A rapidly occluding mid-latidude cyclone over the East Pacific Ocean on 11 November 2013 exhibited a classic “dry swirl” signature on McIDAS images of 4-km resolution GOES-15 6.5 µm water vapor channel data (above; click image to play animation).

The dry swirl signature was beginning to form after about 11 UTC, as seen on an AWIPS image of 1-km resolution MODIS 6.7 µm water vapor channel data (below). There were no buoy reports near the storm center, but one bouy was reporting easterly winds gusting to 37 knots well to the northeast (just north of the occluded front).

Shortly after the time of the MODIS water vapor image, a comparison of 1-km resolution Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images (below) showed similar details in the cloud structure as the occlusion process continued. Since it was still local night-time, the clouds were illuminated primarily by airglow (the Moon was in the waxing gibbous phase, at 68% of full; however, it was below the local horizon at that particular time) — this provides an example of the “visible image at night” capability of the VIIRS Day/Night Band.

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Super Typhoon Haiyan (31W) formed as a tropical depression at low latitudes in the West Pacific Ocean on 03 November 2013 — and by 18 UTC on 07 November was estimated to have peaked at an intensity of sustained 170 knot winds with gusts to 205 knots (Storm track map | ADT plot | JTWC warning text). McIDAS images of 15-minute interval 10.8 µm IR channel data from the Korean COMS-1 satellite (above; click image to play animation; a YouTube video is also available) showed the intense tropical cyclone as it moved westward and made landfall in the Philippines on 07 November. There was a large, nearly symmetric ring of very cold cloud-top IR brightness temperatures in the -80 to -90º C range (violet colors) — and at times there were a few isolated pixels colder than -90º C (yellow enhancement). For comparison, a YouTube video of MTSAT-1 10.8 µm IR imagery is also available.

As the eye was still east of the Philippines, a McIDAS-V image comparison of 375-m resolution Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm IR channel data at 16:15 UTC on 07 November (below; courtesy of William Straka, CIMSS) revealed intricate banding structures within the eyewall region on the IR image, as well as bright streaks on the DNB image due to cloud illumination by intense lightning activity.

The eye and eyewall of Haiyan moved over the eastern Philippine islands of Samar and Leyte (near the city of Tacloban) during the early morning hours, as can be seen in COMS-1 0.675 µm visible channel images (below; click image to play animation; a YouTube video is also available)

 

The nearly annular structure of the eyewall at 21:08 UTC on 07 November was revealed on a DMSP SSMIS 85 GHz microwave image (above) from the CIMSS Tropical Cyclones site. In addition, a sequence of eyewall replacement cycles can be seen during the 06-07 November period using the MIMIC-TC product (below). It appears as though Super Typhoon Haiyan was in the process of undergoing another eyewall replacement cycle as it was making landfall in the Philippines.

Regarding the size of and very cold cloud-top IR brightness temperatures seen with Super Typhoon Haiyan, the IR images below (courtesy of Rick Kohrs, SSEC) show a side-by-side comparison with Category 5 Hurricane Katrina (Haiyan has been artifically superimposed at the same location over the Gulf of Mexico). Note the significantly colder cloud-top IR brightness temperatures associated with Haiyan (-80 to -89 C, violet colors), due to its location in the tropics (near 10 N latitude) where the tropopause was much higher and much colder.

It is interesting to note that during the previous daytime hours (on 06 November), a series of mesovortices could be seen within the eye of Haiyan on COMS-1 visible images (below; click image to play animation; a YouTube video is also available). For more discussion on these mesovortices, see the From the Lee Side blog.

 

As pointed out in the Joint Typhoon Warning Center prognostic reasoning bulletin, factors that favored the intensification of Super Typhoon Haiyan included warm sea surface temperatures (above) and low values of deep layer wind shear (below).

11 November Update: A McIDAS-V image comparison of  “before Haiyan” (31 October) and “after Haiyan” (09 November) night-time Suomi NPP VIIRS 0.7 µm Day/Night Band data (below; courtesy of William Straka, SSEC/CIMSS) showed the extent of the power outages in the Tacloban City area and other towns in the northern portion of Leyte province, caused by devastating damage sustained during the landfall of the powerful typhoon.

21 November update: Rick Kohrs (SSEC) created a large (72 megabyte) animation of hourly MTSAT-1 6.75 µm water vapor channel imagery — covering the life span of Haiyan during the 03-11 November period — superimposed on a Sea Surface Temperature background (below; click image to play animation; a YouTube video is also available).

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The GOES-13 Sounder has been experiencing anomalies that manifest themselves as missing pixels since mid-Summer. The missing pixels apparently arise because of slight fluctuations in the speed of the sounder instrument filter wheel. The number of missing pixels per Sounder image peaked in late September, just after the Equinox, with up to 700 missing pixels (out of 63000) per Sounder image over CONUS. At present, missing pixels vary between 100 and 250, with a maximum typically around 2200 UTC and a minimum between 0600 and 1000 UTC. In the animation above, the missing pixels show as black; the GOES-15 Sounder data have no missing pixels.

Realtime GOES Sounder imagery is available at this link. The Sounder anomalies are present in all 19 of the GOES-13 spectral bands, as evident in the toggle below between an image in late September (when error counts were highest) and early November (when error counts were lower). GOES Engineers continue to monitor this situation and investigate possible solutions.

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Hat tip to NWS Buffalo NY forecasters Jon Hitchcock and David Zaff for letting us know about a number of aircraft dissipation trails (also known as “distrails” or “hole punch clouds”) over the Lake Ontario region on 04 November 2013. A series of McIDAS images of 1-km resolution GOES-13 Visible (0.63 µm) data (above) showed these features as they drifted eastward during the day.

A comparison of AWIPS II images of 375-meter resolution Suomi NPP VIIRS Visible (0.64 µm) visible and the corresponding False Color “Snow Cloud Discrimination” Red-Green-Blue (RGB) at 18:17 UTC (below) indicated that the cloud layer penetrated by aircraft was composed of supercooled water droplets (which appear as brighter shades of white on the RGB image) — but the particles in the aircraft exhaust acted as ice nuclei and caused the cloud to glaciate (ice crystal clouds appear as varying shades of red on the RGB image).

AWIPS images of the POES AVHRR CLAVR-x Cloud Type product confirmed that the cloud layer over the Lake Ontario region was a supercooled water droplet cloud (green color), with the Cloud Top Height product indicating tops in the 7-9 km range (below). However, higher-altitude cirrus clouds were beginning to overspread the region from the west (Cirrus=orange; Thick Ice=yellow; Overlap=violet).

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