Severe Weather Discussion for April 26, 2016. Issued: 04/25/2016

Highlights:

– Significant severe weather event is possible on Tuesday across central and eastern Oklahoma. Primary threats are tornadoes, destructive hail to softball size, and winds to 85mph.

– Severe thunderstorms are also possible Friday across parts of the state.

Discussion:

Little change to prior forecast. Models are in agreement that a closed low will evolve across Colorado by Tuesday morning as a shortwave trof dives into the base of the larger trof and ejects east-northeast on Tuesday. The timing for this is late Tuesday afternoon into the evening across Oklahoma. However, before this occurs, impressive mid/upper level winds will spread across the state characterized 500mb by 50kts in central OK and a 70kt jet in the panhandle. 700mb jet of 50kt is located in central Oklahoma at 4pm. Wind fields increase significantly across the state by early evening as the 300/200mb winds translate into central Oklahoma. Additionally, 850mb winds increase to 35kts across a large part of Oklahoma.

Forecast issues continue regarding placement of surface features, surface winds and convective initiation. All models develop convection on Tuesday and generally between HWY 81 and I-35. Timing is the big issue among the models, with some developing convection @3pm and others closer to 6pm. This includes a mix of high-resolution models with medium range guidance. While high-end impacts are possible, they seem to be destructive hail to softball size and 85mph given SBCAPE of AOA 4500 J/Kg and MLCAPE AOA 3500 J/Kg. It appears that convective initiation time is still undetermined given model QPF/BREF outputs. Indeed, the 4km NAM has -3 MLCIN at 4pm, down for -112 MLCIN at 1pm. Given approach of strong mid-level winds, I do wonder if this could be enough to breach the cap earlier than 4pm, if only 3pm, just tough to say. Unfortunately this hour makes a huge difference in activities around the metro. Storms should move at 35-40mph, so not as quickly as I originally thought. Either way, they won’t be slow movers. Finally, surface winds may be @180 degrees and not quite favorable 150 degrees at convective initiation. This should change by early evening and the 4km NAM reflects this in the Sharppy data. So, while the tornado threat may not be present early in the event, it should evolve during the evening hours. However, I do think the significance of this event is not isolated to just tornadoes, the potential for some really large hail and damaging winds seems to be quite high. It appears that wind fields will not line up with convective initiation and s/w trof location to promote a high-end violent tornado threat.

Probabilities:

Risk area for any part of OK (valid: 04/26, Day 1):

Slight: 100%
Enhanced: 100%
Moderate: 100%
High: 50%

Chase Status:

Going on Tuesday, target area will likely be El Reno.

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