Chase Log: June 13, 2006

6/13/06 Ada County, Idaho
Starting Point: Boise

Summary: Severe storm with tornado warning moving toward chase area. Height of chase was core punch with one inch to golf ball sized hail and intense winds.

The SPC listed us in an area of slight risk, Mesoscale Discussion #1175 for the area.

MESOSCALE DISCUSSION 1175
NWS STORM PREDICTION CENTER NORMAN OK
0607 PM CDT TUE JUN 13 2006

AREAS AFFECTED…WRN AND NRN ID / FAR WRN MT

CONCERNING…SEVERE THUNDERSTORM WATCH 476

VALID 132307Z – 140030Z

INITIAL SHORTWAVE ASSOCIATED WITH LARGE-SCALE WRN TROUGH NOW MOVING THROUGH SRN ID…WITH SURFACE COLD FRONT EXTENDING FROM JUST WEST OF MSO TO EKO. THE RECENT DEVELOPMENT/ADVECTION OF MID/UPPER LEVEL CLOUD DECK OVER ID IS INDICATIVE OF SYNOPTIC-SCALE ASCENT ASSOCIATED WITH AFOREMENTIONED TROUGH AND EXIT REGION OF CYCLONIC JET MAXIMUM ADVANCING NORTHWARD THROUGH EASTERN NV.

THE 1900 UTC TFX RAOB SHOWED A MODERATELY UNSTABLE AIRMASS WITH A WELL MIXED…MOIST BOUNDARY LAYER. ADDITIONAL AFTERNOON INSOLATION PRIOR TO CLOUD DEVELOPMENT HAS LED TO MLCAPES NOW IN EXCESS OF 2000 J/KG OVER NORTHWEST MT TO BETWEEN 1000 AND 1500 J/KG OVER THE SAWTOOTH MOUNTAINS AND TREASURE VALLEY. AS MID LEVEL SHORTWAVE CONTINUES TO ADVANCE NORTHWARD…EFFECTIVE BULK SHEAR IS AT OR ABOVE 45 TO 50 KTS AND WILL CONTINUE TO SUPPORT ORGANIZED CONVECTIVE UPDRAFTS AND SUPERCELLS WITH LARGE HAIL AND DAMAGING WIND.

..BRIGHT.. 06/13/2006

CAPES at around 1000-1500 J/KG.. Shear over 45 knots… Hmm, this could get interesting. I had been watching radar all afternoon. I watched as a storm came over the state line; it showed some organization and possibly rotation. Though, radar in that area is almost non-existent. Just then the National Weather Service issued a tornado warning for Silver City. For those of you who don’t know, Silver City is out in the middle of nowhere in the Owyhee mountains. About 20 minutes after the warning was issued, the TV stations finally broke in with the announcement (real nice guys… ).

When radar showed the storm passing the river I decided to go chase it. Or in this case meet it half way. When you have a storm Southwest of you moving northeast, it’s really hard to get in the right position (southeast of the core) for a chase, it’s more like go sit in front of it and wait to be hit. My chase truck is temporarily out of commission. So if I went, I wouldn’t have all of my radios, I wouldn’t have any photo/video equipment or my cockpit voice recorder and most importantly, I wouldn’t have my laptop with radar access. Oh, and more disappointing is I wouldn’t have my hazard lights, I like my lights.

Anyway from the time I left my house to time I was actually on the road moving they had issued a Tornado warning for Ada and Canyon Counties. Of course as stated I didn’t know this cause my NWS radio and Radar were in my chase truck. All I had was a handheld radio with a mag-mount. Not exactly ideal as I like to have a backup radio… Once you have a mobile radio knocked out by lightning on a chase, you’ll learn why.

W5USN, W7DVR and others were on the air, along with the DHS station. As I was on the connector I had to make the decision on where to go. It was hard to tell the direction of the cell from where I was. I was aiming for the southeast side of the storm but didn’t want to get hung out dry. Several radar reports were relayed to me and I made the decision to take the interstate west and head south once in front of the storm.

One of the nice things about chasing in the plains, no traffic to speak of. Of all the chases I remember in the Midwest, there was only one where I got in traffic that impeded my chase. That was in Des Moines, Iowa.

I was on the interstate headed west and noticed a two areas of the storm that had lowerings. There were reports of a funnel cloud in the area of one lowering. Of the two, I could clearly an updraft downdraft convergence, the other, hard to tell due to dust and scud in the way.

At meridian road I turned south toward Kuna. (I don’t have times for my report points since I didn’t have my voice recorder going). I was caught in traffic for several minutes around the meridian exit. Once I was established on Meridian road southbound, just south of amity road was my first good view of the base of the storm.

At that point I was unimpressed with the organization of the storm. My initial observations:

  • The base of the storm was too high. I’ve never seen a storm with that high of a base produce a tornado to speak of.
  • The striations of the gust front were sharp and defined.
  • The storm column wasn’t defined, very “mushy” actually, not the typical cauliflower texture of a mature storm.
  • Back to the base, there was one area of downdraft right in the middle of the storm with a clearly defined updraft/downdraft convergence associated with it. Not strong enough to label as a wall cloud though.
  • Nothing I could see from that location led me to believe there was any rotation in the lower levels of the storm.
  • Very little lightning.

Still headed south, as I got under the front of the storm, I could tell I was headed just to the east of the core. I also noticed there was no inflow whatsoever. Everything was headed out of the storm as if it were starting to collapse. Just then I started to get those tale-tale rain drops… I knew I was about to get some rather large hail. The rain drops were huge and sounded like artillery as they hit. Within seconds I was in the core. Visibility was ZERO, and the wind was steady near 40 (previously stated, didn’t have a anemometer with me). I’m basing the wind estimate on previous experience and the rate the vehicle was being blown around. Visibility was still near zero and I had slowed to a crawl. I could tell there was several inches of water in the road along with the hail. Small limbs and tumble weed were blowing by my windshield every few seconds. Hail was steady with size of one inch with two inch chunks of ice hitting every few seconds, the hood was covered with hail. The rain became horizontal as the winds changed to perpendicular to the road. I was in the core, on the east side of the downdraft.

I continued south, as the hail started letting up the rain was more intense. I was now on the southeast side of the core. Visibility was still non-existent and suddenly I was the only vehicle on the road. I knew if there was a tornado in the storm, I was in close proximity. (Being in the core of a HP supercell is about the stupidest thing one can do in storm chasing. The Core of a LP storm isn’t much smarter, but only the southern plains get LowPrecip supercells).

This corepunch was somewhat of a calculated risk. Had the results of my previous notes (above) been any different, I would have stopped, got a feel for direction of the core then diverted based on that. But my observations almost guaranteed not tornados. None the less, when I was under it I was still a bit anxious. All the chase videos I’ve seen of core punches gone bad were coming back to mind. Nothing I was seeing made me think tornado. I radioed in a report to W5USN who had taken over the repeater in an informal net. I was vey thankful for someone doing so. I do miss having SKYWARN stations located in the NWS building, being able to radio directly to a Ham in the NWS and have them relay reports to forecasters. I was in the core for several minutes, seemed like forever. Reaching Kuna-Mora road I came out of the core. I immediately looked back and couldn’t find anything to indicate a tornado present or possible. I was in rain for a bit longer and finally broke into Rear Flank Downdraft (RFD) clearing. Blue sky and rainbow. I turned east with the intent to turn back north and chase the southeast corner of the storm north.

Once I had a good view of the flank of the storm I turned north. Again I started hitting traffic, I had no chance of staying with the storm, but I had a good view, I was still in the RFD clearing.

I listened to reports from hams around the valley who were calling in reports to W5USN, everyone was reporting hail and rains. But not much for winds, I believe I got into the core at the height of intensity in our area. I called KD7RBX as he was on the way to work and things were calming down out toward Nampa too.

I chased the storm till the tail end of it had crossed the interstate at that pointed I terminated the chase and headed home reporting into the informal net. It was about that that the net closed.

Notes to self: don’t chase in anything other than my normal chase truck.

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