Drilling rig fire south of the Louisiana coast

July 24th, 2013 |
Suomi/NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

Suomi/NPP VIIRS 3.74 µm shortwave IR and 0.7 µm Day/Night Band images

MODIS 3.7 µm shortwave IR image

MODIS 3.7 µm shortwave IR image

POES AVHRR 3.74 µm shortwave IR image

POES AVHRR 3.74 µm shortwave IR image

The shallow-water natural gas drilling rig Hercules 265 (located in about 150 feet of water, 55 miles off the coast of Louisiana) caught fire late in the evening on 23 July 2013. This fire event was captured by polar orbiting satellites with VIIRS, MODIS, and AVHRR instruments (above) and also by the GOES-13 satellite (below). VIIRS data from the Suomi/NPP satellite (top image) showed a warm thermal signature (yellow color enhancement) co-located with a region of enhanced brightness on the Day/Night Band image at the location of the burning rig. Shortwave IR brightness temperatures were not particularly warm on the VIIRS and MODIS images — 37.5º C and 31.5º C, respectively — because thin high clouds were overspreading the region, and those cold clouds were also being sensed by the radiometer. However, an apparent small break in the high clouds allowed the AVHRR instrument to detect a maximum shortwave IR brightness temperature value of 50.5º C (red color enhancement).

GOES-13 detected a jump in 3.9 µm pixel brightness temperature on the 03:45 UTC image (the actual scan time of that region was 03:50 UTC, or 10:50 PM CDT), as shown below. The brightness temperature increased from 23º C to 29º C as the fire was detected. The thin clouds evident in the imagery were likely responsible for the relatively cool IR brightness temperatures exhibited by this fire.

GOES-13 3.9 µm images at 03:32 and 03:45 UTC

GOES-13 3.9 µm images at 03:32 and 03:45 UTC

GOES-13 3.9 um shortwave IR imagery spanning the first several hours of the fire (below; click image to play animation) captured the appearance of the initial fire hot spot, followed by the periodic partial obscuration from the satellite view as high clouds moved over the region. The fire was declared to have stopped burning early in the day on 25 July, after the well became clogged with sand and sediment, shutting off the supply of natural gas that had been fueling the fire.

GOES-13 3.9 µm shortwave IR images (click image to play animation)

GOES-13 3.9 µm shortwave IR images (click image to play animation)

Mesoscale Convective Vortex (MCV) in southern California

July 20th, 2013 |
Suomi NPP VIIRS 0,7 µm Day/Night Band and 11.45 µm IR channel images

Suomi NPP VIIRS 0,7 µm Day/Night Band and 11.45 µm IR channel images

A comparison of AWIPS images of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel data (above) showed a large mesoscale convective system in southwestern Arizona at 08:40 UTC or 2:40 am local time on 20 July 2013. With ample illumination from the Moon (which was in the Waxing Gibbous phase, at 96% of full), the “visible image at night” capability of the VIIRS Day/Night Band image allowed shadowing from overshooting thunderstorm tops to be clearly seen; the coldest cloud-top IR brightness temperature of the overshooting tops was -83º C (violet color enhancement). In addition, numerous cloud-to-ground lightning strikes were associated with the MCS at that time. A few hours earlier, this storm had produced reports of wind damage in the Phoenix area just after 05 UTC (SPC Storm Reports).

With the arrival of daylight, McIDAS images of GOES-15 (GOES-West) 0.63 µm visible channel data (below; click image to play animation) revealed the emergence of a well-defined and relatively compact Mesoscale Convective Vortex (MCV) that continued to move westward across southern California during the day. The MCV also played a role in helping to iniitate additional convection in areas such as the San Bernadino Mountains of southern California.

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)

A comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 20:05 UTC (below) showed that the clouds associated with the MCV were primarily low to mid-level clouds, which exhibited IR brightness temperatures that were generally warmer than -20º C.

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

For aditional information on MCVs, see the VISIT lesson “Mesoscale Convective Vortices“. For additional information on VIIRS imagery, see the VISIT lesson “VIIRS Satellite Imagery in AWIPS“.

“Midget” tropical cyclone over the West Pacific Ocean?

July 19th, 2013 |
MTSAT-2 visible (daytime) and IR (night-time) images

MTSAT-2 visible (daytime) and IR (night-time) images

A sequence of MTSAT-2 0.675 µm visible channel images (during daytime) and 10.8 µm IR channel images (during the night) revealed the signature of what could be a “midget” tropical cyclone which was moving westward across the western Pacific Ocean during the 17 July – 19 July period (above; click image to play animation).

MTSAT-2 6.75 µm water vapor channel images with overlays of satellite wind derived deep-layer wind shear from the CIMSS Tropical Cyclones site (below; click image to play animation) showed that the region near 21º North latitude 130º East longitude was experiencing generally light to moderate northeasterly wind shear during this time period.

MTSAT-2 water vapor images + deep layer wind shear

MTSAT-2 water vapor images + deep layer wind shear

Record rainfall in San Juan, Puerto Rico

July 18th, 2013 |
MIMIC Total Precipitable Water product (click image to play animation)

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

Abundant moisture associated with a strong tropical wave (18 UTC surface analysis) fueled strong thunderstorms which produced record-setting rainfall at San Juan, Puerto Rico on 18 July 2013. AWIPS images of the MIMIC Total Precipitable Water (TPW) product (above; click image to play animation) showed the westward motion of the tropical wave, which exhibited TPW values greater than 50 mm or 2.0 inches (darker orange color enhancement) over a broad area — in fact, TPW values in the vicinity of Puerto Rico reached 60 mm or 2.4 inches on 18 July. Much drier air with significantly lower TPW values (30-35 mm or 1.2-1.4 inches, cyan to darker blue color enhancement) followed in the wake of the tropical wave passage; this dry air was likely the leading edge of a westward pulse of the Saharan Air Layer or SAL (real-time SAL images).

McIDAS images of 4-km resolution GOES-13 10.7 µm IR channel data (below; click image to play animation) showed numerous clusters of thunderstorms with very cold cloud top IR temperatures — IR brightness temperature values were as cold as -82º C (violet color enhancement) at 17:10 UTC.The location of San Juan is marked by the ‘*‘ symbol on the images.The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes.

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 (below) showed a strong thunderstorm beginning to move over the far eastern end of Puerto Rico at 19:35 UTC.

POES AVHRR 12.0 µm IR image (with METAR surface reports)

POES AVHRR 12.0 µm IR image (with METAR surface reports)