MODIS visible, 11.0 µm IR, and Land Surface Temperature images

A late-season winter storm dumped as much as 29.0 inches of snow across parts of the Upper Peninsula of Michigan during the 19-21 April 2009 period — in fact, the 20.5 inches that fell at Marquette was their 3rd largest late season 2-day snowfall on record. AWIPS images of the MODIS visible channel, 11.0 µm IR window channel, and the Land Surface Temperature (LST) product (above) showed that a few areas of snow cover still remained on 28 April 2009. MODIS IR brightness temperatures were as cold as +2º to +5º C (darker blue colors) over the patches of snow cover, which still appeared as varying shades of white on the visible image. While there were some MODIS Land Surface Temperature values as cold as the middle 40s F (darker green colors) over the patches of snow cover, the coldest areas showed up as black “NO DATA” pixels in the LST product, due to the product algorithm mistakenly identifying the sharp temperature gradients as cloud features.

Unfortunately, there were no National Weather Service Cooperative Observer locations in the region that reported any snow depth on the morning of 28 April, so the true depth of the remaining snow cover was not known — however, according to an email reply from meteorologist  John Dee (who lives on the Keweenaw Peninsula):

The snow that remains is from the season and is quite variable in depth, with shaded areas in the higher terrain still having a foot or a bit more, but unshaded areas being bare and those that catch some sun and some shade having anywhere in between zero and a foot. I’d say probably 2-6″ still remaining if you took the bare with the other areas with varying depth and averaged things out.

AWIPS examples of a 250-meter resolution MODIS true color image and a 1-kilometer resolution MODIS Sea Surface Temperature (SST) product (below) showed two items of interest: (1) there was a good signal of the runoff of snow-melt water as it flowed northward from the Ontonagon River basin into Lake Superior (note the reddish hue of the water immediately offshore, due to the iron-rich sediment), and (2) the water temperatures in Lake Superior were still quite cold, with MODIS SST values generally in the 35º to 38º F range (darker blue colors).

MODIS true color image + MODIS Sea Surface Temperature

GOES-12 IR imagery (Animated GIF)

After passing over Key West on 18 August, Tropical Storm Fay made landfall along the Gulf Coast of the Florida peninsula on 19 August 2008. GOES-12 IR imagery from the CIMSS Tropical Cyclones site (above) showed that Fay was moving slowly northward toward a weakness in the deep layer mean flow. GOES-12 IR cloud top temperatures continued to cool as Fay moved inland (IR brightness temperatures near the Florida coast were as cold as -81º C at 08:40 and 09:15 UTC), with an AWIPS image of the MODIS 11.0 µm IR channel (below) showing an eye structure at 16:10 UTC.

AWIPS MODIS IR image

The appearance of the eye structure continued to improve on GOES-12 visible imagery (below) even as Fay remained over land during the day, and QuikSCAT winds indicated that tropical storm force winds extended out across the adjacent offshore waters of both the Gulf of Mexico and the Atlantic Ocean.

GOES-12 visible image + QuikSCAT winds

The GOES-12 satellite was placed into Rapid Scan Operations (RSO), allowing images at 5-10 minute intervals (below) as the center of Fay grazed Lake Okeechobee in southern Florida. Winds gusted to 78 mph at Moore Haven along the western shore of Lake Okeechobee (MODIS image in Google Earth). It is interesting to note that MODIS Sea Surface Temperatures in Lake Okeechobee on Sunday 17 August were as warm as 91.8 F — this large body of warm water may have acted as an additional source of  evaporation and sensible heat to help fuel convection around the eye of Fay.

Note that Fay almost seemed to exhibit a slight amount of trochoidal oscillation on the GOES-12 images (though nothing like that seen with Hurricane Wilma back in 2005). However, a comparison of GOES-12 and GOES-13 RSO visible images revealed that this apparent “eye wobble” was due to irregularities in satellite navigation (the image-to-image navigation is significantly improved on the newer GOES-13 satellite, due to changes in the spacecraft design).

GOES-12 RSO visible images (Animated GIF)

Due to the aforementioned weak deep layer mean flow regime, the future motion of Fay was very uncertain, as could be seen by the large spread of model forecast tracks (below).

GOES-12 water vapor imagery + model forecast tracks

Even though Fay was not a particularly strong tropical cyclone, the slow forward motion meant an increased threat for heavy rainfall over the southeastern US; the Hydrometeorological Prediction Center 5-day total  precipitation accumulation forecast (below) suggested that rainfall could approach 15-20 inches in parts of Florida and Georgia.

HPC 5-day total precipitation accumulation forecast

** 29 AUGUST UPDATE **

The Melbourne, Florida NWS office received a storm total of 19.62 inches of rain, with  an amazing 27.65 inches reported 8 miles northwest of Melbourne (below).

Total rainfall from Fay (courtesy of NOAA HPC)