Severe thunderstorms and heavy rainfall/flooding in the Upper Midwest

July 12th, 2016

GOES-13 Infrared Window (10.7 µm) images, with SPC storm reports [click to play animation]

GOES-13 Infrared Window (10.7 µm) images, with SPC storm reports [click to play animation]

GOES-13 Infrared Window (10.7 µm) images (above; also available as an MP4 movie file) showed a series of mesoscale convective systems that moved across northeastern Minnesota, northwestern Wisconsin and the Upper Peninsula of Michigan during the 11 July12 July 2016 period. Some of these storms produced tornadoes, large hail, and damaging winds (SPC storm reports) in addition to heavy rainfall, with as much as 9.00 inches in Minnesota and 9.80 inches in Wisconsin (NWS Duluth storm summary). Several highways were closed due to flooding and/or washout, including a portion of Interstate 35 in Minnesota (interstates and highways are plotted in violet on the images).

A sequence of Infrared images from Terra/Aqua MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) (below) showed greater detail in the storm-top temperature structure at various times during the event.

Infrared images from Terra/Aqua MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) [click to play animation]

Infrared images from Terra/Aqua MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) [click to play animation]

===== 19 July Update =====

Comparison of before (09 July) and after (12 July through 19 July) Suomi NPP VIIRS true-color images [click to enlarge]

Comparison of before (09 July) and after (12 July through 19 July) Suomi NPP VIIRS true-color images [click to enlarge]

A comparison of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from before the event (09 July) and after the event (12 through 19 July) (above) revealed the large amounts of sediment flowing offshore into the southwestern portion of Lake Superior.

Another comparison of before (09 July) and after (13 through 19 July) true-color RGB images from Terra and Aqua MODIS is shown below.

Comparison of before (09 July) and after (13 through 19 July) Terra/Aqua MODIS true-color images [click to enlarge]

Comparison of before (09 July) and after (13 July through 19 July) Terra/Aqua MODIS true-color images [click to enlarge]

A toggle between a Terra MODIS Visible (0.65 µm) image and the corresponding MODIS Sea Surface Temperature (SST) product on 16 July (below) showed that the SST values in the sediment-rich nearshore waters were significantly warmer (middle 60s F, red enhancement) than those found closer to the center of Lake Superior (middle 40s F, cyan enhancement).

Terra MODIS Visible (0.65 µm) image and Sea Surface Temperature product [click to enlarge]

Terra MODIS Visible (0.65 µm) image and Sea Surface Temperature product [click to enlarge]

Super Typhoon Nepartak

July 7th, 2016

Track of Super Typhoon Nepartak (03 to 07 July 2016) [click to enlarge]

Track of Super Typhoon Nepartak (03 to 07 July 2016) [click to enlarge]

Super Typhoon Nepartak (02W) formed as a tropical depression in the West Pacific Ocean south of Guam on 02-03 July 2016, and tracked northwestward until making landfall in southern Taiwan on 07 July (above). Nepartak rapidly intensified to a Category 4 storm on 05 July, peaking at Category 5 intensity on 06 July (ADT | SATCON wind | SATCON pressure). Two factors helping the storm to reach and maintain Category 5 intensity for a relatively long period of time were (1) the passage over water having large Ocean Heat Content and Sea Surface Temperature values, and (2) an environment characterized by low deep-layer wind shear (06 July/15 UTC | 07 July/21 UTC).

2.5-minute interval rapid-scan Himawari-8 Infrared Window (10.4 µm) images (below) showed the formation of a well-defined eye with an annular storm structure early in the day on 07 July. The eye became less organized as Nepartak approached the island of Taiwan and made landfall as a Category 4 typhoon around 2150 UTC.

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Surface observations (plot | text) from Feng Nin airport (station identifier RCFN) in Taitung City showed sustained winds of 70 knots (81 mph) with a gust to 99 knots (114 mph) from the north-northeast at 21 UTC, and a pressure of 964.0 hPa (27.47″). iCyclone chaser Josh Morgerman recorded a minimum pressure of 957.7 hPa at 2043 UTC (4:43 am local time) in Taitung City:


Shortly before landfall, a comparison of DMSP-18 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images around 20 UTC (below) showed that the eye was still rather distinct on the microwave image.

DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) and Himawari-8 Infrared Window (10.4 µm) images [click to enlarge]

However, the MIMIC-TC product (below) revealed how quickly the eyewall structure eroded once the circulation of Nepartak encountered the rugged terrain of Taiwan.
MIMIC-TC product [click to enlarge]

MIMIC-TC product [click to enlarge]

Looking back to earlier periods in the storm history, a 2-panel comparison of Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images from 06-07 July (below) revealed the presence of mesovortices within the eye on the visible imagery. The spatial resolution of these Visible (0.5 km) and Infrared (2 km) AHI images is identical to what will be provided by the ABI instrument on GOES-R.
Himawari-8 0.64 µm Visible (top) and 10.4 µm Infrared Window (bottom) images [click to play MP4 animation]

Himawari-8 0.64 µm Visible (top) and 10.4 µm Infrared Window (bottom) images [click to play MP4 animation]

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image from 07 July (viewed using RealEarth) is shown below; the actual satellite overpass time for this image was around 0444 UTC.
Suomi NPP VIIRS true-color image on 07 July [click to enlarge]

Suomi NPP VIIRS true-color image on 07 July [click to enlarge]

During the period of rapid intensification on 06 July, 2.5-minute interval rapid-scan Himawari-8 Infrared Window (10.4 µm) images (below) revealed pulses of storm-top gravity waves which were propagating radially outward away from the eye of Nepartak (especially evident during the later half of the animation period).
Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

Himawari-8 Infrared Window (10.4 µm) images [click to play MP4 animation]

It is also interesting to note that nighttime mesospheric gravity waves could be seen propagating away from the eye/eyewall region of Nepartak at 1729 UTC or 1:29 am local time on a 06 July Suomi NPP VIIRS Day/Night Band (0.7 µm) image (below, courtesy of William Straka, SSEC). Since very little illumination was provided by the Moon (which was in the Waxing Crescent phase, at only 5% of Full), these waves were being illuminated by airglow.
Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

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

The MIMIC-TC product (below) also showed that Nepartak completed an eyewall replacement cycle on 06 July.
MIMIC-TC product [click to enlarge]

MIMIC-TC product [click to enlarge]

Animations of 10-minute interval Himawari-8 Infrared Window (10.4 µm) images spanning nearly the entire life cycle of Nepartak — from a tropical depression south of Guam on 03 July to landfall over mainland China on 08 July — are available as an MP4 movie (139 Mbytes) or an animated GIF (493 Mbytes).

Ice floes off the coast of Labrador and Newfoundland

July 2nd, 2016

Inspired by this as seen on Twitter:


we decided to take a look at some satellite imagery. GOES-13 (GOES-East) Visible (0.63 µm) images (below) captured the fluid motion of ice floes off the coast of Labrador and Newfoundland on 02 July 2016.

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

A comparison of Terra MODIS true-color and false-color Red/Green/Blue (RGB) images viewed using RealEarth (below) aided in the discrimination of cloud vs ice/snow — in the false-color images, snow/ice appeared as shades of cyan, in contrast to supercooled water droplet clouds which appeared as shades of white.

Terra MODIS true-color and false-color images [click to enlarge]

Terra MODIS true-color and false-color images [click to enlarge]

An alternative RGB image for use in the discrimination of cloud vs snow/ice is shown below; in this particular false-color RGB image, snow/ice features appear as shades of red. Surface observations at the time of the Terra MODIS image are plotted in yellow.

Terra MODIS Visible (0.65 µm) and False-color images [click to enlarge]

Terra MODIS Visible (0.65 µm) and False-color images [click to enlarge]

2 days later, 04 July maps from the Canadian Ice Service (below) indicated that much of these larger ice floes consisted of thick first-year ice with concentrations in the range of 4-6/10ths to 8-10/10ths; the existence of such ice concentration at this particular location was 4-6/10ths to 9-10/10ths above normal.

Ice Concentration and Ice Stage maps for 04 July [click to enlarge]

Ice Concentration and Ice Stage maps for 04 July [click to enlarge]

Ice concentration Departure From Normal [click to enlarge]

Ice concentration Departure From Normal [click to enlarge]

Dry trade wind surge approaches Hawai’i

July 2nd, 2016

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The MIMIC Total Precipitable Water product (above) showed the westward movement of a surge of dry trade winds toward Hawai’i during the 28 June – 01 July 2016 period. This push of dry air was being driven by a large area of high pressure centered about 1200 miles northeast of the island chain. A very sharp gradient in TPW existed along the leading edge of the dry surge, with values of 50-55 mm (2.0-2.2 inches) ahead of the boundary dropping to as low as 20-25 mm (0.8-1.0 inch) behind it.

GOES-15 (GOES-West) Visible (0.63 µm) images (below) revealed a sharp contrast in cloudiness east of Hawai’i on 29 June, with far fewer and much smaller marine boundary layer cloud elements seen in the dry air east of the leading edge of the trade wind surge.

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

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

On the following day (30 June), GOES-15 Visible (0.63 µm) images (below) showed a vast expanse of small closed-cell convective clouds in the marine boundary layer — a signature of a stable air mass; in this case, due to strong low-level subsidence — extending to distances as far as 1000 miles east and northeast of Hawai’i.

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

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

The progression of the leading edge of the dry trade wind surge could also be followed on daily composites of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from 26-30 June, as viewed using RealEarth (below).

Suomi NPP VIIRS true-color composite images [click to play animation]

Suomi NPP VIIRS true-color composite images [click to play animation]

Skew-T diagrams of rawinsonde data from the 2 upper air sites in Hawai’i (Hilo PHTO, and Lihue PHLI) are shown below. At Hilo on the Big Island of Hawai’i, the height of the trade wind temperature inversion descended from the typical height of 5500-6000 feet (near the 850 hPa pressure level) on 30 June to an unusually-low height of around 2500 feet (near the 930 hPa pressure level) at 12 UTC on 01 July. Farther to the west at Lihue on the island of Kaua’i, the dry trade wind surge was just beginning to arrive around the time of the 12 UTC sounding on 01 July — a sharpening of and a slight lowering of the trade wind inversion could be seen in comparison to the earlier 00 UTC sounding.

Hilo, Hawai'i rawinsonde reports [click to enlarge]

Hilo, Hawai’i rawinsonde reports [click to enlarge]

Lihue, Hawai'i rawinsonde data [click to enlarge]

Lihue, Hawai’i rawinsonde data [click to enlarge]

As the strong trade wind flow interacted with the terrain of the islands, areas of high wind gusts were observed — for example, 36 knots (41 mph) at Bradshaw Army Air Field on the Big Island of Hawai’i. In addition, the dew point temperature at that site was as low as 21º F within an hour after that peak wind gust on the afternoon of 01 July.