AWIPS images of a composite of 4-km resolution GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel data (above; click image to play animation) showed the development of a large mid-latitude cyclone off the East Coast of the US on 26 March 2014. This cyclone underwent rapid intensification as it moved northeastward, with the storm’s central pressure deepening 43 hPa in 24 hours and reaching a minimum value of 955 hPa (which was lower than the 960 hPa minimum central pressure of the March 1993 “Storm of the Century”). Wind gusts in excess of 100 mph were observed both on offshore buoys (44027) and at coastal sites: as the storm approached the Canadian Maritimes, Wreckhouse in Newfoundland experienced an all-time record maximum wind gust of 116 mph (186 km/hour).

A closer view of the storm’s evolution on GOES-13 6.5 µm water vapor channel imagery with overlays of buoy reports, cloud-to-ground lightning strikes, and analyzed surface pressure and surface fronts is shown below.

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (below; click image to play animation) revealed greater detail in the cloud structures near the center of the storm circulation. The appearance of dual vortices can be seen, with the northernmost vortex appearing to be the dominant one associated with the true storm center.

A night-time view of the storm as it was beginning to intensify off the coast of Virginia at 05:56 UTC or 12:56 AM Eastern Time is seen in a comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm IR channel images (below). The bright white streaks appearing offshore on the DNB image are portions of the cloud illuminated by intense lightning — and there were a number of cloud-to-ground lightning strikes detected in the vicinity of these DNB lightning streaks.

As the period of rapid intensification continued off the eastern coast of the US, the GOES-13 sounder Total column Ozone product (animation) depicted very high values (400-450 Dobson Units, shades of red) just south of the storm center at 09:00 UTC, which was a signature of a potential vorticity anomaly (a lowering of the dynamic tropopause caused by an intrusion of dry, ozone-rich stratospheric air into the upper and middle troposphere). According to the GFS40 model, the height of the dynamic tropopause (taken to be the pressure of the PV1.5 surface) had descended to around the 450 hPa level at 06 UTC. The image comparison below shows that this pocket of high ozone was co-located with a pocket of dry middle-tropospheric air on the water vapor imagery, which became even drier with time to the point that it exhibited a light orange color enhancement around 12 UTC on the closer-view GOES-13 6.5 µm water vapor channel image animation seen above.

Daytime views of the storm structure were provided by comparisons of 1-km resolution MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images at 15:40 UTC or 10:40 AM Eastern Time (above) and 17:19 UTC or 12:19 PM Eastern Time (below).

A comparison of 375-meter resolution (projected onto a 1-km AWIPS grid) Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 17:19 UTC or 12:19 PM Eastern Time is shown below.

The images above demonstrate using the SSEC RealEarth web map server to compare GOES-13 IR and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images of the storm, zooming in on the true-color image for more detail of dual vortex cloud features near the circulation center. The GOES IR image showed the impressively large size of the overall cloud structure associated with the mid-latitude cyclone.

The large size of the cyclone is also apparent in the VIIRS 1.38 µm imagery shown here. This wavelength highlights ice crystals — that is, high clouds — within the storm.

Additional details and satellite images of this storm can be found on the GOES-R and JPSS Satellite Liaison Blog.

View only this post Read Less

McIDAS images of MTSAT-2 10.8 µm IR channel data (above; click image to play animation) showed the southward motion of Cyclone Gillian as it intensified over the far eastern Indian Ocean to Category 5 intensity on 23 March 2014 (Joint Typhoon Warning Center advisory). A Category 5 tropical cyclone in the Southern Hemisphere (and in the Indian Ocean basin) is a relatively rare event.

An MTSAT-2 IR image from the CIMSS Tropical Cyclones site with an overlay of Metop ASCAT surface scatterometer winds at 14:20 UTC (below) showed the tight radius of high winds around the center of circulation.

MTSAT-2 0.675 µm visible channel images (below; click image to play animation) revealed the formation of a well-defined eye on 23 March.

A plot of the Advanced Dvorak Technique (ADT) satellite-based intensity estimate (below) showed the period of rapid intensification on 23 March, with tropcial cyclone Gillian reaching its peak intensity late on 23 March.

A comparison of MTSAT-2 10.8 µm IR channel data and DMSP SSMIS-16 85 GHz microwave brightness temperature data (below) demonstrated the ability of microwave imagery to show important storm details (such as the closed eyewall, and curved spiral bands) that might be obscured by clouds on conventional IR images.

The MIMIC Total Precipitable Water (TPW) product (below; click image to play animation) showed the circulation of high TPW values as Cyclone Gillian began to move southward from Indonesia on 21 March. As the tropical cyclone began to encounter an environment of increasing vertical wind shear poleward of about 20º S latitude, the storm began to rapidly decrease in intensity — and on 26 March Gillian was downgraded to a tropical low.

View only this post Read Less

The GOES-13 (GOES-East) Sounder instrument has been experiencing data anomalies that manifest themselves as missing pixels (link, link). These errors occurred because of slight fluctuations in the speed of the sounder filter wheel, resulting in a time offset. Processing software expects the data to be present at a certain time, but because of the filter wheel speed fluctuations, data were not present when expected. All 19 spectral bands on the GOES-13 Sounder were affected.

Missing data can now be reclaimed using a modified version of the SPS (Sensor Processing System), the ground software that makes the GVAR data stream. GOES Engineers have been testing this software change. The test software modifications properly handle the slight differences in the timing of the data. As of this time, a date has not been slated for operational implementation by NOAA NESDIS.

An example with all 19 bands of the GOES-13 Sounder is shown below, with the current pixel drop-outs (top) and after the software changes were applied (bottom) as part of off-line testing (image toggle).

View only this post Read Less

Kudos to Russ Dengel of the SSEC RealEarth web map server development team for spotting this: a relatively cloud-free overpass of the Landsat-8 satellite which revealed the site of the massive landslide/mudslide near the small town of Oso in northwestern Washington State (north of Seattle). The animation shown above was made using RealEarth to zoom in with the Google Maps base layer, and then toggle between the base map and an overlay of 15-meter resolution Landsat-8 0.59 µm (Band 8) panochromatic visible imagery at 19:03 UTC or 12:03 PM local time on 23 March 2014. It can be seen that debris from the landslide — which occurred a day earlier — covered one mile of State Road 530, cutting off access to the town of Darlington (located east of the landslide site); it also blocked the North Fork of the Stillaguamish River, leading to fears of localized flooding both upstream and downstream of the landslide site.

The Landsat-8 visible image is shown below. The landslide was blamed on ground saturation due to heavy rainfall in the region over the past month (30-day total rainfall | depature from normal).

===== 01 April Update =====

14 days later, there was another overpass of the Landsat-8 satellite; it could be seen on the 0.59 µm panochromatic visible image (above) that the mudslide still covered a significant portion of State Road 530. The 1.61 µm near-IR image (below) revealed that the mudslide had altered the course of the North Fork of the Stillaguamish River, and highlighted areas where some localized flooding was occurring due to a widening of the river (water is a strong absorber at the 1.61 µm wavelength, so it appears dark on the near-IR image).

View only this post Read Less