Gravity waves near Guadalupe Island

March 15th, 2018 |

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation]

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation]

GOES-16 (GOES-East) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) revealed an interesting packet of gravity waves in the vicinity of Guadalupe Island (west of Baja California) on 15 March 2018. The mechanism forcing these waves was not entirely clear, making it a suitable candidate for the “What the heck is this?” blog category.

A similar animation of GOES-16 “Red” Visible (0.64 µm), Mid-level Water Vapor (6.9 µm) and Upper-level Water Vapor (6.2 µm) images (below) did show some smaller-scale waves on Visible imagery within the marine boundary layer stratocumulus cloud field, but they did not appear to exhibit a direct correlation with the higher-altitude waves seen in the Water Vapor imagery. Surface winds were from the northwest at 10-15 knots, as a dissipating cold front was stalled over the region.

GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Mid-level Water Vapor (6.9 µm, center) and Upper-level Water Vapor (6.2 µm, right) images [click to play animation]

A larger-scale view of Mid-level Water Vapor (6.9 µm) images (below) showed that these waves were located to the north of a jet streak axis — denoted by the sharp dry-to-moist gradient (yellow to blue enhancement) stretching from southwest to northeast as it moved over Baja California.

GOES-16 Mid-level (6.9 µm) Water Vapor images [click to play animation]

GOES-16 Mid-level (6.9 µm) Water Vapor images [click to play animation]

GOES-15 (GOES-West) Water Vapor (6.5 µm) images with overlays of upper-tropospheric atmospheric motion vectors and contours of upper-tropospheric divergence (below) indicated that Guadalupe Island was located within the “dry delta” signature often associated with a jet stream break — the inflection point between 2 strong jet streaks within a sharply-curved jet stream. Upper-tropospheric winds were from the west/northwest, with upper-tropospheric convergence seen over the region of the gravity waves.

GOES-15 Water Vapor (6.5 µm) images, with water vapor wind vectors [click to enlarge]

GOES-15 Water Vapor (6.5 µm) images, with atmospheric motion vectors [click to enlarge]

GOES-15 Water Vapor (6.5 µm) images, with contours of upper-tropospheric convergence [click to enlarge]

GOES-15 Water Vapor (6.5 µm) images, with contours of upper-tropospheric convergence [click to enlarge]

An early morning Aqua MODIS Water Vapor (6.7 µm) image with NAM80 contours of 250 hPa wind speed (below) showed the two 90-knot jet streaks on either side of the jet stream break — it could be that speed convergence due to rapidly decelerating air within the exit region of the western jet streak was a possible forcing mechanism of the gravity waves seen on the GOES-16 Water Vapor imagery.

Aqua MODIS Water Vapor (6.7 µm) image, with NAM80 contours of 250 hPa wind speed [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) image, with NAM80 contours of 250 hPa wind speed [click to enlarge]

Summary of the 02-03 March Nor’Easter

March 3rd, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with plots of hourly wind gusts [click to play MP4 animation]

A strong Nor’easter affected much of northeastern portion of the US during 02 March and 03 March 2018. As noted in the previous blog post, the storm produced very strong winds which led to widespread wind damage and power outages. A GOES-16 (GOES-East) Mesoscale Sector was positioned over the storm on 02 March, and “Red” Visible (0.64 µm) images (above) provided a detailed view of the center of circulation over the western Atlantic.

A 2-day animation of GOES-16 Mid-level Water Vapor (6.9 µm) images (below) showed the evolution of the storm as it moved from the Great Lakes to the Atlantic Ocean (surface analyses). A summary of the peak wind gusts and highest snowfall/rainfall totals can be seen here and here.

GOES-16 Mid-level (6.9 µm) images, with plots of hourly wind gusts [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of hourly wind gusts [click to play MP4 animation]

On 03 March, a vortex was seen to develop in GOES-16 “Red” Visible (0.64 µm) images, just behind the occluded frontal boundary — about 30 minutes after a burst of stronger northeasterly winds (with speeds as high as 58 knots) was analyzed in that region by the Metop ASCAT instrument.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with surface fronts and Metop ASCAT surface scatterometer winds [click to play MP4 animation]

A signature of this vortex was also evident in GOES-16 Low-level Water Vapor (7.3 µm) images (below). A toggle between Visible and Water Vapor images at 1605 UTC is available here.

GOES-16 Mid-level (6.9 µm) images, with surface fronts and Metop ASCAT surface scatterometer winds [click to play animation]

GOES-16 Low-level Water Vapor (7.3 µm) images, with surface fronts and Metop ASCAT surface scatterometer winds [click to play MP4 animation]

Finally, a NOAA-20 VIIRS True-color Red-Green-Blue (RGB) image centered over Lake Erie at 1839 UTC on 03 March (below) showed the fresh snow cover left by the storm as it moved across the Great Lakes on 02 March. Snow can be seen across parts of Lower Michigan, southern Ontario, northern Ohio, and far northwestern Pennsylvania. NOAA-20 is the first of the JPSS series of satellites (note: the data are still considered preliminary and non-operational as the instruments and products are being evaluated and tested).

NOAA-20 True-color RGB image, centered of Lake Erie [click to enlarge]

NOAA-20 VIIRS True-color RGB image, centered of Lake Erie [click to enlarge]

Derived Motion Winds near the surface with a strong East Coast Storm

March 2nd, 2018 |

GOES-16 ABI Band 10 (Low-Level Water Vapor, 7.3 µm) Infrared Imagery, 0507-1757 UTC on 2 March 2018 (Click to animate)

The evolution of a very strong Nor’easter on the East Coast of the United States for the twelve hours ending at ~1800 UTC on 2 March 2018 is shown above. During this time period, the storm produced winds that shut down schools and Government in the Nation’s Capitol (and elsewhere), with High Wind Warnings widespread from North Carolina to Massachusetts (Link, from this site). Significant Coastal Flooding is likely in New England with this storm.

One of the Level 2 Products produced with GOES-R Series Satellite (GOES-16 and soon, GOES-17) data are Derived Motion Wind Vectors at various levels. The images below show winds of up to 70 knots (!!) at or below 900 hPa over the Chesapeake Bay between 1627 and 1657 UTC on 2 March. Observations (bottom) show numerous surface gusts exceeding 50 knots in the region during that time.

GOES-16 ABI Band 10 (Low-Level Water Vapor, 7.3 µm) Infrared Imagery, 1627 and 1657 UTC on 2 March 2018, with Derived Motion Winds in excess of 50 knots at ~1000 hPa (red) and ~900 hPa (Magenta) plotted (Click to enlarge)

GOES-16 ABI Band 2 (“Red” Visible, 0.64 µm) Visible Imagery, 1502, 1602 and 1702 UTC on 2 March 2018, with surface observations plotted in green (Click to enlarge)

 

Cyclone Kelvin makes landfall in Australia

February 18th, 2018 |

Himawari-8 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images, with hourly surface plots at Broome [click to play Animated GIF | MP4 also available]

Himawari-8 Visible (0.64 µm, left) and Infrared Window (10.4 µm, right) images, with hourly surface plots at Broome, Australia [click to play Animated GIF | MP4 also available]

Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images (above) showed Cyclone Kelvin as it made landfall in Western Australia as a Category 1 storm on 18 February 2018. Kelvin continued to intensify shortly after making landfall, with estimated winds of 80 gusting to 100 knots — and a distinct eye feature could be seen in the Visible and Infrared imagery (as well as Broome radar data).

A longer animation of Himawari-8 Infrared Window (10.4 µm) images (below) revealed a very large convective burst as Kelvin meandered near the coast early on 17 February — periodic cloud-top infrared brightness temperatures of -90 ºC or colder were seen. After making landfall, the eye structure eventually deteriorated by 18 UTC on 18 February.

Himawari-8 Infrared Window (10.4 µm) images, with hourly surface plots [click to play MP4 | Animated GIF also available]

Himawari-8 Infrared Window (10.4 µm) images, with hourly surface plots [click to play MP4 | Animated GIF also available]

The MIMIC-TC product (below) showed the development of Kelvin’s compact eye during the 17 February – 18 February period; the eye was well-defined around the time of landfall (2147 UTC image on 17 February), and persisted for at least 18 hours (1556 UTC image on 18 February) until rapidly dissipating by 21 UTC.

MIMIC-TC morphed microwave imagery [click to enlarge]

MIMIC-TC morphed microwave imagery [click to enlarge]

Himawari-8 Deep Layer Wind Shear values remained very low — generally 5 knots or less — prior to, during and after the landfall of Kelvin, which also contributed to the slow rate of weakening. In addition, an upward moisture flux from the warm/wet sandy soil of that region helped Kelvin to intensify after landfall; land surface friction was also small, since that portion of Western Australia is rather flat.

Himawari-8 Water Vapor images, with Deep Layer Wind Shear product [click to enlarge]

Himawari-8 Water Vapor images, with Deep Layer Wind Shear product [click to enlarge]

The eye of Cyclone Kelvin could also be seen in Terra MODIS and Suomi NPP VIIRS True-color Red-Green-Blue (RGB) images, viewed using RealEarth (below). The actual times of the Terra and Suomi NPP satellite overpasses were 0154 UTC and 0452 UTC on 18 February, respectively.

Terra MODIS and Suomi NPP VIIRS True-color RGB images [click to enlarge]

Terra MODIS and Suomi NPP VIIRS True-color RGB images [click to enlarge]