GOES-13 0.63 µm visible channel images

Now that GOES-13 is the operational GOES-East satellite again, we have a view that covers the far eastern Atlantic Ocean into the far northwestern portion of Africa. The hazy signature of an outbreak of Saharan Air Layer (SAL) dust streaming off the African coast is evident of GOES-13 0.63 µm visible channel images (above).

The CIMSS SAL product (below; click image to play animation) also indicated that a strong outbreak of dust was moving westward across the Atlantic Ocean.

Meteosat-9 Saharan Air Layer (SAL) product (click image to play animation)

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19 bands of the GOES-13 Sounder (upper panels) and 5 bands of the GOES-13 Imager (lower panels)

GOES-13 became the operational GOES-East satellite once again at 15:45 UTC on 10 June 2013 (following recovery from an anomaly on 22 May) — the multi-panel image above shows all 19 bands of the GOES-13 Sounder along with all 5 bands of the GOES-13 Imager at that time.

The images below show the GOES Sounder 7.4 µm water vapor channel data using AWIPS, and the footprint change from GOES-14 at 14:46 UTC to GOES-13 at 15:46 UTC is obvious.

GOES-West and GOES-East Sounder 7.4 µm water vapor channel

A comparison of all 19 bands of the Sounder instrument on GOES-14 and GOES-13 (below) shows some improvement in noise in a few of the bands (due to an “outgas” procedure being performed on the GOES-13 Sounder during recovery from the anomaly).

Comparison of the 19 Sounder bands on GOES-14 (14:46 UTC) and GOES-13 (15:46 UTC)

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The transition from GOES-14 to GOES-13, as seen in 0.63 µm visible channel data from the Imager instrument

The transition from GOES-14 to GOES-13 is also shown above, using McIDAS images of 0.63 µm visible channel data from the Imager instrument. Once again, the image perspective is different, due to the fact that GOES-14 is positioned over the Equator at 105 W longitude, and GOES-13 is at 75 West longitude. This difference in satellite viewing perspective is very apparent when comparing the Full Disk views of 0.63 µm visible channel images from GOES-14 at 14:45 UTC and GOES-13 at 17:45 UTC (below).

GOES-14 vs GOES-13 Full Disk 0.63 µm visible channel images

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GOES-15 6.5 µm water vapor channel images (click image to play animation)

AWIPS images of GOES-15 6.5 µm water vapor channel data (above; click image to play animation) showed the formation of an unusually dry signature associated with a cut-off low near the coast of southern California during the 08 June – 09 June 2013 period. Water vapor channel brightness temperatures were as warm as -9.0º C (darker orange color enhancement), which is an abnormally warm/dry value to be seen on water vapor imagery.

This warm/dry signal was also very apparent on imagery from the 3 water vapor channels (6.5 µm, 7.0 µm, and 7.4 µm) that are available from the GOES-15 sounder (below; click image to play animation). These 3 GOES sounder water vapor channels sense the amount of mosture within 3 different vertical layers of the atmosphere, and are used to create the GOES sounder Total Precipitable Water (TPW) derived product — which in this case depicted TPW values as low as 11 mm or 0.43 inch at 18:00 UTC. The Blended Total Precipitable Water Percent of Normal product indicated that the TPW values within the dry cut-off low were generally 40-70% of normal for this time of year over that region.

GOES-15 Sounder and Imager water vapor channel images (click mage to play animation)

The very warm/dry signature seen on the GOES-15 water vapor imagery was well-correlated with elevated values of GOES-15 sounder Total Column Ozone, which suggests an abnormally low tropopause within that feature. This was verified with fields from the CRAS model, which indicated that the height of the dynamic tropopause (taken to be the PV1.5 surface) was as low as the 570 hPa pressure level at 18:00 UTC. GOES sounder Total Column Ozone values were as high as 382 Dobson Units within the dry cut-off low.

GOES-15 imager 6.5 µm water vapor channel image + GOES-15 sounder Total Column Ozone product (with overlays of CRAS model fields)

===== 10 June Update =====

Comparison of GOES-15 Sounder and Imager water vapor channel data

The dry cut-off low began to move inland over southern California on 10 June, and an AWIPS image comparison of GOES-15 Sounder and Imager water vapor channel data (above) showed that it was centered approximately over Vandenberg Air Force Base (KVBG) at around 12 UTC that morning. A comparison of the GOES-15 Sounder and Imager water vapor channel weighting functions (below) indicated that the individual water vapor channels were sensing radiation from layers that were at much lower altitudes in the dry air mass over Vandenberg, California than they were farther to the north over Medford, Oregon (KMFR) where the atmosphere had much more moisture distributed within the middle to upper troposphere.

Comparison og GOES-15 Sounder and Imager water vapor channel weighting function plots

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GOES-14 10.7 µm IR images + wind shear and tropical overshooting tops

Tropical Storm Andrea (the first Atlantic Basin tropical cyclone of the 2013 season) formed in the eastern Gulf of Mexico on 05 June 2013. GOES-14 10.7 µm IR images from the CIMSS Tropical Cyclones site (above) showed that the center of Andrea was located along the western edge of deep convection, which exhibited numerous Tropical Overshooting Tops. Andrea was forecast to move northeastward into an environment characterized by increasing values of deep layer wind shear, so rapid intensification was not anticipated.

Due to partial obscuration by high clouds from the deep convection, the low-level center of circulation was difficult to identify on McIDAS images of GOES-14 0.63 µm visible channel data (below; click image to play animation).

GOES-14 0.63 µm visible channel images (click image to play animation)

Early in the day, an AWIPS comparison of 1-km resolution MODIS 11.0 µm IR and 4-km resolution GOES-14 10.7 µm IR images (below) demonstrated that the higher spatial resolution data was able to display the small yet very cold areas of tropical overshooting tops — the coldest IR brightness temperatures seen on the MODIS image were -87º C (violet color enhancement), compared to -78º C (lighter gray color enhancement) on the corresponding GOES-14 IR image.

MODIS 11.0 µm IR channel and GOES-14 10.7 µm IR channel images

===== 06 June Update =====

POES AVHRR 12.0 µm IR channel and 0.85 µm visible channel images

1-km resolution POES AVHRR 12.0 µm IR channel and 0.86 µm visible channel images (above) showed Andrea off the west coast of Florida at 15:05 UTC. There was some suggestion of a closed eye beginning to form on the visible image.

1-km resolution GOES-14 0.63 µm visible channel images (below; click image to play animation) revealed that the center of circulation became more well-defined as the tropical storm made landfall around 21:40 UTC (5:40 PM local time) near Steinhatchee, Florida. Maximum sustained winds at landfall were estimated to be 65 mph.

GOES-14 0.63 µm visible channel images (click image to play animation)

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