“Medicane” in the Mediterranean Sea

October 31st, 2016

EUMETSAT Meteosat-10 Infrared Window (10.8 um) images [click to play MP4 animation]

EUMETSAT Meteosat-10 Infrared Window (10.8 um) images [click to play MP4 animation]

A compact tropical-like cyclone (often referred to as a “medicane“) moved across the Mediterranean Sea during the 28-31 October 2016 period. EUMETSAT Meteosat-10 Infrared Window (10.8 um) images (above; also available as a 71 Mbyte animated GIF) showed the system as it developed over the Ionian Sea between Italy and Greece, initially moved southwestward, and then turned to the east where it eventually passed near the Greek island of Crete on 31 October (producing a wind gust to 52 knots at Chania’s Souda Airport LGSA and causing some wind and water damage: media story 1 | media story 2). In addition, a wind gust to 50 knots was seen on a ship report at 12 UTC on 28 October, just to the west of the storm center.

The corresponding EUMETSAT Meteosat-10 Visible (0.64 um) images (below; also available as a 17 Mbyte animated GIF) provided a more detailed look at the structure of the storm during the daylight hours of those 4 days.

EUMETSAT Meteosat-10 Visible (0.64um) images [click to play MP4 animation]

EUMETSAT Meteosat-10 Visible (0.64um) images [click to play MP4 animation]

Daily snapshots of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images viewed using RealEarth are shown below. The hazy signature of blowing dust/sand from northern Africa could be seen within the broad southeast quadrant of the storm circulation.

Suomi NPP VIIRS true-color images [click to enlarge]

Suomi NPP VIIRS true-color images [click to enlarge]

There was ample moisture available to fuel convection around the storm, as seen in the MIMIC Total Precipitable Water product (below).

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

The surface wind circulation of the medicane was well-sampled on a variety of Metop-A and Metop-B overpasses, using ASCAT plots (below) from this site.

Metop-A and Metop-B ASCAT surface scatterometer winds, 28-31 October [click to play animation]

Metop-A and Metop-B ASCAT surface scatterometer winds, 28-31 October [click to play animation]

Suomi NPP ATMS images (below; courtesy of Derrick Herndon, CIMSS) revealed the areal coverage of the small “warm core” on Channel 8 (54.94 GHz) and Channel 7 (53.596 GHz); a north-to-south oriented vertical cross section showed the depth of the thermal anomaly associated with the medicane.

Suomi NPP ATMS Channel 8 (54.94 GHz) image, 31 October at 0037 UTC [click to enlarge]

Suomi NPP ATMS Channel 8 (54.94 GHz) image, 31 October at 0037 UTC [click to enlarge]

Suomi NPP ATMS Channel 7 (53.596 GHz) image, 31 October at 0037 UTC [click to enlarge]

Suomi NPP ATMS Channel 7 (53.596 GHz) image, 31 October at 0037 UTC [click to enlarge]

 

North-to-south vertical cross section of Suomi NPP ATMS brightness temperature anomaly [click to enlarge]

North-to-south vertical cross section of Suomi NPP ATMS brightness temperature anomaly [click to enlarge]

For additional information, see this blog post from the Capital Weather Gang.

 

3-day transport of airborne Copper River Valley glacial silt/sand over the Gulf of Alaska

October 25th, 2016

GOES-15 Visible (0.63 µm) images, 23 through 25 October 2016, with hourly surface observations [click to play animation]

GOES-15 Visible (0.63 µm) images, 23 through 25 October 2016, with hourly surface observations [click to play animation]

GOES-15 (GOES-West) Visible (0.63 µm) images during the daylight hours on 23, 24 and 25 October 2016 (above) revealed the hazy signature of large amounts of airborne glacial silt and sand from the Copper River Valley being transported southward over the adjacent offshore waters of the Gulf of Alaska. The fine glacial silt and sand particles were being lofted by strong katabatic gap winds being channeled southward down the Copper River Valley — these winds were the result of a strong pressure gradient between arctic high pressure that was moving from the Interior of Alaska to the Yukon Territory of Canada (surface analyses) and a large occluded low centered off the coast of British Columbia and the US Pacific Northwest (24 October visible imagery).

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images on 24 October 2016 [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images on 24 October 2016 [click to enlarge]

Comparisons between Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images on 24 October (above) and 25 October (below) showed that the small airborne glacial silt/sand particles were very reflective to solar radiation, and exhibited a warmer (darker gray to black enhancement) signature in the Shortwave Infrared images (similar to the warmer signature seen due to spherical water droplets at the tops of supercooled stratiform clouds). On 25 October a large aerosol plume was also emerging from Yakutat Bay, moving southwestward.

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images on 25 October 2016 [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images on 25 October 2016 [click to enlarge]

Time series of surface observations at Middleton Island in the Gulf of Alaska [click to enlarge]

Time series of surface observations at Middleton Island in the Gulf of Alaska [click to enlarge]

A time series plot of surface observations from Middleton Island (PAMD) in the northern Gulf of Alaska (above) showed that the surface visibility was reduced to 3 miles on 24 October and 5 miles on 25 October as the Copper River plume periodically passed over the island. The ceiling height on 24 October was reported to be as low as 1400 feet as the surface visibility began to decrease. Along the southern coast of Alaska just west of the Copper River Delta, the visibility at Cordova (PACV) dropped to 5 miles with haze reported late in the day on 25 October as the western edge of the plume drifted over that area (below).

Time series of surface observations at Cordova, Alaska [click to enlarge]

Time series of surface observations at Cordova, Alaska [click to enlarge]

A zoom-in of the 2246 UTC Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image on 24 October (using RealEarth) showed the gray to light tan color of the glacial silt/sand plume.

Suomi NPP VIIRS true-color RGB images [click to enlarge]

Suomi NPP VIIRS true-color RGB images [click to enlarge]

Shown below are toggles between Suomi NPP VIIRS true-color RGB and Aerosol Optical Thickness (AOT) images (from the eIDEA site) for 23, 24 and 25 October. Very high values of AOT (in the 0.8 to 1.0 range) were associated with the Copper River plumes.

Suomi NPP VIIRS true-color RGB and Aerosol Optical Depth images for 23 October [click to enlarge]

Suomi NPP VIIRS true-color RGB and Aerosol Optical Depth images for 23 October [click to enlarge]

Suomi NPP VIIRS true-color RGB and Aerosol Optical Thickness images for 24 October [click to enlarge]

Suomi NPP VIIRS true-color RGB and Aerosol Optical Thickness images for 24 October [click to enlarge]

Suomi NPP VIIRS true-color RGB and Aerosol Optical Thickness images for 25 October [click to enlarge]

Suomi NPP VIIRS true-color RGB and Aerosol Optical Thickness images for 25 October [click to enlarge]

A toggle between Terra MODIS Visible (0.64 µm) and Infrared (11-12 µm, commonly referred to as the “split window difference”) Brightness Temperature Difference (BTD) images on 25 October (below) revealed that there was a very subtle Copper River plume signature in the BTD image (note: the default 11-12 µm BTD color enhancement was modified to better highlight the plume in this example).

Terra MODIS Visible (0.64 µm) and Infrared (11.0-12.0 µm) Brightness Temperature Difference images [click to enlarge]

Terra MODIS Visible (0.64 µm) and Infrared (11.0-12.0 µm) Brightness Temperature Difference images [click to enlarge]

In that respect, the MODIS Infrared “split window” BTD images could be used to help locate the Copper River plume during nighttime as well as daytime, as seen in the image comparison below. The ABI instrument on GOES-R will have similar 11 µm and 12 µm Infrared bands, and will have the capability to provide this type of BTD imagery at 5 minute intervals over the entire Full Disk scan.

Nighttime (0706 UTC) and daytime (2031 UTC) Terra MODIS Infrared (11-12 µm) Brightness Temperature Difference images [click to enlarge]

Nighttime (0706 UTC) and daytime (2031 UTC) Terra MODIS Infrared (11-12 µm) Brightness Temperature Difference images [click to enlarge]

Previous cases of similar airborne Copper River plumes have been documented on this blog: Oct 2014 | Nov 2013 | Oct 2012.

Sequential NUCAPS Profiles at Higher Latitudes

October 20th, 2016
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Suomi NPP Day/Night Band (0.70 µm) and NUCAPS Sounding Locations, 0538 and 0724 UTC on 20 October 2016. Green Dots represent soundings that have passed quality control; Yellow Dots represent soundings for which the infrared retrieval failed; Red dots represent soundings for which both infrared and microwave retrievals failed (Click to enlarge)

The orbital geometry of Suomi NPP is such that regions north of about 43º N latitude can occasionally receive NUCAPS (NOAA-Unique Combined Atmospheric Processing System) Vertical Profiles of moisture and temperature on sequential orbital passes, meaning a given location could have vertical profiles separated by less than 2 hours. This occurred early on 20 October 2016 over Maine and Cape Cod, as shown above: Suomi NPP NUCAPS Vertical Profile locations are indicated over Day/Night Band Visible imagery. Two soundings at approximately the same location are circled in cyan in this small image and are shown below. There are two sequential profiles over Cape Cod, and then the two sequential profiles north of Maine. The atmosphere over Cape Cod was quiescent on this date, and little change between soundings is evident. In contrast, slight cold air advection was occurring north of Maine (Surface analysis from 0900 UTC, 500-mb analysis from 00 UTC), and the NUCAPS Sounding shows mid-level cooling.

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NSharp depictions of NUCAPS Vertical Profiles near 42N, 70W at 0500 and 0700 UTC on 20 October 2016 (Click to enlarge)

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NSharp Depictions of NUCAPS Vertical Profiles near 48 N, 68 W at 0500 and 0700 UTC on 20 October 2016 (Click to enlarge)

For stations in the northern Plains, or in Canada, sequential soundings overnight or perhaps more importantly in the mid-afternoon (Suomi NPP typically overflies the Plains a bit after Noon local time) could give important information about destabilization.

Previous CIMSS Satellite Blog Entries referencing NUCAPS Vertical Profiles are available here.


=============== Added 2100 UTC on 20 October 2016 ===============
The toggle below shows two soundings, from 1700 and 1800 UTC in central Pennsylvania in the region between Harrisburg and Williamsport (click here to see the Sounding Locations), just east of a slight risk issued by the Storm Prediction Center. The time evolution suggests upward motion (the top of the inversion rises) and a weakening in the cap. Severe Thunderstorm Watch #499 was issued 1945 UTC on 20 October for counties just to the west of these NUCAPS Profile locations — and damaging winds were reported in central Pennsylvania beginning at 2154 UTC.

NSharp depictions of NUCAPS Vertical Profiles near 41N, 77W at 1700 and 1800 UTC on 20 October 2016 (Click to enlarge)

Severe Weather in the Pacific Northwest

October 15th, 2016

Window Channel Infrared imagery from COMS-1 (10.8 µm) and GOES-15 (10.7 µm), every 6 hours from 1200 UTC on 7 October through 1800 UTC on 15 October [click to animate]

Infrared Window Channel imagery from COMS-1 (10.8 µm) and GOES-15 (10.7 µm), every 6 hours from 1200 UTC on 7 October through 1800 UTC on 15 October [click to animate]

Strong moisture-laden storms caused abundant precipitation and severe weather over the Pacific Northwest from 13-15 October 2016. The animation above shows two storms making landfall in the Pacific Northwest, one on 13-14 October and a second, on 15 October, which was a storm that originated from the remnants of Typhoon Songda. On 11-12 October, Super Typhoon Songda was recurving, subsequently racing towards the west coast of the United States, and making landfall as a strengthening extratropical cyclone on 15 October. The animation above uses two different satellites (COMS-1 and GOES-15), and includes a seam between the two views because the spectral characteristics of the two infrared window bands are not identical.

Daily precipitation from the Advanced Hydrologic Prediction Center from 13-15 October is shown here, with a weekly total shown below. A large area of precipitation exceeding 6 inches is apparent in the higher terrain.

ahps_7dprecip_15oct_1200

7-day Precipitation Totals ending 1200 UTC on 15 October 2016 (Click to enlarge)

The precipitation amounts were aided by the very moist airmass that accompanied the storms. Total Precipitable Water, shown below, from this site that manipulates data from here, shows the moisture. A larger-scale view that traces the moisture back to the time when Songda first reached typhoon intensity over the West Pacific is available here.

Total Precipitable Water, 12-15 October 2016 [Click to animate]

The strong storm before the one spawned by the remnants of Songda produced an EF2-rated tornado in Manzanita Oregon (YouTube Compilation; SPC Storm Reports; Blog post with damage picture) on 14 October 2016. GOES-15 Visible Imagery, below, shows a storm with overshooting tops moving over northwestern Oregon at the time of the tornado. (GOES-15 was performing a full-disk scan from 15:00-15:26 UTC, so 15-imagery was not available as the tornado moved ashore; the Advanced Baseline Imager on GOES-R will produce CONUS Imagery every 5 minutes in addition to Full-Disk Imagery every 15 minutes). The overshoots are especially apparent in the 1500 and 1530 UTC Images. GOES-13 provided a visible image at about the time of the tornado touchdown, but at a very oblique angle. The cirrus shield of the thunderstorm anvil is apparent, however.

GOES-15 Visible (0.62 µm) imagery, 1445, 1500 and 1530 UTC on 14 October. The Red Square indicates the tornado location [Click to animate]

GOES-15 Infrared Window (10.7 µm) imagery around the time of the severe weather in Oregon, below — which includes locations of SPC storm reports of tornadoes (red) and damaging winds (cyan) — also showed evidence of cold overshooting tops (the coldest clouds tops were around -50º C, yellow enhancement). An infrared image animation showing only the clouds is available here. NOAA-18 flew over the Oregon coast at 1427 UTC, and the AVHRR 12 µm Infrared image showed the parent thunderstorm offshore, upstream of Manzanita (larger-scale view).

GOES-15 Infrared Window (10.7 µm) imagery, 1400-1800 UTC on 14 October [Click to animate]

The Portland, Oregon NWS office issued 10 tornado warnings on 14 October — a record number for a single day.

 

GOES Sounder data can be used to created Derived Product Imagery (DPI) estimates of instability parameters (for example), and many are shown at this site. The GOES-13 Sounder has been offline for about a year after having suffered an anomaly back in November 2015, when the filter wheel became frozen, but the GOES-15 Sounder (and the GOES-14 Sounder) continue to operate. The animation below of GOES-15 Sounder Lifted Index shows values as low as -4ºC upstream of the Oregon Coast for many hours before the tornado; as such, it was a valuable situational awareness tool.

goes_sounder_dpi_14oct2016_1100_1700step

GOES-15 Sounder DPI Estimates of Lifted Index, 1100-1700 UTC on 14 October 2016 (Click to enlarge)

NOAA/CIMSS ProbSevere is a probabilistic estimate that a given thunderstorm will produce severe weather in the next 60 minutes. The animation below shows ProbSevere polygons overlain over radar from 1501 UTC (when the first ProbSevere polygon appeared around the radar cell that ultimately was tornadic) through 1521 UTC. Values from the ProbSevere output are below:

 

TIME PS CAPE SHR MESH GRW GLA FLSHRATE COMMENTS
1501 11% 1048 39.3 0.00 str str 0 fl/min Satellite from 1245/1241
1503 32% 1056 39.7 0.37 str str 0 fl/min Satellite from 1245/1241
1505 32% 1031 39.4 0.37 str str 0 fl/min Satellite from 1245/1241
1507 29% 1013 38.7 0.37 str str 3 fl/min Satellite from 1245/1241
1509 47% 974 37.9 0.62 str str 3 fl/min Satellite from 1245/1241
1511 47% 962 37.6 0.62 str str 3 fl/min Satellite from 1245/1241
1513 32% 745 33.1 0.52 str str 10 fl/min Satellite from 1245/1241
1515 34% 897 35.9 0.52 str str 1 fl/min Satellite from 1245/1241
1517 10% 887 35.7 0.52 N/A N/A 2 fl/min
1519 8% 762 33.6 0.54 N/A N/A 4 fl/min
1521 7% 737 33.1 0.49 N/A N/A 2 fl/min
realearthprobsevere_14october2016_1501_1521anim

NOAA/CIMSS ProbSevere output in RealEarth, 1501-1521 UTC on 14 October 2016 (Click to animate)

The Sounder also has a 9.6 µm “ozone absorption band”, and another example of GOES Sounder DPI is Total Column Ozone, shown below. Immediately evident is the sharp gradient in ozone (yellow to green color enhancement) located just north of the polar jet axis that was rounding the base of a large upper-level low (500 hPa analyses). The GOES-R ABI instrument also has a 9.6 µm band that is sensitive to ozone; however, there are no current plans to produce operationally a similar Total Column Ozone product.

 

GOES-15 Sounder Total Column Ozone DPI [click to animate]

GOES-15 Sounder Total Column Ozone DPI [click to animate]

Suomi NPP Day/Night Band Visible (0.70 µm) Image, 1057 UTC on 14 October 2016, Green Arrow points to Manzanita OR [click to enlarge]

Suomi NPP Day/Night Band Visible (0.70 µm) Image, 1057 UTC on 14 October 2016, Green Arrow points to Manzanita OR [click to enlarge]

Suomi NPP overflew the Pacific Northwest about 4 hours before the severe weather was observed at Manzanita. The Day/Night Visible Image above, courtesy of Jorel Torres at CIRA (Jorel also supplied the NUCAPS Sounding Imagery below), shows a well-developed storm offshore with thunderstorms off the West Coast of the United States (Click here for an image without the Green Arrow). Multiple overshooting tops can be discerned in the imagery.

NUCAPS Soundings are produced from the Cross-Track Infrared Sounder (CrIS, with 1300+ channels of information) and the Advanced Technology Microwave Sounder (ATMS, with 22 channels) that are present on Suomi NPP (in addition to the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument that provides the Day/Night band imagery). The image below shows the location of NUCAPS Soundings — the color coding of the points is such that Green points have passed Quality Control, whereas yellow points denote sounding for which the Infrared Sounding retrieval has failed to converge and Red points denote soundings for which both Infrared and Microwave sounding retrievals have failed to converge).

Suomi NPP Day/Night Band Visible Image, 1057 UTC on 14 October 2016, with NUCAPS Sounding Locations indicated.  The Green Circle shows the location of the Sounding below [click to enlarge]

Suomi NPP Day/Night Band Visible Image, 1057 UTC on 14 October 2016, with NUCAPS Sounding Locations indicated. The Green Circle shows the location of the Sounding below; Refer to the text for the Dot Color meaning [click to enlarge]

NUCAPS Soundings can give valuable information at times other than those associated with radiosonde launches (0000 and 1200 UTC, typically), and over a broad region. The point highlighted above, between the occluded storm and the coast, shows very steep mid-level lapse rates that suggest convective development is likely.

NUCAPS Sounding, location as shown by the Green Circle in the figure above. [click to enlarge]

NUCAPS Sounding, location as shown by the Green Circle in the figure above [click to enlarge]

The imagery below shows soundings a bit farther south, near convection that looks supercellular. The NUCAPS Soundings there suggest very steep mid-level lapse rates.

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