Archive for February, 2007

7:00 P.M. Severe Weather Update
February 28, 2007

The central plains have experienced a decent cap this afternoon, keeping thunderstorms from developing. The cap is the warm air aloft that prohibits air to rise in the upper levels of the atmosphere. Without rising air, thunderstorms can’t build!

The cap is now breaking across central Oklahoma this evening. A trough of low pressure is now swinging trough western Oklahoma, which is now sparking storms across southern Kansas. The storms will likely back build down the dry line and intensify after sundown. Dewpoints continue to rise ahead of the trough, which will help hold the storms together overnight.

Most of the severe activity will stay west of our area this evening; however, after midnight, we’ll expect more showers and storms with large hail and damaging winds. There remains an isolated tornado threat overnight. I’ll have another update before 10 tonight.


Quick Severe Weather Update…
February 28, 2007

Looking at the 0Z data, the timing for severe weather remains in line for Thursday morning. As a warm front moves north tomorrow, we’ll see dew points climb into the 50s. More available moisture means a better chance for nocturnal thunderstorms late Wednesday night into Thursday morning.

The cap is pretty strong for Wednesday afternoon, so other than a stray shower or two, we’ll be windy and mild. The showers will be aided by strong 850 mb winds aloft and the mountainous terrain of eastern Oklahoma and western Arkansas. Southerly winds will move gulf stratus throughout our area on Wednesday, so full on sunshine will be limited. Look for highs in the upper 60s and lower 70s; however, if your area receives more sunshine, expect to see the mercury rise rapidly!

Large hail and damaging winds are the primary threats for severe weather by Thursday morning. These storms will move east during the morning hours, leaving Thursday afternoon dry.

Deja vu? Similar Pattern….
February 27, 2007

Despite strong wind shear on Saturday, most of the area was spared from nasty severe weather due to the lack of available moisture. Straight line winds did create substantial damage in Spiro, OK, but will we see the same situation for Thursday?

Right now we’re watching a trough over the western United States that will deepen and head east across the central plains toward the middle of the week. This current storm system resembles the one we saw over the weekend. Wind shear won’t be as pronounced, however, the timing is identical. We’ll expect a dry line to fire out to our west on Wednesday, providing us a chance for storms late Wednesday night into Thursday morning. Most of these storms will be elevated, or above the cap as the low level jet strengthens. The storms activity will shift east during the day on Thursday, so rain and storms will be confined to the morning hours.

These storms will have more low level moisture to work with, so the SPC has the entire area in a slight risk for severe weather. Large hail and damaging winds remain the primary threats. The tornado probability is low, especially since the winds from 850mb to 250mb are all out of the southwest.

Elevated storms are known for being hail producers, so we’ll continue to update you with the latest information.

February 26, 2007

So, can dust howl? Probably not, but don’t tell that to anyone who was in the area late on Saturday. Steady 40mph winds with gusts as high as 60 kicked up a lot of dust and particulate matter and scattered it hundreds of miles. The impressive picture above comes to us courtesy of the Springfield, MO NWS. It clearly, no pun intended, highlights what brought in the smoggy and gritty conditions to our area. Imagine dusty conditions like we experienced for days, months and even years on end. That is what some folks during the 1930’s had to endure in parts of the central plains. We recently received a question about the great dust bowl and posted below is quite an informative link that Drew found. It’s unbelievable, especially pictures of the dust clouds! Check it out.

We’ve got a few nice days ahead and then we’ll be watching a system that will likely bring us some thunderstorms and rain late Wednesday into Thursday morning. The models have been light with the precipitation but jet energy is strong and dewpoints look to climb into the mid and upper 50’s which could certainly support some big thunderstorms. We’ll continue to monitor developments in the days to come. After the midweek system we look to remain quiet and there’s been some serious waffling in the long range forecast as to whether or not we warm up. The 12z run of the GFS today had us under with 9C air at 850mb for next Sunday, but now the 00z for the same time frame has us in a trough with -3C air at 850mb. Silly GFS, tricks are for the Eta! I for one at this point opt for the warmer solution. Time will tell.

February 25, 2007

Gusts in our area have been in the 35 to 50+ mph range for several hours now. The parent storm that brought us the thunderstorms this morning is now pushing into MO. Central pressure with this intense mid-latitude cyclone has been as low as 988mb, and quite possibly lower. Central pressure in a minimal Category 1 Hurricane is about 980mb; two entirely different storms but, intensity wise, not to0 far apart. As the Low pushes off to the east north east our winds will slowly subside though it will be a very windy night.

Severe weather was isolated this morning even though we were under a tornado watch. The atmosphere probably just didn’t have enough juice / moisture to sustain long lived supercells through our area. The amount of wind shear was off the charts, though general consensus here in the 40/29 weather center was that the amount of wind at mid levels may have in effect cut off inflow of warm moisture laden air to developing storms. Sunshine and heating was absent too; though, later in the day the right combination of ingredients did come together for a series of potent thunderstorms east of Little Rock. Our thoughts and prayers go out to all who were affected by the Dumas tornado as well the several others that hit today close to the AR / MS border.

We’re watching developments closely for what looks to be round two of 2007, thunderstorm-wise. A trough with a lot of energy upstream is digging just of the British Columbia coast. Once again, this will likely develop a surface low to the west of us by the mid week time frame. As mentioned in other discussions recently, position and specific timing will determine the severity of the associated weather.

Kite flying anyone?

February 24, 2007

As of 5:00PM, what were just a few small radar returns have now blossomed into supercell thunderstorms in the central pan handle of Texas. Severe thunderstorm warnings have been issued as well as a few tornado warnings.

For our area we’ll look for thunderstorm development after midnight and a threat of severe weather to remain through the early part of tomorrow afternoon. At this point of most concern will be high gusty winds, large hail and even an isolated tornado out ahead of a probable line of thunderstorms.

We’ll be here monitoring developments with storms throughout the entire evening and overnight period. If there’s weather happening you’ll know about it! Keep it tuned to 40/29, we’ll keep you advised on-air and on the web!

Latest Severe Weather Timing…
February 23, 2007

The latest 0Z run has us in the severe weather window for Saturday morning into the early afternoon. I’m afraid that central and eastern Arkansas will really be under the gun for dangerous storms throughout the Saturday evening time frame.

Large hail and strong damaging winds throughout the area remain the most likely severe weather threats. Isolated tornadoes are still possible, especially given the amount of shear in the atmosphere. The low level jet cranks over 50 knts by Saturday morning, so we may see some elevated hail producing storms before the main line moves in. The bulk of the storms should be moving east as a squall line; however, if any storms form ahead of the line, they will likely rotate and become severe.

We’ll continue to update you on the air and on the web!

February 23, 2007

The picture with the dark blue and violet wind arrows shows how air behaves when it passes through a jetstreak. Breaking up the jetstreak into four quadrants, the following air- flow characteristics develop.

Right entrance region: upper level divergence
Left entrance region: upper level convergance

Right exit region: upper level convergence
Left exit region: upper level divergence

This is assumed for a linear jetstreak, though often jetstreaks occur within curved flow.

The black and white picture above shows a jetstreak within the base of a trough and one at the crest of a ridge. The one on the left is referred to as a cyclonically curved jetstreak. It can be shown mathematically that flow within the exit region which is the area to the right of the trough base, that upper divergence develops with air converging at the surface.

Now lastly, look at the 300mb map with the blue shadings, marking the regions of fastest wind speed. The red dashed line marks the center of the upper level trough. Take note of the position of the jetstreak within the base. Much of eastern OK and western AR are in the within the area of dashed yellow which is where we will have enhanced surface convergance and upper level divergence due to this cyclonically curved jetstreak. There will be a lot of jet enrgy at hand and this positioning will likely coincide with the period within in which we receive our biggest storms. Right now, this appears to be within the early morning to early afternoon window of Saturday.

Keep it tuned to 40/29! We’ve got you covered on-air as well as on the web!

Severe Weather Thoughts….
February 22, 2007

The latest model information has come out, so now it’s time to update the timing for severe weather. I want to remind people that the most ideal time for severe weather and tornadoes is during the late afternoon and early evening; however, given the strong dynamics with this spring-like storm, overnight severe weather will still remain possible.

The 0Z data suggests storms to develop across western Oklahoma during the day on Friday. These storms will head east and move into our area by Saturday morning. A line of storms will race across the region with embedded rotating supercells within the line. The best severe weather timing will likely be from 6 a.m. till Noon. It will be very interesting to see these storms initiate and evolve to our west throughout Friday afternoon.

Large Hail and gusty winds will be the primary threat across eastern Oklahoma and western Arkansas. Isolated tornadoes can’t be ruled out given the wind shear in the atmosphere. We’ll continue to update you on the air and on our weather blog!

February 21, 2007

Saturday’s set up is still on track and developments are being monitored closely. This will likely be a very long day in the weather center and out in the field. Dynamics with this storm still look most impressive and at this point if we destabilize with long breaks of sun late morning and into the early afternoon, we could really see some big thunderstorms. As we’ve been mentioning in our weathercasts a tornado threat may develop too. Review your family’s safe plan and as I recently told a group of scouts that toured the 4029 weather center, remember the scout motto… “Be prepared”!

Taking a peak into quasi-fantasy land, some seven-eight days out, low and behold there’s another storm! We’ve talked about how our long wave pattern is very active right now and how this translates to weather systems passing through about every four days or so. Well, things do not look like they’re slowing down! This could prove to be a very active spring indeed.

Positioning and timing will be key as to the severity in our area for this coming weekend as will be the case for yet another impressive set-up by the middle of next week. As this weekend’s storm is sampled by more and more land originated data sources in the days to come, the forecast will become fine-tuned.

Keep it tuned to 40/29! We’ll keep you advised on-air and on the web!