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Hurricane Fred

Meteosat-9 IR images from the CIMSS Tropical Cyclones site (above) showed that Hurricane Fred began to exhibit a well-defined eye as it rapidly intensified to a Category 3 storm on 09 September 2009. As noted in the National... Read More

Meteosat-9 IR images

Meteosat-9 IR images

Meteosat-9 IR images from the CIMSS Tropical Cyclones site (above) showed that Hurricane Fred began to exhibit a well-defined eye as it rapidly intensified to a Category 3 storm on 09 September 2009. As noted in the National Hurricane Center discussion:


IT IS QUITE UNUSUAL TO HAVE SUCH A POWERFUL SYSTEM SO FAR EAST IN
THE BASIN AND FRED IS ONLY THE THIRD MAJOR HURRICANE NOTED EAST OF
35W IN THE TROPICAL ATLANTIC OCEAN...AND THE STRONGEST HURRICANE SO
FAR SOUTH AND EAST IN OUR DATA RECORD.  THIS TYPE OF SYSTEM...
HOWEVER...WOULD HAVE BEEN VERY DIFFICULT TO ACCURATELY OBSERVE
BEFORE SATELLITE PICTURES BEGAN IN THE 1960S.

Terra MODIS visible image

Terra MODIS visible image

At 12:50 UTC, a “transverse banding” structure was seen on the cold cloud tops surrounding the western periphery of the eyewall region on the  Terra MODIS visible image (above) and the 11.0 µm Terra MODIS IR image (below). MODIS IR brightness temperatures were as cold as -74º C within the transverse bands.

Terra MODIS 11.0 µm IR image

Terra MODIS 11.0 µm IR image

Fred was not expected to undergo much more in the way of intensification, since the cyclone was moving toward increasing values of environmental wind shear and warmer sea surface temperatures (below).

Meteosat-9 IR image with CIMSS wind shear analysis

Meteosat-9 IR image with CIMSS wind shear analysis

Hurricane Fred forecast track + Sea Surface Temperature analysis

Hurricane Fred forecast track + Sea Surface Temperature analysis

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MODIS false color images showing the Station Fire burn scar

A sequence of daily 250-meter resolution MODIS false color images from the SSEC MODIS Today site (above; also available as a QuickTime animation) shows the rapidly increasing size of the burn scar associated with the Station Fire north of Los... Read More

250-meter resolution MODIS false color images

250-meter resolution MODIS false color images

A sequence of daily 250-meter resolution MODIS false color images from the SSEC MODIS Today site (above; also available as a QuickTime animation) shows the rapidly increasing size of the burn scar associated with the Station Fire north of Los Angeles during the 28 August – 07 September 2009 period. The fire burn scar appears as the large darker red feature (which is seen to grow very quickly to the north and east on 30-31 August), while the hottest actively burning fires appear as smaller clusters of  pink to white along the periphery of the burn scar. Thick smoke partially obscured the burn scar area on 01 September, while large pyrocumulus clouds were seen to form over the eastern portion of the fire activity on 02 September.

As of the morning of 08 September, the Station Fire had burned over 160,000 acres, making it the largest fire in Los Angeles County history (and the 9th largest fire in California history).

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GOES-14 vs GOES-12 visible channel

A comparison of enhanced visible channel images from GOES-12 and GOES-14 at 13:15 UTC on 01 September 2009 is shown above — both images have been remapped to a Mercator projection over the state of Wisconsin. The obvious “meteorological” phenomenon is the early morning fog in the Mississippi, Wisconsin, and... Read More

GOES-12 visible image

GOES-12 visible image

GOES-14 visible image

GOES-14 visible image

A comparison of enhanced visible channel images from GOES-12 and GOES-14 at 13:15 UTC on 01 September 2009 is shown above — both images have been remapped to a Mercator projection over the state of Wisconsin. The obvious “meteorological” phenomenon is the early morning fog in the Mississippi, Wisconsin, and Kickapoo River basins, in addition to numerous other valleys and river basins feeding into the Mississippi River.
There are a couple of significant differences to note between the 2 visible images. First of all, the fog is a bit brighter and a little more extensive in the GOES-14 image compared to the GOES-12 image. This is primarily due to the relative age of the visible sensors (which noticeably degrades with time). The second major difference is the relative contrast of lakes, rivers, vegetation, and land usage. GOES-12 has slightly  more  contrast between  land and lakes (and/or other bodies of water) than GOES-14.

On the other hand, GOES-14 is able to discern urban centers more readily than GOES-12, as well as variations in vegetation type. Examples of this are around the large metropolitan region of southeastern Wisconsin and northeastern Illinois (i.e. Milwaukee to Chicago). Also, both the Baraboo Range (located just to the northwest of Madison) and the “Military Ridge” (which runs east to west from Madison to Prairie du Chien) stand out more boldly in the GOES-14 image compared to the GOES-12 image (AWIPS topography image). This difference is primarily due to the slight variation in the spectral width of the two visible bands on the GOES-12 and GOES-14 Imager instruments. A comparison of the visible channel spectral response function for GOES-12 and GOES-14 (below) shows that the sharper cutoff for wavelengths beyond 0.7µm on the GOES-14 visible channel makes it less sensitive to the signal from the mature corn crops, allowing greater contrast between the thick vegetation of the agricultural fields and the more sparsely vegetated cities, towns, and highway corridors.

Spectral response functions for GOES-12 and GOES-14

Spectral response functions for GOES-12 and GOES-14

A time series of GOES-12 visible images (below) illustrates how the cumulus cloud field developed during the morning hours as solar heating increased — convective clouds were seen to develop right over the Baraboo Range and the Military Ridge (AWIPS topography image). At 15:15 UTC and 15:32 UTC, effect of the terrain on cumulus initiation was quite evident, while more “ridge-line cumulus” developed and filled the region by 16:00 UTC and later.

GOES-12 visible image time series

GOES-12 visible image time series

Re-mapped GOES-12 and GOES-14 visible images at 15:45 UTC are shown below, after cumulus development had progressed.

GOES-12 visible image

GOES-12 visible image

GOES-14 visible image

GOES-14 visible image

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Station Fire in southern California

A  wildfire (named the “Station Fire”) had been burning for several days in the Angeles National Forest in central Los Angeles county — and this fire then grew quickly in size from 5500 acres to 35,200 acres during the 29 AugustRead More

MODIS visible and near-IR snow/ice channel images

MODIS visible and near-IR "snow/ice channel" images

A  wildfire (named the “Station Fire”) had been burning for several days in the Angeles National Forest in central Los Angeles county — and this fire then grew quickly in size from 5500 acres to 35,200 acres during the 29 August30 August 2009 period. AWIPS images of the  MODIS visible and the MODIS 2.1 µm near-IR “snow/ice” channels (above) showed the smoke plume which was drifting northward during the afternoon on 29 August, in addition to the cluster of very hot pixels (appearing brightest white on the near-IR snow/ice channel image) around the periphery of the fire complex.

The smoke plume — as well as the patches of cirrus clouds farther to the southeast — did not stand out very well against the surrounding bright, sandy desert soils of the southern California region. However, the 1-km resolution MODIS images below demonstrate that the edges of the smoke feature were easier to identify  using either the MODIS 11.0 µm IR window channel image (where the IR brightness temperature values of the smoke plume were about 25º C colder, making it appear as a lighter gray feature) or the MODIS 1.3 µm near-IR cirrus detection channel image (where the smoke appeared as a brighter feature, due to the efficient scattering properties of the smoke particles).

MODIS visible, IR window, and near-IR cirrus detection channel images

MODIS visible, IR window, and near-IR "cirrus detection channel" images

As the fire burned into the night and on into the morning of 30 August, 4-km resolution GOES-11 3.9 µm shortwave IR images (below) displayed a  large cluster of very hot pixels. A number of the hottest pixels had IR brightness temperatures exceeding the maximum allowable AWIPS IR value of 54.5º C, so AWIPS displayed those hottest pixels as dark black.

GOES-11 shortwave IR images

GOES-11 shortwave IR images

This fire was rather anomalous, in that it was not driven by strong winds (as is usually the case with  most fires in southern California). However, dry vegetation and a hot, dry air mass helped to create a situation that was favorable for rapid fire growth.

===== 31 AUGUST UPDATE =====

The fire continued to grow quickly on 31 August, reportedly reaching a size of 105,000 acres. 250-meter resolution MODIS true color and false color images from the SSEC MODIS Today site  (below) showed a large pyrocumulus cloud and smoke plume associated with the hottest fire that was actively burning in the eastern portion of the fire complex, along with several other active fires (appearing pink to white on the false color image) along the periphery of the burn area.

MODIS true color and false color images

MODIS true color and false color images

===== 01 SEPTEMBER UPDATE =====

The thick plume of smoke could be seen moving northeastward from the Station Fire on 30 August, drifting over the Las Vegas valley region of southern Nevada during the late afternoon and early evening (below). Observe the appearance of a wave structure to the top of the smoke cloud as it moved downwind of the Spring Mountains and the 11,918 foot (3633 meter) peak of Mt. Charleston.

GOES-12 visible images

GOES-12 visible images

The following morning of 31 August, the thick smoke pall had drifted as far to the northeast as Nevada and Utah,  and was now beginning to move eastward  over southern Wyoming and western Colorado (below). Several pilot reports in the region placed the top of the smoke at 17,000-24,000 feet. Note that the smoke was very apparent on GOES-11 (GOES-West) imagery during the later hours of the day (above), and very apparent on GOES-12 (GOES-East) imagery during the earlier hours of the day (below) — this is due to a favorable forward scattering angle (when the sun-smoke-satellite viewing angle approaches 180 degrees), which helps to highlight the airborne smoke layer on the GOES visible imagery.

GOES-11 visible images

GOES-11 visible images

On the morning of 01 September, a portion of the thick smoke cloud had subsided over the Front Range of Colorado, restricting surface visibilities to 3-5 miles at places like Denver, Boulder, and Fort Collins in Colorado and Cheyenne in Wyoming. Late-morning MODIS true color imagery (below, viewed using Google Earth) showed that the smoke  had then begun to drift eastward over parts of Nebraska, Kansas, and the panhandle regions of Oklahoma and Texas .

MODIS true color image

MODIS true color image

===== 03 SEPTEMBER UPDATE =====

MODIS 3.7 µm shortwave IR image

MODIS 3.7 µm shortwave IR image

By 03 September, the Station Fire had burned 148,000 acres, making it the largest fire in Los Angeles County history. Firefighters had made significant progress on controlling the western portions of the blaze, but active fires remained along the eastern periphery of the fire complex. An AWIPS image of the MODIS  3.7 µm shortwave IR channel (above) displayed an arc of very hot fire pixels (darkest black pixels) in the far eastern portion of the fire, located to the north/northeast of El Monte (station identifier KEMT). However, interrogating the 3.7 µm shortwave IR image using AWIPS cursor sampling reported “NO DATA” for the hottest fire pixels, since the brightness temperatures there were above the maximum AWIPS IR threshold. So where were the hottest fire pixels located at that time?

A comparison of the MODIS visible, 3.7 µm shortwave IR, and 2.1 µm near-IR “snow/ice” channels (below) demonstrated that the near-IR “snow/ice” channel imagery could be used in such a case to pinpoint the location of the hottest fires (which show up as the brightest white pixels on the snow/ice channel image).

MODIS visible, 3.7 µm shortwave IR, and 2.1 µm near-IR snow/ice channel images

MODIS visible, 3.7 µm shortwave IR, and 2.1 µm near-IR "snow/ice" channel images

250-meter resolution MODIS true color and false color images from the SSEC MODIS Today site (below) show the size of the Station Fire burn scar (the large red-colored patch located to the west of the smoke feature), in addition to the brighter pink active fire hot spots on the southeastern periphery of the burn area.

250-meter resolution MODIS true color and false color images

250-meter resolution MODIS true color and false color images

Other AWIPS examples of MODIS imagery of the Station Fire can be found on the SPoRT blog from 01 September and from 03 September.

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