Understanding Weather Terms...K-Index

A useful feature for predicting the likelihood of thunderstorms is a set of values called the K-Index. Typically used in upper air analyses, the table below shows a general (not 100% accurate) idea of possible thunderstorm development.

K Index	Thunderstorm Probability (%)
<15	near 0
15 � 20	20
21 �25	20 to 40
26 � 30	40 to 60
31- 35	60 to 80
36-40	80 to 90
> 40	near 100

Meteorologists use stability indices to make a quick determination of how susceptible the atmosphere is to severe weather. Along with the K-index, here is a chart of the other variables that make up the stability indices:

Stability Index	Description	Condition for Severe Weather
Lifted Index	T500 � Tparcel	<-3
K Index	(T850 � T500) + DT850 - (T700 � DT700)	�> 30
Total Totals	(T850 � TD850-2(T500)	> 48
Showalter Index	T500 � T850	<-2

Accessing the Storm Prediction Center's Website (SPC), I've noticed that they have inserted the K-Index tool along with other important parameters such as CAPE, Lifted Index (LI), Lapse Rates, wind shear profiles, and precipitable water (PW). This will help me further to analyze forecast charts and make my own prediction for my backyard, especially regarding severe weather prospects.

MS