A portion of the smoke plume could be seen on Aqua MODIS and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images (below) as it was approaching the southern portion of Great Britain.On the following morning, Meteosat-10 visible images (below; click to play animation) showed that the leading edge of the smoke ribbon was moving over southern Norway. The transport pathway of this smoke feature was rather interesting, as we shall explore with the following sets of images. The 2015 wildfire season in Alaska had been very active — as of 17 July, it was rated as the 4th worst in terms of total acreage burned. In early July, numerous wildfires burning across the interior of Alaska were producing a large amount of smoke, as can be seen in a comparison of of Suomi NPP VIIRS 3.74 µm shortwave IR and 0.64 µm visible channel images at 2131 and 2312 UTC on 06 July (above). The thermal signature of the wildfire “hot spots” showed up as yellow to red to black pixels on the 2 shortwave IR images, while the widespread smoke plumes from the fires are evident on the 2 visible images; even in the relatively short 101 minutes separating the two sets of VIIRS images, notable changes in fire activity could be seen.
Looking a bit farther to the north and west, a sequence of VIIRS 0.64 µm visible images centered over Cape Lisburne (station identifier PALU) in northwestern Alaska covering a 2-day period from 06 to 08 July (below) showed the initial transport of large amounts of smoke from the interior of Alaska northwestward over the Chukchi Sea between Alaska and Russia.Daily composites of Suomi NPP OMPS Aerosol Index covering the period of 04-17 July (below; courtesy of Colin Seftor; see his OMPS Blog post) showed the strong signal of this dense Alaskan smoke (denoted by the red arrows) as it moved from east to west over the far southern Arctic Ocean and along the far northern coast of Russia from 06-10 July. The Aerosol Index signal seemed to stall north of Scandinavia on 12-13 July, but then a small portion began to move toward Iceland and Greenland on 13-15 July around the periphery of a large upper-level low (500 hPa analyses). Finally, some of this smoke was then transported eastward across the Atlantic Ocean around the southern periphery of this upper-level low on 17 July, as was seen on the Meteosat-10 visible images at the beginning of this blog post. CALIOP lidar data from the CALIPSO satellite (below) showed the vertical distribution of the Alaskan smoke over and off the coast of northern Norway on 11 July. The signal of the smoke was located in the center portion of the images; while there appeared to be some smoke at various altitudes within the middle to upper troposphere, a significant amount of smoke was seen in the lower stratosphere in the 10-12 km altitude range.
Himawari-8 10.35 µm infrared imagery showed an unusual (for infrared imagery) double-eyewall structure in Typhoon Nangka over the western Pacific Ocean on 13 July 2015. For such a feature to appear in infrared imagery, the secondary circulations of both the inner and outer eyewall need to be intense enough to support the downdraft/cloud-clearing necessary to create the “moats” between them. Microwave imagery of the storm, below, viewed via MIMIC (from this site), also showed the double eyewall structure quite well. This double-eyewall signature typically indicates that a tropical cyclone is experiencing an eyewall replacement cycle (ERC), which signals that a (temporary) decrease in intensity is soon to follow.
Several hours later, a DMSP SSMIS 85 GHz microwave image at 1756 UTC, below, indicated that the ERC was essentially complete. Subsequently, the Joint Typhoon Warning Center slightly downgraded the intensity of Typhoon Nangka for their 21 UTC advisory. While not as well-defined as in the Himawari-8 imagery, the double-eyewall signature was still evident in the lower-resolution (4-km, vs 2-km) MTSAT-2 IR imagery (animation).
The Himawari-8 Target Sector was centered over Typhoon Nangka during this time; an IR image animation with a 2.5-minute timestep, below (courtesy of William Straka, SSEC), showed the evolution of the double eyewall signature, along with 2 pulses of storm-top gravity waves which propagated radially outward away from the center in the northern semicircle of the typhoon.
Suomi NPP overflew Hurricane Blanca early in the morning on 4 June, during a near-full Moon, and the Day Night Band imagery, above, toggled with the 11.35 µm imagery, show the hurricane. (Day/night band imagery of the eye is here, the entire storm is here, and zoomed out is here; click for 11.35 µm imagery of the eye, the entire storm, and zoomed out). Deep convection overnight did not wrap all the way around the storm. Evidence of dry air entrained into the circulation is apparent.
The 3-hourly animation of 10.7 micron imagery, above, from 3-4 June 2015 shows Hurricane Blanca southwest of the Mexican coast, drifting southwestward. Cold cloud tops that were apparent at the start of the loop warm by the end, perhaps because convection is being suppressed by the presence of dry air. MIMIC Total Precipitable Water (below) suggests that dry air is being entrained into Blanca’s circulation from the north. (Update on Andres, also apparent in the MIMIC Total Precipitable Water animation: This overlay of Metop ASCAT winds on top of GOES 10.7 imagery from ~0530 UTC on June 4 shows a swirl that is offset from the convection. Andres is forecast to become post-tropical later on June 4.)
Visible imagery from GOES-13 from June 3 and June 4, below, show a less distinct/cloudier eye on 4 June compared to 3 June. Multiple overshooting tops persist in the circulation of the system, but the coarse 30-minute temporal resolution of the imagery cannot capture the lifecycle of these quickly evolving events.
Water vapor imagery from GOES-13 from June and June 4, below, also confirm a consistently less organized storm. The dry air penetrating from the north is apparent in the imagery, but it appears not to have entered into the circulation of the storm, at least not at levels detected by the water vapor channel.
Morphed Microwave Imagery (MIMIC) from this website shows the evolution of the central eye structure, below. The eyewall that was much closer to the storm center at the start of the animation has been replaced by a weaker, larger eyewall.