2011-05-18: Chase Forecast (Updated 0900 WDT)

Forecast time: 0100 WDT...From DEN

Looking at the 00z NAM, the 990mb sfc low continues to impress in SE CO by late day with some intense easterly progged winds AOA 20kts near Lamar to Campo. Cloud cover is going to play a big role in limiting sfc heating, and I think the NAM is right about forecast Ts in the 70s near the sfc low. Today in DEN it took a long time even to crest the 60 deg mark, and I'm worried cloud cover currently seen over the CO/NM border (presently 08z as I write this) may keep it cooler in SE CO. I'll have to verify after the morning soundings.

My target area remains firmly close to the sfc low (E CO, along 287) where hodographs favor broad 90 deg clockwise 0-3km shear profiles.










The dryline looks messy due to very poor sfc Tds, but should drape NW to SE, possibly with the hint of a NE bulge somewhere east of Pueblo by 00z. This still puts the best "pooled" moisture close to KS border, and in that respect, I'm hoping for some High Plains Hijinks to aid things. The backing winds should force both upslope flow and some upslope theta-e into the region, but T/Td spreads will still be pronounced.

Things get a bit trickier in the upper levels with the nose of the H5 jet just barely arriving before sunset, but still providing 30-45kt WSW winds over my tentative target area. The 850mb winds look great (ESE AOA 20kt at the CO/KS border). Steep lapse rates and only modest capping should allow convection.

FWIW, yesterday's 00z 4km WRF breaks out a nice, seemingly isolated precip blob in SE CO around 21z, likely reflecting arrival of the nose of the H5 jet with superimposed intensification of the LLJ at around that time. Things will become linear and multicellular after sunset, but sticking to the southerly cells should allow a pretty good opportunity for small tornadoes and some terrific lightning along the dryline into the night.

My chase target is now almost certainly going to be in an area between Lamar and Springfield along Hwy 287 pending am soundings and SAT.

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Forecast update time: 0900 WDT...From DEN

SAT data shows a thick stratocirrus lid on things over almost all of CO, but this should move north and dissipate as the day goes on. W OK alread has cleared considerably, so I think the two targets will both find their daytime highs. I'm not optimistic about W OK hitting its Tc (AOA 95 deg) with H7 temps already in the 8-9 deg region and less forcing from the dryline. That said, my confidence in the CO target has diminished a bit too.

There are two sfc mesolows on obs this am. One is over Raton and should be the one that evolves in SE CO as the day goes on. But to my surprise, there appears to be a second mesolow in the region of the TX PH (mostly noted by wind shifts). If this were to move in a similar trajectory as the western low, it would really have a detrimental affect on both sfc winds and returning moisture to E CO by bringing more northerly winds into what I was hoping would be a strictly easterly upslope situation. That warrants hourly watching for now.

So my chase strategy for now is to get to Pueblo (which I'd be doing anyway), and then make the painful choice of either continuing S on I-25 to Raton to try to hit the Boise City area, or more likely hold up in Pueblo to begin a move eastward on US 50.

Normally most days with targets just a couple of hundred miles away from each other stress me out, but I think keeping my expectations on sculpted supercells today should more than help with indecision I'm feeling.

Packing up. En route to Pueblo.

5/31/2010: Redemption!

I will write a ton more when I have a chance, but these are only two of the ZILLIONS of unprocessed images from yesterday's incredible tornado on the CO/OK border! This was the best tornado of my career...the photo below shows "barber pole" striations moving up the tornado vertically. I am joyful beyond measure. More later!

2010-05-29: NE/SD/ne CO/w KS - CBB

2010-05-29: NE/SD/ne CO/w KS - CBB: "EDIT: 00z RUC now up. Low pressure now forecast to develop on CO/NE borders with backing winds along the state borders Sidney-Kimball. RUC 500mb are 40kt over the area (weakest over CO, but excellent over the NE PH).

The 850mb winds are downright wonky...in the C NE region there is a brisk LLJ with a small diffluent spur that will feed into the NE PH. However, most of the 850mb winds appear to be cyclonic out of the NNW from WY eastward. That the 850s appear to loop completely around my target area is not favorable...for that matter...it's not even clear to this novice forecaster what to make of this.

Likely in response to the sfc low, and therefore low-level wind shear, the 0-3 SRH and EHIs in the region look terrific...but the 850s feel like a juggernaut.

No change in target for now...will hold in Scottsbluff another hour or so and then likely drift south toward Kimball, NE."

Back out on the Plains: Forecast 5/29/2010

I'm back out on the Plains for about a week and half of what looks like modestly impressive setups for several discrete cell systems this year. Beats the hell out of last year already (and that's an understatement).

Currently I'm in the Nebraska Panhandle in a small town called Scottsbluff. My forecast is for areas just south of here. For a technical smorgasbord:

I think my forecast may be getting RUC'd-up at the moment...

Pluses this am:
Morning sfc data for the NE PH area and N KS are showing Tds in the 50-60+ range with sfc winds out of the south at 10-20kt. RUC is forecasting EHI over the Ogallala, NE, area to be in excess of 6 (with 0-3km SRH >400) by 00z suggesting availaible helicity in an area of forecast lapse rates between 6-8deg. SBCAPE will be in excess of 2000 along the I-80 corridor. The LSI shows this area to be under a "perfect" capping inversion (LSIs 1-3) that should suppress convection until either convective temp is reached (unlikely) or convergence/upslope forces convection (possible). The 4km WRF is suggesting that isolated cells will develop by around 22z over Sydney-Ogallala line with a possibly more discrete cell just south into CO.

Negatives this am:
The 00z from yesterday show that the GFS solution for a more progressive trough over the NE PH is unlikely, and that the NAM solution was more correct. This am's RUC appears to split the difference and place the trough just off the WY front range by 21z. Looking at this morning's water vapor image, it seems that the more westerly solution is likely the correct one. If the trough can move a bit more east than that, then the NE PH will be under the influence of the right rear entrance region of the jet and could have further lift from that mechanism as well. This morning's 00z KBLF sounding showed very high LCLs (>1500 ft), and this is without daytime heating that will likely augment the T/Td spreads. Last, an sfc backing is going to have to be due to a mesoscale low event since forecast sfc winds are just a mess on the RUC and NAM for later today.

Preliminary Changes to Forecast:
At this point I'm in Scottsbluff, NE, but will likely begin to meander south to Kimball, NE, where I'll try to further target refine.

As always, you can chase along with me by following my car icon below :)!

High Risk Day--Bad News KS/OK

There are few days that ever are as big in chasing as this one would be (were I to be out). Textbooks will be written based on today's amazing setup, but it means bleak things for those who live in KS/OK.

At the time of this writing (1500 EST), the atmosphere has come alive and things will begin to unfold in a major and destructive tornado outbreak.

Here's the current visible satellite image:



You'll notice that there is a line of convective storms (hard-looking cumulus clouds) in the SW KS/TX & OK PH areas. This area is under incredible atmospheric cues that include: abundant moisture, abundant instability, abundant lift, and synoptic scale features (a triple point: the intersection of a dryline, low pressure system, and surface fronts).

Current surface winds are out of the south over the target area (an area about 50 miles west of I-35 between Wichita, KS, and Oklahoma City, OK). Early radar returns show that the cumulus clouds have rapidly ascended and already are producing rain and in some cases short-lived tornados. This is incredibly fast development and there is still about 8 hours of daytime sunlight to fuel these flames.



Amazing upper level support is moving over the area, and this region is in the left front exit region of a jet streak at 500mb.



The bottom line: this day falls under the term epic and sadly Wichita down to OKC look to be under a very threatening gun. Will update as time allows.

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Latest 500mb analysis qualifies as "the perfect storm". Anticipate huge tornados will begin to form in the next hour or so with very large damage potential.

Tornado Hits Jacksonville, Florida

Photo from Mandarin/Orange Park, FL. Photographers unknown. Copied from WJXT (news4jax.com) and FirstCoastNews.com. June 26, 2009, copyrights unknown.

We moved to Jacksonville in 1997 and since that time, I've managed to miss every single tornado that has ever hit around Jacksonville. Even when I've come up with a good chasing plan, I never did get lucky, and sometimes I'd miss an especially gorgeous tornado by minutes. With the low cloud ceilings (often less than 1kft AGL).

Today, however, luck (I was at work tonight--an unplanned shift to assist a colleague and therefore was in perfect placement) and a terrific friend, colleague, and future storm chaser, Dr. Michael Maniaci conspired to my benefit.

Synoptic Background:

There was no evidence that there would be anything more than pop-up thunderstorms typical of summertime in FL. The sfc observations revealed a very mild low pressure system centered over Alabama with very little in the way of brisk sfc winds. In retrospect, however, the low pressure was sufficient to create marginally good westward sfc winds over the FL PH which likely led to a delay in the normal westward movement of the seabreeze which occurs typically early in the afternoon.

T/Td spreads were around 20 degrees (90/70) in JAX in the morning and were forecast to narrow (90/75) prior to peak daytime heating. The upper air situation was unusual in that 700mb temps were less than 10 degrees as opposed to the usual subtropical temperatures typical during the summertime. As is seen below, the hodograph favored largely stationary storms with high precipitation and no upper level support for large scale storm rotation.

Mesoscale Evolution:

As the afternoon developed, a mesolow appeared over JAX and slightly offshore. The seabreeze did start as usual, but was very delayed by the sfc westward winds resulting in an afternoon seabreeze still laying across the JAX area by 21z. The SB can be easily delineated on BR draped from NW to SE.

The SB led to an area of strong sfc convergence in St. John's Cty (south of JAX) and created a line of typical summer pop-up storms in that area. However, on the northern fringe of the storms, the SB had a kink in it which is also visible in the image above. A separate cell nestled into that area and rapidly developed into a non-embedded cell. Although I don't have enough sfc data to know for sure, I suspect that winds south of the cell were out of the east and north of the cell were out of the NE leading me to believe a mesolow had formed in that area in response to the pinned up SB.

The northerly cell almost immediately developed deviant leftward motion and began to "ride" the SB like a zipper.

As it rode the seabreeze, it immediately developed moderate midlevel rotation seen on the lower tilts.

The storm gradually continued its left turn and accelerated slightly, but continuing to ride the seabreeze. At about 2050z the first reports of a tornado were noted. At 2055z, my partner, Dr. Maniaci, contacted me stating he was staring at a large tornado on the ground (which, after my lackluster season this past year, was something I felt was poor form to tease me about). After a minute of me convincing him that he was hallucinating, he said, "Go LOOK!"

I shot up to the 5th floor of our hospital and immediately saw the tornado. It was a dramatic sight since I'd never ever thought I'd see one here. The T/Td spreads were perfect giving the storm base a relative higher height than is often seen here. There was a perfect cylindrical tornado easy to spot about 10 miles to my west and moving northward at about 5-10mph. I tried to capture images w/ my cell phone, but the distance focus on this thing sucks, so you'll have to trust me when I tell you what it looked like from here. Fortunately, lots of other folks were in much better positions to capture the tornado, and I share their photos here.

This first photo is from the FL Dept of Transportation showing the tornado with good backlighting. While I was sure the storm had been reported, I didn't get my usual phone notification of warnings in our area. I called NWS JAX and told them what I was seeing. This jived with several calls they were getting simultaneously and a TORNADO WARNING was issued for Duval County. I then called our operator at the hospital and asked them to initiate a TORNADO notification overhead (but truthfully, our hospital was never in anyway in jeopardy as the tornado would not move near us).

The next SRV1 tilt shows the tornado in the middle of the warning area, but without a mesocyclone indicator. At that time, visually the tornado had a very classic supercell appearance.

A midlevel feeder band (Beaver Tail) was coming in from the east into the parent storm and there were striations visible along the wall cloud and base. To the north, propagating storms began to form. On the radar, the seabreeze breaks south of the storm and begins to march due west. However, two separate boundaries (the northern portion of the SB) and some other area of convergence "scissored" together in N JAX leading to brief intensifcation of the storm (a mesoscale hiccup) and this can be seen on the following BR image). I should note that visually the boundary to the east of the storm was highly visible with low-level scud getting kicked up along it.

This led to the most visually dramatic portion of the storm which is captured best in the next two photos from Downtown JAX. The first was again anonymous from WJXT. The second photo was sent to me from one of my friends, Dr. Matt Geraci, from Baptist Hospital in Downtown JAX. Unfortunately, since the tornado was at this point over the St. John's River, it was called a waterspout by all popular media and I disagree since I believe this was in fact a true mesocyclone tornado with some non-MST features (weak circulation aloft but with highly visible structure consistent with a typical MST).

After about 20 mins, the tornado dissipated as the RFD wrapped around with a clear slot visible. To the northeast of the occlusion, a new wall cloud formed with intermittent cloud debris seen at the sfc.

In both photos (which were shot from the NE of the TOR looking SW), you can see the occlusion from the RFD behind the storm, the associated wall cloud, and kinking in the base of the tornado due to collision with the easterly boundary. This was not due to any precipitation east of the tornado: there was no precip east of it. So the kink was due to the sfc boundary in that area, I believe.

I did manage to get a single so-so photo of the boundary and the associated updraft and anvil. This was looking NNW from Mayo Hospital and the quality is better than the other photos I have but still pretty grainy/crappy. That said, features can be identified including the low-level convergence field draped from the right to left of the photo and midlevel clouds moving into the parent updraft near the top of the photo with a hint of blue sky just behind the anvil.

My chase partner, Dr. Bill Hark in Virginia, was one of my first contacts (following making sure my wife and children were doing okay with the storm which still passed well west of our home). He was nice enough to send me this animated WeatherTap (c) gif of the radar loop. Notable in the loop is just how quickly the northern cell accelerated after breaking from the other cells, and just how deviant its motion was from the mean.

This was such a great surprise and totally and completely makes me overjoyed. For a short time I was emotionally and spiritually back on the chase, and it reminded me why I so totally love this hobby. It also accentuates just how lucky you have to be sometimes and just how much more there is to learn.

My thanks to everyone who was kind enough to help me get this blog completed. My special thanks to Dr. Maniaci, though: I am delighted you thought first to call me. What a great surprise this was.

Comments/feedback are welcome, naturally. I will willingly remove any photograph that anyone feels is a copyright violation or violates public domain.

The Storm Season That Wasn't...And Isn't

I've spent a wonderful week with the family since coming home early from the Plains. We went to the beach, have spent awesome time together, and actually enjoyed chasing a school of stingrays that had traveled close to the shoreline (something I'd never seen before). It's been wonderful. But, of course, now I'm back to work and missing the Plains a little bit, knowing I'm still about 11 months away before I'll be back out combing the place for severe weather.

It's true that this year is a statistical oddity. A sufficient outlier from the norm, even some of the most veteran chasers I know are struck in amazement at the silence of our usual stomping grounds. I think some perspective is in order. First of all, the following graph is based on the weather in the contiguous lower 48 states. So the bars represent total numbers of reports of severe weather. Here is May, 2009:

The irony, naturally, is that the nadir in weather began EXACTLY on the first day I was out chasing. In contrast, here's May, 2008:

Now, last year there also definitely was a small nadir right before the massive outbreak of storms that resulted in the biggest and most destructive tornadoes I've ever witnessed. But the frequency of severe weather seemed to follow an appropriately oscillating sine wave as would be expected in weather. And while that sine wave is also present on this year's weather reports, the height is absent.

At the moment it appears that this trend will continue with only scattered severe weather here and there. The SPC is reporting that during the latter half of May they issued the fewest number of Severe Weather Watches ever. Just thought this was kinda interesting.