Atmospheric blocking of the jet stream prevents big warm-up

If it continues, then cooler than normal trends will be favored in much of November and December

Coolest air of the season so far for Atlanta this weekend, and the same for next weekend.

When jet streams are blocked they are forced to “go around” the block like water in a stream around a big rock.

This also happens when the Polar Vortex in the Stratosphere above the North Pole is weak thanks to warmer than normal air aloft.

This can come from a stratospheric warming event (SSW) leading to a negative Arctic Oscillation (AO) and or Negative North Atlantic Oscillation (NAO).

When jet streams are forced South of their typical position and then try to “recover” and head back North it can lead to changeable or stormy weather and colder air masses shifting South over time.

The ECMWF, GFS Ensemble and JMA are all projecting high-latitude blocking to various degrees even into December as you’ll see in the maps below.

Certainly NO arctic air is coming to Georgia anytime soon, but no big lasting warm spell either.

FROSTY temperatures are possible next weekend in Metro Atlanta with a freeze possible for the Mountains as the lowest temperatures of Autumn so far are expected.

Temperatures in GEORGIA for the MONTH OF NOVEMBER are still expected to average below-normal for the month on average.

EUROPEAN MODEL ENSEMBLE 500MB JET STREAM PATTERN FORECAST:

JMA AND ECMWF MODELS FORECAST ARCTIC OSCILLATION INDEX FORECAST:

GFS ENSEMBLE FORECAST 16-DAY RAINFALL DEPARTURE FROM AVERAGE:

ECMWF AND GFS ENSEMBLE 10/15-DAY SNOW FORECAST:

ANOTHER NOR’EASTER NEXT WEEKEND:

My winter forecast will come out in November.

For more connect with me on Twitter @MellishMeterWSB.


Kirk Mellish

Kirk Mellish

Meteorologist

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