Big Storm Wrap-Up

To say the very least, it has been windy the past few days. The recent storm was one we will not see for a while. This storm was historical to say the least. I'd like to make a quick correction before diving into this post. In the last post, I said the Edmund Fitzgerald storm reached a pressure as low as 976 mb. The lowest recorded pressure was 980 mb. The 976 mb pressure I discussed was actually from a simulation of the storm.

As for the 980 mb pressure in the Fitzgerald storm, it was blown away by the pressure in this last storm. This recent storm's lowest pressure reached 954 mb! Remember that 1013 mb is standard atmospheric pressure. The low in this storm was almost 60 mb below standard atmospheric pressure, which is extremely rare in mid-latitude cyclones. Here is a surface map from the Hydrometeorological Prediction Center of this storm at its peak intensity:

This surface map only shows the pressure at 956 mb, but just a few hours afterwards, this system hit 954 mb.

Not only did this system hit an astounding low pressure, but it also produced numerous storm reports. At one point, there were tornado warnings extending from Michigan to Alabama, while there was a blizzard in North Dakota, and it was all from the same system. Here are the Storm Prediction Center damage reports over a 3-day period where this system was producing violent weather. Blue marks are damaging wind, green is hail, and red is tornadoes.

October 25, 2010

October 26, 2010

October 27, 2010

The wind damage produced in Illinois on October 25 was mostly overnight into morning. From there, the storm continued producing damaging winds, and it even went on to producing tornadoes.

This storm has mostly moved out of the United States, with just a few remnants of the system remaining. Its pressure has risen back to around 996 mb (not nearly as intense as it was). It is always fascinating how powerful these big historic systems can become. I know I will remember the excitement and awe of watching this storm for a long time.

Dropping a Meteorological Bomb!

Hey all!

First, I apologize for my lack of any posting in months. I thought I'd have time after getting back to school to put up the post, but I then realized I couldn't find the camera cord (so no pictures then). Then classes, homework, and organizations kept my week booked, often leaving me working into the wee hours of the morning. Then bad habits started of not posting, but there's no excuse for my lack of posting now, so I will start posting more often. Again, I apologize.

The reason I had a big urge to post tonight, is because out in the plains right now sits a large low pressure. While this low was sitting out in western Nebraska, storm warnings were being issued by the National Weather Service over Lake Michigan and Lake Superior. The NWS is calling for winds over Lake Michigan to reach up to 60 knots (about 69 mph winds)! They are also predicting wave heights to be as high as 20 feet, with the occasional wave reaching 30 feet high! As of 11:15 pm (Central time), the low pressure with this system was 980 millibar (mb for short). For those not used to pressure in millibar, 1013.25 mb is a standard atmosphere. Basically, this storm is roughly 30 millibar below standard atmospheric pressure, and still intensifying! What makes this storm a bomb is the pressure drop. A meteorological "bomb" is a storm that drops 24 mb of pressure in 24 hours. That is a rapid intensification for any storm, and generally these bombs produce big weather events.

The low pressure is associated with a strong pressure gradient, and this will be the primary reason for the intense winds. Here is the last surface map from the Hydrometeorological Prediction Center. The map will update with time, so it may be different while you examine it.

For some historical reference, the storm that sunk the Edmund Fitzgerald back in 1975, was producing winds around 40-50 knots (46-58 mph)! A reading was from the then nearby ship Arthur M Anderson measured wind gusts at 75 knots (86 mph)! Wave heights with this storm were around 18-25 feet tall waves. Pressure with this storm got as low as 976 mb!

To make this system even more fun, there is a nice cold front associated with this system. This will allow thunderstorms to fire up along the front. The Storm Prediction Center has already been issuing outlooks for severe weather potential over land. A moderate threat for severe weather has been issued by the SPC for Tuesday, October 26, 2010. The primary threat with this system will be damaging winds across most of Illinois. Basically, with the SPC issuing a 45% chance of damaging winds, there is a very good chance of seeing them (scroll over the "wind" portion of the banner to see the percentages). If you noticed the hatch marks on the map, that may require an explanation. Since this is primarily a wind threat, I'll explain with wind. If you are in an unhatched area (and have a probability above your location), you have that percent chance (say 25%, for example) of seeing 50 knot wind damage 25 miles from any point in that location. If it is hatched, then expect that percent (in this case 45%) chance of seeing 65 knot wind damage 25 miles from any point in the hatched area. Since most of the state of Illinois is under a hatched region, there will more than likely be a lot of wind damage reports across the state.

So basically, try not to get blown away (literally), but be ready to be "blown away" (figuratively) by the awesome spectacle we are about to witness. We probably won't see a storm this strong for a while.