GOES-11 6.5 µm water vapor channel images

McIDAS images of GOES-11 6.5 µm water vapor channel data (above) showed evidence of a very strong jet stream oriented from southwest to northeast across the eastern North Pacific Ocean on 26 September 2010, approaching the coast of British Columbia, Canada. The features on the water vapor imagery were seen to be moving very quickly along the jet stream axis.

A GOES-11 water vapor image with an overlay of MADIS 1-hour atmospheric motion vectors at 00 UTC on 27 September (below) displayed one wind target with a speed of 216 knots at a pressure level of 250 hPa (located near 45 N latitude, 140 W longitude).

GOES-11 6.5 µm water vapor image + MADIS 1-hour atmospheric motion vectors

A comparison of these MADIS winds with a number of model forecasts of maximum wind speed at any level (below) demonstrated how much the models can underestimate the maximum wind speeds within the core of a strong jet stream: The ECMWF Low-Resolution model forecast maximum winds just over 140 knots, while the CRAS45 and the CMC Low-Resolution models had maximum winds of just over 150 knots. The GFS90 and the UKMET models were the strongest, with forecast winds speeds of just over 160 knots — but still far less then the 216 knots observed by the MADIS atmospheric motion vector product.

GOES-11 water vapor image + comparison of model maximum wind speeds

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GOES-13 0.63 µm visible image (courtesy of Tony Cristaldi, NWS Melbourne FL)

Tony Cristaldi (National Weather Service Forecast Office in Melbourne, Florida) sent the following email (with the attached GOES-13 visible image shown above):

There is a very small cyclonic swirl to the southwest of Lisa near 12N 35W, that has been firing off central convection since Friday afternoon. Now, one wouldn’t expect a feature of this magnitude to be carried operationally as a TC, since these features are often times transient, being very vulnerable to even modest amounts of low level deformation and mid of upper level wind shear. Nevertheless, since it has persisted since early this morning, I thought I’d pose a couple questions: 1) Looking at visible imagery, does it appear that convection is persisting due to a warm core TC process (CISK) on a very small scale, or a more traditional low level mesoscale convective process? 2) Would you call this feature a “micro-midget?”

At his request, we created a 2-day animation covering the period 24-25 September 2010, using GOES-13 0.63 µm visible images during the daytime and GOES-13 3.9 µm shortwave IR images at night (below). The low-level “swirl” appeared to be propagating southeastward, and it was indeed firing off some impressive convective bursts (with a few cloud top IR brightness temperature values as cold as -70º C).

GOES-13 0.63 µm visible images (daytime) and 3.9 µm shortwave IR images (night-time)

Not quite sure exactly what to call it…but thanks to Tony for bringing this interesting feature to our attention!

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GOES-13 6.5 µm water vapor channel imagery

A strong mid-latitude cyclone intensified over the Lake Superior region on 24 September 2010. This storm produced wind gusts as high as 42 knots (48 mph), which caused some tree damage and some minor coastal flooding in parts of the Upper Peninsula of Michigan.

AWIPS images of 4-km resolution GOES-13 6.5 µm water vapor channel data (above) showed the evolution of the cyclone as it intensified during the day.

Greater detail could be seen in 1-km resolution MODIS 6.7 µm water vapor channel images at 16:21 UTC and 18:24 UTC (below).

MODIS 6.7 µm water vapor channel images

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GOES-13 10.7 µm IR images

Clusters of severe thunderstorms developed across parts of northeastern Nebraska and southeastern South Dakota ahead of a warm frontal boundary that was advancing northward across the region on 22 September 2010. These severe thunderstorms produced a number of reports of large hail and damaging winds. AWIPS images of GOES-13 10.7 µm IR data (above) showed that cloud top IR brightness temperatures were as cold as around -70º C (dark black enhancement) at times.

The corresponding GOES-13 3.9 µm shortwave IR images (below) revealed that a few interesting “darker plumes” developed on the cloud tops of some of the southernmost storms — this darker appearance was a signature of smaller ice crystal particles that were being ejected above the anvil top by some of the stronger thunderstorm updrafts. These smaller ice crystals were better reflectors of incident solar radiation, making them show up as warmer (darker) features on the shortwave IR images.

GOES-13 3.9 µm shortwave IR images

These darker anvil top plumes were also very evident at 16:33 UTC on 1-km resolution MODIS 3.7 µm shortwave IR imagery (below).

MODIS 3.7 µm shortwave IR image

A closer view using 1-km resolution POES AVHRR 10.8 µm IR imagery at 18:56 UTC (below) displayed a well-defined “enhanced-v” signature in southeastern South Dakota (with the coldest cloud top IR brightness temperature value of -82º C, violet color enhancement) — and a large number of hail reports associated with this storm as it tracked through the area, including a report of 3.5 inch diameter hail near Vermillion, South Dakota.

POES AVHRR 10.8 µm IR image (with hail reports)

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