CIMSS Satellite Blog

GOES-12 visible images

GOES-12 visible images (above) revealed the northward propagation of an large convective outflow boundary across the Bay of Campeche (in the far southwestern Gulf of Mexico) on 02 July 2009. A larger-scale GOES-12 visible image (below) showed that at one point this outflow occupied an area approximately the size of the state of Wisconsin!

GOES-12 visible image

An overpass of the QuikSCAT satellite provided SeaWinds near-surface wind data (below) which showed that there was southeasterly flow across much of the Bay of Campeche region, but the wind speeds increased from about 10-15 knots ahead of the outflow boundary to 15-25 knots behind the outflow boundary (the winds at Buoy 42055 gusted to 21 knots around 12 UTC). The QuikSCAT wind vectors showing speeds of 34-50 knots (yellow to red colors) were not valid, due to rain flags greater than 90%. The air temperature and dew point values barely budged with the passage of this outflow boundary, due in part to the very warm (84º F or 29º C) water temperature.

GOES-12 visible + GOES-12 IR + QuikSCAT winds

AWIPS images of the Blended Total Precipitable Water (TWP) product (below) suggest that the TPW dropped from about 57 mm (2.24 inches, red color enhancement) to around 46 mm (1.81 inches, yellow color enhancement) in the wake of this outflow boundary.

Blended Total Precipitable Water product

GOES-12 visible images

GOES-12 visible images (above) showed a nice example of convective initiation along an outflow boundary from thunderstorms a few hours earlier across northeastern Iowa on 25 June 2009. This new convection that developed along the outflow boundary produced hail of 1.5 inch in diameter and damaging winds in extreme northern Illinois (just south of the Wisconsin border) during the 20:42 -21:02 UTC period.

A comparison of AWIPS images of the MODIS visible channel and a Red/Green/Blue (RGB) composite using MODIS bands 01/07/31 (below) showed the value of the false-color RGB imagery to help highlight the darker green patch of wet ground produced by heavy rainfall from the initial area of thunderstorms. Ice crystal clouds appear as varying shades of pink in the RGB image, which also helps to identify growing areas of cumulus clouds that have glaciated.

The next generation of AWIPS (AWIPS2) should offer NWS forecasters the ability to create and display this type of 24-bit RGB imagery (which is not possible using the 8-bit graphics capability of the current AWIPS system).

MODIS visible + false-color RGB image