Good morning bloggers,
We are going into an Omega block. What is it, what does it mean, and what will the impact be on us? I will answer these questions and get to our summer forecast in today's blog.
The symbol ω (lower-case letter) is used to represent what we call an Omega Block (Notes just commented that most meteorologists use the capital letter Omega to describe the Omega bloc, but I still prefer the lower case Omega, which looks exactly like a w) A huge, unseasonably strong upper low is now forming over the western part of the nation. It is helping throw up a big ridge in the middle part of the country which in turn is helping fuel a deep upper low over the Great Lakes. Look below at the forecast map for Thursday morning and notice the letter omega:
The upper low, over southern Canada and the northern Great Lakes is going to fuel a cool air mass that will be just northeast of us Thursday and Friday. One of our big questions is how much of this cool air will get in here and affect the end of the week and the holiday weekend. We will look at this in just a second. But, look at the second map below, valid one day later:
The huge storm in the west is causing the surface pressures to fall over the Rockies. But, since this storm is stuck in the southwest we are not going to see a storm come up from the southwest, like we normally would. This will keep the severe weather threat way out over eastern Colorado and western Kansas this week, but this doesn't mean we have no chance of heavy rain/thunderstorms. Look below at the surface map, valid Thursday afternoon. This is from the GFS model:
There is a warm front across the Oklahoma/Kansas border. The cool air mass from the Great Lakes low is trying to come in at the same time as a hot air mass, with Gulf of Mexico air, is trying to force its way in from the south. This may create a set-up for thunderstorms Thursday and Friday. The NAM is still forecasting well over an inch of rain late Wednesday night into Thursday morning, while the GFS has lesser amounts, but keeps the chance of rain and thunderstorms into Friday and Saturday.
So, the impacts of this Omega block are unknown at this moment. The biggest questions that we will be answering on our weathercasts today and tonight are the following:
- Will the warm front help organize thunderstorms? If rain forms then the warm front will remain strong with outflow boundaries moving out of the thunderstorms, which could lead to a chance of rain Friday into Saturday?
- When will the very warm and humid air move in?
- When will the Omega block break down?
Last night we did our special segment on the summer forecast explaining how this year's LRC is responsible for the shift of tornado alley off to our east, south, and southeast this year. It is this pattern that has created most of the severe weather set-ups east of our local region. And, we believe the pattern will continue, but in a much weaker state as summer approaches. There will be parts of the nation that sizzle this summer, but for eastern Kansas and western Missouri we are forecasting temperatures to be below average with rainfall above average in July and August.
Average highs:
- May 20th: 76
- June 20th: 85
- July 20th: 89
- August 20th: 86
So, expect the average for each month to be a bit below average. Rainfall is forecast to be above average due to the mean trough still located from eastern Missouri north into Canada, even as the flow is very weak during the summer. There will likely be a brief heat wave, but I am not expecting the long stretch of heat we had last August. The flow is very weak aloft, and my confidence isn't so high for this part of the LRC weather pattern, but I think with the trough still existing just east of us in the mean we will see regular cold fronts most of the summer cooling us off just frequently enough to prevent a long term heat wave.
Have a great day. We will add the link to our summer forecast special segment right here once it is posted to our website in a few minutes.
Gary