lystn

The summertime Ridge (dome of heat) developed further north than usual this year. This is likely due to a series of low pressure systems that were in the south. The low pressure in the south also prevented the warm moist flow on the back side of the Bermuda high from influencing the United States and limited thunderstorm activity to the north. Therefore, the dome of heat had less moisture to work with. Dew points approached 60° in many places and even 70° in Minnesota last week. Although this is somewhat humid it falls well short of the norm especially for the more southern cities. Rapid onset drought developed in many locations especially over the Midwest cornbelt from Iowa eastward into the Ohio Valley and northward. Being that this is the 3rd stagnant airmass of warm and dry air that expanded into Canada this year, conditions were drier than usual. The September hurricane downed trees in Nova Scotia. These dry dead trees provide ample fuel for fire in Nova Scotia.  The combination of all this produced good fire weather.  (The other 2 ingredients which allow for rapid fire spread are dry thunderstorms and wind. ) It is not clear why the wild fires are 7 times worse than usual in Canada this year. Regardless as to what the cause of such intensity is, a stationary low pressure system over the gulf of Maine brought a steady flow of winds from southern Canada into the United States. This brought horrific levels of smoke down to the surface across many of the major cities in the Mid-Atlantic area and the northeast. Fortunately for the northeast stagnant northeast winds are not common in the Summer season.  Although the intensity of the smoke in New York became well known, the smoke in Bismarck, North Dakota last month was 3x worse in many ways as the visibility dropped to a blinding 0.25 miles at times. In Chicago the smoke blocked out the Sun to a mere moon like figure which was colored pink around May 18th. Fortunately for Chicago much of the smoke remained above the surface.  In this episode we reiterate the unique synoptic setup that occured in the Midwest and southern Canada last week as summer heat blew in with northeast winds.  Although it is not clear at this time whether the northeast component to this wind from this airmass effected the fire spread in Canada in an unusual way, it is clear that stagnant domes of heat help the spread of wild fires.  It is key to point out that shortly before northeast winds blew hot dry air into the Midwest, there was a stationary high pressure system over New England. (At that time it was producing southeasterly winds in much of the the Midwest. ) This stagnant air likely played a roll in the spread of wildfire in Nova Scotia.  While it is well established that there is a connection between domes of heat and wild fire spread, in this episode we try to make an additional connection between last week's dome of heat in particular. This was done in an attempt to explain the unprecedented intensity of the wildfires currently in Canada. However, the information presented in this episode is not set in stone as of yet.