“Hot spot” from the fire that caused the deadly I-75 crashes in Florida?

January 29th, 2012 |
POES AVHRR 3.74 µm shortwave IR image

POES AVHRR 3.74 µm shortwave IR image

 

Thick smoke from a 62-acre brush fire that was burning in the Paynes Prairie Preserve State Park just southwest of Gainesville, Florida (station identifier KGNV) was blamed for causing a deadly multiple-vehicle crash along Interstate 75 at around 07:45 UTC (3:45 am local time) on 29 January 2012. Detection of the fire “hot spot” on shortwave IR satellite imagery was difficult due to the relatively small size of the fire, and the fact that some thin cirrus clouds were drifting over the region. However, evidence of what could be the fire hot spot was seen on a 06:58 UTC  AWIPS image of 1-km resolution POES AVHRR 3.74 µm data (above), with an IR brightness temperature (BT) of +9 C at the darker black pixel that is circled.

The fire “hot spot” was a bit easier to see on a 06:53 UTC  McIDAS image of 375-meter resolution Suomi NPP VIIRS 3.74 µm data (below). The darker black pixel that is circled exhibited an IR brightness temperature of +24.7 C.

Suomi NPP VIIRS 3.74 µm shortwave IR image

Suomi NPP VIIRS 3.74 µm shortwave IR image

Record cold continues across interior Alaska

January 29th, 2012 |
POES AVHRR 12.0 µm and MODIS 11.0 µm IR images (with METAR surface reports)

POES AVHRR 12.0 µm and MODIS 11.0 µm IR images (with METAR surface reports)

Record cold continued across the interior of Alaska, with Fairbanks reaching a minimum temperature of -50º F on 28 January 2012 and -51º F on 29 January 2012. These were the first -50º F temperatures at Fairbanks since 2006 (NWS Fairbanks public information statements). The coldest temperature reported was -65º F at Galena and by a coopertive observer at Fort Yukon (Fairbanks region temperature and precipitation data).

A sequence of AWIPS images of 1-km resolution POES AVHRR 12.0 µm IR and MODIS 11.0 µm IR data (above) revealed the expansion of surface IR brightness temperatures of -50º C or colder (violet to white color enhancement) during the early morning hours on 28 and 29 January. The coldest surface air temperatures at the times of the IR images included -50º F at Fairbanks (station identifier PAFA) and -60º F at Fort Yukon (station identifier PFYU) and Tanana (station identifier PATA). The signature of cold air drainage into lower elevation terrain (such as the relatively narrow river valleys along the south side of the Brooks Range, and also the broad Yukon Flats) could be seen on the 1-km resolution IR images.

Suomi NPP VIIRS 11.450 µm (Band I5) IR image

Suomi NPP VIIRS 11.450 µm (Band I5) IR image

The pattern of cold air drainage into lower elevations could be seen in even greater detail using McIDAS images of 375-meter resolution Suomi NPP VIIRS 10.450 µm IR data at 12:06 UTC on 28 January, over northwestern Alaska and the Yukon Territory of Canada (above), and also just to the southwest over the eastern interior of Alaska (below). These 2 VIIRS images use a different color enhancement, where the coldest surface IR brightness temperatures are darker blue.

Unfortunately, there was no surface air temperature report for Arctic Village (station identifier PARC) at this time, but the coldest surface IR brightness temperatures within some of the deeper valleys near that site was -58.4º C (-73.1º F).

To the south, a broad area of very cold (dark blue) surface IR brightness temperatures was seen across the Yukon Flats, with a minimum value of -58.3º C (-72.9º F). The hourly surface air temperature at the Fort Yukon (PFYU) reporting station close to the time of the satellite image was -56º F, while the surface IR brightness temperature at that location was -54º F. Although there is not always a direct 1:1 correspondence between satellite-sensed IR surface temperature values and the actual air temperature measured within an instrument shelter at a height of 5 feet above ground level, the IR satellite imagery can be used to located areas that might have the coldest surface air temperatures.

Suomi NPP VIIRS 11.450 µm (Band I5) IR image

Suomi NPP VIIRS 11.450 µm (Band I5) IR image