October 2nd, 2010
MODIS 11.0 Âµm 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 Âµm IR channel data (above) showed a few disorganized cloud bands over Lake Superior, with the coldest cloud top IR brightness temperature values of -13.5Âº 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 Âµm 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 15Âº C). With 850 hPa air temperatures of 0Âº C to -5Âº 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
September 30th, 2010
GOES-13 6.5 Âµm water vapor images + surface frontal analyses
During the 26 September – 30 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.Â
AWIPS images of GOES-13 6.5 Âµm 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)
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)
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)
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 Âµm and POES AVHRR 10.8 Âµm IR channel data (below) revealed features with cloud top IR brightness temperatures in the -80Âº to -88Âº C range (light to dark purple color enhancement).
MODIS 11.0 Âµm IR and POES AVHRR 10.8 Âµm IR images
September 27th, 2010
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
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 0Âº C to -2Âº C across much of the feature.
POES AVHRR Cloud Top Temperature product
September 22nd, 2010
GOES-13 10.7 Âµm IR images
Clusters of severe thunderstorms developed across parts of northeastern Nebraska and southeastern South Dakota ahead of a warm frontal boundary that was advancing northward across the region on 22 September 2010. These severe thunderstorms produced a number of reports of large hail and damaging winds. AWIPS images of GOES-13 10.7 Âµm IR data (above) showed that cloud top IR brightness temperatures were as cold as around -70Âº C (dark black enhancement) at times.
The corresponding GOES-13 3.9 Âµm shortwave IR images (below) revealed that a few interesting “darker plumes” developed on the cloud tops of some of the southernmost storms — this darker appearance was a signature of smaller ice crystal particles that were being ejected above the anvil top by some of the stronger thunderstorm updrafts. These smaller ice crystals were better reflectors of incident solar radiation, making them show up as warmer (darker) features on the shortwave IR images.
GOES-13 3.9 Âµm shortwave IR images
These darker anvil top plumes were also very evident at 16:33 UTC on 1-km resolution MODIS 3.7 Âµm shortwave IR imagery (below).
MODIS 3.7 Âµm shortwave IR image
A closer view using 1-km resolution POES AVHRR 10.8 Âµm IR imagery at 18:56 UTC (below) displayed a well-defined “enhanced-v” signature in southeastern South Dakota (with the coldest cloud top IR brightness temperature value of -82Âº C, violet color enhancement) — and a large number of hail reports associated with this storm as it tracked through the area, including a report of 3.5 inch diameter hail near Vermillion, South Dakota.
POES AVHRR 10.8 Âµm IR image (with hail reports)