Northeast US winter storm

January 13th, 2011
GOES-13 6.5 µm water vapor images (click image to play animation)

GOES-13 6.5 µm water vapor images (click image to play animation)

A strong “Nor’easter” winter storm impacted much of the northeastern US on 12 January 13 January 2011. The storm exhibited a nice presentation on AWIPS images of the GOES-13 6.5 µm “water vapor channel” data (above; click image to play animation). Storm total snowfall amounts included 36.0 inches at Wilmington, Vermont, 34.5 inches at Savoy, Massachusetts, and 29.5 inches at North Haven, Connecticut (HPC Storm Summary).

A comparison of the GOES-13 6.5 µm water vapor image at 18:15 UTC and the corresponding MODIS 6.7 µm water vapor image at 18:16 UTC (below) demonstrates the value of better spatial resolution (1 km on the MODIS image) for depicting subtle storm structures. Also note the slight northwestward “parallax shift” of the features on the GOES-13 image, due to the large viewing angle from GOES-13 (which is positioned over the Equator at 75º West longitude).

MODIS 6.7 µm and GOES-13 6.5 µm water vapor channel images

MODIS 6.7 µm and GOES-13 6.5 µm water vapor channel images

GOES-13 water vapor + RUC80 PV1.5 pressure + Cross Section line

GOES-13 water vapor + RUC80 PV1.5 pressure + Cross Section line

There was a strong Potential Vorticity (PV) anomaly associated with this storm — in fact, a northwest-to-southeast oriented cross section of RUC80 model fields through the developing “comma structure” seen on GOES-13 water vapor imagery at 15 UTC  (above) showed that the tropopause (taken to be the pressure of the PV1.5 surface) had been drawn downward to near the 800 hPa pressure level (below).

RUC80 model cross section

RUC80 model cross section

A sequence of 1-km resolution MODIS 11.0 µm IR and POES AVHRR 10.8 µm IR image (below) showed the development of banding features with IR brightness temperatures as cold as -50 to -60º C (orange to red color enhancement).

MODIS 11.0 µm and POES AVHRR 10.8 µm IR images

MODIS 11.0 µm and POES AVHRR 10.8 µm IR images

After the storm departed, a comparison of a 13 January MODIS 0.65 µm visible channel image with the corresponding MODIS Red/Green/Blue (RGB) image — created using MODIS channels 01/07/07 — showed the extent of some of the snow cover (which appears as the darkest shades of red on the RGB image), as well as the presence of supercooled water droplet clouds and glaciated ice crystal clouds (which show up as light gray and lighter shades of red on the RGB image, respectively).

MODIS 0.65 µm visible image + MODIS false-color Red/Green/Blue (RGB) image

MODIS 0.65 µm visible image + MODIS false-color Red/Green/Blue (RGB) image

Lake Michigan lake-effect snow band enhanced with a mesoscale vortex

January 8th, 2011
MODIS true color and false color Red/Green/Blue (RGB) images)

MODIS true color and false color Red/Green/Blue (RGB) images)

A comparison of MODIS Red/Green/Blue (RGB) “true color” (created using Bands 1/4/3) and “false color” (created using Bands 7/2/1) images from the SSEC MODIS Today site (above) showed a well-defined single lake-effect snow (LES) band running down the length of Lake Michigan on 08 January 2011. On the false color image, snow cover, ice, and glaciated clouds appeared as cyan-colored features, in contrast to the brighter white supercooled water droplet cloud features.

A mesoscale vortex formed during the day along the southern end of the Lake Michigan LES band, which helped to enhance snowfall rates as the band moved inland across southwestern Lower Michigan and northern Indiana. With the heavy snow from this LES band and mesoscale vortex, South Bend, Indiana (station identifier KSBN) set a new record for both 1-day and 2-day snowfall26.0 inches and 36.6 inches, respectively. With the MODIS Sea Surface Temperature (SST) product showing mid-lake SST values over 40º F (+10º C) and the 12 UTC 850 hPa air temperatures at Green Bay WI and Gaylord MI around +4º F (-16º C), the delta-T values were certainly large enough to support the formation of intense LES bands.

A closer view of the southern end of the LES band and the mesoscale vortex using 250-meter resolution MODIS true color RGB images at 17:04 UTC and 18:46 UTC (below) also revealed the movement of small ice floes in the nearshore waters of Lake Michigan.

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

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

The evolution of the mesoscale vortex was evident on McIDAS images of 15-minute interval GOES-13 0.65 µm visible channel data (below; click image to play animation). Also note the numerous long, narrow streaks of snow on the ground across parts of northern Illinois into northern Indiana, left behind from previous events.

GOES-13 0.63 µm visible channel images (with surface weather) - click to play

GOES-13 0.63 µm visible channel images (with surface weather) - click to play

AWIPS images of MODIS 0.65 µm visible channel data with overlays of MADIS 1-hour interval satellite winds (below) indicated that the LES band features were generally propagating southward at speeds of 20-30 knots.

MODIS 0.65 µm visible images + MADIS 1-hour satellite winds

MODIS 0.65 µm visible images + MADIS 1-hour satellite winds

A comparison of a 1-km resolution MODIS 11.0 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image (below) showed that IR brightness temperatures within parts of the LES band feature were as cold as -25 to -30º C (cyan to darker blue color enhancement).

MODIS 11.0 µm IR and GOES-13 10.7 µm IR images

MODIS 11.0 µm IR and GOES-13 10.7 µm IR images

The 1-km resolution POES AVHRR Cloud Top Height (CTH) product (below) indicated that the LES feature exhibited CTH values which were generally in the 2-3 km range (darker violet color enhancement).

POES AVHRR Cloud Top Height product

POES AVHRR Cloud Top Height product

The POES AVHRR Cloud Particle Effective Radius product (below) helped to highlight the glaciated portions of the LES band, where the radius of the larger ice crystals was in the 50-60 µm range (green color enhancement), compared to the supercooled water droplet clouds consisting of smaller particles in the 15-25 µm range (cyan color enhancement).

POES AVHRR Cloud Particle Effective Radius product

POES AVHRR Cloud Particle Effective Radius product

Tornado moves across the Jackson, Mississippi airport

December 31st, 2010
GOES-13 10.7 µm IR images (click image to play animation)

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

A tornado (which produced EF-2 damage at one point along its path) moved directly across the airport grounds and passed just south of the airport terminal at Jackson, Mississippi (station identifier KJAN) around 23:20 UTC on 31 December 2010 — being such a close call, it was cause for the staff at the National Weather Service forecast office at Jackson to shelter in place for several minutes while the tornado moved over the airport. This was part of a large severe weather outbreak across much of the south-central US.

AWIPS images of 4-km resolution GOES-13 10.7 µm IR data (above) showed the cold cloud top IR brightness temperatures associated with the storm, which reached a minimum value of -77º C at 22:10 UTC.

About 1.5 hours before the Jackson MS tornado, AWIPS images of 1-km resolution POES AVHRR 0.63 µm visible and 10.8 µm IR data (below) displayed IR cloud top brightness temperatures as cold as -82º C (violet color enhancement), as well as a prominent shadow that was being cast by that particular overshooting top on the visible image.

POES AVHRR 0.63 µm visible + 10.8 µm IR images

POES AVHRR 0.63 µm visible + 10.8 µm IR images

A comparison of the 1-km resolution POES AVHRR 10.8 µm IR image with the corresponding 4-km resolution GOES-13 IR image (below) is a good demonstration of the problem of parallax error associated with viewing tall storm top features from geostationary satellites. Note how far northward the cloud features are displaced on the GOES-13 IR image — with a POES satellite flying directly overhead, there is minimal parallax error and therefore a more accurate mapping of the cloud features.

POES AVHRR 10.8 µm IR + GOES-13 10.7 µm IR images

POES AVHRR 10.8 µm IR + GOES-13 10.7 µm IR images

East Coast Blizzard

December 27th, 2010
GOES-13 6.5 µm water vapor images (click image to play animation)

GOES-13 6.5 µm water vapor images (click image to play animation)

An intense winter storm impacted a great deal of the eastern US on 26 December27 December 2010, producing blizzard conditions along much of the East Coast (with Blizzard Warnings issued from Virginia to Maine), total snowfall amounts as high as 32.0 inches at Rahway, New Jersey, and significant accumulations as far south as Mississippi, Alabama, and Georgia (HPC storm summary). AWIPS images of 4-km resolution GOES-13 6.5 µm water vapor channel data (above) showed that the storm exhibited a very well-defined dry slot (yellow to orange color enhancement) and comma head structure during the course of its development. Cloud-to-ground lightning strikes could be seen along the periphery of the dry slot, with isolated strikes noted over New Jersey and also Long Island, New York (where thundersnow was reported). An excellent summary of the storm can be found on the AccuWeather WeatherMatrix Blog.

On a series of 1-km resolution POES AVHRR 0.63 µm and MODIS 0.65 µm visible images (below) the shadowing and texture of a number of convective bands could be seen, which were responsible for enhancing snowfall rates. On a longer series of 1-km resolution POES AVHRR and MODIS IR images, IR cloud top brightness temperatures as cold as -40 to -50º C were evident along the East Coast of the US.

POES AVHRR 0.63 µm and MODIS 0.65 µm visible images

POES AVHRR 0.63 µm and MODIS 0.65 µm visible images

Night-time images of 4-km resolution GOES-13 3.9 µm shortwave IR images suggested the presence of a warm “eye-like” signature at the center of the storm, but the subsequent daytime 1-km resolution GOES-13 0.63 µm visible images showed that the presence of extensive low-level cloudiness prevented a well-defined “eye structure” from being seen (below).

GOES-13 3.9 µm shortwave IR and 0.63 µm visible images (click to play)

GOES-13 3.9 µm shortwave IR and 0.63 µm visible images (click to play)

Once the bulk of the cloudiness had cleared in the wake of the storm by the afternoon on 27 December, a comparison of a 1-km resolution MODIS 0.65 µm visible channel image with the corresponding MODIS false-color Red/Green/Blue (RGB) image (created using the 0.65 µm visible channel as the Red and the 2.1 µm “snow/ice” channel as the Blue and Green components of the image) revealed that a rather large “snow hole” remained from central Pennsylvania to northern Virginia (below). Inland snow cover appeared as darker shades of red on the RGB image, in contrast to bare ground (cyan) and supercooled water droplet clouds (lighter shades of white).

MODIS 0.65 µm visible + MODIS false-color Red/Green/Blue (RGB) image

MODIS 0.65 µm visible + MODIS false-color Red/Green/Blue (RGB) image