Deadly tornado in Yancheng, China

June 23rd, 2016

Himawari-8 0.64 µm Visible (top) and 10.4 µm Infrared Window (bottom) images [click to play animation]

Himawari-8 0.64 µm Visible (top) and 10.4 µm Infrared Window (bottom) images [click to play animation]

Himawari-8 AHI Visible (0.64 µm) and Infrared Window (10.4 µm) images (above) showed the east-southeastward propagation of a mesoscale convective system which produced a deadly tornado in Yancheng, China around 2:30 pm local time on 23 June 2016 (Weather Underground blog). The location of Yancheng is denoted by the cyan * symbol, and the animation briefly pauses on the 0630 UTC images which match the reported time of the tornado. Overshooting tops are evident on the visible imagery, and cloud-top infrared brightness temperatures of -80º C or colder (violet color enhancement) also appear, even after the storm crossed the coast and moved over the adjacent offshore waters of the Yellow Sea (note: due to parallax, the apparent location of the storm top features is displaced several miles to the north-northwest of their actual position above the surface). The spatial resolutions (0.5 km visible, 2 km infrared) of the AHI images are identical to those of the corresponding spectral bands that will be available from the ABI instrument on GOES-R.

An experimental version of the MIMIC Total Precipitable Water product which uses the MIRS retrieval TPW from POES, Metop, and Suomi NPP VIIRS satellites (below) revealed the band of high moisture pooled along the Mei-yu front, which appeared to surge northward across eastern China early in the day on 23 June.

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The 23 June/00 UTC rawinsonde report from Nanjing (located about 260 km southwest of Yancheng) indicated a total precipitable water value of 66.2 mm or 2.6 inches (below).

Nanjing, China rawinsonde report [click to enlarge]

Nanjing, China rawinsonde report [click to enlarge]

First full day of Summer: snow in the Brooks Range of Alaska

June 22nd, 2016

GOES-15 Water Vapor (6.5 µm) images [click to play animation]

GOES-15 Water Vapor (6.5 µm) images [click to play animation]

GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above) showed the southeastward migration of an upper-level low across the North Slope and the eastern Brooks Range of Alaska during the 21 June – 22 June 2016 period. A potential vorticity (PV) anomaly was associated with this disturbance, which brought the dynamic tropopause — taken to be the pressure of the PV 1.5 surface — downward to below the 600 hPa pressure level over northern Alaska. Several inches of snow were forecast to fall in higher elevations of the eastern portion of the Brooks Range.

With the very large satellite viewing angle (or “zenith angle”) associated with GOES-15 imagery over Alaska  — which turns out to be 73.8 degrees for Fairbanks — the altitude of the peak of the Imager 6.5 µm water vapor weighting function (below) was shifted to higher altitudes (in this case, calculated using rawinsonde data from 12 UTC on 22 June, near the 300 hPa pressure level).

GOES-15 Imager water vapor (Band 3, 6.5 µm) weighting function [click to enlarge]

GOES-15 Imager water vapor (Band 3, 6.5 µm) weighting function [click to enlarge]

The ABI instrument on GOES-R will have 3 water vapor bands, roughly comparable to the 3 water vapor bands on the GOES-15 Sounder — the weighting functions for those 3 GOES-15 Sounder water vapor bands (calculated using the same Fairbanks rawinsonde data) are shown below. Assuming a similar spatial resolution as the Imager, the GOES-15 Sounder bands 11 (7.0 µm, green) and 12 (7.4 µm, red) would have allowed better sampling and visualization of the lower-altitude portion of this particular storm system. The 3 ABI water vapor bands are nearly identical to those on the Himawari-8 AHI instrument; an example of AHI water vapor imagery over part of Alaska can be seen here.

GOES-15 Sounder water vapor weighting function plots [click to enlarge]

GOES-15 Sounder water vapor weighting function plots [click to enlarge]

As the system departed and the clouds began to dissipate on 22 June, GOES-13 Visible (0.63 µm) images (below) did indeed show evidence of bright white snow-covered terrain on the northern slopes and highest elevations of the Brooks Range.

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

A sequence of 1-km resolution POES AVHRR Visible (0.86 µm) images (below) showed a view of the storm during the 21-22 June period, along with the resultant snow cover on 22 June. However, the snow quickly began to melt as the surface air temperature rebounded into the 50’s and 60’s F at some locations.

POES AVHRR Visible (0.86 µm) images [click to play animation]

POES AVHRR Visible (0.86 µm) images [click to play animation]

The increase in fresh snow cover along the northern slopes and the highest elevations of the central and northeastern Brooks Range — most notably from Anaktuvuk Pass to Fort Yukon to Sagwon — was evident in a comparison of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from 17 June and 22 June, as viewed using RealEarth (below). The actual time of the satellite overpass on 22 June was 2134 UTC.

Suomi NPP VIIRS true-color RGB images, 17 June and 22 June [click to enlarge]

Suomi NPP VIIRS true-color RGB images, 17 June and 22 June [click to enlarge]

Southwest US summer solstice: smoke, and solar panels

June 20th, 2016

 

Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A nighttime comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 0853 UTC on 20 June 2016 (above) revealed 2 key features of the large Cedar Fire that had been burning in eastern Arizona: (1) the fire “hot spot” signature (black to yellow to red pixels) on the Shortwave Infrared image, located about 20 miles southwest of Show Low (KSOW), and (2) an approximately 50-mile-wide pall of dense smoke aloft — illuminated by a nearly-full Moon — that had drifted westward then northwestward during the previous 24 hours and was centered northwest of Prescott (KPRC). Note that there was no signature of this smoke feature on the Infrared Window image, since smoke is effectively transparent to infrared radiation.

During the following afternoon hours, a toggle between 2117 UTC Aqua MODIS Near-Infrared “Cirrus detection” (1.61 µm), Visible (0.65 µm), Infrared Window (11.0 µm) and Topography images (below) showed that the smoke aloft had moved northward during the day and was over far northwestern Arizona and southwestern Utah. On the Visible image, the dense layer of smoke obscured the view of surface features that are normally seen on a cloud-free day, but the edges of the smoke feature were difficult or impossible to identify. However, the smoke feature was quite evident on the Near-Infrared “Cirrus detection” image — due to the fact that this spectral band (which will be on the GOES-R ABI instrument) is useful for detecting features composed of particles that are efficient scatterers of light (such as cirrus cloud ice crystals, airborne dust or volcanic ash, and in this case, smoke). As was seen in the VIIRS example above, there was no signature of the smoke on the Infrared Window image — the cooler (lighter gray) shades seen in that region were a result of higher terrain that exhibited cooler brightness temperatures due to more abundant vegetation.

Aqua MODIS Near-Infrared Cirrus (1.16 µm), Visible (0.65 µm), Infrared Window (11.0 µm), and Topography images [click to enlarge]

Aqua MODIS Near-Infrared Cirrus (1.61 µm), Visible (0.65 µm), Infrared Window (11.0 µm), and Topography images [click to enlarge]

An animation of GOES-15 (GOES-West) Visible (0.63 µm) images (below) showed the aforementioned Cedar Fire smoke in northwestern Arizona early in the day (highlighted by a favorable forward scattering sun-satellite geometry), and also showed the smaller smoke plume from the Reservoir Fire that had just begun burning northeast of Los Angeles. In addition, the brief appearance of bright white flashes across Southern California and extreme southern Nevada (as seen on the 1800, 1830, 1841 and 1845 UTC images) were a result of reflection of sunlight from large solar panel farms.

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

 

Localized heavy rainfall and flooding in south-central Wisconsin

June 15th, 2016

GOES-13 Infrared Window (10.7 µm) images [click to play animation]

GOES-13 Infrared Window (10.7 µm) images [click to play animation]

GOES-13 Infrared Window (10.7 µm) images (above) showed the development of several rounds of deep convection which moved over parts of southern Wisconsin during the 14 June15 June 2016 period; these storms were responsible for heavy rainfall at some locations (NWS Milwaukee summary). As mentioned in a WPC Mesoscale Precipitation Discussion, some of these storms were focused along the nose of a low-level jet that was helping to push a warm frontal boundary (surface analyses) through the region. Moisture was also abundant south of the warm front, with a total precipitable water value of 55.1 mm (2.17 inches) seen in rawinsonde data from Davenport IA.

Landsat-8 false-color image [click to enlarge]

Landsat-8 false-color image [click to enlarge]

A timely cloud-free overpass of the Landsat-8 satellite on the morning of 15 June provided a 30-meter resolution false-color image as viewed using RealEarth (above), which showed areas of flooding — water appears as darker shades of blue — in the Black Earth area of western Dane County in southern Wisconsin. A before/after comparison of Landsat-8 images processed using an equation to highlight water as blue (below, courtesy of Shane Hubbard, SSEC/CIMSS) revealed the areas of inundation due to the 14-15 June thunderstorms.

Landsat-8 derived water change, 30 May vs 15 June 2016 [click to enlarge]

Landsat-8 derived water change, 30 May vs 15 June 2016 [click to enlarge]

Aerial footage from a drone flight (below) showed vivid images of the flooding along Black Earth Creek.

YouTube video from drone flight near Black Earth, Wisconsin [click to play]

YouTube video from drone flight near Black Earth, Wisconsin [click to play]