The story of the Wichita tornado, as told by its airport control tower
Chalk these up to among some of the most dire weather observations I've ever noticed.
As a big tornado approached Wichita, Kansas on Saturday, the weather observations at Wichita's airport helped tell the story. These are in raw "METAR" form which is a bit cryptic (in the same way that upside-down Sanskrit might be "a bit" cryptic) but when decoded, they paint quite the picture.
(I've edited out some of the superfluous stuff like cloud layers and other items that aren't critical to the story in the interest of not to make these too jumbled. If you want to see the full, unedited observations, check out this link.)
Here is the first menacing observation reported at 9:53 p.m. CDT:
KICT 150253Z 17035G49KT 3SM +TSRA BR A2949 AO2 PK WND 17049/0250 TSB18RAB23 S CONS LTGICCG TS SE-SW MOVG NE
The +TSRA means heavy thunderstorm. 17035G49 KTS means 35 knots of wind from the south, gusting to 49 knots, or 56 mph. "CONS LTGICCG" means constant lightning strikes within clouds and cloud-to-ground. The thunderstorms span from the southeast through southwest, moving northeast. Uh oh.
Then, 12 minutes later, the tornado is reported on the ground:
KICT 150305Z 16021G37KT +TSRA BR TWR EVACUATING DUE TO REPORTED TORNADO VC SW MOVG NE CONS LTGICCG TS E-S-SW MOVG NE.
That tells airplanes that they're evacuating the tower due to a tornado "in the vicinity" (VC) and southwest moving northeast.
Over the next few minutes, the weather station keeps reporting the conditions, while also noting that there is no one in the tower:
KICT 150311Z 18037G53KT +TSRAGS FG UNMANNED CONTROL TOWER CONS LTGICCG TS OHD E-S-SW MOVG NE P0043
Also of note here, the wind gusts are now up to 53 knots (61 mph), the lightning is still constant and now the thunderstorm is overhead (OHD). The "P0043" is precipitation in hundredths of an inch since the last "standard" hourly observation, which was the one at 9:53 p.m. So that means 0.43" of rain has fallen in 18 minutes.
The weather station automatically sends out observations every few minutes from here noting subtle changes in the base of the cloud deck -- something the weather equipment is required to do to alert pilots to changing visibilities and ceilings. Aside from that, the observations are pretty consistent noting a heavy thunderstorm with pouring rain and gusts to 60 mph.
It's not until 10:33 p.m. that things get really hairy -- a full 30 minutes after the the tower evacuates. It looks like they came back into the tower to report a sighting of the tornado on the ground:
KICT 150333Z 13013G73KT +FC -TSRA BR TORNADO B32 6SE MOVG NE CONS LTGICCG TS NE-SE MOVG NE P0199
The +FC is something you never want to see on an observation -- it is indicating a tornado on the ground ("Heavy Funnel Cloud", I guess). And the remarks confirm -- a tornado on the ground that began 32 minutes after the hour, 6 miles to the southeast moving northeast. Also note the wind speed there -- 13 knots gusting to 73 knots -- or 84 mph! That was likely a "straight line" wind generated from the thunderstorm's incredible downdrafts and not the tornado which is too far away to really feel its winds.
But check out the "P0199" -- 1.99 inches of rain in 40 minutes! That's more than some entire Seattle summers!
The tornado is reported on the ground for 9 minutes and the weather calms down quite a bit once that cell passes.
By the way, McConnel Air Force Base, which was a lot closer to the tornado's path, didn't report the tornado in its observations -- it's possible it's only an automated data feed, but it did report a gust to 76 mph.