Heavy rainfall over the Hawaiian island of Kauai

April 15th, 2018 |

GOES-15 Water Vapor (6.5 µm, left) and Infrared Window (10.7 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-15 Water Vapor (6.5 µm, left) and Infrared Window (10.7 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

A series of back-building thunderstorms produced very heavy rainfall and flash flooding (Public Information Statement | Local Storm Reports | CoCoRaHS) over the northern and eastern portion of Kauai on 14-15 April 2018. GOES-15 (GOES-West) Water Vapor (6.5 µm) and Infrared Window (10.7 µm) images (above) showed these deep convective storms, which exhibited cloud-top infrared brightness temperatures in the -60 to -70 ºC range (red to black enhancement). 25 April Update: a possible US record for 24-hour precipitation (49.69 inches) is being investigated.

Even though the JMA Himawari-8 AHI instrument provides more frequent Water Vapor and Infrared Window images (every 10 minutes, compared to every 15-30 minutes with GOES-15) at a higher spatial resolution (2-km at satellite sub-point, vs 4-km with GOES-15),  Hawai’i is located near the limb of the Himawari-8 view — so parallax was playing a major role in the apparent location of the important convective features. Note how the primary thunderstorms were displayed to the east of Kauai on the Himawari-8 images, in contrast to directly over the island on GOES-15 images.

Himawari-8 Water Vapor (6.9 µm, left) and Infrared Window (10.4 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

Himawari-8 Water Vapor (6.9 µm, left) and Infrared Window (10.4 µm, right) images, with hourly plots of surface reports [click to play MP4 animation]

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The MIMIC Total Precipitable Water product (above) showed that high amounts of tropical moisture were drawn northward across Hawai’i by the circulation of an upper-level trough — depicted by mid/upper-level atmospheric motion vectors — that was situated west/northwest of the islands (below).

GOES-15 Water Vapor (6.5 µm) images with mid/upper level atmospheric motion vectors [click to play animation]

GOES-15 Water Vapor (6.5 µm) images with mid/upper-level atmospheric motion vectors [click to play animation]

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)