Tropical Storm Michael

October 7th, 2018 |

GOES-16 "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images (above) showed deep convection associated with Tropical Depression 14 east of Belize and the Yucatan Peninsula of Mexico early in the day on 07 October 2018. There was a large area of cloud-top infrared brightness temperatures in the -80ºC to -89ºC range (shades of purple), with isolated small pockets of -90ºC or colder (yellow enhancement).

1-minute GOES-16 “Red” Visible (0.64 µm) images from the UW-AOS site (below) showed numerous convective overshooting tops.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

At 1655 UTC the system was upgraded to Tropical Storm Michael — 1-minute GOES-16 Infrared images (below) showed that deep convection persisted in the eastern semicircle of Michael during the remainder of the day.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

A hint of the elongated low-level circulation could be seen just west of the deep convection on late-day GOES-16 Visible images (below).

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

===== 08 October Update =====

NOAA-20 VIIRS Day/Night Band (0.7 µm), Infrared Window (11.45 µm) and ATMS Microwave (88 GHz) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm), Infrared Window (11.45 µm) and ATMS Microwave (88 GHz) images [click to enlarge]

NOAA-20 VIIRS Day/Night Band (0.7 µm), Infrared Window (11.45 µm) and ATMS Microwave (88 GHz) images at 0721 UTC (above; courtesy of William Straka, CIMSS) indicated that a well-defined convective band was wrapping around the eastern, northern and northwestern portions of the storm center (with some bright lightning streaks showing up on the DNB image in the southeastern segment of this convective band).

In a comparison of DMSP-18 SSMIS Microwave (86 GHz) and GOES-16 Infrared Window (10.3 µm) images at or shortly after 1115 UTC (below), the Microwave imagery showed a very large eye beneath the convective clusters.

DMSP-18 SSMIS Microwave (86 GHz) and GOES-16 Infrared Window (10.3 µm) images [click to enlarge]

DMSP-18 SSMIS Microwave (86 GHz) and GOES-16 Infrared Window (10.3 µm) images [click to enlarge]

Michael was upgraded to a Category 1 hurricane at 15 UTC; 1-minute GOES-16 “Red” Visible (0.64 µm) images (below) revealed abundant deep convection around the core of the storm during the 3 hours leading up to that time.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

Michael had been moving over very warm water since forming on 06 October; analyses of Ocean Heat Content and Sea Surface Temperature (below) showed that while the hurricane was forecast to briefly pass over a region of lower OHC in the far southeastern Gulf of Mexico, the remainder of its journey across the Gulf would be over water possessing modest amounts of OHC and warm SST values of 29-30ºC.

Ocean Heat Content and Sea Surface Temperature analyses, with past and forecast tracks of Michael [click to enlarge]

Ocean Heat Content and Sea Surface Temperature analyses, with past and forecast tracks of Michael [click to enlarge]

Similarly, a relatively cloud-free Terra MODIS Sea Surface Temperature product from 0343 UTC on 06 October (below) showed SST values of 84-85ºF (darker red colors) along much of the forecast path of Hurricane Michael (issued at 2100 UTC on 08 October).

Terra MODIS Sea Surface Temperature product (0343 UTC on 06 October) with Hurricane Michael forecast positions issued at 2100 UTC on 08 October [click to enlarge]

Terra MODIS Sea Surface Temperature product (0343 UTC on 06 October) with forecast positions of Hurricane Michael issued at 2100 UTC on 08 October [click to enlarge]

Leeside frontal gravity wave moves southward across the Plains

October 4th, 2018 |
GOES-17 Upper-level Water Vapor (6.2 µm) images, with surface frontal analyses [click to play MP4 animation]

GOES-17 Upper-level Water Vapor (6.2 µm) images, with surface frontal analyses [click to play MP4 animation]

* GOES-17 images shown here are preliminary and non-operational *

A strong cold front (surface analyses | max/min temperatures) moved southward across the Plains states during the 03 October – 04 October 2018 period — and GOES-17 Upper-level Water Vapor (6.2 µm) images (above) revealed a distinct leeside frontal gravity wave as it propagated from southern Colorado and southern Kansas at 05 UTC to southeastern New Mexico and the southern Texas Panhandle by 20 UTC. Thunderstorms formed along the stalled residual wave along the New Mexico/Texas border after 1930 UTC.

Pilot reports of high-altitude “mountain wave” turbulence (below) were seen at 1559 and 1721 UTC, along the north-to-south oriented portion of the gravity wave that had become stationary over eastern New Mexico.

GOES-17 Upper-level Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to enlarge]

GOES-17 Upper-level Water Vapor (6.2 µm) images, with pilot reports of turbulence [click to enlarge]

A 1-km resolution Aqua MODIS Water Vapor (6.7 µm) image at 0807 UTC (below) showed detailed gravity wave structure over Oklahoma.

Aqua MODIS Water Vapor (6.7 µm) image [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) image [click to enlarge]

A 3-panel comparison of GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images with plots of surface wind barbs (below) showed how the winds changed to northerly/northeasterly as the cold front passed.

GOES-17 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with plots of surface wind barbs [click to play MP4 animation]

GOES-17 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with hourly plots of surface wind barbs [click to play MP4 animation]

Additional images of this event can be found on the Satellite Liaison Blog.

Medicane “Zorbas”

September 29th, 2018 |

NOAA-20 and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

NOAA-20 and Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Medicane “Zorbas” — as named by Freie Universität Berlin (surface analyses) — developed in the Mediterranean Sea late in the day on 27 September 2018. A toggle between VIIRS Day/Night Band (0.7 µm) images from NOAA-20 and Suomi NPP (above; courtesy of William Straka, CIMSS) revealed the well-defined circulation of the storm a few hours after Midnight local time on 28 September. Note the bright streak north of the storm center on the NOAA-20 image — this was an area of clouds illuminated by intense lightning activity. Other less prominent lightning streaks were evident in thunderstorms farther to the east over the Mediterranean Sea. On the Suomi NPP image, a small bright spot could be seen, evidence of minor volcanic activity at Mount Etna on the island of Sicily, as well as the hazy signature of a plume of blowing dust/sand that was moving northward off the coast of Libya. The corresponding VIIRS Infrared images are available here.

During the following daylight hours of 28 September, EUMETSAT Meteosat-11 High Resolution Visible (0.8 µm) images (below) showed the storm as it became better organized and increased intensity. Another dense plume of blowing dust/sand began to move off the coast of Libya late in the day.

Meteosat-11 Visible (0.8 µm) images, with hourly plots of wind barbs (yellow) and wind gusts (red) [click to play animation | MP4]

Meteosat-11 Visible (0.8 µm) images, with hourly plots of wind barbs (yellow) and wind gusts (red) [click to play animation | MP4]

On 29 September, Meteosat-11 Visible (0.8 µm) images (below) showed the Medicane moving inland along the Peloponnese coast of southern Greece — shortly after the storm center passed, winds gusted to 48 knots at Kalamata at 1220 UTC (while a heavy thunderstorm was being reported).

Meteosat-11 Visible (0.8 µm) images, with hourly plots of winds (yellow) and gusts in knots (red) [click to play animation | MP4]

Meteosat-11 Visible (0.8 µm) images, with hourly plots of wind barbs (yellow) and gusts in knots (red) [click to play animation | MP4]

A sequence of Terra and Aqua MODIS True Color Red-Green-Blue (RGB) images from 28 and 29 September from RealEarth (below) showed another view of the Zorbas on those 2 days (the valid time of the Terra MODIS image showing the eye-like feature on 29 September was 0911 UTC). Sea Surface Temperatures were near 25ºC in the central Mediterranean Sea where Zorbas was intensifying.

Terra/Aqua MODIS True Color RGB images on 28 and 29 September [click to enlarge]

Terra/Aqua MODIS True Color RGB images on 28 and 29 September [click to enlarge]

Hourly images of the MIMIC Total Precipitable Water product (below) showed moisture associated with the storm, which produced heavy rainfall and flash flooding in parts of southern Greece — the NESDIS Blended TPW Anomaly product indicated that this moisture was as much as 200% of normal for the region and date. Additional information and videos can be found here.

MIMIC morphed Total Precipitable Water images, 27-29 September [click to play animation | MP4]

MIMIC morphed Total Precipitable Water images, 27-29 September [click to play animation | MP4]

Land breeze convergence cloud band in Lake Michigan

September 23rd, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface and buoy reports [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a narrow cloud band that had developed in Lake Michigan in response to land breeze induced convergence on the morning of 23 September 2018. With inland temperatures cooling overnight into the 30s and 40s F (the coldest in both Wisconsin and Michigan was 29ªF) and lake water temperatures of 64ºF (at the North Michigan buoy 45002) to 69ºF (at the South Michigan buoy 45007), a well-defined nocturnal land breeze was established along the western and eastern shorelines of the lake.

Nighttime VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC (below) showed that the cloud band had not yet formed at those times.

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

VIIRS Day/Night Band (0.7 µm) images from Suomi NPP at 0743 UTC and NOAA-20 at 0832 UTC [click to enlarge]

The Terra and Aqua MODIS Sea Surface Temperature product (below) confirmed that mid-lake water temperatures were generally in the middle to upper 60s F (green to light yellow enhancement) across the entire length of Lake Michigan.

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product [click to enlarge]

An examination of the MODIS SST product with overlays of RTMA surface winds (below) showed that there was no clear signature in the model wind field of enhanced convergence either before or after the mid-lake cloud band had formed.

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

Terra/Aqua MODIS Sea Surface Temperature product, with RTMA surface winds [click to enlarge]

However, an overpass of the Metop-A satellite at 1559 UTC provided ASCAT surface scatterometer winds that did a better job than the RTMA at highlighting the mid-lake convergence that was helping to sustain the cloud band (below). This example underscores the value that satellite-derived winds can have over even high resolution models.

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]

Terra MODIS Sea Surface Temperature product, with RTMA surface winds and Metop ASCAT winds [click to enlarge]