Hurricane Lane in the eastern Pacific Ocean

August 17th, 2018 |

NOAA-20 VIIRS Imagery at 1023 UTC on 17 August 2018. Day Night Band Visible (0.7 µm) and I05 Infrared (11.45 µm) imagery are shown (Click to enlarge)

The active eastern Pacific Hurricane season continues, as Lane has formed. Suomi NPP and NOAA-20 overflew the system early on 17 August 2018. The toggle above, from NOAA-20’s VIIRS Instrument, shows both the Day Night Band 0.70 µm visible Image and the 11.45 µm infrared channels. Lack of lunar illumination means that only Earthglow is making clouds visible; a distinct eye is not present. The step animation below between the NOAA-20 11.45 µm infrared and, 50 minutes later, Suomi NPP’s 11.45 µm Infrared, right at the limb of the scan, also show no distinct eye.

VIIRS I05 11.45 µm Infrared Imagery from NOAA-20 (1023 UTC) and Suomi NPP (1113 UTC) on 17 August 2018 (Click to enlarge)

In fact, however, an eye was likely present at this time. As noted in the National Hurricane Center’s 0900 UTC Discussion (Link), “Recent microwave images show a well-defined low-level eye, but this feature is not yet apparent in geostationary satellite images.”  AMSR-2 (Advanced Microwave Scanning Radiometer 2) estimates of Convective Precipitation and Surface Rainfall in the toggle below (data from 1003 UTC) show a distinct eye.  AMSR-2 is a microwave instrument that flies on JAXA’s GCOM satellite;  microwave views of tropical cyclones are able to penetrate the cirrus shield that is commonly present, revealing important information about the low-level structure of a developing system.

GCOM AMSR-2 estimates of convective precipitation and surface rainfall rates at 1003 UTC on 17 August 2018 (Click to enlarge)

Polar Orbit tracks are available here. For the latest information on Hurricane Lane, refer to the National Hurricane Center or to the CIMSS/SSEC Tropical Weather Website. Imagery from Polar Orbiters are available at this site that shows data from an antenna in Honolulu.

Thank you to William Straka, CIMSS, for the imagery.

Wildfire smoke across the Midwestern US

August 11th, 2018 |

GOES-16 Natural Color RGB images [click to play MP4 animation]

GOES-16 Natural Color RGB images, 09-11 August [click to play MP4 animation]

Numerous wildfires burning in southwestern Canada (primarily British Columbia: NOAA HMS fire/smoke product) produced large amounts of smoke, which was subsequently transported eastward across southern Canada and then southward across the Midwestern US during the 09 August11 August 2018 period. GOES-16 (GOES-East) Natural Color Red-Green-Blue (RGB) images from the AOS site (above) showed this smoke, portions of which were optically very thick at times (and were able to cast shadows owing to its significant vertical depth).

On 09 August the smoke was most highly concentrated over the Dakotas, as shown in a comparison of GOES-16 Aerosol Optical Depth (AOD), Smoke Detection, “Blue” Visible (0.47 µm) and “Red” Visible (0.64 µm) images (below). While much of the smoke was likely aloft within the middle troposphere, some had been mixed downward into the boundary layer and was restricting the surface visibility to 3-5 miles at many locations.

Note that the hazy signature of the widespread smoke was a bit more apparent in the 0.47 µm Visible imagery than the 0.64 µm Visible imagery, especially during mid-day when the sun-satellite “forward scattering angle” was at a minimum. The AOD and Smoke Detection derived products use data from Visible and Near-Infrared bands — so it they are only available during daytime hours (and only at solar zenith angles less than 60 degrees). The Smoke Detection product was more effective during times of enhanced forward scattering (early and late in the day) — but it also was susceptible to false alarms due to solar reflectance off water surfaces. Additional information on GOES-R Aerosol Detection Products in AWIPS is available here and here.

GOES-16 Aerosol Optical Depth (top left), Smoke Detection product (top right).

GOES-16 Aerosol Optical Depth (top left), Smoke Detection product (top right). “Blue” Visible (0.47 µm, bottom left) and “Red” Visible (0.64 µm, bottom right) [click to play animation | MP4]

On 10 August, the smoke was most dense across the eastern Dakotas and Minnesota (below) — and once again, surface visibilities were restricted to 3-5 miles at some locations. On this day pilot reports mentioned flight visibility being restricted to 3 miles at altitudes as high as 12,000 feet.

GOES-16 Aerosol Optical Depth (top left), Smoke Detection product (top right). "Blue" Visible (0.47 µm, bottom left) and "Red" Visible (0.64 µm, bottom right) [click to play animation | MP4]

GOES-16 Aerosol Optical Depth (top left), Smoke Detection product (top right). “Blue” Visible (0.47 µm, bottom left) and “Red” Visible (0.64 µm, bottom right) [click to play animation | MP4]

Finally, on 11 August a north-to-south plume of particularly dense smoke drifted southward across Minnesota and Iowa, as seen in a comparison of GOES-16 Aerosol Optical Depth, “Red” Visible (0.64 µm). Near-Infrared “Cirrus” (1.37 µm) and “Clean” Infrared Window (10.3 µm) images (below). In this case the AOD values were quite high (in excess of 3.0 in northwestern Minnesota), beyond the range of values scaled for display in AWIPS — this led to the swath of black “No Data” values where the smoke was most dense. This plume of thick smoke also exhibited a signature in Near-Infrared “Cirrus” images; higher concentrations of airborne particles that are effective scatterers of light at the 1.37 µm wavelength (such as ice crystals, smoke, volcanic ash, or dust) will be detected using this imagery. Note the lack of a well defined signature on the 10.3 µm imagery — smoke is effectively transparent to radiation at these longer infrared wavelengths.

GOES-16 Aerosol Optical Depth (top left), "Red" Visible (0.64 µm, top right). Near-Infrared "Cirrus" (1.37 µm, bottom left) and "Clean" Infrared Window (10.3 µm, bottom right) [click to play animation | MP4]

GOES-16 Aerosol Optical Depth (top left), “Red” Visible (0.64 µm, top right). Near-Infrared “Cirrus” (1.37 µm, bottom left) and “Clean” Infrared Window (10.3 µm, bottom right) [click to play animation | MP4]

On a side note, the north-south plume of dense smoke over southcentral Canada and the Midwest US on 11 August was also very apparent from a distance of 983,269 miles (1,582,418.07 km) — 44 times the distance of the GOES-16 satellite — in EPIC Natural Color imagery from the DSCOVR satellite (below).

DSCOVR EPIC Natural Color images [click to enlarge]

DSCOVR EPIC Natural Color images [click to enlarge]

Hurricane Chris accelerates away from the United States

July 11th, 2018 |

GOES-16 ABI Band 2 (“Red Visible”) Visible (0.64 µm) Imagery, 1852-2117 UTC on 11 July 2018 (Click to animate)

Hurricane Chris is accelerating away from the United States (although it will likely pass very close to Cape Race, Newfoundland Canada). Visible Imagery (GOES-16 ABI Band 2, “Red Visible”, at 0.64 µm), above, from late afternoon on 11 July shows a well-developed storm with a pronounced eye.

Before Sunrise on 11 July 2018, both NOAA-20 and JAXA’s Global Change Observation Mission (GCOM) Satellite overflew the storm at slightly different times.  The VIIRS (Visible Infrared Imaging Radiometer Suite) instrument NOAA-20 samples in the visible and infrared part of the electromagnetic spectrum whereas the AMSR2 Instrument (Advanced Microwave Scanning Radiometer 2) on GCOM samples in the microwave.  Because microwave energy can penetrate clouds, it can be used to estimate rainfall, and the toggle below steps through the Infrared (11.45 µm) and Day Night Band Visible (0.70 µm) from VIIRS (at 0645 UTC) as well as the Convective Precipitation and Surface Rain rate from AMSR2 (at 0618 UTC). 

Lunar illumination is absent  in the Day Night band visible imagery, but Earth glow nevertheless illuminates the eye of the storm;  in addition, two lightning streaks are visible north and east of the center.  Surface Rain and Convective Rain rates show the heaviest rains near the storm center, as expected (NOAA-20 VIIRS and GCOM AMSR2 imagery courtesy William Straka, CIMSS).

VIIRS Infrared (11.45 µm) and Visible (0.70 µm) Day Night Band Visible Imagery, 0645 UTC on 11 July 2018, and GCOM AMSR2 Convective Precipitation and Surface Rain Rate estimates at 0618 UTC on 11 July (Click to enlarge)

Hurricane Chris

July 10th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed Chris as it rapidly intensified (ADT | SATCON) to a Category 1 Hurricane by 2100 UTC (NHC discussion) on 10 July 2018.

A toggle between 375-meter resolution NOAA-20 Visible (0.64 µm) and Infrared Window (11.45 µm) images (below) revealed cloud-top infrared brightness temperatures as cold as -81ºC (violet enhancement) in a convective burst just northeast of the eye. [Note: the 1821 UTC NOAA-20 images are incorrectly labeled as Suomi NPP images]

NOAA-20 VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

NOAA-20 VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Earlier in the day, a GPM satellite GMI Microwave (85 GHz) image from the CIMSS Tropical Cyclones site (below) showed that Tropical Storm Chris had not yet formed a closed eye at 1326 UTC.

GPM GMI Microwave (85 GHz) image [click to enlarge]

GPM GMI Microwave (85 GHz) image [click to enlarge]

However, a MIMIC-TC animation spanning the 0000 to 1925 UTC time period (below) showed the eye formation process completing as the estimated maximum speed (Vmax) increased from 60 to 75 knots.

MIMIC-TC morphed microwave image product [click to enlarge]

MIMIC-TC morphed microwave image product [click to enlarge]