Cooler risks likely to continue into medium and long range

Much has been made over the past week or two in regards to a gradual warmup across the United States as we approach the middle of the month of August. With seven days of the month gone by, a notable breadth of cooler than normal air has spread throughout the United States. Despite the persistent forecasts for ridging and higher pressure to develop, an active and progressive pattern has remained in place, keeping things cooler and wetter on average.

As we approach the middle of the month of August, medium range forecast models continue to indicate that the risks for cooler than normal air will continue. Understanding exactly how and why these risks are developing will be a critical component to the forecast moving forward; both in terms of understanding the risk itself, and timing exactly when it will end and a transition to warmth will occur.

The current pattern throughout the northern hemisphere remains active and transient. Troughing has progressed into the Central and Eastern United States in the last 5 to 7 days, leading to cooler than normal temperature anomalies in those regions. As a ridge developed on the Western coast of the United States, cooler air was pushed southward out of Canada and into the Central and Eastern parts of the country.

As we look to the future, what is happening in the Pacific Ocean can be pegged as a  harbinger of things to come. In a very fast atmospheric flow (we’ve used the words transient and progressive a few times already) a large, cutoff trough is forecast to develop in the Gulf of Alaska. This will push a large ridge northward into British Columbia and begin to disrupt the flow in the Arctic regions.

Cooler risk in temperature will remain likely across the USA through Augusts third week.

As this ridging builds northward into the Western Arctic, and begins to act in tandem with other ridging over the Central Arctic, cooler than normal air which typically resides over Northern Canada will be dislodged southward. As disturbances swing into the Central United States, this cooler than normal air will have a propensity to be dragged southward with them. As a result, our forecast carries cooler than normal risks in the Central states over at least the next 7 days.

In about 7 days, forecast model guidance are consistent in indicating a ridging height anomaly over Canada and the Arctic regions — again — as a result of the pattern progression throughout the Pacific and Atlantic Oceans. This ridging in the higher latitudes will act to enhance the potential for cooler than normal air moving into the Central and Eastern United States through at least Day 10 (bringing us to August 17th).

An overwhelming amount of data continues to suggest that cooler than normal risks will be widespread throughout the aforementioned regions — from the Central Plains eastward and eventually including parts of the Northeast states — as we move towards the latter half of August. Any warm risk looks relegated to the Western Coast of the USA through this period. The pattern breakdown currently appears far on the horizon and may not truly occur until August’s last week when this high latitude ridging breaks down and allows warmer, Pacific air to gradually push into the USA.

We’ll be continually monitoring for exactly when this looks more likely to occur. Stay tuned for further updates and, as always, inquire if you are looking for specific Long Range, Agriculture, or Energy consultation.