Turbulence over the central Pacific Ocean

December 27th, 2016
Himawari-8 Water Vapor Imagery (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom), 1700-1900 UTC on 27 December 2016 [click to enlarge]

Himawari-8 Water Vapor Imagery (6.2 µm, top; 6.9 µm, middle; 7.3 µm, bottom), 1700-1900 UTC on 27 December 2016 [click to enlarge]

Turbulence over the Pacific Ocean affected at least one flight on Tuesday 27 December 2016 near 24º N, 162º E, as indicated by a pilot report issued at 1745 UTC:

PGUA UUA /OV 24N 162E/TM 1745/FL340/TP B777/TB MOD-SEV/RM ZOA

In the animation above of the three Himawari-8 Water Vapor bands (sensing radiation emitted at 6.2 µm, 6.9 µm and 7.3 µm), a characteristic banded gravity wave structure is evident which is associated with the pilot report of moderate to severe turbulence (Note: the ABI instrument on the GOES-R series of satellites will feature these same 3 upper level, mid-level and lower level water vapor bands). In contrast to a turbulence event earlier this month, documented here on this blog, the wave features responsible for this turbulence were more distinct in 8-bit McIDAS-X imagery, and were also apparent in all three water vapor bands.

The Himawari-8 satellite data were used in the subsequent issuance of a SIGMET (Significant Meteorological Information) advisory:

WSPA06 PHFO 271824
SIGPAS

KZAK SIGMET SIERRA 1 VALID 271825/272225 PHFO-
OAKLAND OCEANIC FIR MOD OCNL SEV TURB FCST BTN FL280 AND FL360.
WI N2640 E16810 – N2120 E16810 – N2120 E16240 – N2640 E16250
– N2640 E16810. MOV E 25KT. BASED ON ACFT AND SAT.

The full 11-bit McIDAS-V imagery from the 6.2 µm Water Vapor band on Himawari-8, below, shows multiple ephemeral signatures of potential turbulence. In contrast to the event on 14 December, the gravity waves in this event perturbed clouds enough that they were also apparent in the Infrared Window band, as shown in this toggle between the 10.4 µm and 6.2 µm images. Himawari-8 Infrared Window brightness temperatures exhibited by the gravity wave were in the -30º to -40ºC range at 1740 UTC, which roughly corresponded to altitudes of 30,000-34,000 feet according to data from the 12 UTC rawinsonde report from Minamitorishima RJAM (IR image | text) located about 890 km or 550 miles to the west of the wave feature. Additional Himawari-8 Water Vapor images created using AWIPS II are here for the 6.2 µm imagery (from 1720-1740 UTC); this is a toggle between 6.2 µm and 7.3 µm imagery at 1720 UTC.

Himawari-8 Infrared Imagery (6.2 µm), 1600-1900 UTC on 27 December 2016 [click to animate]

Himawari-8 Water Vapor (6.2 µm) Imagery, 1600-1900 UTC on 27 December 2016 [click to animate]

The superior spatial resolution of Himawari-8 (2-km at the sub-satellite point) was vital in detecting the gravity wave features causing the turbulence. Water Vapor imagery from COMS-1, with a nominal resolution of 4 km, does not show the features associated with the turbulence report.

COMS-1 Infrared Imagery (6.75 µm), 1630-1800 UTC on 27 December 2016 [click to animate]

COMS-1 Water Vapor (6.75 µm) Imagery, 1630-1800 UTC on 27 December 2016 [click to animate]

Similarly, HimawariCast data that is broadcast at reduced resolution was insufficient to monitor this event. See the toggle below from 1740 UTC.

Himawari-8 Infrared Imagery (6.2 µm) at 1740 UTC on 27 December 2016, native resolution and as distributed via Himawaricast [click to enlarge]

Himawari-8 Water Vapor (6.2 µm) Imagery at 1740 UTC on 27 December 2016, at native resolution and as distributed via Himawaricast [click to enlarge]

Moderate to severe turbulence aloft near the International Date Line

December 14th, 2016

Himawari-8 Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm) images (above; also available as MP4 and McIDAS-V animations) revealed the presence of a subtle packet of upper-tropospheric gravity waves propagating southeastward near the International Date Line (180º longitude over the central Pacific Ocean), just to the west/southwest of Midway Atoll on 14 December 2016 — and there were a few pilot reports of moderate to severe turbulence (which were responsible for at least one injury) in the general vicinity of this gravity wave feature from 1530 to 1740 UTC, at altitudes of 35,000 to 38,000 feet:

PHNL UUA /OV 2800N 18000W/TM 1530/FL380/TP B767/TB MOD-SEV/RM ZOA CWSU
PHNL UUA /OV 2643N 17757W/TM 1732/FL350/TP A330/TB SEV/RM ZOA CWSU
PHNL UUA /OV 2626N 17917W/TM 1740/FL360/TP B747/TB SEV/RM ZOA CWSU

A larger-scale view using all 3 water vapor bands of the AHI instrument on the Himawari-8/9 satellites (below; also available as an MP4 animation) showed that a broad trough was moving eastward away from the International Date Line, with the signature of a jet streak diving southward toward the region of the turbulence reports (Note: the ABI instrument on the GOES-R series of satellites will feature these same 3 upper level, mid-level and lower level water vapor bands).

Himawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.4 µm, bottom) images [click to play animation]

Himawari-8 Water Vapor (6.2 µm, top; 6.9 µm, middle; 7.4 µm, bottom) images [click to play animation]

GFS model 250 hPa analyses (12 UTC | 18 UTC | source) confirmed that the region of turbulence reports was located within the exit region an approaching 50-70 m/s or 97-136 knot upper tropospheric jet, where convergence (red contours) was maximized.


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Similarly, Himawari-8 water vapor image Derived Motion Winds, below, also indicated increasing upper-tropospheric convergence along the International Date Line (180º longitude) between 25º and 30º N latitude from 12 UTC to 18 UTC (below; source).

Himawari-8 water vapor image Derived Motion Winds at 12 UTC, with corresponding contours of Upper-tropospheric divvergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 12 UTC, with corresponding contours of Upper-tropospheric divvergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 15 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 15 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 18 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

Himawari-8 water vapor image Derived Motion Winds at 18 UTC, with corresponding contours of Upper-tropospheric divergence [click to enlarge]

A comparison of 2-km resolution Himawari-8 and 4-km resolution GOES-15 Water Vapor images (below; also available as an MP4 animation) showed that the gravity wave feature was not readily apparent on the lower spatial resolution GOES-15 images (which were only available every 30 minutes, in contrast to every 10 minutes from Himawari-8). The same color enhancement is applied to both sets of images — but because of differences between the Himawari-8 vs GOES-15 water vapor band characteristics (namely the central wavelength and the spectral response function, but also the water vapor weighting function profiles as influenced by the dissimilar satellite viewing angles) the resulting water vapor images differ in their general appearance.

Himawari-8 Water Vapor (6.2 µm, left) and GOES-15 Water Vapor (6.5 µm, right) images, with pilot reports of turbulence [click to play animation]

Himawari-8 Water Vapor (6.2 µm, left) and GOES-15 Water Vapor (6.5 µm, right) images, with pilot reports of turbulence [click to play animation]

This case demonstrated well the importance of viewing all 11 bits of information contained in the Himawari-8 Imagery. The animation at the top of the Blog Post shows an 8-bit display; a similar 8-bit display that uses a different color enhancement is here, courtesy of Dan Lindsey at CIRA. All 8-bit displays are limited to 256 different colors. The image below compares 8-bit (McIDAS-X on the left) and 11-bit (McIDAS-V on the right) displays at 1530 UTC.

Himawari-8 Water Vapor (6.2 µm) image at 1530 UTC, as viewed using 8-bit McIDAS-X (left) and 11-bit McIDAS-V (right) displays [click to enlarge]

Himawari-8 Water Vapor (6.2 µm) image at 1530 UTC, as viewed using 8-bit McIDAS-X (left) and 11-bit McIDAS-V (right) displays [click to enlarge]

Here is a toggle from AWIPS that compares 11-bit and 8-bit displays. The feature causing the turbulence is quite subtle, and 11-bit displays (which allow 2048 different colors) are necessary to accurately show it.

 

Mount Rinjani volcanic ash plume

November 4th, 2015

Suomi NPP VIIRS true-color RGB images [click to enlarge]

Suomi NPP VIIRS true-color RGB images [click to enlarge]

The Mount Rinjani volcano in Indonesia began a period of eruptions on 25 October 2015; the ash plume became very apparent on Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from RealEarth on 03 and 04 October (above). The volcanic ash disrupted flights at Denpasar Airport in Bali (the red dot at the southern tip of the island) for several days.

A GOES-R volcanic ash height product (derived using Himawari-8 AHI data) from the SSEC Volcanic Cloud Monitoring site indicated that the plume reached heights of 10 km (dark blue color enhancement) at times during the 03-04 October period (below).

Himawari-8 Volcanic Ash Height product [click to play animation]

Himawari-8 Volcanic Ash Height product [click to play animation]

McIDAS-V images of Suomi NPP VIIRS Day/Night Band (0.7 µm), near-IR (1.6 µm), shortwave IR (3.74 µm), and IR (11.45 µm) images (below, courtesy of William Straka, SSEC) showed the hot spot and nighttime glow of the summit of the Rinjani volcano at 1733 UTC on 04 November.

Suomi NPP VIIRS Day/Night Band (0.7 µm), near-IR (1.6 µm), shortwave IR (3.74 µm), and IR (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), near-IR (1.6 µm), shortwave IR (3.74 µm), and IR (11.45 µm) images [click to enlarge]

Typhoon Dolphin approaches Guam

May 14th, 2015
Himawari-8 11.22 µm infrared channel images (click to play animation)

Himawari-8 11.22 µm infrared channel images (click to play animation)

The animation above (available here as an mp4, and here on YouTube) shows 11.22 µm infrared imagery at 2.5-minute time steps (bottom) and 10-minute time steps (top) from Himawari-8 on 14 May 2015. Category 2 intensity Typhoon Dolphin is approaching Guam, seen at the left edge of both panels in the frame. The 2.5-minute imagery gives a much better indication of the quick rise and decay of overshooting tops (IR brightness temperatures of the storm tops approach -95º C!). A 10-minute time step cannot fully resolve the evolution of these features. The 2.5-minute time step also better captures the divergent flow (and outward-propagating gravity waves) at the top of the central dense overcast. No eye was yet apparent in the infrared imagery, or on DMSP SSMI 85 GHz microwave imagery.

A similar animation from the previous day, 13 May, is shown here: gif, mp4, YouTube. The better organization of the storm on 14 May is readily apparent.

How high are the clouds in the Central Dense Overcast (CDO)? Cloud Heights are available from CLAVR-x (Clouds from AVHRR Extended). Data from Geostationary Satellites are processed and are available to download here. Values from COMS-1 and from MTSAT-2 (displayed with McIDAS-V) suggest maximum cloud heights near 55,500 feet.

The MIMIC Total Precipitable Water (TPW) product, below, showed that Typhoon Dolphin was able to tap rich moisture from the Intertropical Convergence Zone (ITCZ) during the 13-14 May period; TPW values within the tropical cyclone circulation were often in the 60-65 mm or 2.5-2.6 inch range (darker red color enhancement).

MIMIC Total Preciptable Water product (click to play animation)

MIMIC Total Preciptable Water product (click to play animation)

Visible Imagery from Himawari-8, just after sunrise on 15 May, show continuous development of short-lived overshooting tops to the east of Guam. More information on the storm is available at the CIMSS Tropical Cyclones site, the JMA Tropical Cyclone site and the Joint Typhoon Warning Center.

Himawari-8 0.6363 µm visible channel images (click to play animation)

Himawari-8 0.6363 µm visible channel images (click to play animation)