Madison sets a new record for total winter season snowfall

February 12th, 2008 |

GOES-12 6.5µm water vapor images (Animated GIF)

The previous all-time record for total winter season snowfall in Madison, Wisconsin was 76.1 inches (set in 1978/1979); however, the winter of 2007/2008 decided that would be an easy record to break…and on the morning of 12 February 2008, the old winter season record was finally eclipsed by 1.8 inches of fluffy snowfall. Not content to stop there, the atmosphere conjured up another round of snowfall later in the day, courtesy of a potential vorticity (PV) anomaly that propagated eastward from eastern Iowa into northern Illinois and southern Wisconsin.

AWIPS images of the GOES-12 6.5µm “water vapor” channel (above) showed a warm/dry signature (darker blue enhancement) associated with the core of the PV anomaly — the “dynamic tropopause” (taken to be the pressure of the 1.5 Potential Vorticity Unit surface) was extruded downward to as low as about the 500 hPa pressure level early in the day. PV anomalies tend to induce upward vertical motions as they approach a given area, and in this case the approaching PV anomaly helped to generate another band of moderate snowfall in southcentral Wisconsin, as seen by the radar reflectivites (below) greater than 20 dBz (green enhancement) that added another 2.0 inches to Madison’s ever-growing winter season snowfall total.

Radar base reflectivity (Animated GIF)

An AWIPS image combination of the GOES-12 water vapor imagery (with a different color enhancement) plus the radar base reflectivity is shown below.

GOES water vapor + radar reflectivity (Animated GIF)

Aircraft contrails over the Upper Midwest

February 12th, 2008 |

MODIS images (Animated GIF)

Comparing AWIPS images of the MODIS visible channel, 11.0µm “IR window” channel, 3.7µm “shortwave IR” channel, and 1.6µm near-IR “cirrus channel” (above) showed how certain satellite channels are very useful in the detection of a broad area of aircraft contrails that existed over parts of Illinois, Indiana, and lower Michigan (likely resulting primarily from air traffic to/from Chicago and Detroit) on the morning of 12 February 2008. The 3.7µm shortwave IR and the 1.6µm cirrus channels offered the best depiction of the actual areal coverage of these contrails; the contrail features exhibited a slightly darker signal on the shortwave IR image (due to the smaller ice particle size of the contrails compared to the surrounding cirrus clouds), while they appeared slightly brighter in the cirrus image (since the smaller particles comprising the contrails were better scatterers than those comprising the surrounding cirrus clouds).

Examining other satellite products such as the MODIS Cloud Phase product, MODIS Cloud Top Temperature product, and the GOES sounder Cloud Top Height product (below) from that same time period confirmed that these aircraft contrails existed in an environment that consisted primarily of ice phase clouds (light red enhancement) which exhibited rather cold MODIS cloud top temperatures (-40º to -60º C, cyan to dark blue enhancement) and fairly high GOES sounder cloud top height values (30,000-39,000 feet above ground level, light blue to white enhancement).

MODIS + GOES sounder images (Animated GIF)