Severe weather outbreak across the Southeast US

January 30th, 2013
MODIS 0.65 µm visible channel and 11.0 µm IR channel images, with METAR surface reports and SPC storm reports

MODIS 0.65 µm visible channel and 11.0 µm IR channel images, with METAR surface reports and SPC storm reports

AWIPS images of 1-km resolution MODIS 0.65 µm visible channel and 11.0 µm InfraRed (IR) channel images with an overlay of METAR surface reports and SPC storm reports (above) displayed a number of distinct banded convective features across parts of the Southeast US at 16:04 UTC or 11:04 AM local time on 30 January 2013. This banded structure could also be seen on a sequence of 1-km resolution POES AVHRR visible and IR images. In northwestern Georgia, note the isolated convective feature that produced a cluster of tornado and damaging wind reports — one of these tornadoes (rated EF-3) was responsible for a fatality in Adairsville, Georgia (NWS Peachtree City GA event summary), which ended a record 220-day streak with no tornado fatalities in the US.

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

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

On 4-km resolution GOES-13 10.7 µm IR channel images (above; click image to play animation) and 6.5 µm water vapor channel images (below; click image to play animation) this banded structure was quite evient throughout the morning and afternoon hours within the warm conveyor belt of moisture that was helping to fuel the pre-frontal squall line that was producing widespred severe weather across the region.

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

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

Blended Total Precipitable Water and Surface frontal analysis

Blended Total Precipitable Water and Surface frontal analysis

Large amounts of moisture were being transported northward from the Gulf of Mexico ahead of the advancing cold frontal boundary — Blended Total Precipitable Water (TPW) values were in the 30-40 mm or 1.2-1.6 inch range (above; animation), and these TPW values were in excess of 200% of normal for this region and this time of the year (below; animation).

Percent of Normal TPW and Surface frontal analysis

Percent of Normal TPW and Surface frontal analysis

Sea fog off the southeast US coast

January 29th, 2013
MODIS 11.0-3.7 µm IR brightness temperature difference

MODIS 11.0-3.7 µm IR brightness temperature difference “fog/stratus product”

An AWIPS image of the MODIS 11.0-3.7 µm IR brightness temperature difference “fog/stratus product” (above) indicated that fog/stratus features were in place across parts of the Southeast US, as well as along and just off the coast of Georgia, South Carolina, and North Carolina at 07:33 UTC or 2:33 AM local time on 29 January 2013.

The GOES-13 Instrument Flight Rules (IFR) Probability product (below; click image to play animation) showed very high probabilities of IFR conditions at many inland locations, but also suggested that the fog/stratus features were extending much farther off the coast.

GOES-13 IFR Probability product (click image to play animation)

GOES-13 IFR Probability product (click image to play animation)

During the daylight hours, McIDAS images of GOES-13 0.63 µm visible channel data (below; click image to play animation) showed that the near-shore sea fog did indeed persist for much of the day, especially off much of the Georgia and South Carolina coastlines.

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

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

A comparison of the MODIS 0.65 µm visible channel image and the corresponding MODIS Sea Surface Temperature (SST) product at 18:40 UTC or 1:40 PM local time (below) showed the reason for the persistent sea fog: there was an onshore flow of air with dew points in the lower to middle 60s F, moving over the cooler near-shore waters with SST values in the lower to middle 50s F.

MODIS 0.65 µm visible channel image + MODIS Sea Surface Temperature product

MODIS 0.65 µm visible channel image + MODIS Sea Surface Temperature product

 

“Billow cloud” formations near the Hawaiian Islands

January 28th, 2013
GOES-15 10.7 µm IR images with surface analysis and pilot reports of turbulence (click image to play animation)

GOES-15 10.7 µm IR images with surface analysis and pilot reports of turbulence (click image to play animation)

The AWIPS images above (click to play animation) showed low-resolution GOES-15 10.7 µm IR data with an overlay of the surface analysis and pilot reports of turbulence. A number of reports of moderate turbulence could be seen in the vicinity of the Hawaiian Islands (at altitudes between 9,000 and 27,000 feet), and the diffuse southern end of a surface cold frontal boundary had become semi-stationary over the area. The overall motion of the colder (lighter gray) IR cloud features suggested that the southwesterly flow aloft was becoming diffluent over and northeast of Hawaii.

A closer view using McIDAS images of 1-km resolution GOES-15 0.63 µm visible channel data (below; click image to play animation) revealed the formation of several small banded “billow cloud” features just to the northeast of the island chain. While there appeared to be no pilot reports of turbulence directly associated with the billow cloud features, the continued development of new billow cloud formations could have been a signal that turbulence was possible across the region. In addition, it is unclear whether their formation was due to flow interacting with the topography of the islands.

GOES-15 0.63 µm visible channel images (click image to play animation)

GOES-15 0.63 µm visible channel images (click image to play animation)

The corresponding GOES-15 10.7 µm IR channel images (below; click image to play animation) showed that IR cloud top brightness temperatures were as cold as -27º C (darker blue color enhancement) with the most prominent band of billow clouds at 18:30 UTC. According the the 12 UTC Hilo rawinsonde data, clouds reaching this temperature level would have ascended into the very dry air aloft. It is possible that these billow cloud features formed near the 700 hPa pressure level (where some speed and directional wind shear existed), then continued to build vertically.

GOES-15 10.7 µm IR channel images (click image to play animation)

GOES-15 10.7 µm IR channel images (click image to play animation)

GOES-15 6.5 µm water vapor channel images (below; click image to play animation) seemed to suggest that groups of individual billow cloud formations were developing along north-to-south oriented lines that were propagating eastward across the region during this period.

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

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

It is interesting to note that similar billow cloud formations were seen in that same region northeast of the Hawaiian Islands on Suomi NPP VIIRS 11.45 µm IR images at various times during the previous 24 hours (below).

Suomi NPP VIIRS 11.45 µm IR channel images

Suomi NPP VIIRS 11.45 µm IR channel images

Motion of sea ice near Barrow, Alaska

January 25th, 2013
Suomi NPP VIIRS 11.45 µm IR images (click image to play animation)

Suomi NPP VIIRS 11.45 µm IR images (click image to play animation)

AWIPS II images of 375-meter resolution Suomi NPP VIIRS 11.45 µm IR channel data (above; click image to play animation) revealed a surprising amount of sea ice motion in the vicinity of Barrow, Alaska (station identifier PABR) during the 30-hour period between 12:14 UTC on 24 January and 18:30 UTC on 25 January 2013. Large sea ice features with several ice leads and fractures can be seen moving southward against the land-fast ice to the east of Barrow — while to the west of Barrow, strong winds were helping to break the sea ice into smaller ice floes and transport them rapidly westward.

Suomi NPP VIIRS imagery is now being broadcast at the full native 375-meter resolution over the new “POLARSAT” NOAAPORT SBN channel (currently only available for the Alaska Region), for display in the next generation of AWIPS (AWIPS II).