Winter weather « CIMSS Satellite Blog

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)

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

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

Posted in Arctic, AVHRR, MODIS, POES, Suomi NPP, VIIRS, Winter weather | No Comments »

Unusally cold across the North Slope region of Alaska

January 24th, 2012

POES AVHRR 12.0 µm IR images + surface reports

Unusually cold conditions were seen across the North Slope region of Alaska during the 22 January – 24 January 2012 period. A sequence of AWIPS images of 1-km resolution POES AVHRR 12.0 µm IR channel data (above) showed the expansion of a large area of surface IR brightness temperatures of -50 C and colder (violet to white color enhancement) across the interior portions of the North Slope. Nuiqsut (station identifier PAQT) was as cold as -62 F (-52 C) on 24 January, and Barrow (station identifier PABR) reached a low temperature of -45 F (-43 C) on 23 January (the record low temperature for the date was -47 F, and the normal low for the date is -20 F).

Another feature of interest over the Arctic Ocean was the appearance of a number of what resembled “warm cracks” in the sea ice, where IR brightness temperatures were -30 C or warmer (yellow color enhancement) — significant amounts of thermal energy from the warmer waters below were able to “bleed up” through weaknesses and thinner areas of the sea ice, showing up as warm anomalies on the IR imagery.

A Public Information Statement was issued by the National Weather Service forecast office at Fairbanks:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
700 PM AKST TUE JAN 24 2012

…SEVERE COLD CONTINUES OVER THE NORTH SLOPE OF ALASKA…

A VERY COLD AIR MASS CONTINUES OVER THE NORTH SLOPE…COMBINED
WITH WINDS IN SOME AREAS. HERE ARE SOME LOW TEMPERATURES RECORDED SO FAR TODAY ACROSS THE NORTH SLOPE OF ALASKA.

NUIQSUT……………..62 BELOW
UMIAT……………….59 BELOW
INIGOK………………54 BELOW
ALPINE………………53 BELOW
ATQASUK……………..48 BELOW
DEADHORSE……………47 BELOW
WAINRIGHT……………44 BELOW
KAKTOVIK…………….40 BELOW
BARROW………………39 BELOW

TEMPERATURES OVER THE NORTH SLOPE WILL REMAIN IN THE 40S AND 50S BELOW WITH POCKETS NEAR 60 BELOW FOR THE NEXT FEW DAYS…AND POTENTIALLY INTO THE WEEKEND.

$$

JM

Posted in Arctic, AVHRR, POES, Winter weather | No Comments »

Cold air and snowfall invade the Pacific Northwest

January 15th, 2012

POES AVHRR 0.86 µm visible channel + POES AVHRR 12.0 µm IR channel images

A surge of cold air brought the first measurable snowfall to parts of the Pacific Northwest states on 14 January – 15 January 2012. The Seatle-Tacoma aiport received 2.4 inches of snow on 15 January. A comparison of 1-km resolution POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel data (above) displayed a classic example of “open cell convection” — this type of open-cell mesoscale convective cloud pattern is a signature of strong instability (via boundary layer cold air advection over relatively warmer waters) in an environment of cyclonic flow.

A sequence of 1-km resolution POES AVHRR 12.0 µm IR channel images (below) showed the inland progression of the open cell convection, eventually producing snowfall at Seattle, Washington (station identifier KSEA) and Portland, Oregon (station identifier KPDX).