Monday, August 10, 2009

Ticking Time Bomb

I like severe thunderstorms. They are fun to try to forecast and I find them exciting to experience. I of course don't like it when they do major damage or pose a significant threat to the safety of people. So, you could say there is a certain intangible threshold where a situation goes from enjoyable, to scary. I think we've already crossed that threshold today, and the nearest storms are just starting to pop in eastern Michigan.

Now, if you checked my site early this morning, you would have seen that I had taken it down and had prepared it to sit dormant for the next 10 days or so due to a variety of circumstances. However, things are evolving in such a way that I really feel like I need to be updating today.

Ok, so whats going on. If you haven't stepped outside lately, go do so. You will be greeted by a blast of heat and oppressive humidity when you do. Temperatures have already shot up into the 80s, and dewpoints are in the low 70s. This has already led to instability levels that are rare for our area, and high even by the standards of the Great Plains. So often, I talk about the role of cloud cover in severe weather outbreaks. Often times in our area, clouds in the morning and early afternoon inhibit destabilization, which is why we don't see extreme instability like we are seeing now very often. But it has been sunny and will continue to be sunny through the afternoon, which means things will only continue to destabilze to levels that far exceed anything we have seen this year, possibly even the past few years.

Instability alone is not enough to create a severe weather outbreak. You also need a trigger to get storms going. For us, that is a disturbance moving towards the east along a cold front. Right now, it is over southern Michigan...which is why the storms are forming there. As it moves east, this energy will provide the lift needed to allow storms to continue to form. As they interact with the unstable air, they will intensify. One more piece is needed though, and that is shear, or a change in wind speed or direction with height or horizontal distance. In this case, we are looking at speed shear from both the ground up into the atmosphere, and horizontally from south to north. This is because of an area of strong winds in the jet stream called a 'jet streak' that is to our north. This will provide the shear needed to organize the storms into segments, or even a squall line.

The way I see it right now, all of the ingredients are evolving to come together for a significant severe weather event for all of Central New York. The only question I really have is whether or not a massive squall line will form out of those storms in Michigan, or if there will be multiple, but smaller lines of storms. That is something that will only be determined as the afternoon goes on. Regardless, there is the potential for strong, destructive winds after roughly 4pm tonight. It wouldn't hurt to take some precautions now by putting away lawn furniture, securing loose objects, etc. The biggest threat from the storms is definatly wind and, if I was updating my site as normal, I would likely place it in the 'high' category. I believe that most, if not all counties in Central New York will experience at least some wind damage to trees.

Another danger tonight will be flash flooding....some areas, especially in Cortland County, got 3"+ of rain yesterday, with mudslides and road closures overnight in Cortland County. It won't take much heavy rain to create more problems. NEVER drive through a flooded roadway! Flooding is the number 1 weather killer in the United States, and most of those fatalities occur in automobiles.

Watch for another update between 3 and 5pm, or sooner if a watch comes out. This is one forecast I hope I am not right on.

2 comments:

  1. I like severe thunderstorms. They are fun to try to forecast......

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