Large “hole punch cloud” over Wisconsin

July 18th, 2014

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

A large (approximately 50-mile diameter) “hole punch cloud” or “fall steak cloud” was seen over northwestern Wisconsin during the morning hours of 18 July 2014. An AWIPS 4-panel comparison of GOES-13 0.63 µm visible channel, 3.9 µm shortwave IR channel, 10.7 µm IR window channel, and 6.5 µm water vapor channel images (above; click image to play animation) showed that 10.7 µm IR cloud top brightness temperatures were not particularly cold with this feature (generally in the 0º C to -4º C range), and while 3.9 µm shortwave IR brightness temperatures warmed within the broad cloud deck surrounding the hole punch cloud after sunrise (due to reflection of solar radiation off of water cloud droplets), the center of the feature continued to exhibit colder (lighter gray enhancment) IR brightness temperatures which suggests cloud glaciation.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

A comparison of CLAVR-x POES AVHRR Cloud Type, Cloud Top Height (CTH), and Cloud Top Temperature (CTT) products at 09:32 UTC or 4:32 am Central time (above) showed patches of water droplet clouds with CTH values in the 3-4 km range and CTT values in the 0º C to -4º C range.

A similar comparison at 12:05 UTC or 7:05 am Central time (below) revealed two areas of “cirrus” cloud type (orange color enhancement) exhibiting CTT values in the -35º to -40º C range (darker blue color enhancement) along the northern and southern periphery of the forming hole punch cloud.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

These ranges of AVHRR Cloud Top Temperature and Cloud Top Height values agreed well with the regional rawinsonde data from Davenport IA (KDVN), Minneapolis MN (KMPX) and Green Bay WI (KGRB) shown below.

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Terra MODIS visible and Cloud Phase products at 17:07 UTC or 12:07 pm Central time (below) indicated that a large area of glaciated ice cloud (salmon color enhancement) existed in the center portion of the hole punch cloud feature.

Terra MODIS 0.65 µm visible image and Cloud Phase products

Terra MODIS 0.65 µm visible image and Cloud Phase products

The cause of this large hole punch or fall streak cloud feature — and the other similar but smaller features seen across the region — was likely aircraft that had either ascended or descended through the cloud layer; particles in the aircraft exhaust acted as ice condensation nuclei, causing the process of cloud glaciation to begin.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 imagery (above) shows the Hole Punch cloud from an oblique angle, and highlights how the region was overrun by smoke from wildfires in Canada. Smoke is most easily seen in visible satellite imagery when the sun is low in the sky, allowing for forward scatter. The smoke becomes less apparent in the imagery as the Sun rises. A similar animation for GOES-13 is below. Smoke is not quite so evident in this image because there is less forward scatter to GOES-13 over 75º W. Animations from both satellites show a hole punch cloud in Iowa as well.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]

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)

Two Tropical Storms in the Pacific

June 30th, 2014
GOES-15 0.62 µm visible channel images (click to play animation)

GOES-15 0.62 µm visible channel images (click to play animation)

Tropical Storms Douglas (center of the image) and Elida (right-hand side of the image) have formed in the tropical Pacific to the west of Mexico. From the animation above (click here for an animation of the 10.7 µm imagery), Elida is in an environment of northerly/northwesterly shear: the strongest convection is forming south of the low-level circulation. This should in the short term inhibit significant strengthening. Douglas is moving into a region of cooler Sea-surface temperatures and is therefore weakening (SST imagery was captured here). Note, for example, how strong convection is not forming in the center of Douglas’ circulation.

One observation that can be related to the vigor of a tropical cyclone is the number of overshooting tops (OTs) within the storm circulation. This website displays OTs for any active storm. The still image below shows the OTs detected over Douglas and Elida at 2130 UTC on 30 June. It is uncommon for a storm to weaken significantly in the short term when OTs persist. There are more OTs over Elida than over Douglas in this image. Here are time series for the number of OTs with Douglas and with Elida.

GOES-15 0.62 µm visible channel images (click to enlarge)

GOES-15 Automated Overshooting Tops detected over the eastern Pacific (click to enlarge)

Hurricane Cristina

June 13th, 2014
Advanced Dvorak Technique (ADT) time series plot

Advanced Dvorak Technique (ADT) time series plot

A tire series plot of the CIMSS Advanced Dvorak Technique (above) showed that Hurricane Cristina experienced a period of very rapid intensification during the day on 12 June 2014. Hurricane Cristina reached Category 4 status, making this the first time in the satellite era that there have been two Category 4 storms by the month of June in the East Pacific basin (the first this year was Hurricane Amanda).

McIDAS images of 4-km resolution GOES-15 10.7 µm IR channel data (below; click image to play animation) showed the rapid formation of the well-defined eye on 12 June.

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

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

An SSMIS-18 satellite 85 GHz microwave image from the CIMSS Tropical Cyclones site (below) showed the well-defined eyewall at 14:33 UTC on 12 June.

SSMIS-18 85 GHz microwave image

SSMIS-18 85 GHz microwave image

About 3 hours later, an overpass of a Metop satellite provided ASCAT surface scatterometer winds (below).

GOES-15 10.7 µm IR image with ASCAT surface scatterometer winds

GOES-15 10.7 µm IR image with ASCAT surface scatterometer winds