I like to look at the guidance for the 850 mb level temps for a variety of reasons. In the winter, the 0C line is a good approximation of the rain-snow line. In the warmer seasons, the 850 mb temps give one a good idea as to what the surface temp might be in a well mixed atmosphere (i.e. breezy day). Thursday will be a breezy day as shown by the map below. Winds will be NW at all levels and near the surface, we will see winds routinely hitting 20-25 mph during the afternoon when the sun also helps in the differential heating and mixing of the atmosphere. Note the streamlines advecting air from Huron to Erie to Harrisburg....doesn't have that same sound as Tinkers to Evers to Chance now does it?
That graphic above is a well mixed atmosphere! So tomorrow we have the opportunity to try the forecast of the surface temps based on the 850 mb temps. Using the normal dry adiabatic rate of 5.5F/1000 feet and considering that the 850 mb is roughly 5,000 feet up, lets look at the forecast temps at a mile up.
Upon close inspection of the map below, KMDT appears to be around the 8C isotherm (46.4F). Thus at 18Z tomorrow, KMDT should be very close to 46.4 + 27.5 = 73.9F! If it is warmer than that, we can blame it on global warming. If it is cooler than that, we can blame that on global warming as well since the warmer global temps created a more energetic atmosphere to create a stronger NW wind to bring in even cooler air from further north in O Canada!
When looking at the straight model guidance for temps tomorrow at the surface, this is what the model paints for 18Z tomorrow:
What a difference a day makes! Just like my colleague stated at the end of today that he is now 40% lighter! I bit???.....the seniors bonehead! I also spoke with some others about the temps not hitting 90F in quite some time again here at KMDT. We do have chance on Sunday, but I think clouds and potentially some thunderstorms will prevent that from happening. Then we lock into a sustained NW flow of seasonable and dry wx for the foreseeable future. I just watered the garden this evening as the storms passed to our east as I suspected might happen. Believe it or not, agricultural and gardening interests could use some rain after that bout of early season heat. The numerical guidance is also hinting at tropical development in the next 10-15 days as well....different post for a different day.
Enjoy the beginning of the end of the school year 2010-11!
Smitty
AA: 74F at 2 pm tomorrow at Harrisburg International Airport and we could use some rain again and the seniors are gone!
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