“River-effect” snow in South Dakota

November 13th, 2014
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 0.63 µm visible channel images (above; click image to play animation) revealed the presence of numerous cloud streamers originating over the Lake Oahe and Lake Sharpe reservoirs along the Missouri River in South Dakota on 13 November 2014. At times these cloud bands were producing snow that was reducing surface visibility to 4 miles at Pierre (KPIR) and 5 miles at Chamberlain (K9V9).

Aqua MODIS 0.65 µm visible channel image, False-color RGB image, and Sea Surface Temperature product at 19:48 UTC

Aqua MODIS 0.65 µm visible channel image, False-color RGB image, and Sea Surface Temperature product at 19:48 UTC

Comparisons of visible channel and false-color Red/Green/Blue (RGB) images from Aqua MODIS (above) and Suomi NPP VIIRS (below) demonstrated the value of RGB products to more easily identify such supercooled water droplet cloud features (which appear as varying shades of white) in areas that have underlying snow cover (which appears as varying shades of red). In addition, the MODIS Sea Surface Temperature (SST) product (above) showed that SST values were in the 40-50º F range (cyan color enhancement) in those Missouri River reservoirs, making them significantly warmer than the cold arctic air mass that had overspread the region.

Suomi NPP VIIRS 0.64 µm visible channel image and False-color RGB image at 19:51 UTC

Suomi NPP VIIRS 0.64 µm visible channel image and False-color RGB image at 19:51 UTC

Displaying NUCAPS data from CLASS

November 12th, 2014

NUCAPS data have been flowing into AWIPS 2 for months; in the recent past, these data started flowing into the NOAA CLASS data archive as well (click here for a tutorial on accessing the data). How can the NOAA CLASS output be displayed? This post will compare McIDAS-V plots to the data displayed using AWIPS-1, below.

GOES Sounder Total Column Ozone DPI Values Plotted with NAM 500-mb heights and NAM Pressure on the 1.5 PVU surface (click to enlarge)

GOES Sounder Total Column Ozone DPI Values Plotted with NAM 500-mb heights and NAM Pressure on the 1.5 PVU surface (click to enlarge)

Suomi NPP overflew the central United States at about 0850 UTC on 12 November, and ozone concentrations from the NUCAPS soundings at three different levels (~500, 300 and ~200 mb) are shown below. Note that the color scaling is not quite the same in the three plots as the range for each pressure level is different. Maxima in Ozone at all levels occur in the same region — the Dakotas — as indicated by the GOES Sounder Total Column Ozone DPI, above. NUCAPS soundings also show data in cloudy regions because microwave data from ATMS is used in the NUCAPS processing. Note that values at the edge of the color shading have been extrapolated outwards; values in western Nevada and Indiana, for example, are not from direct NUCAPS observations. This plot of 500-mb temperatures (that includes the actual values) shows the horizontal extent of data and the amount of interpolation at the edge.

Contours of Ozone Mixing Ratio (parts per billion) from NUCAPS Soundings at ~0848 UTC on 12 November 2014 (click to enlarge)

Contours of Ozone Mixing Ratio (parts per billion) from NUCAPS Soundings at ~0848 UTC on 12 November 2014 (click to enlarge)

An extratropical storm containing the remnants of Ana makes landfall in North America

October 27th, 2014
GOES-15 6.5 µm water vapor channel images (click to play animation)

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

A strong storm that contains the remnants of former central Pacific Hurricane Ana began to make landfall along the West Coast of North America on 27 October 2014 (12 UTC surface analysis). The 17-day animation of GOES-15 6.5 µm Water Vapor channel imagery, above, shows Ana emerging out of the Intertropical Convergence Zone, skirting south of Hawai’i, weakening and meandering in the central Pacific (showing the effects of strong vertical wind shear), briefly reaching Hurricane intensity again on 25 October, and eventually moving eastward after having been picked up and absorbed by a strong system in the Westerlies. Recurving tropical systems can sometimes be prolific rain producers in the mid-latitudes; however, the animation of MIMIC Total Precipitable Water, below, suggests that most of the tropical moisture that was associated with Ana was no longer present.

MIMIC Total Precipitable Water for 72 hours ending 1200 UTC 27 October 2014 (click to enlarge)

MIMIC Total Precipitable Water for 72 hours ending 1200 UTC 27 October 2014 (click to enlarge)

The annotated animation below shows 1200 UTC imagery from 11-27 October. The red arrow points to Ana, either as a developing tropical cyclone, Hurricane, or post-tropical system. An animation without the red arrow is here.

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

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

Shadow of partial solar eclipse

October 23rd, 2014
GOES-15 0.63 µm visible channel images

GOES-15 0.63 µm visible channel images

McIDAS images of GOES-15 (GOES-West) 0.63 µm visible channel data (above) showed the west-to-east progression of the lunar umbra (the Moon’s shadow) from a partial solar eclipse that occurred on 23 October 2014. The shadow was most obvious across the northern portion of the images, moving over Alaska, the Gulf of Alaska, western/northern Canada, and the far northwestern portion of the Lower 48 States of the US. The partial eclipse shadow could also be seen on GOES-13 (GOES-East) 0.63 µm visible channel images (below).

GOES-13 0.63 µm visible channel images

GOES-13 0.63 µm visible channel images

According to EarthSky.org the point of greatest eclipse (75% coverage of the solar disk by the Moon) was near Prince of Wales Island, Nunavut, Canada at 21:44 UTC. In a sequence of before, during, and after-eclipse AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel data (below), a darkening of Canada’s Yukon Territory — which covered most of the center portion of the images — could be seen.

Suomi NPP VIIRS 0.64 µm visible channel images

Suomi NPP VIIRS 0.64 µm visible channel images