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Posts Tagged ‘Iowa’
Uncertainty Remains with Weekend Storm System
Good afternoon,
I posted on the social media pages yesterday about how the mid-range models were showing a powerful upper level system moving through the Central United States later this weekend, and how it was pretty darn impossible to say anything with certainty. Even a day later, we’re still having that problem. I wanted to show you what kind of data we’re dealing with when it comes to this system.
06Z GFS - Dewpoints at 7 PM Saturday
06Z GFS - Mixed Layer Convective Available Potential Energy (MLCAPE) at 7 PM Saturday
This data comes from the Global Forecast System (GFS) and is from the 06Z run from early this morning. The first graphic shows the dewpoint output at 7 PM on Saturday. Notice that the dewpoints are fairly low along/ahead of the dryline across Texas with values from 50F to 54F. As a result of the low dewpoint values, instability is non-exsistant on this run. If this run were to verify, we would be lucky to get a rumble of thunder, with absolutely no severe weather to be found. Now, lets take a look at the same model except the 12Z version that was run later in the morning.
12Z GFS - Dewpoints at 7 PM Saturday
12Z GFS - Mixed Layer Convective Available Potential Energy (MLCAPE) at 7 PM Saturday.
Now we fast forward to another model run from the GFS, the 12Z version run about 6 hours later. This is the same time period at 7 PM on Saturday with the same graphics as the 06Z run, except a few important differences. With the 12Z GFS, rich gulf moisture returns northward. 50F degree dewpoints are drawn northward along the cold front/dryline northward into Iowa. Dewpoints at/above 60 degrees spread inland across Texas and make it up to the Red River. Concentrating on Texas, notice how a 5 to 8 degree increase in dewpoints affects instability values. On the 06Z GFS with dewpoint values around 54F, there is no instability. With the 12Z run and with dewpoint values near 60-65F, a large instability pool is able to develop. Mixed Layer Instability is able to build up to 1000-1500 joules per kilogram (J/Kg). For a fall event in early November, that is a moderate to decently high amount of instability.
12Z GFS - 500 MB Winds/Heights at 7 AM Saturday
Here we’re looking at 500 MB (18,500 feet) winds and heights at 7 AM on Saturday from the 12Z GFS. While the instability/moisture questions remain, models are remaining fairly consistent on the position/strength of the upper level disturbance. Timing differences remain which would also have a significant impact on the forecast for the weekend, but the point I’m trying to make here is that this is a very powerful system. Winds at 500 MB exceed 80 to 100 knots. If moisture and instability are in place when this system arrives, there could be some severe weather issues. Even modest amounts of instability could do the job with this kind of a setup.
Can you understand why we can’t be specific yet on what we might be dealing with this weekend? We’ll be able to provide more details as we get closer to this possible event. Heck, it’s possible that there won’t be any event! We’re still over 125 hours away from this and high resolution model guidance doesn’t really kick in until 3 days out. Moisture return is a big question. The cold front that’s going to move through the region tomorrow night is going to really dry us out. Whether or not moisture can get back in here in time to produce any severe weather is the big question, as it normally is for fall/winter events. Stay tuned!
Severe Weather Update – 4 PM
We’re still looking at the potential for a large severe weather event across the Northern Plains this afternoon, although some details have changed since the discussion made this morning. The primary chance is the severe weather threat area has been extended further south to include portions of Kansas and Missouri. The graphic above displays the probability of a tornado occurring within 25 miles of any given point (such as your house). The Storm Prediction Center actually had upgraded a portion of this area to a 15% risk earlier this morning, but returned it to the 10% due to uncertainties related to storm coverage. Undoubtedly, there is the potential for a serious tornado threat this afternoon and evening. The ten percent probability extends from northeastern Kansas into northwest Missouri, northward into Nebraska and South Dakota, eastward into Iowa and parts of Minnesota. This coverage a fairly large area. In addition, the white dotted line indicates an enhanced risk for seeing significant tornadoes, or tornadoes that are strong to violent (EF2-EF5).
This graphic comes from the High Resolution Rapid Refresh model. We’re looking at the simulated reflectivity at 10 PM tonight. I’d like to remind you that this is only a model and should be taken with caution, but it does perform fairly well when it comes to severe weather. At 10 PM tonight, the HRRR has a area of strong to severe convection over Northern Missouri into Iowa. The strongest convection being indicated at this point is just west of Kansas City, impacting areas such as Topeka. Storm motion is to the east, and it moves that cluster of very severe storms eastward into Missouri, causing major impacts to Kansas City. Like I said, this is only a model, but those living in these areas should be ready to take protective action later this evening.
An interesting note, Connor is actually in Northern Missouri today on an unrelated visit to storm chasing, however, he is chasing in NW MO today, but has a flight to catch out of Kansas City back to Dallas around the time these storms are shown moving into Kansas City. While Connor won’t be streaming today (It is rather expensive to take all your chase equipment on an aircraft nowadays) he does have video equipment and will be providing occasional updates, so stay tuned! In addition, we’ll be covering today’s severe weather event throughly with several updates as we continue through the evening. Stay tuned to our social media networks for the latest!
Severe Weather; including Tornadoes likely in the Northern Plains Today
An active severe weather day is expected across the Northern Plains, with a higher-end standard risk of severe weather issued across most of Nebraska and South Dakota. Unlike the past several days, there is an enhanced risk of Tornadoes today. The chance of a tornado within 25 miles of any given point (such as your house) is the main graphic (largest section) in the image above. For areas in Northern Nebraska into the eastern half of South Dakota, there is a 10% chance of seeing a tornado within 25 miles of any given point. This is higher then the average risk of 5% and reflects an enhanced risk of tornadoes in that area. In the two smaller graphics to the left, the chance of seeing severe hail (1.00 inches and larger) is in the top left graphic. Areas within the white hatched area have an increased chance of seeing destructive hail over the size of two inches. The bottom left graphic features the chance of seeing severe winds in excess of 58 MPH. In review, there is a good chance that severe weather will be present across these areas by this afternoon into tonight. While we won’t be chasing this event due to the distance from Texas, we will be providing live updates on our social media feeds (Facebook and Twitter) of events as they unfold, including live streams of chasers who are chasing today. If you’re not already following us on Facebook and Twitter, be sure to do so for the latest information as it unfolds later today!
Video from tonight’s Derecho in Kearney, NE
Texas Storm Chaser Connor McCrorey shot this footage just after 8 PM in the vicinity of Kearney, Nebraska as a violent derecho was moving through the city. Several strong gustnados occurred with this storm as it moved through the city, causing some damage and tossing farm equipment. Outside of the specific gustnados, widespread straight-line winds over 80 MPH (with a measured gust to 90 MPH) moved across a large portion of Eastern Nebraska and Kansas, cutting off power to large areas.
Contact Information:
Connor McCrorey – (214) 392-3767
Active Pattern Next Week
Good morning,
Sorry for the lack of any meaningful discussions over the past few weeks. It’s been pretty busy and its pretty hard to find time to sit down and crank one of these out. After the epic late April period where we ended up chasing six days in a row, with the Great Dixie Outbreak occurring just over a week ago, we’ve had a down period which we much appreciated. While we like to chase storms, we did need a break to catch our breath and get a few things taken care of. After another quiet weekend, things look to be heating up for next week across the plains.
0Z GFS for Monday Evening - Dewpoints
By later today, moisture will begin to return from the Gulf of Mexico after a week of dry weather allowed for unseasonably cool temperatures across a good portion of the nation. Moisture will continue to flow northward unabated through the weekend, and by Monday very high amounts of moisture will have bade it as far north as Interstate 80 with some models suggesting very high dewpoints for this early in the year. This will create a muggy atmosphere that many northerners I’m sure will be happy to feel after this winter. With the amount of high moisture in place across a large portion of the plain states, the stage will be set for severe weather possibilities from Texas all the way up into SD/NE/IA area, just to name a few locations. We’re still too far out and don’t have enough agreement in the models to begin looking at specific days, but as of right now it looks like there will be a strong inversion (cap) in place across the nation next week. This will make forecasting severe weather even more difficult as the cap’s strength will determine if we get a widespread outbreak of severe storms one day verses a clear, blue sky. Those details will become clearer over the weekend, but as of this morning we’re watching Sunday through Thursday for the possibility of chases all the way from Texas up to Nebraska. We’re going to be working on a few website updates/maintenance items over the weekend to get ready for a potentially busy upcoming week. In addition, we are planning to conduct at least one ride-along ‘tour’ next week as our schedule permits. If you have not already done so and are interested in riding along with us, head up to the tour page for more information.
Thanks for stopping by! I’ll try to have another update posted by Friday Evening.
- David
Chase Status
This shows the probability of a storm chase within the next 5 days.
By roczag
By weatherworm