NUCAPS soundings near a Tropical Disturbance

July 1st, 2014
Suomi/NPP 11.35 µm infrared channel, 0717 UTC on 1 July 2014 and NUCAPS sounding locations in green (click to enlarge)

Suomi/NPP 11.35 µm infrared channel, 0717 UTC on 1 July 2014 and NUCAPS sounding locations in green (click to enlarge)

Suomi/NPP overflew the developing tropical depression #1 (now Tropical Storm Arthur) east of Florida early in the morning on July 1st. The CrIS and ATMS instruments on board S/NPP provide data for NUCAPS soundings that are routinely distributed to AWIPS II. The image above is an overlay of the 11.35 µm infrared imagery with the sounding locations plotted as green dots. Seven sounding locations are indicated on the image above (Here is the image without the seven sounding locations) How well do NUCAPS soundings represent the tropical atmosphere that is supporting the development of Arthur?

The 7 soundings indicated in the plot above are: 1 (Just south of Pensacola, FL), 2 (Off the coast of Georgia), 3 (northeast of Arthur in the tropical Atlantic), 4 (Cape Canaveral), 5 (north of Tampa Bay), 6 (the western tip of Cuba) and 7 (northeastern Cuba).

GOES Sounder DPI Total Precipitable Water at 0700 UTC on 1 July 2014 (click to enlarge)

GOES Sounder DPI Total Precipitable Water at 0700 UTC on 1 July 2014 (click to enlarge)

How does Precipitable Water from the NUCAPS soundings compare to observations from other satellite-based systems? GOES Sounder DPI TPW from 0800 UTC shows values around 50 mm over interior the southeast United States, and over the tropical Atlantic to the northeast of the tropical system. A corridor of lower values, around 30-35 mm, extends northeast of Jacksonville, FL. Smaller values (30-40 mm) also extend southeastward from the lower Mississippi River valley into the Gulf of Mexico. A similar pattern in the precipitable water is evident in the blended product, here. Precipitable water values from the NUCAPS soundings appear, for this case, to be too low. The value at Cape Canaveral (point 4), for example, is 1.59″ (40 mm, versus close to 50 mm from the Sounder and the Blended Product); off the coast of Georgia (point 2), 1.30″ (33 mm vs. close to 41 mm from the Sounder and Blended Product); south of Pensacola (point 1), 1.25″ (31 mm vs. 35 mm from the Sounder and the Blended Product); north of Tampa Bay (point 5), 1.46″ (37 mm vs 47 mm from the Sounder and the Blended Product); northeast of the tropical system (point 3), 1.84″ (47 mm vs 49 mm from the Sounder/Blended Product); western Cuba (point 6), 1.70″ (43 mm, similar to the 44 mm from the Sounder/Blended Product); and northeast cuba (point 7), 1.22″ (31 mm vs. 39 from the Sounder and 34 from the Blended Product). The lowest 3 kilometers of the atmosphere (where most of the moisture resides) is the most difficult part for a satellite-based sounding, but there do appear to be differences between the two satellite-based sounding products (GOES and NUCAPS) in this case.

Severe Weather in Nebraska

June 16th, 2014

Unusual twin tornadoes (click here for a summary of photos/videos from the Capitol Weather Gang) formed in northeastern Nebraska (Storm Reports from SPC) late in the afternoon of the 16th of June 2014. How did satellite data anticipate the development and progression of the severe convection? GOES-13 Sounder data painted a picture of ongoing destabilization in the area. For example, the CIMSS NearCast Product, which  arises from a two-layer Lagrangian Transport Model of Equivalent Potential Temperature, shows increasing stability in a forecast for 2100 UTC on 16 June in forecasts from 1800, 1900 and 2000 UTC, below.

CIMSS NearCast forecasts of Theta-e Differences between two layers, all at 2100 UTC, with initial times at 1800, 1900 and 2000 UTC (click to animate)

CIMSS NearCast forecasts of Theta-e Differences between two layers, all at 2100 UTC, with initial times at 1800, 1900 and 2000 UTC (click to animate)

The NearCast output, derived from GOES Sounder data, can predict in advance where axes of instability (and more importantly, where gradients in instability; see also comments on NearCast here and here) will occur. GOES Sounder data can also be used to diagnose the present state of the atmosphere. On this particular day, GOES Sounder estimates of Lifted Index (1400, 2000 and 0000 UTC) and CAPE (1400, 2000 and 0000 UTC) all showed ongoing destabilization over the Plains.

GOES-13 Sounder DPI Analyses of Lifted Index and Convective Available Potential Energy at 1400 and 2000 UTC on 16 June and at 0000 UTC on 17 June

GOES-13 Sounder DPI Analyses of Lifted Index and Convective Available Potential Energy at 1400 and 2000 UTC on 16 June and at 0000 UTC on 17 June

The products above outline the general area where convection might develop. Once the convection has developed, the NOAA/CIMSS ProbSevere product can be used to diagnose/monitor the likelihood of severe weather (large hail, strong winds, or tornadoes) developing — specifically, the likelihood of when severe weather might first occur. The animation below shows the evolution of the tornadic cell as it moved northeastward through Nebraska. Satellite predictors (Normalized Vertical Growth Rate and Maximum Glaciation Rate) for this cell were strong; both were observed at 1925 UTC, nearly an hour before the observed severe weather. ProbSevere first exceeded 50% at 1950 UTC, 13 minutes before the warning at 2003 UTC. 1-inch diameter hail was reported at 2016 UTC. The first tornado report occurred at 2040 UTC.

NOAA/CIMSS ProbSevere model

NOAA/CIMSS ProbSevere model

MUCAPE in the ProbSevere product above is around 4000-5000 J/kg. A special sounding at OAX (1900 UTC) shows similar CAPE values.

The Suomi NPP satellite had a timely overpass over the Great Plains at around 2000 UTC on 16 June 2014. NUCAPS Soundings from Suomi NPP are available, as plotted below, and can be used to estimate instability.

Suomi NPP VIIRS 11.45 µm imagery with NUCAPS sounding positions (Green Dots) Superimposed (Click to enlarge)

Suomi NPP VIIRS 11.45 µm imagery with NUCAPS sounding positions (Green Dots) Superimposed (Click to enlarge)

A sounding at ~42º N, ~97.8º W, below, shows CAPE values around 1000. However, note that the boundary layer temperature and dewpoint are too cool (surface temperature = 21º C) and too dry (surface dewpoint = 12º C). A benefit of the Sounding Software in AWIPS II, however, is that soundings can be easily modified. If the boundary layer is altered such that dewpoints are closer to observed METAR values (20º C), then CAPE values increase to 3000; if the temperatures are modified to be closer to observed values, CAPE increases to more than 4800.

NUCAPS Sounding at 42.07 N, 97.78 W, ~2000 UTC on 16 June 2014 (Click to enlarge)

NUCAPS Sounding at 42.07 N, 97.78 W, ~2000 UTC on 16 June 2014 (Click to enlarge)

Suomi NPP VIIRS data at different wavelengths (0.64 µm visible, 1.61 µm near-IR and 11.45 µm longwave IR), below, give a view of the storm just before severe hail was observed. The 1.61 µm imagery suggests a fully-glaciated anvil, and the 11.45 µm imagery shows evidence of several isolated overshooting tops.

Suomi NPP VIIRS data (0.64 µm, 1.61 µm and 11.45 µm) at 2004 UTC on 16 June 2014 (Click to animate)

Suomi NPP VIIRS data (0.64 µm, 1.61 µm and 11.45 µm) at 2004 UTC on 16 June 2014 (Click to animate)

Click here for a visible image animation from GOES-13; here is an infrared image animation. The famous twin tornadoes in Elkhart, IN, during the Palm Sunday outbreak in 1965 can be seen here.

GOES-14 SRSOR: Thunderstorm development over Kentucky

May 22nd, 2014
GOES-13 DPI Convective Available Potential Energy (CAPE) on May 22, times as indicated (click to play animation)

GOES-13 DPI Convective Available Potential Energy (CAPE) on May 22, times as indicated (click to play animation)

GOES-14 operations in SRSOR mode deliver the ability to monitor convective development at very short time-scales. A good example of this occurred over the lower Ohio Valley/western Kentucky on May 22nd. The animation of GOES-13 Sounder Derived Product Imagery of CAPE (above) and of Lifted Index (1300 and 1700 UTC) showed considerable instability waiting to be released.

GOES-14 SRSOR animations can be used to monitor the evolving cumulus field in the search for the tower that will break the cap (Nashville, TN/Lincoln IL Soundings from 1200 UTC). The animation below shows visible imagery from 1800 UTC through 2011 UTC, at which time the convection has developed. Initial convection dissipates, but eventually develops along the Ohio River in western Kentucky (cumulus clouds continue to grow/dissipate over the Mississippi River valley throughout the animation).

GOES-14 Visible Imagery (0.62 µm) on May 22, times as indicated (click to play animation)

GOES-14 Visible Imagery (0.62 µm) on May 22, times as indicated (click to play animation)

By 1900 UTC, convective development over the lower Ohio Valley is vigorous enough that Cloud-Top Cooling algorithm from CIMSS (below) has flagged growing clouds, with values exceeding 20º C/15 minutes.

Instanteous Cloud-Top Cooling computed from GOES-13 at 1900 UTC 22 May 2014 (click to enlarge)

Instanteous Cloud-Top Cooling computed from GOES-13 at 1900 UTC 22 May 2014 (click to enlarge)

How does the NOAA/CIMSS ProbSevere model  then change with time as the convection intensifies? The 1904 and 1906 UTC ProbSevere products, toggled below, shows values increasing from 49% to 54% as Satellite Growth rates at 1900 UTC are incorporated at 1906 UTC. ProbSevere values then dropped (1912 UTC, 1922 UTC) as MRMS MESH decreased.

NOAA/CIMSS ProbSevere from 1904 and 1906 UTC on 22 May 2014 (click to enlarge)

NOAA/CIMSS ProbSevere from 1904 and 1906 UTC on 22 May 2014 (click to enlarge)

By 1936 UTC, ProbSevere has again increased above 50%, in two regions where MRMS has MESH sizes over 0.50″. MESH values are equivalent in the two regions, as are environmental values, but higher satellite predictors associated with the smaller eastern radar object drive higher ProbSevere values there.

NOAA/CIMSS ProbSevere from 1936 UTC on 22 May 2014 (click to enlarge)

NOAA/CIMSS ProbSevere from 1936 UTC on 22 May 2014 (click to enlarge)

The animation below shows the evolution of NOAA/CIMSS ProbSevere from 1948 UTC through 2000 UTC, with focus on a second cell that was warned. NOAA/CIMSS ProbSevere is designed to give an estimate of when severe weather might initially occur. Severe weather was not reported in Kentucky with these storms (link); however, observations of severe weather did occur as the storms moved near Nashville.

NOAA/CIMSS ProbSevere from 1948-2000 UTC on 22 May 2014 (click to animate)

NOAA/CIMSS ProbSevere from 1948-2000 UTC on 22 May 2014 (click to animate)

Related Hazardous Weather Testbed blog posts on this event can be found here, here, and here.

GOES-14 SRSOR: severe thunderstorms over the central Plains

May 11th, 2014
GOES-14 0.63 µm visible channel images (click to play animation)

GOES-14 0.63 µm visible channel images (click to play animation)

The GOES-14 satellite continued to be in Super Rapid Scan Operations for GOES-R (SRSOR) mode on 11 May 2014, capturing the development of thunderstorms along a dryline that stretched from the Texas Panhandle into far southwestern Kansas. As a southward-moving cold front intersected this dryline, McIDAS images of 1-minute interval GOES-14 0.63 µm visible channel data (above; click image to play animation; also available as an MP4 movie file) showed that the narrow line of storms later developed into large discrete supercell thunderstorms over Kansas, with widespread reports of tornadoes, large hail, and damaging winds (SPC storm reports).

Farther to the northeast, other large supercell thunderstorms could be seen growing over eastern Nebraska along a warm frontal boundary — these storms exhibited numerous signatures of vigorous overshooting tops. Near the end of the animation, winds gusted to 82 mph at Omaha, Nebraska at 00:51 UTC.

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product imagery (click to play animation)

GOES-13 sounder Convective Available Potential Energy (CAPE) derived product imagery (click to play animation)

AWIPS images of GOES-13 sounder Convective Available Potential Energy or CAPE (above; click image to play animation) and Total Precipitable Water or TPW (below; click image to play animation) with surface frontal analyses revealed the sharp gradient of both instability and moisture across the dryline — just to the east of the dryline, CAPE values exceeded 4000 J per kg (darker purple color enhancement), while TPW values were generally in the 30-40 mm or 1.2-1.6 inch range (shades of yellow). In addition, GOES-13 sounder Lifted Index values were in the -8 to -10º C range across parts of Kansas into southeastern Nebraska prior to convective initiation.

GOES-13 sounder Total Precipitable Water (TPW) derived product imagery (click to play animation)

GOES-13 sounder Total Precipitable Water (TPW) derived product imagery (click to play animation)

A 19:36 UTC Suomi NPP VIIRS 11.45 µm IR channel image (below) showed the early stages of convective development along the dryline in far southwestern Kansas; the coldest cloud-top IR brightness temperature value at that time was -80º C, just west of Dodge City, Kansas KDDC (corresponding GOES-14 visible image).

Suomi NPP VIIRS 11.45 µm IR channel image, with METAR surface reports

Suomi NPP VIIRS 11.45 µm IR channel image, with METAR surface reports

A comparison of POES AVHRRR 12.0 µm IR channel images (below) showed the explosive convective growth over Kansas and Nebraska in the 3-hour period between 19:56 UTC and 22:53 UTC.

POES AVHRR 12.0 µm IR channel images

POES AVHRR 12.0 µm IR channel images

Additional details on this event can be found on the RAMMB GOES-R Proving Ground Blog.