GOES-13 10.7 µm IR images

Severe thunderstorms that developed along an advancing cold frontal boundary during the pre-dawn hours of 18 September 2010, producing hail up to 1.75 inch in diameter in south-central Wisconsin (NWS Milwaukee/Sullivan news story). AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data (above) showed the development of increasingly colder IR cloud top brightness temperatures as the storms moved over the Madison, Wisconsin area (station identifier KMSN).

A series of 1-km resolution MODIS 11.0 µm IR and POES AVHRR 10.8 µm IR images between 03:32 UTC and 10:23 UTC  (below) displayed greater detail in the cloud top brightness temperature structure as the thunderstorms moved southeastward across the region.

MODIS 11.0 µm IR + POES AVHRR 10.8 µm IR images

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GOES-11 0.65 µm visible channel images

McIDAS images of GOES-11 0.65 µm visible channel data (above) revealed some interesting cloud features over the far eastern North Pacific Ocean on 17 September 2010: (1) a large “hole” in the stratoculumus cloud field, which contained an intersecting pattern of ship condensation trails (or “ship tracks”), and (2) a subtle train of von Karman vortices extending downwind of Guadeloupe Island off the coast of Baja California. These cloud features were propagating southeastward, due to northwesterly winds within the marine boundary layer.

The pattern of ship tracks on the corresponding GOES-11 3.9 µm shortwave IR images (below) displayed a darker (warmer) signature — this was caused by the reflection of incoming solar radiation off the tops of the ship track plumes (which were composed of rather small water droplets compared to the surrounding stratocumulus clouds) during the day when the sun angle was high. Note how this “dark/warm signal” disappeared at the end of the shortwave IR image animation, when the sun angle became lower in the early evening hours.

GOES-11 3.9 µm shortwave IR channel images

A bit more detail can be seen in AWIPS images of the MODIS 0.65 µm visible channel, the 3.7 µm shortwave IR channel, and the 11.0 µm IR window channel data (below). Note how the ship tracks exhibited very little signal in the IR window image, since that channel is not sensitive to the reflection of solar radiation.

MODIS 0.65 µm visible, 3.7 µm shortwave IR, and 11.0 µm IR window images

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GOES-13 0.63 µm visible channel images

McIDAS images of GOES-13 0.63 µm visible channel data on 16 September 2010 (above) showed a nice example of the role that a pre-existing convective outflow boundary can play in helping to act as a forcing mechanism for new convection — and also to help intensify existing strong convection that encounters the outflow boundary. Morning thunderstorms along the Texas/Oklahoma border region produced an outflow boundary that later moved southward and westward during the early afternoon hours. New convection was then seen to develop in Oklahoma and Texas along the old outflow boundary after about 20 UTC.

In addition, new thunderstorms that had developed in the Texas Panhandle around 19 UTC appeared to intensify once they moved eastward and encountered the aforementioned outflow boundary that was left behind from the earlier storms. According to the SPC Storm Reports, the large thunderstorms in the Texas Panhandle produced hail up to 4.00 inches in diameter, with surface wind gusts up to 75 mph.

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GOES-13 10.7 µm IR images

AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data (above) showed a large convective complex that developed over extreme eastern Colorado and then tracked eastward across Kansas and Nebraska during the pre-daylight hours on 15 September 2010. According to the SPC Storm Reports, this severe convection produced a few tornadoes, hail up to 1.75 inch in diameter, and surface winds gusts as high as 78 mph across Kansas.

A comparison of the 1-km resolution POES AVHRR 10.8 µm IR image with the corresponding 4-km resolution GOES-13 10.7 µm IR image (below) demonstrates the improved ability to detect such mesoscale storm top features as overshooting tops and packets of concentric gravity waves. At that particular time, the coldest AVHRR IR brightness temperature was -80º C, compared to -71º C on the GOES-13 IR image. The parallax error associated with geostationary satellite imagery was also apparent, with the slight northwestward shift of the location of the features on the GOES-13 image.

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

The AHPS 24-hour total precipitation analysis (below) indicated a large swath of substantial rainfall was produced by this convective system, which included amounts in excess of 4 inches in northern Kansas.

24-hour precipitation (ending at 12 UTC on 15 September 2010)

At 19:48 UTC, AWIPS images of 1-km resolution MODIS 0.65 µm visible channel and 3.7 µm shortwave IR data (below) revealed the very large swath of wet ground (as indicated by the lighter shades of gray on the shortwave IR image); however, little evidence of this wet ground could be seen on the visible image.

MODIS 0.65 µm visible channel and 3.7 µm shortwave IR images

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MODIS 3. µm shortwave IR image + METAR surface reports

Looking at plots of the surface METAR data (above) and the daily maximum temperatures (below), the large area of wet ground appeared to be holding surface air temperatures down a few degrees compared to adjacent sites across the region.

MODIS 3.7 µm shortwave IR image + daily maximum temperatures for 15 September

On a side note, it is interesting to point out that smoke from wildfires burning in the western US was concentrated along and just ahead of the cold frontal boundary that was moving across Nebraska – this was seen very clearly on a MODIS Red/Green/Blue (RGB) true color image from the SSEC MODIS Today site (below).

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

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