Convection Returns to the central Great Plains

March 24th, 2015
Suomi NPP VIIRS 11.45 µm infrared channel images (click to enlarge)

Suomi NPP VIIRS 11.45 µm infrared channel images (click to enlarge)

The ongoing change in seasons was accompanied last night by a round of convection over the Missouri River Valley. Suomi NPP 11.45 µm imagery from overnight shows scattered convection over Kansas, Missouri and Iowa at 0728 and 0909 UTC. Coldest cloud tops are around -65 C. The Day-Night band showed lightning streaks at both times as well, over east-central Kansas at 0728 and north-central Kansas 0909 UTC.

Suomi NPP VIIRS 0.70 µm Day-Night band visible channel images (click to enlarge)

Suomi NPP VIIRS 0.70 µm Day-Night band visible channel images (click to enlarge)

GOES Sounder DPI Lifted Index, times as indicated (click to enlarge)

GOES Sounder DPI Lifted Index, times as indicated (click to enlarge)

The GOES Sounder showed the unstable air that was feeding into this convection. Imagery at three-hourly intervals, above, shows values between 0 and -4 persisting over the central Plains. Plots of 850-mb data on top of the GOES Sounder DPI Lifted index, below, shows the development of strong warm advection over the central Plains that helped feed moisture into the developing convection.

GOES Sounder DPI Lifted Index and Radiosonde data at 850 hPa, times as indicated (click to enlarge)

GOES Sounder DPI Lifted Index and Radiosonde data at 850 hPa (click to enlarge)

NUCAPS soundings, created from both CrIS and ATMS data on board Suomi NPP, below, showed steepening mid-level lapse rates over/near Kansas. This convection likely was not surface-based.

Suomi/NPP NUCAPS Soundings near Kansas City (07z) and over Eastern Kansas (09z) with an individual sounding from the starred point plotted (click to enlarge)

Suomi/NPP NUCAPS Soundings near Kansas City (07z) and over Eastern Kansas (09z) with an individual sounding from the starred point plotted (click to enlarge)

Sea fog along the northeast Florida coast

March 21st, 2015
GOES-13 0.63 µm visible channel images (click to play animation)

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

GOES-13 (GOES-East) 0.63 µm visible channel images (above; click to play animation) showed a patch of sea fog just off the coast of northeastern Florida on 21 March 2015. As daytime inland heating increased, a sea breeze circulation began to draw some of the offshore sea fog toward the coast.

A closer view is provided by a Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image at 18:08 UTC (below), visualized using the SSEC RealEarth web map server site. The surface visibility at New Smyrna Beach was reduced to 1 mile at the time.

Suomi NPP VIIRS true-color image

Suomi NPP VIIRS true-color image

A web camera image at 18:17 UTC or 2:17 PM local time (below) showed the dramatic reduction in visibility as the dense sea fog moved inland at Dunlawton Beach (near Daytona Beach).

Dunlawton Beach webcam image

Dunlawton Beach webcam image

A comparison of Suomi NPP VIIRS 0.64 µm visible channel, 3.74 µm shortwave IR channel, and 11.45 µm longwave IR images (below) showed that the patch of sea fog exhibited a strong signal on the shortwave IR image (due to the efficient reflection of incoming solar radiation by the spherical water droplets), but no signal at all on the longwave IR image (since the temperature of the sea fog feature was nearly identical to that of the surrounding ocean waters).

Suomi NPP VIIRS 0.64 µm visible channel, 3.74 µm shortwave IR channel, and 11.45 µm longwaveIR channel images

Suomi NPP VIIRS 0.64 µm visible channel, 3.74 µm shortwave IR channel, and 11.45 µm longwaveIR channel images

The easterly to northeasterly onshore flow along the coast (enhanced by the sea breeze circulation) was well-depicted by the 18 UTC Real-Time Mesoscale Analysis (RTMA) surface winds (below).

Suomi NPP VIIRS 0.64 µm visible channel image, with RTMA surface winds

Suomi NPP VIIRS 0.64 µm visible channel image, with RTMA surface winds

Solar Eclipse as seen from GOES-13 and NOAA-18

March 20th, 2015
GOES-13 0.65 µm visible channel images (click to enlarge)

GOES-13 0.65 µm visible channel images (click to enlarge)

A total solar eclipse occurred on 20 March before sunrise over the USA. Its appearance on visible imagery from Meteosat-10 was documented here and here. Did GOES-13 also view this event? The imagery above, half-hourly from 0845 through 0945 UTC, shows evidence of darkening (the lunar shadow) initially near 40 N, then a very dark slice in the atmosphere at 0915 UTC and a hint of darkness at 0945 UTC at the extreme limb of the satellite, beyond Iceland. Note also how the terminator in the image, the boundary between day and night, is parallel to longitudinal lines. Happy Equinox!

The shadow of totality was also captured on a NOAA-18 AVHRR 0.86 µm visible channel image at 0907 UTC (below). The shadow extends out over the Atlantic Ocean well to the northeast of Newfoundland.

NOAA-18 AVHRR 0.86 µm visible channel image

NOAA-18 AVHRR 0.86 µm visible channel image

Strong arctic cold front: grass fires, blowing dust, and a lee-side frontal gravity wave

March 17th, 2015
GOES-13 3.9 µm shortwave IR channel images (click to play animation)

GOES-13 3.9 µm shortwave IR channel images (click to play animation)

After a day of record high temperatures in parts of Nebraska — the 91º F at North Platte set a new record high for the month of March, and was also the earliest temperature of 90º F or above on record at that site — a strong arctic cold front plunged southward across the state late in the day on 16 March 2015. With strong winds (gusting to 40-50 knots at some locations) in the wake of the frontal passage and dry vegetation fuels in place, GOES-13 3.9 µm shortwave IR images (above; click image to play animation) showed the “hot spot” signatures (black to yellow to red pixels) associated with a number of large grass fires that began to burn across the state.

The strong northwesterly winds behind the cold front also lofted dry soil into the boundary layer, creating blowing dust whose hazy signature was evident on GOES-13 0.63 visible channel images (below; click image to play animation). Visibility was reduced to 7 miles at some locations.

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

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

After sunset and into the pre-dawn hours on 17 March, a lee-side frontal gravity wave signature could be seen on GOES-13 6.5 µm water vapor channel images (below; click image to play animation). This warmer/drier (darker blue color enhancement) arc on the water vapor imagery followed the position of the surface cold front, which meant that the upward-propagating frontal gravity wave reached altitudes where the water vapor channel was sensing radiation.

GOES-13 6.5 µm water vapor channel images (click to play animation)

GOES-13 6.5 µm water vapor channel images (click to play animation)

As the frontal gravity wave was approaching the Kansas/Oklahoma border region around 05 UTC, a pilot reported light to moderate turbulence at altitude of 6000 feet (below).

GOES-13 6.5 µm water vapor channel image with pilot report of turbulence

GOES-13 6.5 µm water vapor channel image with pilot report of turbulence

A 4-panel comparison of the three Sounder water vapor channels (6.5 µm, 7.0 µm, and 7.4 µm) and the standard Imager 6.5 µm water vapor channel (below; click image to play animation) showed that the southward propagation of the frontal gravity wave signature was most evident on the Sounder 7.0 µm and Imager 6.5 µm images, although there was also a more subtle indication on the Sounder 7.4 µm images. The new generation of geostationary satellite Imager instruments (for example, the AHI on Himawari-8 and the ABI on GOES-R) feature 3 water vapor channels which are similar to those on the current GOES Sounder, but at much higher spatial and temporal resolutions

GOES-13 Sounder 6.5 µm (upper left), 7.0 µm (upper right), 7.4 µm (lower left), and Imager 6.5 µm (lower right) - click to play animation

GOES-13 Sounder 6.5 µm (upper left), 7.0 µm (upper right), 7.4 µm (lower left), and Imager 6.5 µm (lower right) – click to play animation

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GOES-13 Sounder and Imager water vapor channel weighting functions for North Platte, Nebraska

GOES-13 Sounder and Imager water vapor channel weighting functions for North Platte, Nebraska

The depth and altitude of the layer from which a particular water vapor channel is detecting radiation is shown by plotting its weighting function — for example, at North Platte, Nebraska (above), the Imager 6.5 µm plot (black) and the 7.0 µm plot (green) exhibited lower-altitude secondary peaks around the 500 hPa level — while farther to the south at Dodge City, Kansas (below) these 2 water vapor channel plots had their peaks located slightly higher in the atmosphere. Even though the bulk of the radiation was being detected from higher altitudes (due to the presence of moisture and cirrus clouds aloft over much of the southern Plains region), the sharp signal of the lower-altitude cold frontal gravity wave was strong enough to be seen in the deep layer average moisture brightness temperature depicted in the water vapor images.

GOES-13 Sounder and Imager water vapor channel weighting functions

GOES-13 Sounder and Imager water vapor channel weighting functions