River valley fog over southwestern Wisconsin

July 19th, 2011 |
GOES-13 fog/stratus product + GOES-13 visible channel images

GOES-13 fog/stratus product + GOES-13 visible channel images

AWIPS images of the 4-km resolution GOES-13 “fog/stratus product” at night followed by 1-km resolution GOES-13 0.63 µm visible channel data (above) showed that there was a great deal of river valley fog along the portion of the Mississippi River where Wisconsin borders Minnesota and Iowa, as well as some of the tributaries across southwestern Wisconsin on the morning of 19 July 2011. Not surprisingly, much more detail in the fog structure was evident in the higher spatial resolution visible images after sunrise, compared to that seen using the night-time 2-channel IR brightness temperature difference employed to create the standard operational fog-stratus product.

Another example showing how improved spatial resolution aids in river valley fog detection could be seen below with a comparison of the 1-km resolution MODIS fog/stratus product with the 4-km resolution GOES-13 fog/stratus product images around 07:30 UTC (2:30 am local time). Along the Wisconsin River Valley at that particular time, Lone Rock (station identifier KLNR) and Boscobel (station identifier KOVS) were both reporting surface visibilities restricted to 0.25 mile with fog.

GOES-13 fog/stratus product + MODIS fog/stratus product images

GOES-13 fog/stratus product + MODIS fog/stratus product images

More quantitative information about the fog features is available using products such as the Fog Depth and Marginal Visual Flight Rules (MVFR) Probability products (below), which blend model fields with satellite imagery. Fog depth values along the Mississippi River were greater than 700 feet (blue color enhancement), and MVFR Probability was near 50% (lighter green color enhancement) at 09:15 UTC (4:15 am local time). CIMSS participation in the GOES-R Proving Ground includes the distribution of these types of products to select NWS forecast offices for testing and evaluation.

GOES-13 Fog/Stratus product, Fog Depth product, and MVFR Probability product

GOES-13 Fog/Stratus product, Fog Depth product, and MVFR Probability product

McIDAS images of GOES-13 0.63 µm visible channel data (below) offered a slightly clearer view of the river valley fog dissipation during the morning hours.

GOES-13 0.63 µm visible channel images

GOES-13 0.63 µm visible channel images

Farther to the east, there was extensive fog/stratus over southern Lake Michigan, which was discussed on the GOES-R Proving Ground Hazardous Weather Testbed blog.

Wildfires and thick smoke in Ontario, Canada

July 18th, 2011 |
MODIS 3.7 µm shortwave IR images

MODIS 3.7 µm shortwave IR images

AWIPS images of 1-km resolution MODIS 3.7 µm shortwave IR data (above) revealed a large number of “hot spots” (black to red to yellow color enhancement) due to wildfires that were burning across parts of western Ontario, Canada on 17 July18 July 2011.

McIDAS images of GOES-13 0.63 µm visible channel data (below) showed the unusually dense smoke plume resulting from these wildfires. Over Ontario, most of the smoke was located aloft (see the US Air Quality Smog Blog for more details), but surface visibilities were still being restricted to 2-5 miles at some locations. Farther away from the source region, the leading edge of the smoke moving over portions of New England and the Canadian Maritime Provinces exhibited significantly less optical thickness.

GOES-13 0.63 µm visible channel images

GOES-13 0.63 µm visible channel images

The hazy extent of the smoke plume could be more readily seen on a MODIS “true color” Red/Green/Blue (RGB) image from the SSEC MODIS Direct Broadcast site (below). As an aside, note that there are still some large ice floes in the open water of Hudson Bay.

MODIS true color Red/Green/Blue (RGB) image

MODIS true color Red/Green/Blue (RGB) image

Tropical Storm Bret

July 17th, 2011 |
GOES-13 0.65 µm visible channel images (click image to play animation)

GOES-13 0.65 µm visible channel images (click image to play animation)

McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) showed the cyclonic circulation of clouds and the convective bursts associated with the development of Tropical Storm Bret in the western Atlantic Ocean north of the Bahamas on 17 July 2011.

A morning AWIPS image of MODIS 11.0 µm IR channel data with an overlay of MetOp Advanced Scatterometer (ASCAT) surface winds (below) indicated a broad cyclonic flow with maximum velocities around 22 knots at 14:23 UTC.

MODIS 11.0 µm IR image + ASCAT surface scatterometer winds

MODIS 11.0 µm IR image + ASCAT surface scatterometer winds

Later in the day, a DMSP-18 SSMIS 85 GHz microwave image from the CIMSS Tropical Cyclones site (below) showed that the deep convection was limited to the eastern semicircle of the tropical cyclone at that time, due to the presence of some westerly wind shear.

DMSP-18 SSMIS 85 GHz microwave image + deep layer wind shear

DMSP-18 SSMIS 85 GHz microwave image + deep layer wind shear

Upper Midwest Derecho, and a Seiche in southern Lake Michigan

July 11th, 2011 |
GOES-13 10.7 µm IR images (click image to play animation)

GOES-13 10.7 µm IR images (click image to play animation)

AWIPS images of GOES-13 10.7 µm IR data (above; click image to play animation) showed the progression of two long-lived Mesoscale Convective Systems (or “derechos”) on 11 July 2011 — one moving southeastward from the Dakotas and Minnesota, and another moving northeastward from Nebraska. These two MCS features were responsible for a large number of severe weather reports (SPC: 10 July reports | 11 July reports).

Note the elongated band of cirrus that developed  behind the departing MCS feature, curving across parts of Iowa, Nebraska, Kansas, and Colorado toward the end of the IR image animation above — this striated cloud band marked the location of a well-defined deformation zone. Areas of light to moderate turbulence aloft are often present in association with such deformation zones, as was seen by the number of pilot reports overlaid on a GOES-13 6.5 µm water vapor channel image at 17:45 UTC (below).

GOES-13 6.5 µm water vapor channel image + pilot reports of turbulence

GOES-13 6.5 µm water vapor channel image + pilot reports of turbulence

The GOES-13 sounder Total Precipitable Water (TPW) derived product (below; click image to play animation) showed that abundant moisture (TPW values of 50-60 mm or 2.0 to 2.4 inches, violet color enhancement) was in place ahead of the storms as they moved rapidly eastward.

 

 

GOES-13 sounder Total Precipitable Water product (click to play animation)

GOES-13 sounder Total Precipitable Water product (click to play animation)

A closer view of GOES-13 10.7 µm IR images with overlays of the Automated Overshooting Top Detection product (below; click image to play animation) revealed a number of overshooting tops, with the minimum cloud top IR brightness temperature of -81ºC occurring over eastern Iowa at 09:45 UTC. The overshooting tops were very evident after sunrise on GOES 0.63 µm visible channel imagery, as they cast shadows upon the thunderstorm anvil tops below (11:45 UTC visible image + overshooting top detection product comparison).

GOES-13 10.7 µm IR images + Overshooting Top Detection (click to play animation)

GOES-13 10.7 µm IR images + Overshooting Top Detection (click to play animation)

A set of three comparisons of 1-km resolution POES AVHRR 10.8 µm IR images with their corresponding 4-km resolution GOES-13 10.7 µm IR images (below) demonstrated the value of improved spatial resolution for more accurate detection of the location and magnitude of the coldest cloud tops on severe thunderstorms. On the 08:22 UTC, 08:47 UTC, and 11:37 UTC POES AVHRR images, the coldest cloud top IR brightness temperatures were -84ºC, -90ºC, and -85ºC, respectively (the coldest GOES-13 IR brightness temperatures were -78ºC for all three of those times). Note that the apparent northwestward displacement of cloud features on the GOES-13 images is a result of parallax error due to the large viewing angle from the geostationary satellite.

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

1-km resolution POES AVHRR 10.8 µm IR and 4-km resolution GOES-13 10.7 µm IR images

Very strong surface winds were observed along and in the wake of the well-defined bow echo seen on radar — peak wind gusts included 74 mph at Dubuque, Iowa, 75 mph at Chicago Midway Airport, and 85 mph at Michigan City, Indiana. These strong winds created a seiche across southern Lake Michigan (Seiche Warning | NWS Chicago event summary), with oscillations in water levels seen at Calumet Harbor, Illinois, Milwaukee, Wisconsin, and Holland, Michigan.