September 8th, 2014
GOES-15 10.7 µm IR channel images (click to play animation)
McIDAS images of 4-km resolution GOES-15 10.7 µm IR channel data (above; click image to play animation; also available as an MP4 movie file) showed the merger of two large mesoscale convective systems (MCS) which produced an all-time record maximum calendar day precipitation amount of 3.29 inches at Phoenix Sky Harbor Airport (PHX) on 08 September 2014. Some locations in the Phoenix area received in excess of 5 inches of rainfall (NWS Phoenix event summary).
An AWIPS-II image of 375-meter resolution Suomi NPP VIIRS 11.45 µm IR channel data (below) showed the MCS pair at 09:07 UTC or 3:07 AM local time — this was prior to the merger, and the southeastern storm exhibited a minimum cloud-top IR brightness temperature of -84º C (purple color enhancement), which was much colder than the -71º C seen with the northwestern storm. At the onset of the heavy thunderstorms at PHX, southerly to southeasterly winds — likely outflow from the southeastern MCS — gusted as high as 31 knots (36 mph) and visibility was reduced to 0.8 mile (surface reports: text | graph).
Suomi NPP VIIRS 11.45 µm IR channel image
As the circulation of former-Hurricane Norbert continued to spin over the Pacific Ocean west of Baja California, deep tropical moisture kept working its way farther inland — GOES sounder Total Precipitable Water (TPW) values in excess of 50-60 mm (2.0 to 2.4 inches) were eventually seen across the southwestern half of Arizona (below; click image to play animation).
GOES sounder Total Precipitable Water derived product images (click to play animation)
The Blended Total Precipitable Water product (below; click image to play animation) also showed values of 50-60 mm working their way into southwestern Arizona during the 06-08 September period.
Blended Total Precipitable Water product (click to play animation)
The Percent of Normal TPW product (below; click image to play animation) indicated that these TPW values were in excess of 200% of normal (yellow color enhancement) over large portions of the Desert Southwest. On the morning of 08 September, the TPW value of 2.03 inches derived from rawinsonde data at Tucson, Arizona set a record high for the month of September at that location.
Percent of Normal TPW product (click to play animation)
August 26th, 2014
Before (12 August) and after (26 August) MODIS false-color RGB images
Some locations in northeastern Montana received up to 7-8 inches of rainfall over a 5-day period (NWS Glasgow rainfall map), which led to flooding in many areas. A comparison of before (12 August) and after (26 August) 250-meter resolution MODIS false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed the areal extent of flooding (cyan to darker blue areas on the 26 August image). The RGB images use MODIS bands 7/2/1 to help highlight the areas of of floodwater.
The maps below show the total observed rainfall, the departure from normal, and the percent of normal for the 7-day period ending on 26 August.
Observed 7-day rainfall
7-day rainfall departure from normal
7-day rainfall percent of normal
August 19th, 2014
Suomi NPP VIIRS Day/Night Band at 0659 UTC and 0838 UTC, 19 August 2014 (click to enlarge)
The VIIRS Day/Night Band image toggle above shows nighttime cloud cover over southern Wisconsin associated with a line of deep convection; note how some city lights are not seen (Madison WI KMSN at 0659 UTC, and Milwaukee WI KMKE at 0838 UTC). There are several reasons this may have happened. For example, the convection could have knocked out power over a large region (this did not happen). Scattering associated with the thick convective clouds may have attenuated the city light so much that it could not be detected.
The toggle below of the corresponding VIIRS 11.45 µm Infrared imagery shows very cold cloud tops (-60º to -70º C, near the tropopause) over Madison at 0659 UTC (the observation at 0653 UTC at the Madison airport was Heavy Rain with a Thunderstorm) and over Milwaukee at 0838 UTC (when the Milwaukee airport was having Moderate Rain; they received a half-inch of rain between 0753 and 0853 UTC). The combination of the thick convective cloud and especially the heavy rain is very likely why city lights cannot be seen at certain times, as liquid water is an excellent absorber of visible light. This radar image (from this story) shows the areal extent of the heavy rain at 0745 UTC on 19 August.
Suomi NPP VIIRS 11.45 µm Infrared imagery at 0659 UTC and 0838 UTC, 19 August 2014 (click to enlarge)
August 14th, 2014
GOES-14 0.63 µm visible channel images (click to play animation)
The GOES-14 satellite was placed into Super Rapid Scan Operations for GOES-R (SRSOR) mode on 14 August 2014, providing imagery at 1-minute intervals with the goal of monitoring the western US for convection and/or wildfire activity. McIDAS images of 0.63 µm visible channel data (above; click image to play animation; also available as an MP4 movie file) showed the development of clusters of slow-moving thunderstorms in the Las Vegas, Nevada region. These storms produced strong winds (gusts estimated at 60 mph) and heavy rainfall which caused flash flooding: Boulder City in far southern Nevada (located just east of Henderson, station identifier KHND) received 0.75 inch of rain in only 30 minutes. In addition to the state boundaries and yellow station identifiers, Interstate highways are drawn in red and State highways are cyan.
Another item of interest to note on the GOES-14 visible images: Lake Mead located to the east of Las Vegas was at an all-time record low level (1080.19 feet on 12 August) since it was filled back in the 1930s. The dark blue map outline represents the boundary of the lake as recently as the mid-1990s; the current area occupied by the darker water in Lake Mead’s Overton Arm (which extends northward) is drastically smaller in size, a result of the long-term severe to extreme drought.
AWIPS-2 images of the GOES-15 sounder Total Precipitable Water (TPW) derived product (below; click image to play animation) showed that these thunderstorms developed along a very sharp moisture boundary that was oriented roughly southwest to northeast across the area — TPW values of 30-40 mm (1.2-1.6 inches, yellow to red color enhancement) were seen east of the boundary, with TPW values of 10-20 mm (0.4-0.8 inch, shades of blue) west of the boundary.
GOES-15 sounder Total Precipitable Water derived product images (click to play animation)