MODIS 0.65 µm visible channel + 2.1 µm "snow/ice channel" images

Snow cover was beginning to accumulate into the 12-24 inch range at some locations across the higher terrain of the Rocky Mountains in Colorado on 27 October 2010. While the snow-covered mountains appeared as brighter white features in contrast to the surrounding bare ground areas on AWIPS images of the MODIS 0.65 µm visible channel data, a comparison with the corresponding MODIS 2.1 µm “snow/ice channel” image (above) showed how it was possible to easily discriminate between areas with deep snow cover (which appeared as much darker features on the snow/ice image) and supercooled water droplet clouds (which appeared as brighter white features on the snow/ice image). The large area of cirrus clouds covering the northeastern corner of the image also appeared as a slightly darker shade of gray on the snow/ice image, due to their ice crystal composition.

Another method to easily discriminate between deep snow cover and supercooled water droplet clouds is to use a false color Red/Green/Blue (RGB) image (below), generated using the MODIS visible channel as the Red component and the MODIS snow/ice channel as the Green and Blue components of the image. Deep snow cover then appears as darker red features, in contrast to supercooled water droplet clouds which appear as brighter white features on the image. Again, the large area of cirrus clouds covering the northeastern corner of the image also appeared as a lighter shade of red on the RGB image, due to their ice crystal composition.

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

It can also be informative to compare the MODIS 3.7 µm shortwave IR image to the corresponding MODIS 11.0 µm IR window image (below). Some of the cloud features over northwestern Colorado were exhibiting 11.0 µm IR window brightness temperatures of -20º C and colder (cyan to blue color enhancement), suggesting that they could possibly be getting cold enough for glaciation to occur — however, these cloud features still appeared as darker features on the 3.7 µm shortwave IR image, indicating a strong component of reflection of incident solar radiation off of supercooled water droplets.

MODIS 3.7 µm shortwave IR image + MODIS 11.0 µm IR window image

One of the more interesting comparisons is between the 0.65 µm MODIS visible channel image and the corresponding MODIS 6.7 µm water vapor image (below). Note the presence of widespread mountain waves to the lee of the higher terrain of the Rocky Mountains on the water vapor image — the vast majority of these waves were in cloud-free air according to the visible channel image. Such mountain wave signatures on water vapor imagery can indicate regions where clear air turbulence might be likely.

MODIS 0.65 µm visible channel image + MODIS 0.67 µm water vapor image

CIMSS has been making MODIS imagery and products available in AWIPS format to National Weather Service forecast offices as a part of the GOES-R Proving Ground project.

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GOES-13 6.5 µm water vapor imagery + surface analyses + storm reports

An unusually large and strong mid-latitude cyclone rapidly intensified over the western Great Lakes region on 26 October 2010 (see HPC 18 UTC surface analysis and 22 UTC SPC Watches, Warnings, and Advisories). AWIPS images of GOES-13 6.5 µm water vapor channel data with overlays of surface analyses and SPC storm reports (above) showed a well-defined dry slot (yellow color enhancement) wrapping into the southern and eastern quadrants of the storm. Very strong surface wind gusts (NWS Milwaukee | NWS Green Bay | HPC) associated with this cyclone were reported in Wisconsin (79 mph at Sherwood), the Upper Peninsula of Michigan (70 mph at Point Aux Barques), South Dakota (70 mph at Union Center), and Minnesota (65 mph at Mehurin).

AWIPS Northern Hemisphere composite water vapor images covering the period 23-27 October 2010 (below; also available as a QuickTime movie) revealed the large amount of jet stream energy that was approaching the Lower 48 states from the central and eastern Pacific Ocean during the days leading up to the development of the strong Great Lakes cyclone.

Northern Hemisphere composite water vapor images (23-27 October 2010)

One notable aspect of this storm is that it set new all-time lowest barometric pressure readings for the states of Wisconsin and Minnesota (which were the equivalent to those that would be seen in a Category 3 hurricane):

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE DULUTH MN
1227 PM CDT WED OCT 27 2010

…LOW PRESSURE RECORDS BROKEN ON OCTOBER 26 2010…

THIS IS A PRELIMINARY STATEMENT ON THESE PRESSURE RECORDS. HERE IS WHAT WE KNOW SO FAR ABOUT THE LOW PRESSURE RECORDS SET ON OCTOBER 26TH:

A FEW OF THE RECORDS HAVE BEEN RECALCULATED TO ADJUST FOR TRUE MEAN SEA LEVEL PRESSURE. SOME OF THE PREVIOUS VALUES WERE CALCULATED USING A STANDARD ATMOSPHERE ASSUMPTION /THE ALTIMETER SETTING AT THE STATION/. THE VALUES IN MILLIBARS ARE THE ONES THAT WILL BE MORE EXACT.

AN UNUSUALLY INTENSE LOW AFFECTED THE STATE OF MINNESOTA. AT 513 PM CDT…THE AUTOMATED WEATHER OBSERVING SYSTEM AT BIGFORK MINNESOTA RECORDED A 955.2 MILLIBAR /28.21 INCHES/ PRESSURE. THIS BREAKS THE ALL TIME MINNESOTA STATE RECORD FOR THE LOWEST OBSERVED PRESSURE.

THE PREVIOUS RECORD WAS 962.7 MB SET ON NOVEMBER 10 1998 AT ALBERT LEA AND AUSTIN IN SOUTHERN MINNESOTA. THE RECORD WAS INITIALLY BROKEN SHORTLY AFTER 10 AM AS THE LOW PASSED BY AITKIN MINNESOTA. HOWEVER…THE LOW CONTINUED TO INTENSIFY INTO THE AFTERNOON OVER NORTH CENTRAL MINNESOTA WHERE THE RECORD PRESSURE READING WAS ULTIMATELY ESTABLISHED AT BIGFORK.

.DULUTH…THE LOW PRESSURE RECORD AT DULUTH WAS SET AT 1115 AM WITH A PRESSURE OF 960.2 MILLIBARS /28.35 INCHES/. THE PREVIOUS RECORD WAS 964.3 MILLIBARS WHICH OCCURRED ON NOVEMBER 10 1998.

.INTERNATIONAL FALLS…THE LOW PRESSURE RECORD AT INTERNATIONAL FALLS WAS SET AT 345 PM WITH A PRESSURE OF 956.0 MILLIBARS /28.23 INCHES/. THE PREVIOUS RECORD WAS 971.9 MILLIBARS ON OCTOBER 10 1949.

.WISCONSIN…THE LOW PRESSURE RECORD FOR THE STATE OF WISCONSIN WAS SET IN SUPERIOR AT 1115 AM WITH A PRESSURE OF 961.3 MILLIBARS /28.39 INCHES/. THE PREVIOUS RECORD WAS 963.43 MILLIBARS /28.45 INCHES/ WHICH OCCURRED AT GREEN BAY ON APRIL 3 1982.

$$

LAMERS

A comparison of 1-km resolution MODIS 6.7 µm and 4-km resolution GOES-13 6.5 µm water vapor images (below) demonstrated the advantage of higher spatial resolution for detecting subtle wave features that could be indicators of possible turbulence. In this case, the MODIS water vapor image did indicate the presence of a subtle packet of waves aloft over central Lake Michigan — and there were pilot reports of moderate turbulence very near these wave features at 20,000 and 23,000 feet. Satellite-derived atmospheric motion vectors also showed that the axis of highest jet stream winds (134 knots at 300 hPa) was located along the far eastern edge of the dry slot on the water vapor image.

MODIS vs GOES-13 water vapor images + turbulence reports + satellite winds

AWIPS images of 1-km resolution POES AVHRR 10.8 µm IR data with overlays of surface analyses (below) showed the evolution of the deepening storm, which exhibited very detailed cloud top structure on many of the IR images.

POES AVHRR 10.8 µm IR images + surface analyses

To get a feel for the overall size of the cyclone, a GOES-13 false color full disk image is shown below (courtesy of Rick Kohrs, SSEC).

GOES-13 false color full disk image (14:15 UTC , 27 November)

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MTSAT-1R 0.68 µm visible channel images

MTSAT-1R 0.68 µm visible channel images (above) tracked the eye of Super Typhoon Megi making landfall across the northern portion of the island of Luzon in the Philippines on 17-18 October 2010.

The Morphed Integrated Microwave Imagery at CIMSS (MIMIC) product (below) showed the well-defined eye of Megi prior to making landfall, along with the effect that the rugged terrain of Luzon had on the typhoon before it later emerged into the South China Sea.

Morphed Integrated Microwave Imagery at CIMSS (MIMIC)

A Terra MODIS 11.0 µm IR image (below; zoomed-in version) revealed the eye and surrounding concentric eyewall structure of Megi at 02:30 UTC on 19 October — the coldest IR brightness temperature seen at that time was -82º C (purple color enhancement) to the south of the eye.

Terra MODIS 11.0 µm IR image

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POES AVHRR visible, IR, and Mean Sea Level Pressure contours

AWIPS images of POES AVHRR visible and IR channel data with an overlay of Mean Sea Level Pressure contours (above) showed a very intense Storm Force low that was approaching the Alaska Panhandle region at 20:42 UTC on 12 October 2010. This large storm was producing widespread reports of strong winds and heavy rainfall, with wind gusts as high as 126 mph reported from a boat equipped with wind instruments in Thomas Basin near Ketchikan. There were also reports of multiple trees down in nearby Saxman.

The cloud features at 20:42 UTC could be further characterized examining the POES AVHRR Cloud Type, Cloud Top Temperature (CTT), and Cloud Top Height (CTH) products (below). CTT values within portions of the large “comma cloud” were as cold as -50 to -55º C, with CTH values as high as 8-9 km.

POES AVHRR Cloud Type, Cloud Top Temperature, and Cloud Height products

The evolution of this Storm Force low can be seen in a series of POES AVHRR IR images (below) — from the tell-tale “cusp” cloud feature indicative of strong cyclogenesis early in the day, to a closed-off, almost eye-like cloud structure later in the day.

POES AVHRR IR images

A POES AVHRR visible image with an overlay of 1-hour-interval GOES-derived Atmospheric Motion Vector (AMV) winds (below) showed the broad swath of strong winds associated with a low-level jet that was moving inland — a large number of AMVs had speeds in excess of 60 knots.

POES AVHRR visible image + GOES-derived Atmospheric Motion Vector winds

A comparison of an 8-km resolution GOES-11 water vapor image with the corresponding 1-km resolution MODIS water vapor image (below) revealed a well-defined dry slot moving inland. Strong momentum aloft was being transported downward to lower altitudes within this dry slot, contributing to the high winds that were being reported at the surface.

MODIS water vapor image + GOES-11 water vapor image

An animation of GOES-11 6.7 µm water vapor channel images (below) depicted the evolution of this dry slot during the day.

GOES-11 water vapor channel images

A comparison of the 12:00 UTC GOES-11 water vapor image with the corresponding MIMIC Total Precipitable Water product (below) indicated that a long atmospheric river of rich moisture was feeding into the developing cyclone. Note that not all  of the  “moist” features on the water vapor image necessarily correspond to areas of high total precipitable water content.

GOES-11 water vapor image + MIMIC Total Precipitable Water product

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