Satellite winds « CIMSS Satellite Blog

Gravity waves over the Gulf of Mexico and Florida

January 22nd, 2020 | Scott Bachmeier

GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) showed a packet of gravity waves over the eastern Gulf of Mexico and southern Florida on 22 January 2020. Later time in the time period, there were isolated pilot reports of moderate turbulence in the vicinity of the waves (though it’s uncertain whether the gravity waves were directly responsible).

What caused these gravity waves to form and slowly propagate southeastward is also uncertain — earning this example its place in the “What the heck is this?” blog category. The SPC Mesoscale Analysis at 07 UTC (below) did show weak convergence of 300 hPa ageostrophic winds (dark blue oval) in the entrance region of a secondary jet streak “J” over the Gulf of Mexico — this convergence could have played a role in the gravity wave development.

SPC Mesoscale Analysis valid at 07 UTC, showing 300 hPa height, isotachs and ageostrophic winds [click to enlarge]

GOES-16 Derived Motion Winds (calculated using 6.9 µm imagery) in the vicinity of the gravity waves (below) had velocities in the 50-60 knot range at pressure levels of 370-380 hPa (0916 UTC).

GOES-16 Water Vapor (6.2 um) Derived Motion Winds [click to enlarge]

GOES-16 Water Vapor (6.9 µm) Derived Motion Winds [click to enlarge]

Also of note was the fact that the surface of Florida was sensed by Low-level Water Vapor imagery (below). With an unseasonably cold, dry air mass moving southward over the peninsula, the 7.3 µm water vapor weighting function was shifted to lower altitudes — this allowed the thermal contrast between relatively cool land surfaces and the surrounding warmer water to be seen in the 7.3 µm imagery.

GOES-16 Low-level (7.3 µm) Water Vapor images, with pilot reports of turbulence [click to play animation | MP4]

At Key West, Florida the Total Precipitable Water value of 0.3 inch calculated from 12 UTC rawinsonde data (below) was a new record for the date/time (the previous record minimum value was 0.36 inch).

Climatology of Total Precipitable Water for the Key West, Florida rawinsonde site [click to enlarge]

Posted in GOES-16, Satellite winds, What the heck is this? | No Comments »

Tropical Cyclone Tino in the South Pacific Ocean

January 16th, 2020 | Scott Bachmeier

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

JMA Himawari-8 “Clean” Infrared Window (10.4 µm) images (above) showed the development of Tropical Cyclone Tino in the South Pacific Ocean on 16 January 2020. Tino was moving southeast toward the island nation of Fiji. Convection around the tropical cyclone exhibited extensive cloud-top infrared brightness temperatures (IRBTs) of -90ºC and colder (shades of yellow embedded within the dark purple enhancement), including a few red -100ºC pixels at 1630 UTC.

Plots of rawinsonde data from Fiji (below) showed a tropopause around 100 hPa, where the temperature was around -85ºC — so the tropical overshooting tops with IRBTs in the -90 to -100ºC range were extending into the stratosphere.

Plots of rawinsonde data from Fiji [click to enlarge]

Plots of rawinsonde data from Nandi, Fiji [click to enlarge]

Plots of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) indicated that Tino gradually intensified within a narrow zone of light shear.

Plots of deep-layer wind shear [click to enlarge]

===== 17 January Update =====

GOES-17 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

A GOES-17 (GOES-West) Mesoscale Domain Sector was positioned over Tropical Cyclone Tino on 17 January, providing images at 1-minute intervals — “Clean” Infrared Window (10.35 µm) images (above) showed the continued development of convective bursts, which at times exhibited IRBT values as cold as -100ºC (red pixels on the coldest portion of the enhancement).

Posted in GOES-17, Himawari-8, Satellite winds, Tropical cyclones | No Comments »

Typhoon Kammuri in the West Pacific Ocean, with record cold cloud-top temperatures

November 30th, 2019 | Scott Bachmeier

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

2.5-minute interval JMA Himawari-8 AHI “Clean” Infrared Window (10.4 µm) images (above) showed a large canopy of cold cloud-top infrared brightness temperatures (BTs) associated with Category 1 Typhoon Kammuri in the West Pacific Ocean on 30 November 2019. Between 00 UTC and 05 UTC, many of the pulsing overshooting tops exhibited BTs -100ºC or colder (shades of red embedded in black on the coldest end of the scale).

Plots of the coldest overshooting top 10.4 µm brightness temperatures on Himawari-8 Target Sector (2.5-minute interval) and Full Disk (10-minute interval) images during the 0002-0502 UTC time period on 30 November (below) showed that the closest (in time**) Full Disk image BTs were often within a degree C of the Target Sector images — but the magnitude of rapid fluctuations of BT seen in the 2.5-minute data were well not captured by the 10-minute data. For the 4 Target Sector images exhibiting BTs of -103ºC and colder (0112, 0127, 0204 and 0259 UTC) only one of the closely-corresponding Full Disk images exhibited a similarly cold BT (0110 UTC, with -103.0ºC). The coldest Target Sector BT was -103.55ºC at 02:59:44 UTC, while the coldest Full Disk BT was -103.0ºC at 01:13:34 UTC.

**The actual time that closely-corresponding Target Sector and Full Disk scans were imaging Kammuri differed by about 1 minute and 15 seconds — for example, the 01:12:15 UTC Target Sector scanned Kammuri’s coldest overshooting tops at 01:12:19, while the 01:10:00 Full Disk scanned those same overshooting tops at 01:13:34 UTC.

Plots of coldest Himawari-8 10.4 µm brightness temperatures on 2.5-minute Target Sector (blue) and 10-minute Full Disk (green) images [click to enlarge]

Plots of coldest Himawari-8 infrared (10.4 µm) brightness temperatures on 2.5-minute Target Sector (blue) and 10-minute Full Disk (green) images [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0421 UTC as viewed using RealEarth (below) revealed an area of very cold cloud-top infrared BTs (highlighted by the yellow region near the center of the storm). The coldest BT within that yellow area was -109.35ºC — which would qualify as the coldest cloud-top temperature on record as sensed by a meteorological satellite (Weather Underground). In addition, on the plot of Himawari-8 infrared BTs shown above it can be seen that the previous record for coldest documented BT (-102.2ºC with Tropical Cyclone Hilda in 1990) was eclipsed on 9 Target Sector and 4 Full Disk images.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0420 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 0421 UTC [click to enlarge]

The NOAA-20 VIIRS Infrared image at 0421 UTC is shown below with 2 different color enhancements — the darker blue colors of the 160-to-200 K enhancement help to highlight the colder BT regions (including the coldest 163.8 K or -109.35ºC pixel).

NOAA-20 VIIRS Infrared Window (11.45 µm), with different color enhancements (credit: William Straka) [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) image at 0421 UTC, with 2 different color enhancements (credit: William Straka, CIMSS) [click to enlarge]

The Himawari-8 Infrared image closest (time-wise) to the NOAA-20 image was at 04:22:15 UTC, and its coldest cloud-top BT was -102.5ºC. In a toggle between magnified Himawari-8 Visible and Infrared images at that time (below), the -102.5ºC BT was located within the northernmost cluster of red pixels (where shadowing and texture in the Visible image highlighted the overshooting top).

Himawari-8 Visible (0.64 µm) and Infrared (10.4 µm) images at 0422 UTC [click to enlarge]

The nearest upper air site was Babelthuop Airport/Koror on Palau Island, located south of the storm — the coldest temperature in their 00 UTC rawinsonde data (below) was -81.9ºC at an altitude of 16.7 km. Assuming that the overshooting top cooled at a lapse rate of around 7.5ºC per km of ascent beyond the -81.9ºC tropopause (reference), the altitude of the coldest -109.35ºC cloud top was likely near 19.5 km.

Plots of 00 UTC and 12 UTC rawinsonde data from Koror, Palau Island [click to enlarge]

During the daylight hours on 30 November, Himawari-8 “Red” Visible (0.64 µm) images (below) revealed widespread cloud-top gravity waves which were moving outward away from intense convection with overshooting tops near the storm center. Many of these gravity waves were propagating along the tops of tendrils of transverse banding — especially within the southern semicircle of Kammuri.

Himawari-8 “Red” Visible (0.64 µm) images [click to play animation | MP4]

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Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1604 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1604 UTC (credit: William Straka, CIMSS) [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images from Suomi NPP at 1604 UTC (above) and NOAA-20 at 1654 UTC (below) showed mesospheric airglow waves propagating southward in the DNB images.

NOAA-20 Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 1654 UTC (credit: William Straka, CIMSS) [click to enlarge]

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6.9 µm) images, with contours of Deep-Layer Wind Shear [click to enlarge]

Himawari-8 Water Vapor (6.2 µm) images, with contours of Deep-Layer Wind Shear [click to enlarge]

Himawari-8 Water Vapor (6.2 µm) images with contours of Deep-Layer Wind Shear (above) indicated that Kammuri was moving through an environment of low to moderate shear. Himawari-8 Water Vapor images with plots of satellite-derived Atmospheric Motion Vectors (below) showed a well-defined outflow channel north of the tropical cyclone.

Himawari-8 Water Vapor (6.9 µm) images, with Derived Motion Winds [click to enlarge]

Himawari-8 Water Vapor (6.2 µm) images, with plots of Derived Motion Winds [click to enlarge]

Himawari-8 (courtesy JMA) and GEO-KOMPSAT-2A or GK2A (courtesy KMA) visible imagery were combined to create stereoscopic imagery of the storm on 30 November, as shown below from 2100 UTC on 29 November to 0820 UTC on 30 December. View the 3-dimensional image by crossing your eyes and focusing on the third image that becomes apparent in between the two images shown.

Visible (0.64 µm) Imagery from Himawari-8 (left) and GK2A (right) from 2100 UTC on 29 November to 0820 UTC on 30 November 2019 (Click to animate)

10-minute Full Disk images of GK2A Cloud Top Temperature and Cloud Top Height products (source) are shown below. A large canopy of CTT values as cold as -80ºC and CTH values up to 15 km were seen associated with Typhoon Kammuri during the period 0000-0500 UTC.

KMA GK2A Cloud Top Temperature product [click to play animation | MP4]

KMA GK2A Cloud Top Height product [click to play animation | MP4]

Posted in GK2A, Himawari-8, NOAA-20, RealEarth, Red-Green-Blue (RGB) images, Satellite winds, Suomi NPP, Tropical cyclones, VIIRS | No Comments »

Hurricane Lorenzo reaches Category 5 intensity

September 29th, 2019 | Scott Bachmeier

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images (above) showed Hurricane Lorenzo during the time it intensified to a Category 5 storm around 0130 UTC on 29 September 2019. A plot of the CIMSS Advanced Dvorak Technique (below) indicated a peak intensity estimate of 143 knots from 0220-0820 UTC.

Plot of the CIMSS Advanced Dvorak Technique (ADT) for Hurricane Lorenzo [click to enlarge]

#Lorenzo has strengthened into a Category 5 hurricane at 45°W – the farthest east Category 5 #hurricane in the Atlantic on record. Previous record was Hurricane Hugo in 1989 at 54.6°W. pic.twitter.com/FXGgKFPc3m

— Philip Klotzbach (@philklotzbach) September 29, 2019

A toggle between NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 0425 UTC is shown below.

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (courtesy of William Straka, CIMSS) [click to enlarge]

GOES-16 Water Vapor images, with contours and streamlines of deep-layer wind shear [click to play animation]

GOES-16 Water Vapor (6.9 µm) images, with contours and streamlines of deep-layer wind shear [click to play animation]

Lorenzo was moving through an environment characterized by low values of deep-layer vertical wind shear (above). In addition, Lorenzo was moving over water having warm Sea Surface Temperatures but only modest Ocean Heat Content (below).