July « 2016 « CIMSS Satellite Blog

Heavy rainfall and flash flooding in Maryland

July 30th, 2016 | Scott Bachmeier

GOES-13 0.63 µm Visible (top) and 10.7 µm Infrared Window (bottom) images [click to play animation]

A 2-panel comparison of GOES-13 (GOES-East) Visible (0.63 µm) and Infrared Window (10.7 µm) images (above) showed a band of thunderstorms oriented southwest-to-northeast across northern Virginia and northern Maryland late in the day on 30 July 2016. Cells within this band produced very heavy rainfall and extreme flash flooding at Ellicott City, Maryland — located northwest of Baltimore/Washington International Airport KBWI, and marked with a cyan * symbol — with a total of 6.60 inches of rain in just over 2 hours (NWS Baltimore/Washington Public Information Statement | Event summary). The coldest cloud-top IR brightness temperature was -67º C at 0045 UTC on 31 July (8:45 pm local time).

The MIMIC Total Precipitable Water product at 3-hour intervals (below) indicated the presence of TPW values in the 2.0 to 2.5 inch range over parts of the region.

MIMIC Total Precipitable Water product [click to enlarge]

Upstream rawinsonde data profiles from Washington Dulles International Airport in northern Virginia (below) showed TPW values of 46.8 mm or 1.83 inches at 12 UTC on 30 July, and 49.2 mm or 1.94 inches at 00 UTC on 31 July (although the later data looks suspect, given the balloon was launched as strong thunderstorms were approaching).

Washington Dulles VA rawinsonde profiles [click to enlarge]

Posted in GOES-13, Heavy rain / flooding, Other Satellites | No Comments »

River valley fog in Wisconsin, Minnesota and Iowa

July 26th, 2016 | Scott Bachmeier

Suomi NPP VIIRS 11.45 µm – 3.74 µm Infrared brightness temperature difference (“fog product”) at 0735 UTC [click to enlarge]

A nighttime image (above) of the Suomi NPP VIIRS 11.45 µm – 3.74 µm Infrared brightness temperature difference (often referred to as the “fog/stratus product”) showed the development of narrow fingers of river valley fog in parts of southwestern Wisconsin, southeastern Minnesota and northeastern Iowa at 0735 UTC or 2:35 am local time on 26 July 2016. At that time the surface visibility was reduced to 1/4 mile at Boscobel, Wisconsin (station identifier KOVS).

During the subsequent daylight hours, GOES-13 Visible (0.63 µm) images (below) revealed the extent of the valley fog which had formed (the yellow symbols denote stations reporting fog). However, this fog quickly dissipated quickly with strong heating from the July sun.

GOES-13 Visible (0.63 µm) images [click to play animation]

This region frequently experiences such episodes of river valley fog, but they are most common during the Autumn months as nights grow longer and nighttime temperatures get colder. In this late July event, the primary ingredient favoring fog formation was high soil moisture due to recent heavy rainfall (below), much of which occurred on 24 July.

7-day precipitation, departure from normal, and percent of normal {click to enlarge]

Posted in Fog detection, GOES-13, Suomi NPP, VIIRS | No Comments »

Transverse banding: a signature of potential turbulence

July 20th, 2016 | Scott Bachmeier

GOES-13 Infrared Window (10.7 um) images, pilot reports of turbulence, Turbulence AIRMET boundaries [click to play animation]

GOES-13 (GOES-East) Infrared Window (10.7 µm) images (above) showed the formation of tendrils of transverse banding along the northern semicircle of decaying mesoscale convective systems as they moved eastward across Nebraska and Iowa on 19 July 2016. Pilot reports of turbulence are plotted on the images, along with Turbulence AIRMET polygons issued at 0800 UTC and 1400 UTC. Most of the pilot reports of turbulence were in the Light to Moderate category, although there was one report of Moderate to Severe intensity at 1612 UTC over eastern Iowa.

The corresponding GOES-13 Water Vapor (6.5 µm) images (below) perhaps highlighted the transverse banding features a bit better at times, since the weighting function for that spectral band generally peaks in the middle to upper troposphere where the transverse banding cloud features existed.

GOES-13 Water Vapor (6.5 um) images, pilot reports of turbulence, Turbulence AIRMET boundaries [click to play animation]

A sequence of Infrared Window images from POES AVHRR (10.8 µm) and Suomi NPP VIIRS (11.45 µm) (below) showed a higher-resolution view of the initial formation of transverse banding during the 0411 to 1008 UTC time period.

Infrared Window images from POES AVHRR (10.8 µm) and Suomi NPP VIIRS (11.45 µm) [click to enlarge]

Shown below are two other types of satellite imagery that can be helpful for identifying the areal extent of transverse banding cloud features: the Suomi NPP VIIRS Day/Night Band (0.7 µm), and the MODIS Cirrus band (1.37 µm). A similar Cirrus band will be part of the ABI instrument on GOES-R.

Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) and Cirrus (1.37 µm) images [click to enlarge]

Posted in AVHRR, Aviation, GOES-13, GOES-R, MODIS, POES, Suomi NPP, Terra, VIIRS | No Comments »

Severe thunderstorms and heavy rainfall/flooding in the Upper Midwest

July 12th, 2016 | Scott Bachmeier

GOES-13 Infrared Window (10.7 µm) images, with SPC storm reports [click to play animation]

GOES-13 Infrared Window (10.7 µm) images (above; also available as an MP4 movie file) showed a series of mesoscale convective systems that moved across northeastern Minnesota, northwestern Wisconsin and the Upper Peninsula of Michigan during the 11 July – 12 July 2016 period. Some of these storms produced tornadoes, large hail, and damaging winds (SPC storm reports) in addition to heavy rainfall, with as much as 9.00 inches in Minnesota and 9.80 inches in Wisconsin (NWS Duluth storm summary). Several highways were closed due to flooding and/or washout, including a portion of Interstate 35 in Minnesota (interstates and highways are plotted in violet on the images).

A sequence of Infrared images from Terra/Aqua MODIS (11.0 µm) and Suomi NPP VIIRS (11.45 µm) (below) showed greater detail in the storm-top temperature structure at various times during the event.

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

===== 19 July Update =====

Comparison of before (09 July) and after (12 July through 19 July) Suomi NPP VIIRS true-color images [click to enlarge]

A comparison of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from before the event (09 July) and after the event (12 through 19 July) (above) revealed the large amounts of sediment flowing offshore into the southwestern portion of Lake Superior.

Another comparison of before (09 July) and after (13 through 19 July) true-color RGB images from Terra and Aqua MODIS is shown below.

Comparison of before (09 July) and after (13 through 19 July) Terra/Aqua MODIS true-color images [click to enlarge]

Comparison of before (09 July) and after (13 July through 19 July) Terra/Aqua MODIS true-color images [click to enlarge]

A toggle between a Terra MODIS Visible (0.65 µm) image and the corresponding MODIS Sea Surface Temperature (SST) product on 16 July (below) showed that the SST values in the sediment-rich nearshore waters were significantly warmer (middle 60s F, red enhancement) than those found closer to the center of Lake Superior (middle 40s F, cyan enhancement).