GOES-14 0.62 µm visible imagery, above, (here as an mp4, and here as a very large (220+ megabytes) animated gif) shows the development of convection over eastern North Carolina in a region of slight risk according to SPC (below).

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Mesoscale Discussion #713 from SPC, below, referenced the Super-Rapid scan imagery:

MESOSCALE DISCUSSION 0713
NWS STORM PREDICTION CENTER NORMAN OK
1111 AM CDT THU MAY 21 2015

AREAS AFFECTED…E-CNTRL AND ERN NC / SC GRAND STRAND

CONCERNING…SEVERE POTENTIAL…WATCH POSSIBLE

VALID 211611Z – 211745Z

PROBABILITY OF WATCH ISSUANCE…60 PERCENT

SUMMARY…SCATTERED STORMS ARE FORECAST TO DEVELOP OVER THE NEXT FEW
HOURS. AN ISOLATED SEVERE THREAT WILL LIKELY DEVELOP AND A WATCH
WILL STRONGLY BE CONSIDERED.

DISCUSSION…SUBJECTIVE SURFACE MESOANALYSIS PLACES A LOW 30 MI W
SOP WITH A WEST-EAST ORIENTED WARM FRONT AND A TRAILING COLD FRONT
ACROSS THE SC PIEDMONT. A PREFRONTAL CONFLUENCE/SURFACE TROUGH
EXTENDS FROM THE LOW SEWD THROUGH THE GRAND STRAND VICINITY.
OBSERVATIONS TO THE E OF THE SURFACE TROUGH AND LOCATED WITHIN THE
WARM SECTOR SHOW TEMPS WARMING TO NEAR 80 DEG F WITH BOUNDARY LAYER
DEWPOINTS IN THE MID-UPPER 60S INLAND AND AROUND 70 NEAR THE COAST.
SUPER RAPIDSCAN VISIBLE IMAGERY SHOWS A BUILDING TCU FIELD
IMMEDIATELY E OF THE LOW AND ALONG THE PREFRONTAL TROUGH/CONFLUENCE.

WATER VAPOR IMAGERY LATE THIS MORNING IMPLIES A WEAK LEAD
DISTURBANCE MOVING ACROSS W-CNTRL NC AHEAD OF THE MID MS VALLEY
SHORTWAVE TROUGH FORECAST TO APPROACH THE CNTRL APPALACHIANS LATER
TODAY. IT SEEMS THE WEAK UPPER FORCING FOR ASCENT PROVIDED BY THE
LEAD IMPULSE COUPLED WITH ADDITIONAL DIABATIC HEATING WILL ERODE THE
CAP OVER THE NEXT 1-2 HOURS AND SCATTERED STORM COVERAGE IS PROBABLE
BY THE 18-19Z TIMEFRAME.

VEERING AND A GRADUAL STRENGTHENING OF WINDS WITH HEIGHT WILL
SUPPORT STORM ORGANIZATION ONCE A FEW VIGOROUS UPDRAFTS BECOME
ESTABLISHED. FORECAST SOUNDINGS DEPICT MODERATE BUOYANCY AS OF 16Z
ACROSS THE WARM SECTOR AND THIS SHOULD FAVOR STORM INTENSIFICATION
OVER THE NEXT SEVERAL HOURS ONCE INITIATION COMMENCES. ISOLD LARGE
HAIL AND DMGG WINDS WILL BE THE PRIMARY THREATS. DESPITE TEMPERED
LOW-LEVEL SHEAR…A TORNADO MAY ALSO BE POSSIBLE ESPECIALLY IF A
SUPERCELL CAN DEVELOP AND FAVORABLY TRACK ALONG THE WARM FRONT.

..SMITH/THOMPSON.. 05/21/2015

ATTN…WFO…AKQ…MHX…RAH…ILM…CAE…

LAT…LON 35267979 36097844 36297643 35847549 34977597 33737851
33897960 34497991 35267979

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The GOES-13 Sounder captured some of the destabilization that occurred ahead of the developing line of convection. Values less than -5 are widespread over southeastern North Carolina at 1600 UTC, after which time cirrus blowoff obscured the satellite view.

Suomi NPP’s orbits on 21 May allowed successive views of the developing convection, once at 1725 UTC and once near 1905 UTC. The convection developed near the edge of the swath in both images, however, so NUCAPS soundings did not view the environment closest to the storms. Infrared imagery, below, shows the quick evolution of convection.

VIIRS visible (0.64 µm) and near-infrared (1.61 µm) imagery, below, shows that the developing storms glaciated quickly; the 1.61 µm imagery over the convection shows the darker grey values characteristic of regions where ice crystals are strongly absorbing radiation. Water-based clouds — over Kentucky, for example — appear as bright white in both channels.

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GOES-14, in SRSO-R mode, animation, above (YouTube video), captured the development of an isolated cell over northeastern Andrews County in west Texas. Intersecting boundaries helped force the isolated convection, above, that was strong enough to produce a signal in the NOAA/CIMSS ProbSevere product, with ProbSevere peaking at around 15%.

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Thunderstorms began to develop across West Texas during the afternoon hours on 19 May 2015, along and ahead of an eastward-moving dryline. One of the storms went on to produce a few brief tornadoes, and hail as large as 3.0 inches in diameter (SPC storm reports). Different views of this storm were provided by GOES-15 (GOES-West), GOES-14 (in SRSO-R mode), and GOES-13 (GOES-East) 0.62 µm visible channel images (above; click image to play 190 MB animated GIF; also available as an MP4 movie file, or on YouTube). This comparison highlights the advantages of 1-minute interval Super Rapid Scan images (which will be available from GOES-R) compared to the standard 15-minute interval Routine Scan images provided by the current generation of GOES.

One interesting feature seen on the visible channel images above was the apparent merger of the large dominant dryline storm and a smaller northward-moving storm that had formed in Mexico (radar animation). In GOES-13 10.7 µm IR imagery with an overlay of SPC storm reports (below; click image to play animation), one report of 2.0-inch diameter hail was seen around or shortly after the time of the storm merger.

With higher spatial resolution IR imagery from MODIS (1-km), VIIRS (375-meter), and AVHRR (1-km), much colder cloud-top IR brightness temperatures were seen (below) compared to the corresponding 4-km resolution GOES IR imagery at those times — especially during the early formative stages of the thunderstorms captured with MODIS and VIIRS. The coldest cloud-top IR brightness temperature on the 2128 UTC AVHHRR image was -80º C, compared to -67º C on the 2130 UTC GOES image.

A more detailed discussion of this event can be found on the RAMMB GOES-R Proving Ground Blog.

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GOES-14 is producing imagery at 1-minute intervals as part of Super-Rapid Scan Operations for GOES-R (SRSO-R). Sectors that are scanned change each day and are determined by likely weather events. The animation above, in the southwest corner of the Monday May 18 sector shows strong convection over northern Louisiana. (A similar animation in mp4 format is available here (YouTube)) A benefit of 1-minute imagery is that it can capture the entire lifecycle of overshooting tops, cloud-top features that typically form and decay in less than 10 minutes.

GOES-R is scheduled to launch in March 2016. It will have the capability to provide routine 1-minute imagery over mesoscale-sized domains such as those sampled in the next three weeks by GOES-14. Real-time GOES-14 SRSO imagery is available through the SSEC RealEarth web map server and the GOES-14 SRSOR Imagery site.

Rapid Scan Operations allow the eye to distinguish between upper- and lower-level clouds that typically move at different speeds or in different directions. In the animation below (similar mp4 available here), high clouds over western Pennsylvania are moving over dissipating river fog in the central part of the state. Upper level clouds over southern New York are moving southward; low clouds are moving westward behind a back-door cold front: winds at White Plains, Newark, Trenton (and other stations) have all switched to easterly.

Another feature of interest was a thin layer of lake fog that was streaming northward across Lake Michigan during the morning hours, as seen in the animation below (also available as an mp4 movie file). Note the appearance of an undular bore propagating southeastward through the northern portion of the fog at the end of the animation; this may have been caused by an internal reflection of the strong southerly flow impinging upon the rugged southern coastline of the Upper Peninsula of Michigan. According to buoy data and the Terra MODIS Sea Surface Temperature product, Lake Michigan waters were still in the upper 30s to low 40s F — it was the pre-cold-frontal southerly flow of much warmer air with dew point values in the 50s and 60s F that led to the formation of the lake fog.

Rounds of deep convection persisted over parts of the Gulf Coast states during the day, which can be seen in the sunrise-to-sunset animation of GOES-14 visible images below (also available as an MP4 movie file). In Louisiana, some of these storms produced heavy rainfall and flash flooding, with a few water rescues necessary.

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