Severe weather in the Oklahoma City area

May 31st, 2013 |
GOES-14 sounder Convective Available Potential Energy (CAPE) product (click image to play animation)

GOES-14 sounder Convective Available Potential Energy (CAPE) product (click image to play animation)

Only 11 days after the devastating EF-5 tornado that struck Moore, Oklahoma, another round of severe weather brought tornadoes (including the EF-5 El Reno tornado) large hail (up to 2.5 inches in diameter), damaging winds (gusts as high as 87 mph), and heavy rain that led to flash flooding to the Oklahoma City area on 31 May 2013 (SPC storm reports| NWS Norman summary). AWIPS images of the 10-km resolution GOES-14 sounder Convective Available Potential Energy (CAPE) derived product (above; click image to play animation) showed the trend of rapid destabilization across the region during the hours leading up to convective initiation — widespread CAPE values in the 5000-6000 J/kg range were seen (lighter purple color enhancement).

Once convective initiation began the storm growth was explosive, as revealed by McIDAS images of 1-km resolution GOES-14 0.63 µm visible channel data (below; click image to play animation; also available as a QuickTime movie). The GOES-14 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes. Complex storm-top structures were evident in the visible imagery, including numerous overshooting tops and anvil gravity waves. In addition, later in the animation a smoke plume can be seen approaching from the west (originating from a large fire that was burning in New Mexico). OKC denotes the location of Oklahoma City.

GOES-14 0.63 µm visible channel images (click image to play animation)

GOES-14 0.63 µm visible channel images (click image to play animation)

Not long after the first large thunderstorms began to develop west of Oklahoma City, a 1-km resolution POES AVHRR 12.0 µm IR channel image (below) displayed cloud-top IR brightness temperatures as cold as -78º C at 21:51 UTC or 4:51 PM local time (shortly before the first report of 1.25-inch diameter hail at 21:59 UTC). A 1-km resolution AVHRR vs 4-km resolution GOES-14 IR image comparison demonstrated two important advantages of polar-orbiter satellite imagery: (1) more accurate depiction of the coldest overshooting tops (-78º C on AVHRR, vs -64º C on with GOES-14), and (2) limited parallax error, helping to more accurately determine the true location of the overshooting tops.

POES AVHRR 12.0 µm IR channel image

POES AVHRR 12.0 µm IR channel image

AWIPS image combinations of GOES-14 10.7 µm IR channel data with overlays of Cloud Top Cooling (CTC) Rate and Overstooting Top (OT) Detection products (below; click image to play animation) showed the following: (1) the first region of significant CTC that was flagged with the newly-developing Oklahoma City storm was at 21:15 UTC, with a CTC rate of -8.8º C compared to the previous GOES-14 IR image; (2) the CTC rate increased to -26.9º C for the following 21:25 UTC IR image; (3) the CTC rate jumped to a remarkable -60.2º C for the following 21:32 UTC IR image (an indicator of the explosive rate of storm development); (4) OT detection icons began to appear once GOES-14 IR images exhibited IR brightness temperature values of -60º C and colder (beginning at 21:55 UTC).

GOES-14 10.7 µm IR image + Cloud Top Cooling Rate and Overshooting Top Detection products (click image to play animation)

GOES-14 10.7 µm IR image + Cloud Top Cooling Rate and Overshooting Top Detection products (click image to play animation)

===== 02 June Update =====

A comparison of before/after (14 May/02 June) 250-meter resolution true-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed the damage path from the 31 May El Reno, Oklahoma tornado. The lakes and rivers appear brighter on the 02 June image due to sun glint off the bodies of water (the sun-satellite geometry was different than it was on 14 May).

Before/after (14 May/02 June) MODIS true-color Red/Green/Blue (RGB) images

Before/after (14 May/02 June) MODIS true-color Red/Green/Blue (RGB) images

The tornado damage path is also highlighted on the 02 June MODIS true-color RGB image, viewed using Google Earth (below).

MODIS true-color RGB image (viewed using Google Earth)

MODIS true-color RGB image (viewed using Google Earth)

Hurricane Barbara

May 29th, 2013 |
GOES-14 0.63 µm visible channel images (click image to play animation)

GOES-14 0.63 µm visible channel images (click image to play animation)

McIDAS images of GOES-14 0.63 µm visible channel data (above; click image to play animation) showed Tropical Storm Barbara as it intensified to Category 1 hurricane shortly before making landfall along the coast of the Gulf of Tehuantepec in southeastern Mexico on 29 May 2013. Since reliable records began for the Eastern Pacific Basin in 1966, Hurricane Barbara was the second-earliest hurricane landfall, as well as the easternmost landfall location.

An AWIPS image of ASCAT surface scatterometer winds overlaid on a GOES IR image (below) depicted a maximum wind speed of 53 knots at 16:01 UTC (while Barbara was still at tropical storm intensity).

ASCAT surface scatterometer winds

ASCAT surface scatterometer winds

A 375-meter resolution Suomi NPP VIIRS 11.45 µm IR image at 19:35 UTC (below) showed the very cold cloud-top IR brightness temperatures (primarily in the -80 to -90 C range, enhanced with varying shades of violet) associated with convective clusters around the center of Hurricane Barbara as the storm was making landfall along the Mexican coast.

Suomi NPP VIIRS 11.45 µm IR image

Suomi NPP VIIRS 11.45 µm IR image

 ===== 30 May Update =====

GOES-14 0.63 µm visible channel images (below; click image to play animation) seem to suggest that the low-level circulation of Barbara remained intact after crossing the rugged terrain of southern Mexico, and emerged into the Gulf of Mexico on 30 May. The GOES-14 satellite had been placed into Rapid Scan Operations (RSO), providing images as frequently as every 5-10 minutes.

GOES-14 0.63 µm visible channel images (click image to play animation)

GOES-14 0.63 µm visible channel images (click image to play animation)

Ice jam flooding along the Yukon River in Galena, Alaska

May 28th, 2013 |
Suomi NPP VIIRS 1.61 µm

Suomi NPP VIIRS 1.61 µm “snow/ice discrimination channel” images

A sequence of AWIPS images of Suomi NPP VIIRS 1.61 µm near-IR “snow/ice discrimination channel” data covering the period from 13:47 UTC on 27 May to 23:24 UTC on 28 May 2013 (above) showed the effects of ice jam flooding along the Yukon River in the vicinity of Galena, Alaska (station identifier PAGA). In addition to snow and ice, water is also a strong absorber at the 1.61 µm near-IR wavelength — so it appears darker on the images. This dark signature of water inundation can be seen increasing in areal coverage during that 1.5 day period. This flooding forced the evacuation of aruond 300 residents of Galena, as many homes were extensively damaged by the flooding.

A comparison of Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm “land/water discrimination channel”, and 1.61 µm “snow/ice discrimination channel” images at 21:43 UTC on 28 May (below) showed that the Yukon River downstream of Galena was still snow/ice covered (appearing brighter white on the 0.64 µm and 0.86 µm images). Meanwhile, the darker signature of floodwaters near and upstream of Galena was evident to some extent on the 0.86 µm image, but was even more pronounced on the 1.61 µm image. The Yukon River ice jam flooding in the Galena area occurred about a week after similar ice jam floding occurred much farther upstream in the Fort Yukon area.

Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm land/water discrimination channel, and 1.61 µm snow/ice discriminatioon channel images

Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm land/water discrimination channel, and 1.61 µm snow/ice discriminatioon channel images

Unusual late-season Nor’easter

May 26th, 2013 |
GOES-14 6.5 µm water vapor channel images (click image to play animation)

GOES-14 6.5 µm water vapor channel images (click image to play animation)

An unusual late-season nor’easter storm produced heavy rainfall (as much as 6.14 inches at Whiting, Maine) and heavy snow (as much as 13.4 inches at Mount Mansfield in Vermont and 34 inches at Whiteface Mountain, New York) during the 24 May26 May 2013 period. McIDAS images of GOES-14 6.5 µm water vapor channel data (above; click image to play animation) displayed some interesting storm structures during the 25-26 May timeframe.

AWIPS images of the MIMIC Total Precipitable Water product (below; click image to play animation) showed that a long atmospheric river was transporting abundant tropical moisture northward, which was then wrapping inland around the storm circulation.

MIMIC Total Precipitable Water product (click image to play animation)

MIMIC Total Precipitable Water product (click image to play animation)

A comparison of 1-km resolution Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images at 05:52 UTC or 1:52 AM local time on 26 May (below) showed cloud features associated with the storm as it was centered just off the coast of Maine. Strong northerly/northwesterly winds along the back side of the storm (gusting as high as 102 mph at Mt. Washington, New Hampshire) were producing bands of orographic waves clouds over parts of Vermont and New York. This example helps to highlight the “visible image at night” capability of the VIIRS Day/Night Band (given ample illumination by moonlight).

Suomi NPP VIIRS 0.7 µm Day/Night Band abd 11.45 µm IR channel images (with overlay of surface analysis)

Suomi NPP VIIRS 0.7 µm Day/Night Band abd 11.45 µm IR channel images (with overlay of surface analysis)