GOES-13 0.63 µm visible images, with Cloud-Top Cooling Rate, Overshooting Tops Detection, and SPC storm reports (click to play animation)

A deepening area of low pressure (21 UTC surface analysis) was moving northeastward across the Midwest region of the US on 09 April 2015; GOES-13 0.63 µm visible images combined with the Cloud-Top Cooling Rate and Overshooting Tops Detection products (above; click image to play animation) showed a line of severe thunderstorms which quickly developed along the associated cold frontal boundary as it moved eastward across Iowa and Missouri during the afternoon hours. Cloud-Top Cooling Rates with some of the storms in Missouri were in excess of 50º C per 15 minutes (violet color enhancement) during their early stage of development (18:25 UTC image).

A comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 18:51 UTC or 1:51 PM local time (below) showed that the line of thunderstorms was beginning to produce a number of cloud-to-ground lightning strikes.

Suomi NPP VIIRS 11.45 µm IR channel image and 0.64 µm visible channel image with cloud-to-ground lightning strikes

Focusing our attention on eastern Iowa and northern Illinois — where there were widespread reports of large hail, damaging winds, and tornadoes (SPC storm reports) — the organization of large, discrete supercell thunderstorms can be seen on GOES-13 0.63 µm visible channel images (below; click image to play animation), which exhibited numerous overshooting tops.

GOES-13 0.63 µm visible channel images, with SPC storm reports (click to play animation)

The corresponding GOES-13 10.7 µm IR channel images (below; click image to play animation) showed that the coldest cloud-top IR brightness temperatures were -67º C (darker black enhancement).

GOES-13 10.7 µm IR images, with Overshooting Top Detection and SPC storm reports (click to play animation)

The NOAA/CIMSS ProbSevere product (below; click image to play animation) gauges the likelihood of a storm first producing severe weather (of any kind) within the next 60 minutes. It combines information about the environment (Most Unstable CAPE, Environmental Shear) from the Rapid Refresh Model, information about the growing cloud (Vertical Growth Rate as a percentage of the troposphere per minute and Glaciation Rate, also as a percentage per minute), and Maximum Expected Hail Size (MESH) from the MRMS. In this event, the ProbSevere product performed well for the storm that spawned the EF-4 tornado, although due to the cloudiness of the satellite scene the ProbSevere model was unable to diagnose vertical growth rate and glaciation rate (which diminished the potential lead-time). Below is a chronological timeline of events for that storm:

2308 UTC: first ProbSevere > 50%
2310 UTC: first ProbSevere > 70%
2311 UTC: NWS Severe T-Storm Warning
2312 UTC: ProbSevere = 88%
2323 UTC: 1.00″ hail 2 SE Dixson (15 min lead-time for ProbSevere@50, 13 min for ProbSevere@70, 12 min for NWS Svr Warning)
2335 UTC: NWS Tornado Warning (ProbSevere = 94%)
2340 UTC: Tornado report 2 NE Franklin Grove

Radar reflectivity with NOAA/CIMSS ProbSevere model contours and NWS warning polygons (click to play animation)

In spite of widespread cloudiness, the GOES-13 Sounder single-field-of-view Lifted Index (LI), Convective Available Potential Energy (CAPE), and Total Precipitable Water (TPW) derived product images (below) were able to portray that the air mass in the warm sector of the low ahead of the strong cold front was was both unstable — LI values of -4 to -8º C (yellow to red color enhancement) and CAPE values of 3000-4000 J/kg (yellow to red color enhancement) — and rich in moisture, with TPW values of 30-40 mm or 1.2 to 1.6 inches (yellow to red color enhancement).

GOES-13 Sounder Lifted Index derived product images (click to play animation)

GOES-13 Sounder CAPE derived product images (click to play animation)

GOES-13 Sounder Total Precipatable Water (TPW) derived product images (click to play animation)

On the following day (10 April), it was cloud-free as the Landsat-8 satellite passed over northern Illinois at 16:41 UTC or 11:41 AM local time — and the 30.2 mile long southwest-to-northeast oriented tornado damage path that produced EF-4 damage and was responsible for 2 fatalities and 22 injuries (NWS Chicago event summary) was evident on 15-meter resolution Band 8 0.59 µm panchromatic visible images viewed using the SSEC RealEarth web map server (below). An aerial survey of part of the tornado damage path can be seen here.

Landsat-8 0.59 µm panchromatic visible image of southwestern portion of tornado damage track (click to enlarge)

Landsat-8 0.59 µm panchromatic visible image of northeastern portion of tornado damage path (click to enlarge)

A Landsat-8 false-color image (using Bands 6/5/4 as Red/Green/Blue) is shown below. The 2 tornado-related fatalities occurred in Fairdale.

Landsat-8 false-color image (using Bands 6/5/4 as R/G/B)

On a side note, in the cold (northwestern) sector of the low it was cold enough for the precipitation type to be snow — and up to 4 inches of snow fell in western Iowa. GOES-13 0.63 µm visible channel images (below; click image to play animation) showed the swath of snow cover as it rapidly melted during the daytime hours on 10 April.

GOES-13 0.63 µm visible channel images (click to play animation)

In fact, the swath of snow cover across eastern Nebraska and western/northern Iowa was also evident on a Suomi NPP VIIRS Day/Night Band (DNB) image at 08:49 UTC or 3:39 AM local time (below), highlighting the “visible image at night” capability of the DNB (given ample illumination from the Moon).

Suomi NPP VIIRS 0.7 µm Day/Night Band image

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GOES-15 6.5 µm water vapor channel images (click to play animation)

GOES-15 (GOES-West) 6.5 µm “water vapor channel” images (above; click image to play animation; also available as an MP4 movie file) revealed an interesting transition in the signal displayed by the 2 summits (Mauna Kea and Mauna Loa) on the Big Island of Hawai’i on 06 April 2015 — beginning as a pair of colder (darker blue color enhancement) areas during the nighttime hours, becoming a pair of warmer (brighter yellow color enhancement) areas as daytime heating warmed the land surfaces.

As was discussed in a previous blog post, the water vapor channel is essentially an Infrared (IR) channel that senses the mean temperature of a layer of moisture — usually a layer which is located in the middle troposphere. However, if the middle troposphere is dry, the water vapor detectors are able to “see” lower into the atmosphere and detect radiation from the lower atmosphere (or even high-elevation terrain features, such as Mauna Kea and Mauna Loa). A comparison of the 00 UTC and 12 UTC rawinsonde profiles from Hilo (below) showed that the middle troposphere was indeed quite dry, with the typical tropical moisture residing below the 700 hPa pressure level.

Hilo, Hawai’i rawinsonde data profiles (00, 12 UTC)

The altitude (and depth) of the layer being sensed by a water vapor channel is defined by its weighting function, which depends on (1) the temperature and moisture profile of the atmosphere, and (2) the satellite viewing angle or “zenith angle”. This site allows you to select a rawinsonde site of interest, and the GOES Imager (and Sounder) water vapor channel weighting functions are calculated and plotted. The GOES-15 Imager water vapor channel weighting functions for the 2 Hilo soundings are shown below (along with the weighting function for the US Standard Atmosphere). It can be seen that the peak of the weighting function response is at a lower altitude for both Hilo soundings than it would be for the US Standard Atmosphere, which in part allows the strong cold/warm thermal signatures of the two Big Island summits to be seen on the GOES-15 water vapor imagery.

Hilo, Hawai’i GOES-15 imager water vapor weighting functions, compared with the US Standard Atmosphere

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Visible satellite images and surface observations (click to play animation)

Visible satellite images from the SSEC RealEarth web map server (above; click image to play animation) revealed the hazy light gray signature of a major sandstorm that was advancing south-southeastward across the Arabian Peninsula on 02 April 2015. An Aqua MODIS true-color Red/Green/Blue (RGB) image (actual satellite overpass time was 10:20 UTC or 2:20 PM local time) is shown below — the dense cloud of airborne sand appeared as a lighter shade of tan.

Aqua MODIS true-color image

A Suomi NPP VIIRS true-color image from the previous day (below) depicted the beginning phase of the sandstorm in the northern portion of Saudi Arabia, which consisted of a number of smaller plumes of blowing sand prior to consolidating into the large feature seen on 02 April.

Suomi NPP VIIRS true-color image (01 April)

The blowing sand reduced surface visibility to near zero at some locations, disrupting ground transportation, air traffic, and also closing schools. Visibility was reduced to 0.1 mile for several hours at Dubai International Airport (below), which is one of the world’s busiest in terms of volume of flights.

Time series of weather conditions at Dubai International Airport

During the previous nighttime hours, McIDAS-V images of Suomi NPP VIIRS 0.7 µm Day/Night Band data (below; images courtesy of William Straka, SSEC) showed the arc-shaped leading edge of the sandstorm as it stretched from the United Arab Emirates across Saudi Arabia at 22:01 UTC or 1:01 AM local time. Since the Moon was in the Waxing Gibbous phase (at 98% of Full), it provided ample illumination for these “visible images at night”.

Suomi NPP VIIRS 0.7 µm Day/Night Band image

Suomi NPP VIIRS 0.7 µm Day/Night Band image

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Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

McIDAS-V images of Himawari-8 AHI 0.64 µm visible channel data (above; click image to play animation; images courtesy of William Straka, SSEC) showed the evolution of Category 2 Typhoon Maysak over the West Pacific Ocean on 30 March 2015. A number of large convective bursts can be seen surrounding the eye, along with more subtle features such as transverse banding.

An 11:01 UTC MTSAT-2 10.8 µm IR image with an overlay of 11:11 UTC Metop ASCAT surface scatterometer winds from the CIMSS Tropical Cyclones site (below) revealed the wind field in the eastern semicircle of the tropical cyclone.

MTSAT-2 10.8 µm IR image with Metop ASCAT surface scatterometer winds

Several hours later, a comparison of a 19:01 UTC MTSAT-2 10.8 µm IR image with a 19:00 UTC DMSP SSMIS 85 GHz microwave image (below) showed that the microwave instrument was able to “see” through the clouds surrounding the eye to depict the larger size of the eyewall structure.

MTSAT-2 10.8 µm IR image + DMSP SSMIS 85 GHz microwave image

During the later hours of 30 March, Typhoon Maysak underwent a period of rapid intensification from a Category 2 to a Category 4 storm, as depicted on a plot of the Advanced Dvorak Technique (ADT) intensity estimate (below). Rapid intensification occurred as the tropical cyclone was moving over an area of relatively high ocean heat content.

Advanced Dvorak Technique (ADT) intensity estimate plot for Typhoon Maysak

MTSAT-2 10.8 µm IR channel images during this period of rapid intensification are shown below (click image to play animation).

MTSAT-2 10.8 µm IR images (click to play animation)

The MIMIC Total Precipitable Water (TPW) product (below; click image to play animation) depicted TPW values in excess of 60 mm or 2.36 inches (darker red color enhancement) associated with Maysak as the tropical cyclone moved between the islands of Guam (PGUM) and Yap (PTYA). Yap recorded over 4 inches of rainfall.

MIMIC Total Precipitable Water product (click to play animation)

31 March 2015 Update: Maysak intensified to a Category 5 Super Typhoon (ADT plot). Full-resolution visible imagery from Himawari-8 AHI is shown below; a faster animation is available here. A number of mesovortices could be seen within the eye of Maysak; these mesovortices were also evident in photos of the eye of the typhoon taken by an astronaut on the International Space Station, as posted on Twitter here and here.

Himawari-8 AHI 0.64 µm visible channel images (click to play animation)

Images from all 16 channels from the Himawari-8 AHI can be combined into one animation, showing the different information provided by each of the spectral bands — such an animation is shown below, using data from 0600 UTC on 31 March 2015. The Infrared data is shown at full (2-km) resolution; Visible/near Infrared imagery is scaled down by a factor of 2 (0.46 µm, 0.51 µm, 0.85 µm) or by a factor of 4 (0.64 µm). A similar animation, but without annotation or color enhancement, is available here.

Himawari-8 AHI images for all 16 channels at 0600 UTC (click to enlarge)

Maysak had remained in an environment of relatively low deep-layer wind shear (below; click image to play animation), which was favorable for its trend of continued intensification.

MTSAT-2 10.8 µm IR channel images, with deep-layer wind shear (click to play animation)

However, in a comparison of MTSAT-2 10.8 µm IR channel and TRMM TMI 85 GHz microwave images around 14 UTC (below), it can be seen that the microwave image indicated that an eyewall replacement cycle might be underway (which would suggest a subsequent decrease in the typhoon’s intensity within the coming hours). This was supported by the ADT intensity estimate plot, which dropped the intensity of Maysak just below 140 knots after 18 UTC on 31 March.

MTSAT-2 10.7 µm IR image and TRMM TMI 85 GHz microwave image

01 April Update: A nighttime comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR images at 16:58 UTC on 01 April (below; images courtesy of William Straka, SSEC) showed the eye of Typhoon Maysak after it had weakened to a Category 4 storm.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

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