May 26, 2009
Last night Scott and I witnessed the bat flight from Carlsbad Caverns. Because of the dry conditions locally the usual number of bats had not been making this flight; there were not enough insects for them to forage. The previous night the rangers told us only 10 bats had come out. The usual size for the colony is 400,000 bats. When Thom and my nephew Bruce and I saw this event in the early 2000s, it was an awesome vortex of black rushing out of the natural opening of the cave.
Well, fortunately, last night a respectable bat flight did occur. Though smaller in size than I remember it, the flight still probably had 100,000 bats or so exiting over 15 minutes.
Today, we are leaving early to descent into the caverns for the two to three hour walk (goes about three miles). This will be my sixth time through, and I have yet to tire of this spectacular descent into a wonderland of colors, shapes, and spaces.
Posted by John Monteverdi and Thom Trimble at 6:47 AM
May 25, 2009
Our initial plan is to hope that the dry line does not set up too far east today. But, even if it is in southeastern New Mexico, where the shear environment appears somewhat favorable for a rotating storm or two, the moisture return from the Gulf is still meager. There is still a disjoint between where the greatest buoyancy is and the best shear. This has been showing up in the last few runs of the models.
We'll reevaluate as we travel. Meanwhile, we are planning to see Carlsbad Caverns...the bat flight tonight, and the caverns themselves tomorrow morning before all the tourists overun it.
Here's another picture of the fabulous rotating storm we witnessed yesterday.
Posted by John Monteverdi and Thom Trimble at 8:57 AM
May 24, 2009
...New Mexico, that is. Which is where Scott Landolt and I are overnighting. We left Thom off at Denver Airport but decided to stay in the area. A Denver Convergence Zone was developing again, basically a reprise of yesterday. And, this decision paid off for us all.
It turns out that we ended up chasing right to Denver Airport. Thom's flight was in the late afternoon, so while we were chasing and he was waiting, a supercell developed west of Denver Airport. The radar development was spectacular, and the storm ended up producing a marvelously wrapped wedding cake, corkscrew updraft area.
Yes, Thom was in the Airport when the tornado warning was issued, the sirens wailed, the klaxons sounded, and all were asked to the tornado shelters and planes were vectored off.
We are not sure if the storm produced a tornado. We did see two funnel clouds with earlier storms, and Cameron Redwine reported a funnel at the time of maximum development. I'll post more when I get my pictures downloaded.
Posted by John Monteverdi and Thom Trimble at 7:52 PM
May 23, 2009
The morning's surface weather maps shows, basically, a reprise of yesterday's pattern. A subsynoptic low is centered northeast of Denver, and, for this portion of the Plains, a rich supply of moisture is evident (basically, dew points in the mid 50s at 4000-5000 feet corresponds to dewpoints in the low 60s at sea level).
For Thom's last "chase" day, we will be playing the Palmer Divide, east of Denver. This is the sort of pattern in which strong, early updrafts can spawn a non-supercell tornado (called, popularly, "landspouts"). Here's a picture of the two of us at Mt. Rushmore.
This has been an uneventful trip so far (and likely to end so for me too). However, our frustration is tempered by the successful trips we had in 2004 and earlier years. This year's pattern is particularly frustrating for the participants of the VORTEX2 experiment.
This huge operation, involving over 40 vehicles stationed at three locations over the Great Plains, and deployed to observe the microscale meteorology around tornadic storms, has been deployed exactly once since the operation started on May 10. That was this past Tuesday, when we saw a few supercells in the Nebraska Panhandle. However, these were not close to being tornadic.
Thunderstorms are likely to occur over this region (as they have occurred the last few days) over the next weeks or so, but projected shear patterns do not indicate that they will be tornadic. Hence, many chasers are making the decision to abandon their quests this year...the mission is not to find thunderstorms (which is an easy thing to do) but to find rotating thunderstorms (which is a much more challenging proposition).
Posted by John Monteverdi and Thom Trimble at 9:41 AM
May 22, 2009
A Denver Convergence Zone developed in the late afternoon. This took the high dew point air previously described in a counterclockwise spiral around Denver International Airport, with some strong storms developing.
We were hoping for a non-supercell tornado (very common with this type of pattern) but, alas, although we had some fun chasing a strong storm (see right) near Akron, the whole area eventually erupted in moderate and heavy rain.
Posted by John Monteverdi and Thom Trimble at 7:30 PM
Very sluggish flow in the midlevels today....but if the 20 knots of southwesterly flow at 500 mb verifies, surmounting 15 knots of southeasterly flow, there are adequate dewpoints and moderate CAPE in northeast Colorado and southern Nebraska Panhandle today. Adequate for briefly rotating thunderstorms...
...of course, there has to be thunderstorm initiation, which did NOT occur yesterday. We overnighted in Garden City, KS, and we both got good workouts in....Thom running 10 miles on a bike trail here, and me 4 miles or so, plus a good long weight workout at the YMCA. It is now 11:30AM and we are now about to depart.
Posted by John Monteverdi and Thom Trimble at 9:34 AM
May 21, 2009
Today's pattern suggests a bit of a focus for rotating storms in northwest KS today, but the "ifs" are really problematic. The mid-tropospheric winds have weakened, but the surface easterly flow should yield reasonable vertical shear values....however, not quite phased with the highest dew points (about 30 miles out of phase). Nevertheless, we are here to chase potential storms, so we will shortly drop south from Ogalalla, Nebraska into that area.
Yesterday, the marginal moisture at lowest levels had the effect we expected. We did indeed get rotating storms....two supercells that we witnessed, albeit with high bases. The cloud base rotation was quite evident in the swirls where theupdraft was centered. We also saw VORTEX2's armada....over 40 vehicles...quite impressive.
The upcoming pattern does not look good for storm researchers. I am liable to leave the Plains earlier than I have ever in previous chase years. Thom is leaving on Sunday, and Scott and I are liable to try one last play in Texas early next week
See more pictures.
Posted by John Monteverdi and Thom Trimble at 10:14 AM
May 20, 2009
Post frontal upslope flow along and just south of the South Dakota border should bring some marginal dew points into that area this afternoon. The environment is developing a shear profile very favorable for supercells in that area too. The large dew point depressions are liable to produce high lifting condensation levels, though, and the storms are likely to have high bases.
There is a tug of war between the RUC and the WRF models today, with the WRF having higher dew points spread over a larger areas,
and moderate to high values of CAPE (s
ee forecast Valentine sounding). Right now it appears that we will see an LP supercell today...but there is always the hope of a "mesoscale" accident producing a supercell tornado, as Thom and I saw near Miami, TX in 1994. Non-supercell tornadoes are very possible today, and we'll take one of those.
Yesterday we visited Mt. Rushmore. This was the first time I have seen Rushmore, and I have to say it is impressive. On our way south today we may stop in at Wind Cave National Park.
Posted by John Monteverdi and Thom Trimble at 9:44 AM
May 19, 2009
Both the RUC and the WRF persist in bringing relatively high dew points into a modestly good shear environment (see forecast sounding/hodograph for Rapid City this afternoon--favorable for rotating storms that will persist for a short while until the precip plume overwhelms the updraft). Hence, we are going to hang around the Black Hills and areas north today (perhaps taking in Mt. Rushmore).
Today I have included a picture of our chase vehicle, the Jeep Commander that Thom has told you about in Wild Geese. It's actually a good vehicle. Plenty of room, and it gets around 20 mpg. The rear panel folds up and provides protection from rain, and there is a wide bench to hold our cameras back there.
Posted by John Monteverdi and Thom Trimble at 10:09 AM
May 18, 2009
The basic prognosis remains the same. The wind profiles look marginal to good for the region initially just north of Rapid City, SD (Tuesday), the Nebraska Panhandle into SW SD (Wednesday) and nw KS to sw Nebraska (Thursday).
However, the moisture profiles look poor to marginal initially, to marginal by Thursday. Dew points are expected in the 50s to upper 50s in this region (see graphic for Tuesday).
So, we are on our way north to Rapid City, SD today. With the shear profiles during the period, isolated storms are liable to rotate briefly before being enswirled by their own precipitation plumes.
But, at least there is a risk for rotating storms.
Posted by John Monteverdi and Thom Trimble at 10:28 AM
May 17, 2009
May 16, 2009
We are in Denver, and plan to overnight in Boulder. The latest run of the medium range models still suggest that both deep layer and low level shear will be adequate for severe storms/supercells during the Tuesday-Thursday period in the region about 150 miles radius from Rapid City, South Dakota.
The largest issue remains the circulation in the Gulf of Mexico, which is taking Gulf air southeastward into a developing tropical system. Nevertheless, either locally produced, or imported moisture does make it northward through the Tuesday-Thursday period. I have posted the dew point field forecast for Wednesday afternoon. It does represent the most robust dew point field of the week, and it does suggest some hope for storms, possibly supercells, in the region of favorable shear.
Dew points would need to be higher in order for LCLs to be low enough to get tornadic storms, however, even if the dew point field verifies.
Posted by John Monteverdi and Thom Trimble at 9:14 AM
May 15, 2009
The models are still advertising two of the three ingredients in supercell production to be in place in the northern Plains starting about Monday or Tuesday. The one "missing" ingredient is boundary layer moisture.....which would appear with southerly or southeasterly flow at the surface usually....but NOT if the big cyclone development occurs down in the Gulf of Mexico.
The models "think" that a hurricane may form that way, which may actually take moisture headed for the northern Plains and shunt it southward into the circulation. We shall see...although it looks like that will occur.
Meanwhile, there still will be storms in the Dakotas, perhaps northwest Nebraska and eastern Wyoming and Montana starting around Monday, perhaps Tuesday, and that is we are likely to head after landing in Colorado and spending a day or so in Boulder.
Posted by John Monteverdi and Thom Trimble at 3:50 PM
May 14, 2009
I've attached the 500 mb, surface pressure, and surface dew point forecasts for next Tuesday, which is similar, with slight modifications, to those for next Wednesday and Thursday afternoons. If the pattern verifies, we will be drifting northward from Boulder on Sunday to South Dakota.
The focus appears to be setting up for some place with a radius of 150 miles of Rapid City or so. That's conditioned on the model being correct, of course. The pattern is somewhat favorable, but highly contingent on dew points rising into the mid 50s to get high-based supercells. We'd really need much higher surface dew points to see more dramatic storms. But at least there is some possiblity for T-Th
The Ensembles still show a majority of members favoring the progression of a trough into the West Coast after Saturday. So that's our plan now.
Posted by John Monteverdi and Thom Trimble at 11:39 AM
May 9, 2009
This is today's run of the ECMWF's ensembles. It's valid for Sunday, 17 May, and shows basically what the GFS has been showing....most of the ensemble members have a sharp shortwave trough in the southern branch just entering the central and northern Plains on Saturday night to Sunday morning.
If this trend continues, this will be yet another validation of our decision in the early 2000s to make our entrance airport Denver's.
Posted by John Monteverdi and Thom Trimble at 12:22 PM
May 7, 2009
Just a heads up...the GFS ensembles are suggesting a favorable pattern in the central Great Plains for the first few days of our trip.
Posted by John Monteverdi and Thom Trimble at 8:50 PM