One of the more pronounced in a series of pulses of Saharan dust moving westward across the Atlantic Ocean was seen during the 14 July – 16 July 2012 time period. The Meteorsat-9 “split window” Saharan Air Layer (SAL) tracking product (above; click image to play animation) displayed a very strong signal of a large area of SAL dust (yellow to orange to dark red color enhancement) approaching the Lesser Antilles and the Greater Antilles islands of the West Indies.

The hazy signature of the dust cloud was also seen during the daytime hours on Meteosat-9 pseudo-natural color images  Red/Green/Blue (RGB) images (below; click image to play animation). A large area of sun glint was prominent over the middle Atlantic Ocean on the 18:00 UTC images, but the dust cloud could always been seen to the west of the sun glint.

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McIDAS images of 1-km resolution NOAA-15 0.6 µm visible channel and 10.8 µm IR channel images from 01:30 UTC on 16 July 2012 or 5:30 PM local time on 15 July (above) showed the development of the first thunderstorm recorded at Barrow, Alaska since July 2004:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
556 PM AKDT SUN JUL 15 2012

…FIRST THUNDERSTORM IN BARROW SINCE 2004…

A LINE OF THUNDERSTORMS DEVELOPED JUST EAST OF BARROW LATE THIS AFTERNOON. A FEW RUMBLES OF THUNDER WERE HEARD AT THE NATIONAL WEATHER SERVICE OFFICE IN BARROW BETWEEN 515PM AND 535PM. THE ALASKA FIRE SERVICES LIGHTNING DETECTION NETWORK RECORDED FEW STRIKES JUST SOUTHEAST OF DEASE INLET.

THIS IS THE FIRST THUNDERSTORM AT BARROW SINCE JULY 3RD 2004.

$$
RT JUL 12

The coldest thunderstorm cloud-top IR brightness temperature on the 01:22 UTC NOAA-15 image was -37º C (green color enhancement). The surface winds at Barrow had switched to light northerly at the time of the thunderstorm, but a few hours prior to that had been from the southeast at 15-20 mph (helping to increase dew point temperatures into the low 50s F).

Due to the extreme viewing angle from the GOES-15 (GOES-West) satellite, the narrow line of weak thunderstorms was poorly resolved on Infrared (10.7 µm) images (below), and the apparent location was shifted to the north over the Arctic Ocean due to the parallax effect.

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An AWIPS image of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) data (above) revealed the bright signature of the Aurora Borealis along the US/Canadian border region at 07:33 UTC (1:33/2:33 AM local time) on 15 July 2012 (NOAA Space Weather Prediction Center auroral oval map). While the corresponding VIIRS 11.45 µm IR image did show some areas of clouds (particularly over North/South Dakota and southern Manitoba/Saskatchewan), there was very little cloud illumination from the waning crescent phase of the Moon (only 9% of the moon was visible) — so the vast majority of the bright DNB signal was from the Northern Lights activity.

A few of the smaller bright spots seen on the DNB image across parts of eastern Manitoba and western Ontario were due to flames from wildfires that were burning in that region, as seen in a comparison of VIIRS DNB and 3.74 µm shortwave IR images (below). The larger fires exhibited a small “hot spot” (yellow to red color enhanced pixels) on the shortwave IR image.

Brief glimpses of the Aurora Borealis activity could be seen from the northwest-facing camera on top of the SSEC/AOS building on the University of Wisconsin – Madison campus (below; night-time images provided by Pete Pokrandt, AOS).

===== 16 July Update =====

The bright auroral oval was again seen on VIIRS Day/Night band imagery the following night, at 07:14 UTC on 16 July. A comparison of the 15 July and 16 July DNB images (below) shows that the auroral oval was retreating northward on 16 July, as the impact of the geomagnetic storm triggered by a Coronal Mass Ejection (CME) from the sun was beginning to subside.

 

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The daily maximum temperature at Death Valley, California was 128º F (53.3º C) on 11 July 2012. A comparison of AWIPS images of 1-km resolution MODIS 0.65 µm visible channel data and the corresponding Land Surface Temperature (LST) product (above) showed that LST values were in the 150-160º F range (darker red color enhancement) in parts of the Death Valley region (which is generally oriented north to south, just to the east of station identifier K4SU).

The following morning, the surface air temperature at Death Valley only dropped to 107º F (41.7º C), which was the second warmest daily minimum temperature on record for that location:

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE LAS VEGAS NV
950 AM PDT THU JUL 12 2012

…SECOND WARMEST LOW TEMPERATURE EVER RECORDED AT DEATH VALLEY ON RECORD…

THE LOW TEMPERATURE AT THE OFFICIAL DEATH VALLEY WEATHER STATION IN FURNACE CREEK THIS MORNING ONLY FELL TO 107 DEGREES. THIS BREAKS THE RECORD FOR THE HIGHEST MINIMUM TEMPERATURE FOR JULY 12TH OF 100 DEGREES SET IN 1931.

THE LOW OF 107 DEGREES THIS MORNING IS THE SECOND WARMEST MINIMUM TEMPERATURE EVER RECORDED AT DEATH VALLEY SINCE RECORDS STARTED IN JUNE 1911. ONLY JULY 5TH 1918…WHEN THE LOW TEMPERATURE FELL TO 110 DEGREES HAS BEEN WARMER. THE LAST TIME DEATH VALLEY RECORDED A LOW OF 105 DEGREES OR GREATER WAS ON JULY 11TH 1920. A LOW OF 101 WAS RECORDED ON JULY 19TH 2010 AND THIS WAS THE LAST TIME A MINIMUM IN THE TRIPLE DIGITS WAS RECORDED IN DEATH VALLEY.

THE ABOVE INFORMATION IS PRELIMINARY AND IS SUBJECT TO A FINAL REVIEW BEFORE BEING CERTIFIED BY THE NATIONAL CLIMATIC DATA CENTER.

$$

STACHELSKI

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