Sunday, March 18, 2012

Why The 2012 Severe Season is Starting So Early.

Hi Rebecca here again, as I've been saying with the ridiculously warm winter, severe weather season is starting very early across the county. Last week had almost 3000 records broken.  The winter of 2011 - 2012 will go down as the 4th warmest on record. According to the NWS 36 states will have a warmer than average spring. The pattern we've been stuck in has severe weather and tornado reports setting a near-record pace. We've already had outbreaks in January, February, and  the exceptionally deadly outbreak on March 2nd and 3rd. The destructive tornadoes in Michigan the other day is the latest example. The tornado that struck Dexter, Michigan had winds of 135 mph; it caused considerable damage that will cost millions to rebuild, fortunately no-one was killed.  The one thing that really stands out with the Michigan tornadoes is many of the counties reported their earliest tornadoes in history. Looking at all the long-range climate forecast models, things look a bit alarming temperature wise. If the models are right, we will have well above average temps for most if not all of the spring of 2012. If this is indeed the case, there could be trouble brewing for many areas across the country, including the Northeast. The sad fact is many of these areas, don't have a lot of experience with large destructive tornado outbreaks.

Why is this happening?

If you've been following my weather page, you know I've been blaming the extremely warm winter, on many of the weather woes we've seen across the country this spring. As I said earlier, the Severe / tornado Season for 2012 is off to near-record setting pace, when compared to average  standards. There are many reasons for what we've seen unfold so far this year.

One of the biggest reasons is the lack of winter that we have had this year across the United States. This  has allowed for well above average temperatures to be in place farther north than normal for mid March. Normally, storms weaken this early in year as they move north, However, because of the jet stream pattern we've been in for the last 3 months this modification is not occurring. The current Jet pattern is pulling the extremely warm and moist Gulf air northward. And as most of us are aware, warm moist air is a major ingredient in thunderstorm formation. The Tennessee and Ohio river valleys, parts of the Southeast, and now Michigan have been in the crosshairs, There are a few other factors in play as well, the Rockies are about the only place in the country that has a decent snowpack. Also the Southwest has had extremely dry conditions. Therefore, there is lots of cold dry air that is available for the southwesterly winds to transport northward. 

Another thing that is effecting things is the weakening  La Nina. During La Nina years we do see higher amounts of tornado outbreaks, I have seen evidence that during a weakening La Nina tornado outbreaks tend to be more to the north and often east of the Mississippi. One reason for this is La Nina drives different weather patterns which produce warmer environments throughout the United States.. John B. Knowles and Roger A. Pielke Sr, wrote a paper that talks about EL Nino's and La Nina's effects on tornadic actively.

With the lack of cold air in the eastern two thirds of the  country and all of these atmospheric  dynamics coming together, as far north as they have been. It could be a active year in the northern half of the country. The Northeast normally sees its severe season around May and June. However, As I've said on my weather page, the tornado season seems to be running about 6 weeks ahead of schedule. So for the Northeast, we will just have to wait and see how things play out.

Our next severe outbreak potential is starting tomorrow March, 18th in parts of Texas up into Kansas. The severe threat could be a three or four day ordeal. Now while it doesn't look like the set-up we had going into March 2nd.  It looks like we could have a few days of an elevated risk.

Here are a few images of the weather set up on March 19th  for the southern part of Tornado Alley. Right now, the big threat looks to be strong damaging winds, large hail, and flooding rains. But at least a few tornadoes are going to be added to the mix.

                                                                      The NAM 500mb bulk shear  
                                                                      The NAM Helicity 0-1k

                                                                       The NAM dewpoints for Monday
                                                                      The NAM Helicity 0-3K

NAM Lifted Index values

                                                               The NAM 300mb Jet stream pattern

                                                                        Monday's simulated radar                                                                

                                                                   SPC's Convective Outlook

                                                                      SPC's Probabilistic Outlook

As we move more into the severe season, it will be important to keep your eyes on the sky. I'm losing count on how many times I've said you have to be prepared for severe weather. So, if you don't have a NOAA weather radio and a severe weather plan. Please take the time to take care of both of those issues.  Because sooner or later, most likely sooner,  the Northeast will be dealing with severe weather. Let hope it's not as bad as we've seen so far this year.

Thank you for taking the time to read this post; your readership means the world to me.


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