It’s “Bowling Ball” season

Closed upper lows, weatherman’s woes

March and April are famous months for closed upper level low pressure systems that on an upper level weather chart resemble round bowling bowls as they roll across the nation. This is a sign in nature that Spring is coming and it happens as the wave-lengths of the jet stream shorten and long-wave troughs “cut-off” low pressure within the flow during a transition from one season to another.

Bowling ball is just a nickname we use in the profession, it’s not in the meteorology textbooks.

Upper-level cut-off lows are notoriously hard to forecast and have an extreme variety of weather across a large area impacted by them with sharp gradients between one type and another with great complexity. The global models struggle with them because they are best at the large-scale broad view and not systems that are vertically stacked and relatively small compared to the hemispheric jet stream flow. They often do wacky things.

The next two weeks look unsettled and changeable as we still have a split-jet stream pattern with a vigorous and juicy Southern sub-tropical jet stream entering the U.S. in the Baja region. Cold air comes and goes quickly in this type pattern and highs in the 70s and 80s will return again before March is over.

The bowling balls will bring mostly rain and temperature swings in front of them and behind them:


FORECAST SURFACE WEATHER NEXT 3 DAYS:

FORECAST RAINFALL ESTIMATE TUESDAY AFTERNOON INTO VERY EARLY WEDNESDAY:

For daily updates follow me on Twitter @MellishMeterWSB and listen to 95.5 WSB RADIO.

Kirk Mellish

Meteorologist

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