Southwest US monsoon convection: GOES-15 vs GOES-16

July 12th, 2018 |

GOES-15 Visible (0.63 µm, left) and GOES-16 Visible (0.64 µm, right) images [click to play MP4 animation]

GOES-15 Visible (0.63 µm, left) and GOES-16 “Red” Visible (0.64 µm, right) images [click to play MP4 animation]

GOES-15 (GOES-West) Visible (0.63 µm) and GOES-16 (GOES-East) “Red” Visible (0.64 µm) images — displayed in the native projection of each satellite, and centered on Las Vegas, Nevada — are shown above, depicting the development of deep convection across parts of the Desert Southwest on 12 July 2018. While the GOES-15 satellite was in Rapid Scan Operations mode (providing 2 extra images nearly every hour, at :11 and :41), a GOES-16 Mesoscale Sector was providing images at 1-minute intervals. Numerous flash flood watches, warnings and advisories were issued by NWS Las Vegas during the course of the day as some of the storms produced heavy rainfall (with as much as 0.75 inch at Cal Nev Ari and 0.61 inch at Needles, California KEED).

Note that the GOES-15 Visible images do not appear as bright as those from GOES-16 — prior to the GOES-R Series of satellites, the performance of visible detectors degraded over time, leading to imagery that appeared more dim as the Imager instrument aged. Visible detectors on the new ABI instrument benefit from on-orbit calibration to remedy this type of degradation.

The corresponding GOES-15 Infrared Window (10.7 µm) and GOES-16 “Clean” Infrared Window (10.3 µm) images (below) revealed cloud-top infrared brightness temperatures around -70ºC (black enhancement) associated with some the stronger thunderstorms; this was the tropopause temperature at an altitude of 16.7 km / 48,300 feet on 00 UTC Las Vegas rawinsonde data. The improvement in spatial resolution from 4 km (at sub-satellite point) with GOES-15 to 2 km with GOES-16 is very apparent — even though the satellite viewing angle is about 10 degrees higher for GOES-16 than it is for GOES-15.

GOES-15 Infrared Window (10.7 µm, left) and GOES-16 "Clean" Infrared Window (10.3 µm, right) images [click to play MP4 animation]

GOES-15 Infrared Window (10.7 µm, left) and GOES-16 “Clean” Infrared Window (10.3 µm, right) images [click to play MP4 animation]

Higher spatial resolution Infrared Window images from Terra/Aqua MODIS and Suomi NPP VIIRS (below) revealed a cloud-top infrared brightness temperature as cold as -79ºC in far northwestern Arizona on the 2017 UTC VIIRS image.

Infrared Window images from Terra/Aqua MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) [click to enlarge]

Infrared Window images from Terra/Aqua MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) [click to enlarge]

In addition to heavy rainfall, some thunderstorm winds created areas of blowing sand:

The GOES-16 Total Precipitable Water derived product (below) showed that rich moisture was present across the Desert Southwest, fueling the development of the widespread convection. TPW values in the 1.0 to 2.0 inch range were seen over southeastern California, southwestern Arizona and far southern Nevada.

GOES-16 Total Precipitable Water derived product [click to play MP4 animation]

GOES-16 Total Precipitable Water derived product [click to play MP4 animation]

A 4-km resolution Terra/Aqua MODIS Total Precipitable Water product (below) indicated values in the 40-55 mm or 1.6-2.2 inch range.

Terra/Aqua MODIS Total Precipitable Water product [click to enlarge]

Terra/Aqua MODIS Total Precipitable Water product [click to enlarge]

Summer solstice TROWAL over the Upper Midwest

June 21st, 2018 |

Aqua MODIS Water Vapor (6.7 µm) image, with overlays of surface pressure/fronts (cyan), RUC model 310K equivalent potential temperature (red) and 24-hour precipitation (green) [click to enlarge]

Aqua MODIS Water Vapor (6.7 µm) image, with overlays of surface pressure/fronts (cyan), RUC model 310K equivalent potential temperature (red) and 24-hour precipitation (green) [click to enlarge]

A nighttime Aqua MODIS Water Vapor (6.7 µm) image (above) showed the well-defined circulation of a mid-latitude cyclone that was centered over northwest Iowa at 0814 UTC (3:14 am local time) on 21 June 2018. Contours of RUC model equivalent potential temperature along the 310 K isentropic surface indicated that a Trough of Warm Air Aloft (TROWAL) existed just to the north of the occluded surface frontal boundary, curving cyclonically from northeastern Iowa across southern Minnesota into southeastern South Dakota and then southward across eastern Nebraska. 24-hour precipitation totals in excess of 2-3 inches had already been observed at that time.

Suomi NPP VIIRS Infrared Window (11.45 µm) images (below) displayed minimum cloud-top brightness temperature values of -50 to -55ºC (yellow to orange enhancement) near the TROWAL axis.

Suomi NPP VIIRS Infrared Window (11.45 µm) images, with plots of surface reports [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) images, with plots of surface reports [click to enlarge]

An animation of GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (below) revealed that the storm system moved very slowly during the 00-20 UTC time period, while moderate to occasionally heavy rainfall was observed beneath the TROWAL air stream. 24-hour precipitation amounts reached 4-6 inches by 12 UTC in parts of southwest Minnesota, northwest Iowa and southeast South Dakota (FSD PNS) — and a number of river gauges were reporting minor to major flooding by the afternoon hours.

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

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

It should be noted that TROWAL formation is rather unusual over this region during the summer months — but during the cold season a TROWAL can help to produce heavy snowfall (some examples are documented here, here and here).

Convection and Flooding over northern Wisconsin

June 17th, 2018 |

GOES-16 ABI Clean Window (10.3 µm) Infrared Imagery, 0200-0559 UTC on 17 June 2018 (Click to animate)

Persistent convection over northern Wisconsin, Minnesota and upper Michigan late Saturday (16 June)/early Sunday (17 June) caused significant flooding.  The animation above shows GOES-16 ABI “Clean Window” Infrared Imagery from 0200-0600 UTC on 17 June.  Note the persistence of the cold overshooting tops over western Bayfield County in northwestern Wisconsin! A longer Infrared animation (0110-1200 UTC) which includes hourly plots of precipitation type (yellow) and SPC storm reports of damaging winds (cyan) is available here. 7-day precipitation departures in some areas were 4 to 8 inches above normal for that period (or 600% of normal).

This link from Wisconsin Emergency Management shows aerial pictures of the flood damage. Of note is the break in US Highway 2 to the west of Ashland WI.

The heavy rains also affected runoff into Lake Superior. MODIS imagery, below, from the MODIS Today site (also available from RealEarth: Link), shows considerable offshore flow of sediment on 19 June (a similar image from 18 June is here, with a toggle between the 2 days here).

True-Color Imagery from Aqua MODIS on 19 June 2018 (Click to enlarge)

A Landsat-8 False-Color image, below, showed pockets of flooding (darker blue) adjacent to the Nemadji River in Superior WI on the morning of 19 June — water also cover a portion of US Highway 2/53. The Nemadji River had crested in Superior at a record 29.5 feet on the evening of 17 June (NWS Duluth summary).

Landsat-8 False-Color image (Click to enlarge)

False-Color image from Landsat-8 on 19 June 2018 (Click to enlarge)


============================ Added 22 June ==============================
 

NOAA’s Hydrometeorological Design Studies Center (Link) created an Exceedance Probability Analysis for this event at 6-hour, 24-hour and 72-hout time spans, available here (from this link). Probabilities suggest this was an exceedingly rare event.

The continuation of sediment flow into Lake Superior could be seen in a series of daily MODIS True-Color images here.

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]