10 July 2014
Mid-Summer Taste of Autumn Next Week? Probably!
Posted by Dan Satterfield
What is going on? Is it the revenge of the polar vortex? Actually, it’s probably connected to Japanese Typhoon Neogori that at one time was packing 260 kph winds. It is moving into southern Japan now, but the global weather models all indicate that it will push a lot of warm and humid air into the high latitudes north of Japan. This will push the jet-stream northward, and the downstream effects will lead to a deep trough over the U.S. Great Lakes next week. (See the upper level wind flow at 500 mb (around 6 km) for next week below).
The jet stream winds form on the boundary between a cool atmosphere and a warm atmosphere, and the bigger the difference and the sharper the boundary, the stronger the winds. Meteorologists call this the thermal wind. That, and the fact that the wind flow is kind of like a water-bed (in that if you push it down in one place, it rises in another) is what is happening here. The upper level trough will act to steer cool and dry air from north of 60 degrees latitude well to the south.
Now, I suspect that we may get a few record lows next week, and probably a few meteorologists will get the “So much for global warming” email as well. Obviously, we do not take the planet’s temperature in Wisconsin and while we are getting some relief from the heat, the folks in California and Eastern Russia will be seeing just the opposite. Just looking at the height anomalies on the chart above shows how much of a critical thinking fail that kind of thinking is. (I just added this paragraph in, so I can just reply with the link to this blog post when I get the email next week!)