Global Instability Index

17 Minutes

Jarno Schipper
Marianne Koenig

Global Instability Index

Published: 04 May 2011

The European geostationary Meteosat Second Generation satellite (MSG) offers a variety of channels to use for various purposes, including nowcasting of convection. A number of applications have also been developed to make use of these new capabilities for nowcasting, especially for the detection and prediction of severe weather. The MSG infrared channel selection makes it possible to assess the air stability in pre-convective, i.e. still cloud free, conditions. Instability indices are traditionally derived from radiosonde profiles. Such indices typically combine measures of the thermal and the moisture properties and often only use a small quantity of vertical profile parameters. MSG based temperature and moisture retrievals are used for the derivation of stability indices, which are a part of the MSG meteorological products derived centrally at EUMETSAT. Such indices are of highly empirical nature and are often only applicable to certain geographic regions, but they can assess the likelihood of convection within the next few hours. Numerous test cases and the more quantitative verification process that was initiated by the South African Weather Service show the generally good warning potential of the derived instability fields. The added capability of a continuous monitoring of the instability fields that is guaranteed by MSG’s 15 minute repeat cycle is most valuable, since it provides nowcasters with new information much more regularly than the twice-a-day soundings at only limited number of stations. The current EUMETSAT instability product is aimed at helping a forecaster to focus his attention to a certain region, which he can then monitor more closely with other means like satellite imagery and radar data over the next hours.

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Filed under Keywords:

Convection, Thunderstorm, RTTOV, Optimal Estimation, Global Instability Index