Severe thunderstorms in Arizona

October 5th, 2010 |
GOES-11 (left), GOES-15 (center), and GOES-13 (right) visible images

GOES-11 (left), GOES-15 (center), and GOES-13 (right) visible images

Multiple rounds of severe thunderstorms moved northward across southern Arizona on 05 October 2010, producing hail as large as 2.5 inches in diameter, wind gusts as high as 75 mph, and rainfall in excess of 2 inches at some locations (SPC Storm Reports). According to a Phoenix Public Information Statement, the 2.5 inch diameter hail was some of the largest hail ever reported in Arizona.

A 3-panel comparison of visible channel images from GOES-11, GOES-15, and GOES-13 (above; also available as a QuickTime movie) showed the large clusters of convection, some of which moved through the Phoenix area (station identifier PHX). After 18:30 UTC, the GOES-11 satellite was placed into Rapid Scan Operations (RSO) mode, allowing images as frequently as every 5-7 minutes (in contrast to the standard operational 15-minute image interval on GOES-15 and GOES-13).

AWIPS images of the MODIS 0.65 µm visible channel and 11.0 µm IR Window channel (below) showed a closer view of the storms at 21:01 UTC (3:01 pm local time). MODIS cloud top IR brightness temperatures were as cold as -61º C (darker red color enhancement). Cloud-to-ground lightning strikes, severe reports of hail and wind, and surface METAR reports are also overlaid on the MODIS images.

MODIS 0.65 µm visible and 11.0 µm IR Window images

MODIS 0.65 µm visible and 11.0 µm IR Window images

An AWIPS image of the POES AVHRR Cloud Top Temperature (CTT) product (below) displayed a minimum CTT value of -63º C just southeast of Chandler/Williams Air Force Base (station identifier KIWA) at 21:23 UTC (3:23 pm local time).

POES AVHRR Cloud Top Temperature product

POES AVHRR Cloud Top Temperature product

Changes in color of the Fall foliage across parts of MI, WI, and MN

October 3rd, 2010 |
MODIS true color images (19 and 26 September, and 03 October 2010)

MODIS true color images (19 and 26 September, and 03 October 2010)

The series of three 250-meter resolution MODIS true color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed the changes in color of the Fall foliage across parts of the Upper Peninsula of Michigan, far northern Wisconsin, and the Arrowhead of northeastern Minnesota on 4 different days: 19 September, 26 September, and 03 October 2010. These Red/Green/Blue images are created using MODIS Bands 01/04/03.

First lake-effect snow flurries of the season in the Upper Peninsula of Michigan

October 2nd, 2010 |
MODIS 11.0 µm IR image + surface and buoy reports

MODIS 11.0 µm IR image + surface and buoy reports

The first lake-effect snow flurries of the season were observed in the Upper Peninsula of Michigan at Gwinn, Sawyer Airport (station identifier KSAW) on 02 October 2010. An AWIPS image of MODIS 11.0 µm IR channel data (above) showed a few disorganized cloud bands over Lake Superior, with the coldest cloud top IR brightness temperature values of -13.5º C over the KSAW area.

Looking at the buoy data and the ASCAT winds over Lake Superior (below), the wind speeds over the water were not particularly strong — but the winds at KSAW gusted as high as 36 mph during the day. The could be attributed in part to terrain interaction, as the surface winds encountered a rather abrupt change in topography immediately inland across the Upper Peninsula of Miichigan (where the elevations quickly rise to 1000-1800 feet).

MODIS 11.0 µm IR image + surface and buoy reports + ASCAT surface winds

MODIS 11.0 µm IR image + surface and buoy reports + ASCAT surface winds

The AVHRR Sea Surface Temperature (SST) product from late in the day on 01 October (below) indicated that SST values across much of the central and eastern part of Lake Superior were in the middle to upper 50s F (around 12 to 15º C). With 850 hPa air temperatures of 0º C to -5º C, the “Delta-T” values were not of sufficient magnitude for the formation of well-defined lake-effect snow bands.

AVHRR Sea Surface Temperature product + surface and buoy reports

AVHRR Sea Surface Temperature product + surface and buoy reports