Storm Chase June 20 2011

This is hurricane Adrian in the East Pacific on June 10th, which had an estimated minimum central pressure 0f 946 mb with wind at 120 knots on the night of the 9th, and 956 mb 110 knots at the time of this image.
I had a very successful storm chase on June 20th in Nebraska east of Grand Island. Here is what we saw.

A brief touchdown seen looking west from the Hamilton/York County line 1 mile west of Henderson at the intersection of County Road A and County Road 6 at 5:22 PM CDT. Debris is faintly visible on the ground. The funnel was visible from 5:20-5:25 PM.



At 2242Z (5:42 PM CDT) a second, much longer track tornado touched down and was seen from the intersection of Hampton Spur and County Road 11 looking east. It was observed continuously until it became obscured by precipitation at 5:55 PM. It was seen again from 5:58-6:01. It was rated an EF-2.

Tornado at 5:43 PM:
5:44 PM:
5:45 PM:
5:47 PM from 3 miles southeast of Hampton while driving east of Hampton Spur on County Road 11:
5:49 PM from 3 miles southeast of Hampton while driving north of County Road 11 on County Road Y looking northeast:
5:51 PM from 2 miles east of Hampton while driving north of County Road 11 on County Road Y looking east:
5:58 PM from 1 mile west of Bradshaw looking north from US 34 between County Roads C and D.
6:00 PM from 1 mile northwest of Bradshaw while driving north on County Road D about 1 mile north of US 34.
Video of the Hampton tornado:






At 6:20 PM we see damage southwest of Stromsburg from somewhere on Road 123 looking north.
At 6:21 PM the tornado is spotted to the north. This was a third tornado which was rated EF-3.



The radar imagery from 2244Z to 2317Z (5:44-6:17 PM CDT) shows the large cell which produced all three tornadoes just north of I-80:
These tornadoes developed in an area with 6,000+ CAPE/-11 lifted index:
This was underneath a left exit region of a 65 knot mid level jet:
A 989 mb low produced east to southeast surface winds across southeastern Nebraska.
0-1 km helicity increased rapidly in the vicinity of this supercell in the late afternoon due to a strengthening and veering low level jet, from 100 M2/S2 at 21Z (4 PM CDT) to 300 M2/S2 by 0Z (7 PM CDT):
By 138Z (8:38PM CDT) the thunderstorms had merged into a smooth continuous arc from South Dakota to Oklahoma.
Much more on this event here.

Tornadoes May 2011

In late April and early May, it was reported that the Mississippi River was so high that some its tributaries were flowing backwards.

On May 9th, this 988 mb storm off the east coast took on a very interesting appearance in water vapor imagery:
On May 22nd, 159 people were killed when a mile wide EF-5 tornado hit Joplin, MO. Radar showed an incredible strongly curved hook, intense couplet, and a debris ball over the Joplin area:
More radar images here. What I found most interesting about the Joplin tornado was how quickly it grew, which can be seen here.

Just two days after Joplin, a 989 mb low ejected into the southern plains, producing numerous tornadic supercells from Kansas to Texas:
This included an EF-5 which hit El Reno, OK, killing 9. 0Z RUC analysis had warm sector 0-1 km storm relative helicity at 600 M2/S2 over central Oklahoma, where a 45 knot westerly low level jet was directly over southerly surface winds. The 0-1 km SRH was almost as high as the 0-3 km.
On May 25th, the same system produced a squall line with embedded supercells that prompted tornado warnings that went from Effingham, IL to Dyersburg, TN:
On May 29th, this trough with 500 mb winds up to 90 knots produced a 984 mb low in Utah:

Blizzards and Historic Tornado Outbreak

During my last post on April 14th, a blizzard was in progress in Nebraska and northwest Kansas on the backside of this storm:Up to 16" of snow fell in Nebraska (Paxton) with drifts to 5 feet in the western portion of the state. A 120-mile segment of I-80 was shut down. The band of snow reached Dodge City later that night:
The next morning, the surface low was 992 mb.
Winds in the Dodge City area gusted up to 74 mph, causing significant damage.
This same storm system also produced a tornado outbreak from Oklahoma to North Carolina, killing 17.

On April 22nd, an EF-4 tornado hit St. Louis including Lambert Airport.

On the afternoon of April 26th, tornadic supercells rapidly developed in Texas and Arkansas.This was only the beginning of the historic multi-day tornado outbreak which killed over 300 people. The number of tornadoes is still unknown, but NWS surveys have confirmed 25 from the 25th (12Z 25-12Z 26), 40 on the 26th, and 132 on the 27th. This includes at least 2 EF-5s, 12 EF-4s and 21 EF-3s.

The event was well forecasted by the Storm Prediction Center. I don't remember ever seeing SPC's probabilities for tornado (30%) or wind (60%) as high as they were on April 26th.
Then the next day, the tornado probability was up to 45%.
Here is a water vapor loop of the entire event starting on the 26th:

High resolution visible loop from the 27th:

Here are some RUC analysis charts from 0Z 28 (7PM CDT on the 27th):
Dewpoints were mostly in the low 70s with some mid 70s.
This contributed to both the high cape values and low lifted condensation levels. The sounding from near Birmingham, Al at 0Z 28 put the LCL at only 928 mb despite a surface temperature around 80. Notice also the mid-level dry slot and that the helicity is at 847.
Sounding from Nashville, TN:
And from Peachtree City, GA (about 30 miles southwest of Atlanta)On April 30th, blizzard warnings (in red) were issued for much of North Dakota.
Another 7.9" fell at Williston where they had already had their snowiest season on record. The total is now 107.2", and the old record was 94.7" set in 1895/96.

Last night, freeze warnings (light blue) and frost advisories (blue) were issued down to southeast Missouri:
Frost advisories for tonight include Nashville and part of Alabama: