Rapidly intensifying mid-latitude cyclone off the East Coast of the US

March 26th, 2014
Composite of GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel images (click to play animation)

Composite of GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel images (click to play animation)

AWIPS images of a composite of 4-km resolution GOES-15 (GOES-West) and GOES-13 (GOES-East) 6.5 µm water vapor channel data (above; click image to play animation) showed the development of a large mid-latitude cyclone off the East Coast of the US on 26 March 2014. This cyclone underwent rapid intensification as it moved northeastward, with the storm’s central pressure deepening 43 hPa in 24 hours and reaching a minimum value of 955 hPa (which was lower than the 960 hPa minimum central pressure of the March 1993 “Storm of the Century”). Wind gusts in excess of 100 mph were observed both on offshore buoys (44027) and at coastal sites: as the storm approached the Canadian Maritimes, Wreckhouse in Newfoundland experienced an all-time record maximum wind gust of 116 mph (186 km/hour).

A closer view of the storm’s evolution on GOES-13 6.5 µm water vapor channel imagery with overlays of buoy reports, cloud-to-ground lightning strikes, and analyzed surface pressure and surface fronts is shown below.

GOES-13 6.5 µm water vapor channel images (click to play animation)

GOES-13 6.5 µm water vapor channel images (click to play animation)

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (below; click image to play animation) revealed greater detail in the cloud structures near the center of the storm circulation. The appearance of dual vortices can be seen, with the northernmost vortex appearing to be the dominant one associated with the true storm center.

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

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

A night-time view of the storm as it was beginning to intensify off the coast of Virginia at 05:56 UTC or 12:56 AM Eastern Time is seen in a comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm IR channel images (below). The bright white streaks appearing offshore on the DNB image are portions of the cloud illuminated by intense lightning — and there were a number of cloud-to-ground lightning strikes detected in the vicinity of these DNB lightning streaks.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images at 05:56 UTC

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images at 05:56 UTC

As the period of rapid intensification continued off the eastern coast of the US, the GOES-13 sounder Total column Ozone product (animation) depicted very high values (400-450 Dobson Units, shades of red) just south of the storm center at 09:00 UTC, which was a signature of a potential vorticity anomaly (a lowering of the dynamic tropopause caused by an intrusion of dry, ozone-rich stratospheric air into the upper and middle troposphere). According to the GFS40 model, the height of the dynamic tropopause (taken to be the pressure of the PV1.5 surface) had descended to around the 450 hPa level at 06 UTC. The image comparison below shows that this pocket of high ozone was co-located with a pocket of dry middle-tropospheric air on the water vapor imagery, which became even drier with time to the point that it exhibited a light orange color enhancement around 12 UTC on the closer-view GOES-13 6.5 µm water vapor channel image animation seen above.

GOES sounder Total Column Ozone product and GOES imager 6.5 µm water vapor channel data

GOES sounder Total Column Ozone product and GOES imager 6.5 µm water vapor channel data

MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images at 15:40 UTC

MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images at 15:40 UTC

Daytime views of the storm structure were provided by comparisons of 1-km resolution MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images at 15:40 UTC or 10:40 AM Eastern Time (above) and 17:19 UTC or 12:19 PM Eastern Time (below).

MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images at 17:19 UTC

MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images at 17:19 UTC

A comparison of 375-meter resolution (projected onto a 1-km AWIPS grid) Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 17:19 UTC or 12:19 PM Eastern Time is shown below.

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 17:19 UTC

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 17:19 UTC

SSEC RealEarth comparison of GOES-13 IR and Suomi NPP VIIRS true-color RGB images

SSEC RealEarth comparison of GOES-13 IR and Suomi NPP VIIRS true-color RGB images

The images above demonstrate using the SSEC RealEarth web map server to compare GOES-13 IR and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images of the storm, zooming in on the true-color image for more detail of dual vortex cloud features near the circulation center. The GOES IR image showed the impressively large size of the overall cloud structure associated with the mid-latitude cyclone.

The large size of the cyclone is also apparent in the VIIRS 1.38 µm imagery shown here. This wavelength highlights ice crystals — that is, high clouds — within the storm.

Additional details and satellite images of this storm can be found on the GOES-R and JPSS Satellite Liaison Blog.

Blowing dust from Baja California

March 16th, 2014
GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

McIDAS images of GOES-15 (GOES-West) 0.63 µm visible channel data (above; click image to play animation) revealed large plumes of blowing dust and sand, which were moving south/southwestward from the coast of Baja California and western Mexico on 16 March 2014. There were no surface observations in the immediate vicinity of the Baja California dust plume source regions, but farther to the southeast at Loreta (station identifier MMLT) winds gusted to 37 knots or 43 mph at 19 UTC (12 Noon local time), and surface visibility was reduced to 3 miles. Surface winds were likely channelled by the upstream mountainous terrain to reach higher speeds near the dust plume source regions.

A comparison of AWIPS images of Aqua MODIS 0.65 µm visible, 1.38 µm “cirrus detection”, 3.7 µm shortwave IR, 11.0 µm “IR window”, and 6.7 µm water vapor channel data at 21:40 UTC (below) showed the following: (1) the dust/sand plume could also be seen on the 1.38 µm “cirrus detection channel” image, since this channel can be used to identify any airborne particles that are effective scatterers of light (such as cirrus ice crystals, volcanic ash, haze, or dust/sand); (2) while there was no obvious dust/sand signal on the conventional IR window channel image, the much warmer (darker black) signature on the shortwave IR image was due to reflection of incoming solar radiation off the dust/sand particles; (3) on the water vapor image, an undular bore appeared to be developing near the leading edge of the dust/sand plume. According to 1-hour interval MADIS satellite-derived atmospheric motion vectors (green wind barbs), the plumes were moving toward the southwest at speeds as fast as 25 knots at the time.

Aqua MODIS 0.65 µm visible, 1.38 µm cirrus channel, 3.7 µm shortwave IR, 11.0 µm IR, and 6.7 µm water vapor channel images

Aqua MODIS 0.65 µm visible, 1.38 µm cirrus channel, 3.7 µm shortwave IR, 11.0 µm IR, and 6.7 µm water vapor channel images

Metop ASCAT surface scatterometer winds (cyan wind barbs) at 17:43 UTC (below) indicated that winds were northeasterly at speeds around 20 knots just off the western coast of Baja California; 18 UTC GOES-15 satellite-derived winds (green wind barbs) tracked the southwestward motion of the dust plumes at speeds of 20-31 knots.

GOES-15 0.63 µm visible image with GOES-15 satellite-derived winds and Metop ASCAT surface scatterometer winds

GOES-15 0.63 µm visible image with GOES-15 satellite-derived winds and Metop ASCAT surface scatterometer winds

A sequence of true-color Red/Green/Blue (RGB) images from Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS viewed using the SSEC RealEarth web map server (below) showed the southwestward progression of the tan-colored dense plumes of airborne dust/sand from Baja California. In the initial Terra MODIS image, the source region of many of the plumes appeared to be near the El Vizcaíno Biosphere Reserve.

Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS true-color RGB images

Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS true-color RGB images

Fog and stratus along the California coast

March 14th, 2014

In their Area Forecast Discussion issued at 11:57 UTC or 4:57 AM local time on 14 March 2014, the NWS San Francisco/Monterey Bay Area forecast office mentioned the Suomi NPP VIIRS Day/Night Band imagery which showed the coverage of coastal fog in their area of responsibility:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
457 AM PDT FRI MAR 14 2014

.DISCUSSION...AS OF 4:10 AM PDT FRIDAY...THE DRY TAIL END OF A
WEATHER SYSTEM MOVING IN TO THE PACIFIC NORTHWEST IS APPROACHING
OUR DISTRICT...AND RESULTING IN ENHANCEMENT OF THE MARINE LAYER
AND A RETURN OF THE MARINE STRATUS. LATEST GOES FOG PRODUCT
IMAGERY...AND IN RATHER SPECTACULAR DETAIL JUST REC`D SUOMI VIIRS
NIGHTTIME HIGH RES VISUAL IMAGE...SHOW COVERAGE ALONG MUCH OF THE
COAST FROM PT REYES SOUTH TO THE VICINITY OF THE MONTEREY
PENINSULA...AND A BROAD SWATH EXTENDING INLAND ACROSS SAN
FRANCISCO AND THROUGH THE GOLDEN GATE TO THE EAST BAY. LATEST
BODEGA BAY AND FT ORD PROFILER DATA INDICATE A MARINE LAYER DEPTH
OF ABOUT 1300 FT. SOME THIN HIGH CLOUDS ARE ALSO PASSING THROUGH ABOVE.

A comparison of AWIPS images of the Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and the corresponding 11.45-3.74 µm IR brightness temperature difference (BTD) “fog/stratus product” (below) showed this band of fog and stratus at 09:39 UTC or 2:39 AM local time. With ample illumination by moonlight (the Moon was in the Waxing Gibbous phase, at 97% of full), the DNB image served as a “visible image at night” to help highlight the fog/stratus features along the coast. Farther inland over the eastern portion of the satellite scene, the bright signature of deep snow cover in the higher elevations of the Sierra Nevada was also very evident on the DNB image.

Suomi NPP VIIRS 0.7 µm Day/Night Band and IR BTD "Fog/stratus product" images

Suomi NPP VIIRS 0.7 µm Day/Night Band and IR BTD “Fog/stratus product” images

A sequence of three 1-km resolution IR BTD images (below) — Terra MODIS at 06:33 UTC, Suomi NPP VIIRS at 09:39 UTC, and Aqua MODIS at 10:44 UTC — offered detailed views of the inland progression of the fog/stratus features, especially in the San Francisco Bay area and also down the Salinas Valley. The appearance of degraded resolution of the features seen on the 10:44 UTC MODIS image is due to the so-called “bow-tie effect” near the edge of a MODIS scan swath — even with a bow-tie correction algorithm applied, the MODIS images tend to look less crisp and clear along the scan edges.

Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS IR BTD "fog/stratus product" images

Terra MODIS, Suomi NPP VIIRS, and Aqua MODIS IR BTD “fog/stratus product” images

A GOES-R “Cloud Thickness – Highest Liquid Cloud Layer” product created using GOES-15 data (below; click image to play animation) showed the southward advancement of the band of fog/stratus during the overnight hours. The maximum thickness displayed was in excess of 1200 ft (lighter cyan color enhancement), which agreed well with the profiler depths mentioned in the NWS forecast discussion above.

GOES-15 Cloud Thickness product (click to play animation)

GOES-15 Cloud Thickness product (click to play animation)

Additional GOES-R products such as Marginal Visual Flight Rules (MVFR), Instrument Flight Rules (IFR), and Low Instrument Flight Rules (LIFR) Probability are shown below. These products help to better quantify the potential aviation impacts that features seen on the conventional BTD “fog/stratus product” might have.

GOES-15 MVFR Probability product (click to play animation)

GOES-15 MVFR Probability product (click to play animation)

GOES-15 IFR Probability product (click to play animation)

GOES-15 IFR Probability product (click to play animation)

GOES-15 LIFR Probability product (click to play animation)

GOES-15 LIFR Probability product (click to play animation)

For additional information on this event, see the GOES-R Fog Product Examples blog.

Strong offshore winds across the Alaska Panhandle region

March 1st, 2014
Suomi NPP VIIRS 0.64 µm visible channel and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 0.64 µm visible channel and 0.7 µm Day/Night Band images

A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and 0.7 µm Day/Night Band (DNB) data (above) demonstrated the superior ability of the broadband spectral response of the DNB to detect the plumes of airborne aerosols which were being lofted by strong offshore winds in the southern Alaska Panhandle region on 01 March 2014.

These strong offshore winds were the result of the strong pressure gradient between a ridge of high pressure inland over Canada and a trough of low pressure located off the coast (below). The air was quite cold and dry across inland Canada (plot of minimum temperatures), and this air experienced further drying as it was forced through the various mountain passes and then descended toward the coast.

Suomi NPP VIIRS 0.7 µm Day/Night Band image with surface pressure and frontal analysis

Suomi NPP VIIRS 0.7 µm Day/Night Band image with surface pressure and frontal analysis

McIDAS images of GOES-15 6.5 µm water vapor channel data (below; click image to play animation) showed a trend of strong middle-tropospheric drying during the day, as seen by the growth in areal coverage of the warmer (yellow-enhanced) region moving southwestward over the Alaska Panhandle region.

GOES-15 6.5 µm water vapor channel images (click to play animation)

GOES-15 6.5 µm water vapor channel images (click to play animation)

It is interesting to note that the surface observations at Klawock, Alaska (below) included “Snow” as the wind speeds increased and the aerosol plume became evident on satellite imagery. However, given the relatively warm surface air temperatures and the very low dew points (along with the fact that the sky conditions were reported as “Clear” during the entire day), it is likely that automated sensors mistook the airborne aerosol particles as snow.

Time series of Klawock, Alaska surface observations

Time series of Klawock, Alaska surface observations

Klawock, Alaska surface observations

Klawock, Alaska surface observations