Mesovortex over Lake Michigan

July 19th, 2012 |
GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

A mesoscale vortex developed in northern Lake Michigan early in the day on 19 July 2012; AWIPS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation) showed that the mesovortex then propagated southward across the western portion of the lake during the afternoon hours. Early in the animation, ship WBD4889 (plotted in red) appeared to have captured the periphery of the circulation of the developing vortex, with south-southeast winds at 20 knots (at 15 UTC)  which transitioned to northeasterly winds at 25 knots (at 17 UTC). Along the coast of Wisconsin, winds gusted to 19 knots at Sheboygan (KSBM) at 20 UTC, 23 knots at Milwaukee (KMKE) at 22 UTC, and 19 knots at Racine (KRAC) at 23 UTC as the vortext was moving to the east of those locations.

POES AVHRR Cloud Top Height product

POES AVHRR Cloud Top Height product

The 1-km resolution POES AVHRR Cloud Top Height product (above) indicated that the tops of the clouds associated with the mesovortex were only around 1 km (light pink color enhancement), so the mesovortex was not a vertically-deep feature. This low cloud top height was supported by the relatively warm Suomi NPP VIIRS IR cloud top brightness temperatures (below), which were around +10 C.

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

A 250-meter resolution MODIS true-color Red/Green/Blue (RGB) image from the SSEC MODIS Today site (below; viewed using Google Earth) showed hints of some organized cloud banding structure within the center of the mesovortex as it was just east of Sheboygan, Wisconsin at 18:58 UTC (1:58 PM local time).

MODIS true-color Red/Green/Blue (RGB) image (viewed using Google Earth)

MODIS true-color Red/Green/Blue (RGB) image (viewed using Google Earth)

As noted by the NWS Milwaukee/Sullivan forecast office:

AREA FORECAST DISCUSSION   NATIONAL WEATHER SERVICE   MILWAUKEE/SULLIVAN WI   914 PM CDT THU JUL 19 2012

.UPDATE… AN INTERESTING MESO LOW THAT LIKELY FORMED OVER THE NORTHERN REACHES OF LAKE MICHIGAN WHERE COOL AIR INTERACTED WITH THE WARM LAKE TEMPS…ROLLED DOWN THE LAKE SHORE AND HAD REACHED THE SOUTHERN TIP OF THE LAKE BY MID EVENING. THE ADDED FORCING AND LOW LEVEL CONVERGENCE FROM THIS FEATURE LEAD TO SHOWERS ACROSS THE FAR SOUTHEAST CORNER OF THE CWA THIS EVENING. THAT SHOULD ALL END BY MIDNIGHT.

The following day was cloud-free across Lake Michigan, allowing a nice view of the lake using the 1-km resolution MODIS Sea Surface Temperature (SST) product (below) — this showed a transition from SST values in the upper 60s F (green color enhancement) in the middle of the lake to middle 70s F (orange color enhancement) in the southern part of the lake.

MODIS Sea Surface Temperature product

MODIS Sea Surface Temperature product

Leave a Reply