|
Chase Log 20056863 Miles TotalLast Updated
|
Supercell In Fading Light Near Holly, CO, May 24, 2005 |
Updated
|
Chase Log 20056863 Miles TotalLast Updated
|
Supercell In Fading Light Near Holly, CO, May 24, 2005 |
Updated
The storm had a wonderful look on radar for about one hour or so, and had a bellshaped lowering, with interesting collar, lower midlevel inflow bands (stingers). However, it was relatively high-based...and never had the "look" of a supercell ready to cascade to tornadogenesis.
We are spending the night in Rapid City, SD, preparing to drop into extreme ne Nebraska tomorrow.
But we stuck with it. The morning surface analysis indicated a narrow sweet spot in which adequate CAPE (dew points), low level and deep layer shear would be favorable for supercells. But would storms initiate, given the monstrous cap, only overcomable if dew points got up to the upper 60s/low 70s?
Well the NAM overestimated the dew points and CAPE. So, initial storms near Vermillion SD struggled....but eventually coalesced into a briefly interesting storm....with several attempts at making something of itself. But, eventually these incipient storms drifted off into Iowa and dissipated. But throughtout all of this we noted that the updraft towers were severely tilted, and very ragged at the top. We at least got an obligatory "god shot" of gorgeous crepuscular rays.
We are overnighting in Omaha...tomorrow we may drop into Oklahoma...but only if the deep layer shear seems favorable. Out initial target is the Oklahoma border area between Tulsa and Ponca City....
The early storm that developed on the south slopes of the divide between Colorado Springs and Limon became a supercell quickly. It looked very good on radar, and visually (though in this picture a second storm that became a supercell had formed and was obscuring the view). The storm continued to move in deviate fashion and we considered chasing it. However, though it had a good luck, a series of other storms developed east of it, bowing south into the better air...depriving the first storm of the best moisture. Later, a cluster of storms developed north of Burlington, and briefly looked good on radar, but it was clear that the shear profiles were not favorable, despite the Tornado Watch (our third in four days).
Here is a shot of a sunshaft that we first thought might be a landspout...and its location relative to radar.
Tomorrow we are likely to be in this same general area.
The day dawned with an optimistic outlook. Although initial wind fields in eastern Colorado were disorganized and dew points were not as high as on the previous day, the models forecast that a short wave over the intermountain west would be associated with (a) backing wind fields to southeasterly over Colorado; (b) deep layer shear favorable for supercells, initially classic; (c) anvil level flow at least briefly favorable for classic supercells, but with any storms moving southeast moving into weaker shear environments, and likely to morph into HP mode.. In addition, a CAPE bullseye in an area of moisture convergence was forecast for the same area. The SPC outlook was consistent with this reasoning, and they later upgraded to a Moderate Risk. The short wave was clearly visible on the water vapor imagery, with the synoptic scale upward motion generating storms in Utah in the early morning. We joined Matt Crowther and Dave Blanchard and company at the Yuma library to await developments.
 |
 |
Storms first formed on the Front Range of the Rockies in the early afternoon, and then emerged out into the Plains as the shear enviroment became more favorable for supercells. The first radar plot shows the Akron and Otis supercells, discussed below. The colors for the counties indicate either that the respective county was under a tornado warning (red) or a severe thunderstorm warning (yellow).
The Otis storm was the first one we intercepted. It had a massive bowl shaped lowering, which was clearly rotating. Several times significant whirls of dust developed under it. In its later stages, these were clearly related to shelf like fingers extending into the lowering surmounting bursts of outflow. But early on, the whirls may have been pretornadic whirls or, even, weak tornadoes. In this picture, you can see that the small vortex was embedded in a much larger cyclonic circulation under the lowest part of the "bowl" and that a curtain of dust has ascended to cloud base. Later on this storm had minor attempts at creating wall clouds, with bursts of dust and cyclonic whirls ascending to cloud base that might have been either weak tornadoes, or gustnado features.
In the distance, we had a clear view of the Akron storm, and several of the features that may have led to erroneous tornado reports, such as this inflow feature surmounting a burst of outflow. This storm rapidly took on the look of an HP supercell, with a massive beaver tail, obvious hail shafts, all either converging or surrounding the main bell shaped lowering, which had green, gray, yellow and other colors. There were several shear funnels on the leading lip of the lowering.
We pushed on eastward ahead of this beast, noting a new storm near the Nebraska border, which rapidly became a supercell near Laird. We noted several funnel clouds with this, including a beautiful narrow laminar tube (note...this was on video and will be added as a screen shot later).
These northern storms coalesced into an MCS, while storms developing near Kit Carson became supercells.
The best storm of the day was northeast of Lamar. Unfortunately, we got there after the sun had set. But this storm appeared to have the best structure of the day...and had tornadoes reported associated with it. We played tag with it in the dark...and it was an exciting chase because eventually this storm chased us.... Our plan was to overnight in Lamar, but by the time we were on the last 15 miles into the city, the Lamar storm had joined with two others to form a potent bow echo, that was bearing down on us from the west.
We decided it was too dangerous to proceed, and went back to Holly, putting the car in a car wash, and watched (and videoed) the effects of the storm on the town, including 70 knot winds, downed tree limbs, flooding, power outages, as we were hiding in the car wash.
All in all, this was a wonderful day of chasing. No dramatic tornadoes, but great storm structure, and exciting chasing.
This day's shear environment served as an illustration that bulk shear, not the 500 mb flow alone, determines whether storms can be supercellular, if adequate buoyancy is present. The 500 mb flow was forecast to be weak, at best, with 25 to 30 knots of west northwest flow expected over northeastern New Mexico by afternoon. However, south of a synoptic scale boundary, a surge of outflow from the previous night's convection (the same storms we witnessed in Colorado had coalesced into an MCS and moved south across OK to TX), had created a surge of moisture rich easterlies of 10-15 knots into the high plains of New Mexico, with 2000-2500 J/kg. That created a bulk shear of nearly 40 knots!!
In addition, the progged wind field resulted in a highly looped hodograph favorable for rotating updrafts and deviate right movers, although the storms would move quickly into a different shear environment and would probably morph from classic supercells to HP.
The SPC outlook had argued for the same scenario.
Storms developed first on the Raton Mesa and the Sangre de Cristo range of the Rockies northwest of Las Vegas NM. We targeted the southern most storms, which became supercells rapidly. The first Las Vegas storm developed while we were on mountain roads, and unable to stop to set up cameras. Unfortunately, this storm had tremendous structure, a barber pole, with helical striations, and wild mammatus, bulbously plunging downward from the anvil. In between traffic, hills and trees, Thom snapped two pictures of a tornado associated with this, while we were looking south (and driving towards the west). The first shows the storm structure, with the distant needle funnel, and the second was a close up of the funnel. Shortly after the second picture, we were immersed in rain associated with the second Las Vegas supercell.
The radar plot at 1830 MDT clearly shows the hook, kidney bean aspect of both storms, though this was well after the time we saw the tornadoes with the first storm. We tried to catch up to the second storm, and drove through the rain and hail to get to it and finally got to the flanking line (with first storm visible in far distance).
Unfortunately, the storm was then ingesting stable, rain cooled air from the first storm, as you can tell by the mushy appearance of the wall cloud, though you can see the striations on it, viewed from the southeast towards the northwest. Shortly after this picture, the core of the storm caught up to us on Interstate 40 (with no road options for escape) and we got clobbered by continuous hail for around 10 minutes, mostly marble size, but some up to the size of ping pong balls (the white pebble things are hail stones in this picture). You can also see "hail fog" at the top of this picture.
As we concluded another satisfying chase day, full of beautiful storms, lightning, supercells and one tornado, the fading light caught dissipating storms to the west.
Thom leaves May 29, and Scott Landolt joins me. Daily updates will resume when the pattern picks up again.
After leaving Thom off at DIA, I was joined by Scott Landolt and later, Chuck and Vickie Doswell. The outlook for the day had relatively favorable conditions for thunderstorms in the Raton/Trinidad area. So, Chuck and I looked for signs, while Scott chatted with Vickie. The surface plot showed southeasterly flow into the area, but deep layer shear was marginal. RUC forecasts had marginally favorable shear conditions for supercells in the afternoon. But it was worth the trip.
A boundary north of the Raton Mesa greeted us in the early morning hours of May 30. Easterly to southeasterly flow south of the Mesa and in a narrow zone north of the mountains, brought moderate CAPE under an increasingly favorable shear environment during the day. Clearing north of the mountains and in the Raton area allowed the area to develop adequate (but not large) CAPE. The moderate CAPE gave us a narrow window of opportunity...too much shear for the CAPE and storms would be tilted and torn. Too little shear and we would have HP supercells again.
We targeted a storm developing rapidly west of Raton in the late afternoon. This storm developed a lowering, and finally, an RFD slot and funnel cloud. Unfortunately, as the storm continued to develop, it propagated into a roadless area. It still had an RFD and a quasi-funnel as we lost it temporarily (although we tried to stay with it on mountain roads, and briefly saw what could have been a tornado).
Later, near Des Moines, another supercell produced a tornado as we photographed the storm. Here you can see the early stages of the tornado, with the RFD slot clearly visible. The tornado remained visible for nearly seven minutes before "roping out."
After that exciting development, subsequent towers tried against the strong shear, but failed to produce a major storm in our area. So we ended a satisfying day with a celebration at Eklund's Hotel Restaurant in Clayton.
Began the day in Clayton, NM with Scott Landolt, Chuck and Vickie Doswell, and Kevin Scharfenberg. Original target area was between Clovis and Hobbs, NM where the shear and CAPE looked to be the best in upslope moist flow. SPC outlooked the same area, and later upgraded to a Moderate Risk in the area. A synoptic scale boundary was sagging south into northeastern New Mexico and the northern Texas Panhandle, with an outflow boundary draped from northwest to southeast from Dalhart to Childress connecting to that. Clearing was ongoing south of the cold front and west of the outflow boundary.
As we headed south out of Clayton, Mobile Threat Net showed a storm developing just north of Hereford, TX. We decided to intercept and headed east towards Hereford. The storms slow movement allowed us to catch up to it in Hereford. The storm looked good both on radar and visually (as a classic supercell), with a verified tornado at the time we were watching the lowering from its west flank (tornado was hidden by the rain hook) but as we began to head south in front of it, it went from classic to HP. There were some great sharks teeth and we heard reports of softball sized hail falling North of Hereford. The storm also had a mother ship appearance as it approached Nazareth with a giant beaver tail that was nearly scraping the ground. Shelf Inflow fingers formed and reformed with gustnadoes underneath them. The storm assumed a wonderful stacked plate appearance. As we headed south to stay in front of it, storms began going up east and west . One storm in particular to the west had gone up south of the rest of the storms and seemed to be fairly detached from the rest of the evolving complex. We decided to intercept it and headed south and west to finally catch it in Littlefield, TX. As we approached the storm from the east, it appeared to have classic characteristics with a well-defined precip core to the right and what appeared to be a wall cloud to the south. When we finally caught up to it near Amherst, we could see and several dust whirls in the field below it. Knowing that this storm had gone up in the same environment as the others, we figured it would do the same thing as the others and before long, it too took on HP characteristics. We let it move past us before heading to AMA to stay the night.Here are Scott and Kevin evaluating the portents.
After our travel day, we (Scott Landolt, Chuck and Vickie Doswell, and I) hung out in the Comfort Inn Lobby, which had a strong wireless signal and a very understanding staff (kudos to them). It seemed that it was a perfect setup...a mesolow in northwestern KS, with a deep flow of high dew point air around its east side. Shear profiles seemed favorable for supercells, with deep layer shear showing 30-40 knots (0-6 km) (although northwestern KS was just on the fringe of the favorable 500 mb flow) and the Haviland profiler showing a highly looped hodograph, suggesting that right moving supercells would be interacting with highly sheared air in the low level (0-1 km) environment. Forecast soundings looked like we might be in the middle of a tornadic supercel outbreak, and SPC upgraded to a Moderate Risk.
As we waited and waited, it was clear that our target area would not experience convective initiation. SPC issued a Tornado Watch because of the explosive potential, but the only storms that developed, were those on the Rockies that drifted and propagated into the Plains. Two of these became supercells...one north along Colorado 36 and the other approaching Limon. The first storm had produced a tornado early, but had morphed into an HP supercell. The second was "catchable" for us, because it was in an earlier state as it approached Limon.
So we drove west on I70 and quickly approached this storm. This shot shows us driving west, with the rain free base visible on the left. About three miles later, a ragged wall cloud was visible. This storm developed into a gigantic HP-beast, with softball hail devastating the cars on the freeway, and quickly turned into a John-Scott-Chuck-Vickie chase, rather than a storm chase. We struggled to stay ahead of this storm, as it broke windshields, and produced 80 mph outflow winds. The structure of the storm was one of the best that I have seen, with a layer-cake stack of plates, surrounding a green hail area core. We escaped by taking a southbound road, and ended up in Garden City KS for the night. Although we saw no tornadoes, this chase was remarkable for the structure we witnessed, and the excitement of being chased by the storm (the third time this has happened on this trip).
A closed low over SW KS greeted us this morning, with a few boundaries evident. We decided to play the upslope southeast winds expected to develop in SE Colorado on the north side of the Raton Mesa because although the surface wind field was favorable over KS southeast of the low, mid tropospheric winds appeared weak. So we "blew KS off." This was a mistake.
Cloud cover around the closed low precluded the expected diurnal heating and the development of sufficient instability, despite the presence of favorable dewpoints (which had developed as forecast). Meanwhile, the thermodynamic environment was favorable for a few "low topped storms and supercells, which indeed developed in KS, and produced at least one tornado.
As we waited and waited, it was clear that our target area would not experience convective initiation. We drifted back towards Garden City, and drove through the cyclonic circulation associated with the closed low. By this time, all storms were multicells, but a few may have had some weak rotation. This is a few north at the two rain cores north of the road at A (on the radar). Here we were driving under a weakly rotating inflow finger that developed on the west side of the northward moving cell at B (on the radar). And, here we saw what might have been a weakly rotating lowered base at C just northwest of Garden City.
First, surface winds in our target area near ICT never backed to southeasterly. This left hodographs in the area unidirectional, favorable for splitting storms, and not the stronger right movers. Second, there was the suggestion in the hodographs of a cyclonic loop, implying that at least in that area of KS left movers would be favored. Third, the sbCAPE never materialized the 4000 J/kg forecast...thus the initial towers developed strongly, but ultimatelyh were mushy, and sheared over.
Storms finally developed along a line, and there were a few tornadoes, but long after we had abandoned the chase for the long drive back to Goodland, to be in striking distance of DIA for my exit the next day.
After dropping Scott off in Denver, I flew off to Oakland. This was a very successful trip of storm intercepts, with supercells many of the days, and a couple of tornado days as well.Thanks to all the colleagues and friends who contributed to the success of the trip while I was chasing with Thom, Scott, Chuck and Vickie. See you all again next year.
