August level heat, but hints of cooler to come 

Posted: 10:00 am Monday, September 17th, 2018

By Kirk Mellish

Temperatures up to 10 degrees above normal this week into the weekend but humidity drops for at least a few days. Then it’s back to humid and warm to hot by the weekend.

But there’s some record cold and record snow in parts of Canada while its hot down here.

“Summer has come and passed
The innocent can never last
Wake me up when September ends
Like my fathers come to pass
Seven years has gone so fast
Wake me up when September ends…” —Green Day

The “big three” global models are projecting a ‘positive PNA’ (+PNA) jet stream pattern to develop AFTER a period of hot and mostly dry high pressure aloft replacing Florence, this would replace the upper-level ridging with a fall-like trough by late September or to open October (ridge West/Trough East) providing at least a few days of normal to below normal temperatures and very dry Canadian air:

GFS DETERMINISTIC:

Screen Shot 2018-09-17 at 9.35.20 AMScreen Shot 2018-09-17 at 9.17.03 AM

EUROPEAN ENSEMBLE:

Screen Shot 2018-09-17 at 9.18.24 AM

GFS DETERMINISTIC:

Screen Shot 2018-09-17 at 9.20.03 AM

CANADIAN ENSEMBLE:

Screen Shot 2018-09-17 at 9.24.54 AM

(Pivotal Weather 4 maps)

If correct this could mean a day or two of highs in the 70s with lows in the 50s, possibly some upper 40s.

Of course the global equation variants differ on the timing and the details of how much ridge and trough so we’ll have to wait and see if consistency grows in the days ahead. The numbers below will certainly change as we get closer to the change.

We also have to watch the Gulf and Caribbean for any tropical developments over the next couple weeks while the main Atlantic breeding ground goes quiet. If something were to develop it could change the long-term pattern to something different from this:

gefs_t2anom_16_noram_1KATL_2018091700_eps_min_max_15KATL_2018091706_min_max_16

(WeatherBell 3)

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