EWP Blog

Bill and Brian have been encouraged by Greg to check out the small azimuthal velocity couplet south of KDDC. There are several waves rolling up along the gust front. They’re considering a low probability tornado swath all along the line and including the bow. Wait, they’re actually dong it! This could be the biggest swath created in this experiment to date. They’ll consider a 20% probability. Brian entered 270deg at 35 kts and a high uncertainty since the line is just forming up.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

Cynthia and Craig are still following the lead supercell and the trailing storm which is bowing. Craig’s thinking they’ll have to extend the trailing threat area down the growing line. They’ll keep the hail probabilities at 100% for both storms. Their storm motions between the two teams vary by as much as 20deg.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

Bill and Brian are watching intense inflow into the storm and in fact, one chaser reported damaging inflow with power poles down and roof damage ahead of the lead supercell. But there is no substantial circulation at low-levels. The storm has an appearance of a big HP blob with occluding low-level mesos quickly surrounded by heavy rain, hail and probably cold air. However, they feel that it still deserves a 40% probability.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

Hail:

0035UTC: MESH is only showing 1.75″ in the lead storm. The trailing storm is coming up. The lead storm recently came in with softball report according to SHAVE. Cynthia and Craig went with 90% for the lead and 80% for the trailing storm.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

New updraft is going up after the last occlusion.

Bill and Brian are considering going higher TOR probs with a new update. They centered the ellispse in the notch and are going with storm motion 290 23, Cynthia’s going 295 20. TOR probabilities are going higher – 80% dropping to 70% in 20 min.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

Hail threat:

Cynthia’s turning off that irritating ellipse and going with a multi-vertex polygon because the shape of the hail threat according to MESH is not an ellipse anymore. There’s still some issues with building the correctly shaped threat polygon.

The storm wrapped up again and the updraft intensity’s come down a bit. However the trailing storm is now merging with the lead supercell through the initiation of intervening cells. Does Cindy and Craig combine the two storms into one threat area? They’ll keep them separate for now.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

Brian and Bill are to issue TOR probabilities. They’re going with Initial probabilities of 50% but they think it’ll recycle so they want the probabilities to go down and then go up. To play it conservative they’ll go down to 40% in 20 min. They’d go with a legacy TOR but they aren’t going higher because the initial TVS is totally rain wrapped and has come down in velocity difference. There’s no report either.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

The supercell is recycling as MESH values rose and the reflectivity is rising as well as the velocity couplet.

The initial storm motion was a little fast so Cindy and Brian lowered it down to 20 kts. They’ll be keeping the hail prob of 100% initial and 90% in 30 min. Their storm motion uncertainty is 15deg and 10kts. They went with ellipses because the initial hail signature was circular. They’ll have to issue a new threat ID if the storm changed shapes.

So far the team has not been issuing TOR prob guidance. Greg’s starting up a new machine for TOR prob warnings.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

Cindy is in the driver’s seat for probwarn while Craig, Bill and Brian are contributors. The southeastern supercell underwent a major occlusion with an incredibly aggressive, hail-filled RFD and now the storm cycled down a little. However 100% hail probability is gauranteed and ended with 70% at 30 min. The storm following behind was warned for a 70% hail and kept it that high.

The low-level reflectivity and even the MESH show a hole in the middle of the storm as a result of the core in the RFD wrapping all the way around until it met the forward flank core. New convection exploded on the leading edge of the RFD.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)