Weather

First heat wave of the season in sight

Extended period of above-normal temps paired with below-normal rain

In the summertime...

We are still up and down for a few more days on the thermometer. But then data is growing that shows the first heat wave of summer 2022 is coming, with above-normal temps (on average) from June 12th or so to July 4th or so. Rainfall during that period looks drier than normal on average.

I tweeted June 4th about the first indications of a coming build up of summer heat:

Evidence of pattern change back in early June

We’ve had some high humidity of late but temperatures have been running a little below-normal for this time of year with a dip in the jet stream and that is repeating as we end this week and head into the weekend.

The jet stream flows around upper level low pressure and high pressure troughs (L) and ridges (H).

500mb jet stream forecast GFS Ensemble

The result:

Forecast temperature departure from avg. GFS Ensemble
Tweet Wednesday June 8th

The drop in the global wind oscillation or GLAAM paired with MJO movement into phases 2+3 are signals for warmer and drier weather trends East of the Missouri River in the months of June and July and models support this, suggesting a building “heat dome” (cTw air mass) upper level ridge next week and beyond, with a possible conjoined Sonoran and Bermuda High at 500mb.

Underneath the heat ridge dome we will have to watch the tropics for any systems that sometimes form with this type pattern.

GFS Ensemble 500mb jet stream forecast
Negative GLAAM June/July temp correlation
MJO Phase 3 in summer
GFS Ensemble forecast temp anomaly
GFS Ensemble forecast temp anomaly
ECMWF Ensemble forecast temp anomaly
GFS Ensemble forecast temp anomaly
GFS Ensemble forecast 500mb jet stream

Heat in the summer of course is a standard feature of Atlanta and the rest of the South hardly unusual. However, what is coming IS warmer than usual for this time of year.

Climate return interval for 5,000 ft (850mb) temp forecast North American Ensemble Forecast System
NOAA/NWS hazard outlook

Here is the typical range in the number of days with a high in the 90ºs for the nation and our region:

Average number of days in the 90s

MODEL OUTPUT DISAGREES ON JUST HOW HOT AND HOW FAST BUT THE TREND IS OBVIOUS:

Canadian ensemble
Blend of models
European Ensemble
GFS Ensemble
GFS Model Output Statistics (MOS)

A good thing to remember is that the models typically bring the start of heat too fast and also depict it hotter than reality. A rule of thumb is to look at the model and know that it will be around 3º above OR below that number.

For more follow me on Twitter @MellishMeterWSB.

©2022 Cox Media Group