playing catch-up. Will comment later.
Wx briefing indicated increasing chances of UH tracks in our area, especially in our northeastern counties…watching for supercells with tornadoes and hail…and some severe wind
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The images above are 2.5km LAPS taken at 1700z and 1715z, respectively. The third image is just zoomed in to the area of interest.
Station observations were overlayed onto LAPS model data to compare the model performance. A general bias of about 1-3 degrees existed in the LAPS data through the region. However, there were more notable departures in portions of Iowa and Illinois. The second image illustrates two of these locations in West Central Illinois, just east of Quincy and southeast of Macomb. In these areas, the model data departed from the station plots by about 8 degrees.
Jared Maples
The final day of week 1 is already in progress and a complicated forecast it is (due primary to overnight convection). Our initial thought was to play in the moderate risk associated with the low pressure and warm front, but with the presence of ongoing convection and the desire to utilize many of the GOESR products meant for the pre-CI and CI environment we decided to shake it up. One group of forecasters (Rudge/Bickford) remains in the moderate risk in Des Moines (DMX) CWA while the other pair (Maples / Thoren) is operating in the Wichita (ICT) CWA and looking for possible development ahead of the surface cold front/dryline. While some convection is already ongiong in the north and eastern DMX CWA, expectation is that supercell storms (and tornadoes) will develop in the area clearing farther west. Severe activity in the ICT CWA is a bit more uncertain and timing is likely a later this afternoon and evening if it were to occur.
Super-Rapid Scan (1 min imagery) is in it’s first day of operations. The animated gif (click to show animation) below shows the Cu development along the cold front into the ICT domain and clearing in the western DMX domain.
-K. Calhoun, Week 1 Coordinator
CI product not very excited about convective develop (0-2hrs) with cu forming along frontal boundary at ~19z.
The forecasters were able to complete something more of a stress test on Wednesday, May 7th. We started the day in both the Norman (OUN) and Cheyenne (CYS) county warning areas (CWA) with the CYS team transitioning to the North Platte (LBF) CWA before the end of the operational period. Both teams put together forecast discussions before transitioning to warning operations.
Almost all of the products were evaluated. Blog posts specifically examined the CI algorithm, overshooting tops, pGLM and lightning jump, and ProbSevere.
-K. Calhoun, Week 1 Coordinator
EWP Status for 8 May 2014: 12:30-8:30 pm Shift
A second day in a row of significant severe weather is possible for EWP operations tomorrow. A number of possibilities for locations exist extending from Minnesota / Iowa associated with the surface low pressure and cold front to farther south through Missouri and Arkansas in the warm sector. Severe storms including supercells will be possible during our shift.
Exact timing, nature, and location tomorrow may be somewhat contingent upon convection overnight tonight.
We will begin in the DevLab at 12:30 pm and move to the HWT at 1pm for the map discussion.
-K. Calhoun, Week 1 Coordinator
Storms initiated across far western OK along and near a Theta E Difference boundary.
At 20Z
At 21Z
At 22Z
At 23Z
At 2330Z – Henrietta Storm quickly developed a hook with a report of a rapidly rotating wall cloud.
Scott Rudge.
The line of storms that has produced a TOR in NE CO and SVRs in our CYS area has shown a slow weakening trend. Many of these cells are now outside the CO total lightning coverage area so we can not view this.
Of interest is an area of stronger storms with multiple SVR and TOR form NE CO into the North Platte, NE CWA…
These cells developed in a much more favorable environment…heating into the 60s and 70s today. Areas under the “old” convection in WY/CO are in the 40s and 50s.
Also of interest:
The deeper Nearcast instability is now mainly centered in NE. Best threat for further convective development and more strong to severe storms looks like it will be mainly focused just to the east (and to some extent southeast into NE CO) of the CYS CWA for the duration of the afternoon/evening.
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I am watching a void area on the radar (bottom image) to see if there is any additional development northeast of Denver. CI values have picked up a bit (top image) in this general vicinity with some 70% probabilities. In that last few minutes probabilities have dropped. Waiting to see the outcome…
Update…Radar did not fill in at all here. The earlier probabilities did not translate into any additional rainfall/development.
Jared Maples
