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).

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 (33°23?N, 120°7?E) 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]

Wildfire on the Kamchatka Peninsula of Russia

June 7th, 2016

Himawari-8 Visible (0.64 µm) images [click to play animation]

Himawari-8 Visible (0.64 µm) images [click to play animation]

A large wildfire had been burning for several days from late May into early June 2016 (VIIRS fire detection hot spots) near the west coast of the Kamchatka Peninsula of Russia. On 07 June, Himawari-8 Visible (0.64 µm) images (above) showed smoke from the wildfire which became entrained within the clockwise circulation of a weak area of low pressure (surface analyses) just off the coast over the Sea of Okhotsk. Beneath the smoke aloft, a swirl of low-level stratus cloud associated with this low was also very apparent. Other features of interest seen in the 0.5 km resolution 10-minute imagery include the intermittent formation of standing wave clouds over the high terrain (east of the fire), and small ice floes drifting westward just off the coast of Magadan Oblast (northwest of the fire).

A closer view using Himawari-8 Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (below) revealed numerous hot spots (dark black to yellow to red pixels) around the periphery of the burn scar of the large fire, along with the brief development of small pyrocumulus clouds over some of the larger, more active fires. Note that the ABI instrument on GOES-R will provide similar imagery at high spatial (0.5 km visible, 2 km infrared) and temporal (5 minute Full Disk coverage) resolutions.

Himawari-8 0.64 µm Visible (top) and 3.9 µm Shortwave Infrared (bottom) images [click to play animation]

Himawari-8 0.64 µm Visible (top) and 3.9 µm Shortwave Infrared (bottom) images [click to play animation]

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image viewed using RealEarth (below) provided a high-resolution view of the fire region and the plume of smoke curving around the low pressure feature.

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

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