Showalter Index Calculator

Gusty Winds in the Mid-Atlantic and Northeast; Atmospheric River to Impact the Northwest

Gusty winds are expected from portions of the Mid-Atlantic into the Northeast through the night following the system that brought rain to the area. An atmospheric river will move into the Northwest late today into Saturday bringing moderate to heavy rainfall, mountain snow, windy conditions, and high surf to the area over the weekend. Read More >

Showalter Index

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What does my answer mean?

Showalter Index greater than 0: Stable, but weak convection possible for SI = 1-2 if strong lifting is present.
Showalter Index between 0 and -3: Moderately unstable.
Showalter Index between -4 and -6: Very Unstable.
Showalter Index between less than -6: Extremely Unstable.

Gusty Winds in the Mid-Atlantic and Northeast; Atmospheric River to Impact the Northwest

Showalter Index

by Tim Brice and Todd Hall

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What is the formula for the Showatler Index?