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

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

Historic rainfall event along the US East Coast

September 30th, 2010
GOES-13 6.5 µm water vapor images + surface frontal analyses

GOES-13 6.5 µm water vapor images + surface frontal analyses

During the 26 September30 September 2010 period, copious amounts of moisture (which included the remnants of Tropical Storm Nicole) continually streamed northward along the US East Coast, causing historic rainfall totals (which were also accompanied by high winds and even several tornadoes: SPC Storm Reports). In Wilmington, North Carolina they received an amazing 23.36 inches of rainfall during the 5-day period. 

AWIPS images of GOES-13 6.5 µm water vapor channel data during the 29-30 September period (above) showed that a great deal of clouds and moisture were flowing northward along a stalled frontal boundary.

AWIPS images of the Blended Total Precipitable Water (TPW) product (below) showed TPW values as high as 60 to 75 mm (2.4 to 2.9 inches) moving northward along the Eastern Seaboard during much of the 5-day period.

Blended Total Precipitable Water product (26 - 30 September)

Blended Total Precipitable Water product (26 - 30 September)

These high TPW values were in excess of 200% of normal (below) for that region and for that time of year.

Percent of Normal Total Precipitable Water product (26 - 30 September)

Percent of Normal Total Precipitable Water product (26 - 30 September)

AWIPS images of the MIMIC Total Precipitable Water product (below) suggested that a portion of the moisture feed may actually have been coming from the tropical Pacific!

MIMIC Total Precipitable Water product (26 - 30 September)

MIMIC Total Precipitable Water product (26 - 30 September)

Within this plume of rich tropical moisture, vigorous convective cells were developing over the warm waters of the Gulf Stream and then feeding northward. AWIPS images of 1-km resolution MODIS 11.0 µm and POES AVHRR 10.8 µm IR channel data (below) revealed features with cloud top IR brightness temperatures in the -80º to -88º C range (light to dark purple color enhancement).

MODIS 11.0 µm IR and POES AVHRR 10.8 µm IR images

MODIS 11.0 µm IR and POES AVHRR 10.8 µm IR images

Fog and stratus over the Upper Midwest region

September 27th, 2010
GOES-13 night-time fog/stratus product + daytime visible imagery

GOES-13 night-time fog/stratus product + daytime visible imagery

AWIPS images of the night-time 4-km resolution GOES-13 fog/stratus product and the daytime 1-km resolution GOES-13 visible images (above) showed two features of interest on 27 September 2010: (1) narrow fingers of river valley fog forming during the overnight hours — and then burning off during the early morning hours — over parts of the Mississippi River valley and the Wisconsin River valley, and (2) a larger patch of stratus cloud that lingered over southern Lake Michigan and the Chicago region.

Note the improvement in the detection of the actual structure of the river valley fog features with the change from the 4-km resolution fog/stratus product images to the 1-km resolution visible images — the importance of spatial resolution for detecting river valley fog is also obvious on a comparison of the 1-km resolution MODIS fog/stratus product image with the corresponding GOES-13 fog/stratus product image (below).

1-km resolution MODIS vs 4-km resolution GOES-13 fog/stratus product images

1-km resolution MODIS vs 4-km resolution GOES-13 fog/stratus product images

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POES AVHRR Cloud Top Height product

POES AVHRR Cloud Top Height product

Other satellite products that could be utilized to further characterize the large patch of stratus cloud over southern Lake Michigan and the Chicago region are the 1-km resolution POES AVHRR Cloud Top Height (CTH) product (above), which showed CTH values of around 3 km, and the 1-km resolution POES AVHRR Cloud Top Temperature (CTT) product (below), which depicted CTT values of 0º C to -2º C across much of the feature.

POES AVHRR Cloud Top Temperature product

POES AVHRR Cloud Top Temperature product