Updated: 07/11/2014 12:54 AM
Created: 07/10/2014 9:43 PM KAALtv.com
By now I’m sure most of you have heard that a burst of cold air is going to overtake the upper midwest for next week. It's the kind of cold that will likely bring out at least a few hoodies and jeans, maybe even the jackets overnight.
Let’s backtrack a little bit first, because it hasn’t exactly been the warmest of springs/summers so far. For the last 90 days we’re averaging about a degree Fahrenheit below average in temperature. Not too bad really, but we haven’t seen much of a surge of warm air. If you look back to May and months earlier, that temperature anomaly was much much more pronounced. Rochester, and many others, have yet to reach 90° this summer. Only a dozen or so years have seen the first 90° come after July 10th. Four years did not see the a 90° reading, the last being 2008.
You can see the trend so far this month we’ve been far cooler than average, by about 3°C (5.4°F).
We’ve been struggling to break a pattern consistently bringing troughing over the middle of the country. These troughs, bring in a surge of cooler air from our north. Into next week, beginning Monday, another potent trough develops. It’s a very winter-like pattern, so why does it keep happening in the warmer seasons? There are a lot of teleconnections between ocean currents and temperatures and other major weather phenomenon that are occurring. One big influence could certainly be attributed to a developing El Nino in the Pacific Ocean. Another being Typhoon Neoguri near Japan. Phenomena such as these do have some push and pull in the weather pattern.
One major point of interest close to home could be the Great Lakes. Remember the brutal winter we had, and all the ice that covered the great lakes. Lake ice was finally out of Superior by the second week of June this year, far behind normal ice out which usually occurs by the end of April. Right now lake temperatures on Lake Superior are still below 40° in some spots, nearly 12° cooler than average at this point in July.
It’s not just Superior too… all the Great Lakes are running far cooler than normal. The cooler lake temps have a cooling effect on the atmosphere in the region.
As for next week, the Jet Stream is becoming kinked, jutting down from the north forming a huge trough, sinking in over the Great Lakes. This trough will bring some unseasonably cold air into the middle of the country.
Could the cooler region surrounding our continent's largest lakes be coming into play? It could at least a little bit by enhancing the pattern on the small scale especially in areas immediately surrounding the Great Lakes. It's a pattern that is fairly typical in summer, found after a winter of high ice coverage on the Great Lakes.
But as mentioned earlier, there are other teleconnections impacting the pattern too. Teleconnections that are larger and would have more of an impact on a global scale. Jeff Boyne from the National Weather Service says right now, there's a warmer eastern Pacific Ocean and a developing El Nino would likely have a more drastic effect on the current weather patterns. This impact has a warming effect to the atmosphere, north, up the Canadian Coast and Alaska. This displaces the colder air that typically resides in this area. Eventually the balance will shift, but for now we’ve been struggling to break these persistent little blasts of cooler air from the north, especially in the last couple of weeks.
Because of this pattern, the middle part of the country will be dealing temperatures far below normal. All the while, a ridge builds on the west cost, mountain west bringing in warm conditions.