As we head for August’s end and the traditional ‘heart’ of hurricane season, the pattern is starting to become favourable both over N America as well as in the deep tropics.

We’re seeing the classic end of summer/start of fall upper air pattern with heights rising further north which supports increased tropical concerns along the US coastline.

We’ve now got Hurricane Christobal but thankfully this system remains offshore for the US but it’s the environment left behind which bears watching. Note another feature the NHC has highlighted east of Christobal.

In the most recent infrared imagery, note a large and complex Christobal which appears to have TWO balls of deep convection. Could we see a piece split away and head westward?

Note in the below 16 day 500mb height anomaly chart for North America and how a big blocking high builds northeast from the Plains up into eastern Canada. As heights build over eastern Canada, so we see lowering heights underneath and over crucial areas such as the Caribbean and western tropical Atlantic. The dry air and Saharan dust, though still around, isn’t as extensive or deep.

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Though there’s nothing immanent, the large-scale mid and low latitude pattern is becoming more favourable as you would expect it to at this time of year.

The MJO is becoming favourable for the Western Atlantic Basin.

Pressures are lowering.

Shear is dropping off. (Reason by Christobal is now a hurricane)

Indy Get’s First 90, St Louis, first 100

It may be late but this pattern of building heights north and eastward has finally brought Indianapolis their first 90 of the year yesterday.

Yesterday’s highs. Toasty for the Plains and Midwest for sure!

St Louis saw their first 100 yesterday. While this summer’s heat is rather late, it’s pretty toasty now but how does this ‘heatwave’ compare to the past in St Louis? Here’s a nice graphic produced by the St Louis NWS.

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