An optimization to the GOES-13 scanning schedule (discussed here) that provides, among other things, better coverage of the Caribbean Sea, became operation at 1600 UTC on May 6, 2014. Half-hourly imagery (in this case, 10.7 µm) from before the switch show intermittent coverage over the Caribbean Sea (at :15 and :45 minutes after the hour); CONUS imagery at :02 and :32, however, only extended to 14 N and to 63 W.

GOES-13 Infrared (10.7 µm) Imagery, times as indicated, before the switch to an Optimized Schedule (click to enlarge)

GOES-13 schedule optimization allows the :00 and :30 (note the slight shift in nominal time) images to scan to 5 N. (and also east to 54 W) Thus, an animation with 15-minute imagery (below) shows more complete coverage over the Caribbean.

GOES-13 Infrared (10.7 µm) Imagery, times as indicated, after the switch to an Optimized Schedule (click to enlarge)

View only this post Read Less

NOAA/CIMSS ProbSevere superimposed on MRMS radar display over southeastern Virginia. Times as indicated. (Click to enlarge)

The Hazardous Weather Testbed (HWT) exercise (Click here for the HWT blog) is ongoing at the Storm Prediction Center.  One of the new products being tested by forecasters is the NOAA/CIMSS ProbSevere product. ProbSevere in the animation above highlighted a cell that produced hail. The AWIPS-2 readout suggests strong vertical growth, and strong glaciation, at 0215 UTC. (The HWT Blog entry on this storm is here) What did the satellite view?

GOES-13 Visible Imagery (0.63 µm), times as indicated. (Click to enlarge)

Visible imagery, above, from just before sunset, shows nascent convective development east of Lynchburg over southeastern Virginia, and also older convection over the Chesapeake Bay and Delmarva Peninsula. The infrared imagery (10.7 µm), below, shows rapid development of convection over southeastern Virginia after 0000 UTC. The first convective cell, which cell is east of the Outer Banks of North Carolina at 0315 UTC, had cloud-tops that cooled about 12 C in 17 minutes (between 0115 and 0132 UTC); the storm that produced hail, and was warned, had cloud-tops that cooled 20 C in 13 minutes, between 0202 UTC and 0215 UTC. This strong vertical growth contributes to a big increase in the ProbSevere value.

GOES-13 Infrared Imagery (10.7 µm), times as indicated. (Click to enlarge)

When interpreting the radar and satellite imagery, be aware of the effects of parallax on the satellite imagery. GOES-13 imagery displayed here is not corrected for parallax. GOES-13 data are parallax-corrected when used in ProbSevere computations, of course.

View only this post Read Less

Meteosat-10 0.75 µm visible channel image (click to play animation)

McIDAS images of EUMETSAT Meteosat-10 0.75 µm visible channel data (above; click image to play animation) showed a beautiful example of a von Kármán vortex street downwind of Madeira Island on 01 May 2014. Northeasterly winds in the marine boundary layer were perturbed by the topography of the island, whose highest point rises to an elevation of 1,862 m (6,109 ft) above sea level. Note how some of the downwind vortices rotate in a clockwise direction, while other rotate counterclockwise.

View only this post Read Less

Radar-estimated Storm Total Precipitation for the 24-hour period ending at 13:47 UTC on 30 April

A large Mesoscale Convective System (MCS) developed ahead of a slow-moving cold front and moved over the Gulf Coast region of the US on 29 April – 30 April 2014, producing record rainfall totals (WeatherUnderground) and creating widespread severe flooding across parts of southern Alabama and the western Florida Panhandle. The 24-hour WSR-88D Storm Total Precipitation as visualized using the SSEC RealEarth web map server (above) showed swaths of radar-estimated precipitation in excess of 10 inches (violet color enhancement) — but some locations reported actual storm total rainfall amounts exceeding 20 inches (NWS Mobile/Pensacola).

AWIPS images of the MIMIC Total Precipitable Water (TPW) product (below; click image to play animation; Atlantic sector animation) indicated that there were multiple northward surges of TPW values in the 45-50 mm or 1.78-2.0 inch range (darker orange color enhancement) during the 28-30 April time period.

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

4-km resolution GOES-13 10.7 µm IR channel images (below; click image to play animation) displayed large areas of unusually cold GOES cloud-top IR brightness temperatures (colder than -80º C, violet color enhancement) — in fact, the coldest GOES-13 10.7 µm IR cloud-top brightness temperature seen was -86º C at 12:15 UTC.

GOES-13 10.7 µm IR channel images (click to play animation)

This MCS also produced very large amounts of cloud-to-ground lightning (below; click image to play animation), with the highest number of 15-minute interval lightning strikes being 5379 negative and 697 positive at 11:15 UTC.

GOES-13 10.7 µm IR channel images with cloud-to-ground lightning strikes (click to play animation)

A 1-km resolution MODIS IR image at 04:11 UTC on 30 April (below) displayed a minimum cloud-top IR brightness temperature of -87º C (darker violet color enhancement).

MODIS 11.0 µm IR channel image

375-meter resolution (mapped onto a 1-km AWIPS grid) Suomi NPP VIIRS 11.45 µm IR channel images (below) displayed a minimum cloud-top IR brightness temperature of -90º C (dark violet color enhancement) at 06:57 UTC on 29 April.

Suomi NPP VIIRS 11.45 µm IR channel images

1-km resolution POES AVHRR 12.0 µm IR channel images (below) exhibited a minimum cloud-top IR brightness temperature of -93º C at 10:12 UTC and 11:07 UTC on 30 April.

POES AVHRR 12.0 µm IR channel images

Brightness temperatures seen on a single-channel IR image do not always indicate the true cloud top temperature value — but in this case, the -93º C value (which was also seen on the corresponding POES AVHRR 10.8 µm IR image) agreed with minimum value on the POES AVHRR CLAVR-x Cloud Top Temperature product. The POES AVHRR Cloud Top Height product indicated values of 15-16 km in these areas of extremely cold IR temperatures (below).

POES AVHRR 10.8 µm IR channel, Cloud Top Temperature product, and Cloud Top Height product at 11:07 UTC

As we have seen with previous cases of strong convection exhibiting intense overshooting tops, nighttime Suomi NPP VIIRS 0.7 um Day/Night Band imagery (below) showed that this MCS produced a large pattern of concentric mesospheric airglow waves that could be seen traveling away from the storm for a considerable distance.

Suomi NPP VIIRS 0.7 um Day/Night Band image

View only this post Read Less