NOAA/CIMSS ProbSevere for an isolated storm in Nebraska

July 9th, 2014
NOAA/CIMSS ProbSevere product, and National Weather Service Warning Polygons, 2302-2334 UTC 9 July 2014 (click to enlarge)

NOAA/CIMSS ProbSevere product, and National Weather Service Warning Polygons, 2302-2334 UTC 9 July 2014 (click to enlarge)

The storm in the animation above produced baseball-sized hail in Nebraska (Visible animation is here, courtesy Dan Lindsey from NOAA at CIRA) although MRMS Mesh Hail sizes were “only” in the 1-inch range (that is, nickel to quarter size). How did the ProbSevere product, which product includes MRMS Mesh size as a predictor, perform?

The visible and infrared satellite animation, below, shows quick development in the absence of cirrus obscuration, and the ProbSevere Satellite components from 2230 UTC are both characterized as ‘Strong’. The model components of ProbSevere (MUCAPE around 2000 J/kg, shear exceeding 30 knots) are also strong. Probabilities increased from 40% to >80% before the warnings for the cell were issued.

MRMS values in this case were not extreme; indeed, when the first warning was issued, MESH was still less than 1″ (but ProbSevere was >80%). Satellite growth rates and environmental information in this case compensated for the modest MRMS Mesh values.

GOES-13 Visible (0.63 µm, top) and Infrared (10.7 µm, bottom) from 2200 UTC 9 July through 0200 UTC 10 July (click to animate)

GOES-13 Visible (0.63 µm, top) and Infrared (10.7 µm, bottom) from 2200 UTC 9 July through 0200 UTC 10 July (click to animate)

Long-range transport of Canadian wildfire smoke

July 8th, 2014

GOES-15 (top) and GOES-13 (bottom) 0.63 µm visible channel images [click to play animation]

GOES-15 (top) and GOES-13 (bottom) 0.63 µm visible channel images [click to play animation]

On 08 July 2014 a comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel images (above; click image to play animation; also available as an MP4 movie file) showed the southward and southeastward transport of dense smoke from wildfires that were burning in the Northwestern Territories of Canada. Over the Lower 48 states, the leading edge of the smoke made it as far south as Iowa and northern Illinois. The bulk of the dense smoke was aloft, but at the surface the visibility was reduced to 3-5 miles at some locations in North Dakota.

The above example serves as a good demonstration of the principle of “forward scattering”: the smoke was more evident on visible imagery from GOES-15  early in the day (as the sun was rising), and more evident on visible imagery from GOES-13 later in the day (as the sun was setting).

Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server (below) showed the areal coverage of the hazy pall of smoke on 06 July, 07 July, and 08 July.

Suomi NPP VIIRS true-color images

Suomi NPP VIIRS true-color images

The IDEA-I forward airmass trajectory model applied to targets of high Aerosol Optical Depth (AOD) which were detected by the Terra MODIS instrument over Canada on 08 July are shown below. Such a tool can be used as an aid in air quality forecasting.

IDEA-I MODIS Aerosol Optical Depth and forward trajectories (click to play animation)

IDEA-I MODIS Aerosol Optical Depth and forward trajectories (click to play animation)

===== 09 July Update =====

The Terra MODIS AOD product (below; click to play animation) indicated that the leading edge of the Canadian wildfire smoke had advanced as far southward as northwestern Missouri. The bulk of the highest AOD values over the Dakotas was forecast to be transported slowly east-northeastward toward the Great Lakes region.

IDEA-I MODIS Aerosol Optical Depth and forward trajectories (click to play animation)

IDEA-I MODIS Aerosol Optical Depth and forward trajectories (click to play animation)

Typhoon Neoguri threatens Okinawa

July 7th, 2014
COMS-1 0.675 µm and MTSAT-2 0.73 µm Visible channel images (Click to enlarge)

COMS-1 0.675 µm and MTSAT-2 0.73 µm Visible channel images (Click to enlarge)

Typhoon Neoguri is forecast to move west of Okinawa later today. The visible images above, from COMS-1 (left) and MTSAT-2 (right) show the storm at around 0800 UTC on 7 July 2014. A distinct eye filled with low-level clouds is apparent.

COMS-1 (left) and MTSAT-2 (right) visible channel images [click to play animation]

COMS-1 (left) and MTSAT-2 (right) visible channel images [click to play animation]

Magnified views of the storm center (above; click image to play animation; also available as an MP4 movie file) revealed the presence of mesovortices within the eye of Neoguri. The more frequent imaging schedule of COMS-1 (generally every 15 minutes, compared to every 30 minutes with MTSAT-2) allowed the cyclonic circulation of the mesovortices to be more easily identified. Another curious feature seen on the early morning visible imagery was a northwest-to-southeast oriented “cloud cliff” shadow just north of the eye, which was cast by the taller clouds of an eyewall convective burst just to the east. This same signature was seen again on the following morning, in nearly the same location relative to the eye (MTSAT-2 visible/IR image comparison).

METOP-B ASCAT winds over Neoguri and Observed SSTs (Click to toggle)

METOP-B ASCAT winds over Neoguri and Observed SSTs (Click to toggle)

ASCAT winds from METOP-B (above) show the structure of the typhoon, with 70-knot winds indicated. The Sea Surface Temperature (SST) image (taken from the CIMSS Tropical Cyclones site) also shows the extreme warmth of the western Pacific Ocean.

COMS-1 10.8 µm and MTSAT-2 10.8 µm Infrared channel images (Click to animate)

COMS-1 10.8 µm and MTSAT-2 10.8 µm Infrared channel images (Click to animate)

Infrared imagery from the past 24 hours show a decline in the satellite structure of the storm. Cold cloud tops have eroded from the northern and western quadrants of the storm, and a circular ring of cold cloud tops around the eye is no longer apparent.

Suomi NPP VIIRS 11.45 µm  Infrared channel image (Click to enlarge)

Suomi NPP VIIRS 11.45 µm Infrared channel image (Click to enlarge)

Suomi NPP overflew the storm on Saturday 5 July at 1620 UTC. The color-enhanced VIIRS 11.45 IR image, above (courtesy William Straka, SSEC/CIMSS), shows very cold cloud tops (185 K) southeast of a developing eye.

Hurricane Arthur transitions to an extratropical cyclone

July 6th, 2014
GOES-13 6.5 µm water vapor channel images with surface pressure and frontal analyses

GOES-13 6.5 µm water vapor channel images with surface pressure and frontal analyses

GOES-13 6.5 µm water vapor channel images with overlays of surface pressure and frontal analyses (above) showed Category 2 Hurricane Arthur (NHC discusions | blog post) transitioning to a powerful extratropical (or “post-tropical”) storm as it moved northward over the Maritime Provinces of Canada on 05 July 2014. Impacts of Hurricane Arthur along the East Coast of the US included a peak wind gust of 101 mph at Cape Lookout, North Carolina, and over 6 inches of rainfall in eastern Maine.

A long animation of 4-km resolution GOES-13 6.5 µm water vapor channel images covering the period 00:15 UTC on 05 July to 12:15 UTC on 06 July (below; click image to play animation; also available as an MP4 movie file) showed a very pronounced area of dry air (bright yellow to red color enhancement) wrapping into the circulation of the storm. Also evident on the water vapor imagery was the subsequent development of a “sting jet” signature along the southwestern and southern flank of the storm — this feature was associated with very strong winds (peak gust of 138 km/h or 86 mph) being transported down to the surface over parts of Nova Scotia and New Brunswick (Canadian Hurricane Centre statement). The sting jet signature resembles a “scorpion tail” (22:45 UTC image); note that there is a significant parallax offset with the >50 degree satellite viewing angle of GOES-13 imagery over this region, so the sting jet signature was actually located farther to the south over Nova Scotia (where the strongest surface winds were observed). Other notable sting jet cases appear here, here and here.

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 an aside, it is interesting to examine the effect that the northeastward passage of Hurricane Arthur had on the pattern of sea surface temperatures in the far western Atlantic Ocean off the East Coast of the US. The Suomi NPP VIIRS Sea Surface Temperature (SST) product at 17:27 UTC on 05 July (below) revealed a number of filaments and eddies along the path of the tropical cyclone. A comparison with the 00 UTC 05 July Real-Time Global Sea Surface Temperature High-Resolution (RTG_SST_HR) analysis showed that even a 1/12 degree resolution model had difficulty resolving many of these subtle SST features — this helps to underscore the value of high-spatial resolution satellite imagery for making highly-accurate assessments of such fields as SST.

Suomi NPP VIIRS Sea Surface Temperature product, with a comparison to the RTG_SST_HR analysis

Suomi NPP VIIRS Sea Surface Temperature product, with a comparison to the RTG_SST_HR analysis