Tropical Storm Gabrielle

September 4th, 2013
GOES-13 0.63 µm visible channel image (click image to play animation)

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

1-km resolution GOES-13 0.63 µm visible channel images (above; click image to play animation) revealed a pronounced convective burst associated with Tropical Depression #7, which was centered just southeast of Puerto Rico late in the day on 04 September 2013. On the final visible image before darkness, a pair of small but distinct overshooting tops could be seen, which actually signalled the beginning of another convective burst.

The corresponding 4-km resolution GOES-13 10.7 µm IR channel images (below; click image to play animation) showed that there were a series 3 well-defined convective bursts (2 more followed after darkness), each exhibiting areas with cloud-top IR brightness temperatures of -80º C or colder (violet color enhancement). On the final image in the animation (at 02:45 UTC), the coldest IR brightness temperature was -86º C This was about the time that Tropical Depression #7 was upgraded to Tropical Storm Gabrielle.

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)

A 1-km resolution POES AVHRR 12.0 µm IR image at 01:16 UTC (below) showed one overshooting top that exhibited an IR brightness temperature of -90º C (dark violet enhancement).

POES AVHRR 12.0 µm IR image

POES AVHRR 12.0 µm IR image

Two GOES-13 IR images at 03:45 UTC on 05 September from the CIMSS Tropical Cyclones site (below) showed that (1) Gabrielle was in an environment characterized by a light amount (around 10 knots) of deep layer (200-850 hPa) wind shear, and (2) a well-defined low-level cyclonic circulation was difficult to distinguish with the ASCAT surface scatterometer winds at that time.

GOES-13 IR image with deep layer wind shear analysis

GOES-13 IR image with deep layer wind shear analysis

GOES-13 10.7 µm IR image with ASCAT surface scatterometer winds

GOES-13 10.7 µm IR image with ASCAT surface scatterometer winds

 

===== 05 September Update =====

 

DMSP-17 SSMIS 85 GHz microwave brightness temperature

DMSP-17 SSMIS 85 GHz microwave brightness temperature

On the morning of 05 September, a DMSP-17 SSMIS 85 GHz microwave brightness temperature image at 10:42 UTC (above) and GOES-13 10.7 µm IR images (below) suggested that the mid-level circulation center of of Gabrielle was reforming well to to the east of the original fix location low-level circulation center. Around the time of the end of the IR image animation, Gabrielle was downgraded to a Tropical Depression.

GOES-13 10.7 µm IR images

GOES-13 10.7 µm IR images

 

Landsat-8 images of the Rim Fire in California

August 31st, 2013
Google Maps terrain, with Landsat-8 0.45 µm visible channel and 2.29 µm shortwave IR channel images

Google Maps terrain, with Landsat-8 0.45 µm visible channel and 2.29 µm shortwave IR channel images

Google Maps terrain along with 30-meter resolution Lansdat-8 0.45 µm visible channel and 2.29 µm shortwave IR channel images of the Rim Fire in California at 18:42 UTC on 31 August 2013 are shown above. While there were some scattered clouds in the satellite scene, a great deal of optically-thick smoke could be seen in the visible image (along with some new smoke plumes from a cluster of active fires). On the shortwave IR image, the active fire “hot spots” appear as bright white features around the perimeter of the fire burn scar. These Landsat-8 images are displayed using the SSEC Web Map Server.

As of 31 August, the Rim Fire had burned 222,777 acres, making it the 4th largest fire on record for the state of California; the fire was estimated to be 45% contained at that time. The corresponding 31 August Landsat-8 false-color Red/Green/Blue (RGB) image — created using Bands 7/5/3 — shows the large areal extent of the fire burn scar (darker red colors), along with the active fires along the perimeter (brighter pink colors).

Google Maps terrain, with Landsat-8 false-color Red/Green/Blue (RGB) false-color image

Google Maps terrain, with Landsat-8 false-color Red/Green/Blue (RGB) false-color image

Credits: original RGB image created by Sam Batzli, SSEC; RGB image converted for WMS display by Russ Dengel, SSEC.

Update on the Rim Fire in California

August 30th, 2013
Daily MODIS true-color RGB images (18 August - 30 August 2013)

Daily MODIS true-color RGB images (18 August – 30 August 2013)

A sequence of daily 250-meter resolution MODIS true-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site — covering the period 18 August to 30 August 2013 (above; click image to play animation) — shows the changes in the growth and smoke plume production of the Rim Fire in California. This has now become the 6th largest fire on record in California, and is curently the largest fire so far in the US in 2013 (with 201,894 acres burned as of 30 August).

A sequence of AWIPS images of Suomi NPP VIIRS 3.74 µm shortwave IR images (below) shows the growth of the perimeter of fire “hot spots” (black to yellow to red color enhancement) during the 27-30 August period.

Suomi NPP VIIRS 3.9 µm shortwave IR images (27 August - 30 August)

Suomi NPP VIIRS 3.9 µm shortwave IR images (27 August – 30 August)

A comparison of 250-meter resolution MODIS true color and false-color RGB images on 28 August (below) shows the large size of the fire burn scar on the false-color image.

MODIS true-color and false-color RGB images (28 August)

MODIS true-color and false-color RGB images (28 August)

Daily comparisons of AWIPS images of Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR data during the 27 August – 30 August period (below) show night-time images of the fire hot spots on the shortwave IR along with the bright glow of the fires on the Day/Night Band.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (27 August)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (27 August)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (28 August)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (28 August)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (29 August)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (29 August)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (30 August)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images (30 August)

 

Bore Feature over Wisconsin

August 26th, 2013
Radar Composite over Midwest (click image to play animation)

Radar Composite over Midwest (click image to play animation)

Satellite and especially radar revealed the tell-tale signs of an undular bore over southern Wisconsin on the morning of 26 August. The parallel lines of enhanced radar return, above, suggest that the outflow from the convective complex over northern Wisconsin organized into a bore, in part because the atmosphere over Wisconsin (as sampled, for example, by the 1200 UTC Green Bay Sounding) included a stable layer. The wind at Madison’s Truax Airport shifted to northeast at 1453 UTC as the bore moved overhead. This is typical. Winds are parallel to the bore motion and perpendicular to the linear bore feature. What did the visible imagery show?

GOES-14 was in SRSO-R mode over the midwest on 26 August, providing one-minute imagery. As shown below, an abundance of cirrus obscured information from the lower cloud deck throughout the early part of the morning. However, parallel lines of low clouds do occur, marking the edge of the bore, later in the loop (after 1600 UTC northwest of Madison). The GOES-14 animation also shows the transformation of the atmosphere from convectively unstable at the beginning, with transverse bands in the cirrus outflow suggestive of turbulence, to an atmosphere with mid-level cumuliform clouds (over northwest Wisconsin) in the wake of a departing Mesoscale system. Finally, the Mesoscale system exits the state as cirrus continues to erode. Low- and mid-level clouds have dissipated. As the lower atmosphere destabilizes due to diurnal heating, the bore must dissipate, as it requires a stable layer to propagate.

GOES-14 0.63 µm visible channel images (click image to play large animation)

GOES-14 0.63 µm visible channel images (click image to play large animation)

(Click here for a QuickTime movie of the animation above. It has a much smaller file size).

GOES-13 imagery of the same event shows the general evolution of the atmosphere, but the temporal resolution is very coarse, with half-hourly imagery between 1445 UTC and 1545 UTC due to a Full-disk scan and subsequent housekeeping. This is a period during which GOES-14 shows considerable weakening of the convective complex. The coarse time steps also make it difficult to infer the presence of a bore.

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)

Landsat-8 imagery (below) shows that the parallel lines of clouds persisted past 1642 UTC. Note that the Landsat-8 imagery is also available through the SSEC Web Map Server: Link.

Landsat-8 0.56 µm visible channel image

Landsat-8 0.56 µm visible channel image

 

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)

Regarding the aforementioned transverse bands in the cirrus outflow, there were a few pilot reports of turbulence that appeared to be associated with these cloud features as they were dissipating over northern Lower Michigan and adjacent portions of Lake Michigan and Lake Huron. AWIPS images of GOES-13 10.7 µm IR channel data (above; click image to play animation) and GOES-13 6.5 µm water vapor channel data (below; click image to play animation) showed the location of pilot reports of turbulence.

Most notable was the report of Severe turbulence at an altitude of 39,000 feet over northeastern Lower Michigan at 19:20 UTC (which the pilot reported as a “mountain wave”). Farther to the southeast, there was a report of Moderate turbulence at 19:00 UTC as the aircraft was descending from 40,000 to 32,000 feet. By these later times, the transverse banding signature was becoming difficult to identify on the 4-km resolution GOES-13 IR and water vapor imagery. However, the transverse banding signature was a bit more evident on a 1-km resolution POES AVHRR 12.0 µm IR image at 18:08 UTC (around the time of a report of light to moderate Clear Air Turbulence at an altitude of 35,000 feet).

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)