Historic Winter Storm Along the US East Coast

January 22nd, 2016 |

MIMIC Total Precipitable Water, 1500 UTC 19 January -- 1400 UTC 22 January [click to enlarge]

MIMIC Total Precipitable Water, 1500 UTC 19 January — 1400 UTC 22 January [click to enlarge]

A storm forecast to produce near-record snowfalls over the Nation’s Capitol has started to move up the east coast of the United States on 22 January 2016. Snow that will fall requires two things: abundant moisture, and cold temperatures. The MIMIC Total Precipitable Water Product, shown above for the 72 hours ending at 1400 UTC on 22 January (Source) shows the circulation of the developing storm drawing moist air northward from both the Gulf of Mexico and the western Atlantic Ocean. Similarly, the toggle below shows the NESDIS Operational Blended Total Precipitable Water Product (Source, a product that ‘blends’ Total Precipitable Water observations from GPS and GOES-Sounder*). Significant moistening is apparent over the southeastern part of the United States.

*As the GOES-13 Sounder continues to be off-line due to an anomaly (Link), the principle driver of this product over the eastern US is now GPS data.

NESDIS Blended Total Precipitable Water, 1400 UTC on 21 and 22 January 2016 [Click to enlarge]

NESDIS Blended Total Precipitable Water, 1400 UTC on 21 and 22 January 2016 [click to enlarge]

Cold air is also present. The MODIS Land Surface Temperature product from 0731 UTC on 22 January shows temperatures (in cloud-free regions) colder than -5º C southward into Virginia. Dewpoints in this region are colder than -10º C. High Pressure over the East Coast is promoting cold air damming along the Appalachians as well.

MODIS-based Land Surface Temperature, 0722 UTC and the 0900 UTC WPC Surface Analysis, 22 January 2016 [Click to enlarge]

MODIS-based Land Surface Temperature, 0722 UTC and the 0900 UTC WPC Surface Analysis, 22 January 2016 [click to enlarge]

Suomi-NPP carries on board two instruments that provide vertical profiles of moisture and temperature in the atmosphere, the CrIS and the ATMS. NUCAPS Soundings combine information from those two soundings. NUCAPS Soundings sites from the early morning Suomi NPP Pass on 22 January are shown superimposed on the MODIS Land Surface Image below; five sounding sites (highlighted in red) were selected: northwest of Boston, over western Connecticut, New York City, Washington DC and central Virginia. These soundings all have common attributes: They are dry (although the vertical profiles from DC and Virginia show the most moisture: ~0.3″ of total precipitable water), they are too warm near the surface (detection of low-level inversions from satellite data is difficult) and they show lapse rates at mid-levels that suggest vigorous ascent may be possible. The 0600, 1200 and 1800 UTC Soundings from KIAD (below) also show dry air (at least initially: total precipitable water doubled from 0.24″ at 1200 UTC to 0.49″ at 1800 UTC) and steep mid-level lapse rates.

MODIS-based Land Surface Temperature, 0722 UTC and 0700 UTC NUCAPS Sounding Sites (in green) and the 0900 UTC WPC Surface Analysis, 22 January 2016 [Click to enlarge]

MODIS-based Land Surface Temperature, 0722 UTC and 0700 UTC NUCAPS Sounding Sites (in green) and the 0900 UTC WPC Surface Analysis, 22 January 2016 [click to enlarge]

Rawinsonde from KIAD (Dulles International Airport) at 0600, 1200 and 1800 UTC on 22 January 2016 [Click to enlarge]

Rawinsonde from KIAD (Dulles International Airport) at 0600, 1200 and 1800 UTC on 22 January 2016 [click to enlarge]

The Aqua Satellite, bearing the MODIS instrument, overflew the eastern United States shortly before 1900 UTC on 22 January 2016. MODIS samples the atmosphere at 36 different wavelengths, and selected images are shown below.

The toggle between the Visible (0.65 µm) and the ‘Snow Ice’ Channel in MODIS (1.63 µm), below, highlights regions of ice clouds. Ice particles absorb radiation with wavelength of 1.63 µm but water droplets scatter such radiation. Thus, regions in visible imagery that are white that include mostly ice crystals (or snow on the ground), for example the cirrus shield on the East Coast, will appear dark in the 1.63 µm imagery but bright in visible because clouds are highly reflective to visible light. Water-based clouds (over Mississippi, for example, or southeastern West Virginia; in fact, low clouds are apparent just to the west of the cirrus shield associated with the developing baroclinic leaf, from West Virginia southward to Savannah Georgia!) will appear bright in both channels.

MODIS Visible (0.65 µm) and near Infrared (1.63 µm) Imagery at 1836 UTC [Click to enlarge]

MODIS Visible (0.65 µm) and near Infrared (1.63 µm) Imagery at 1836 UTC [click to enlarge]

MODIS also includes a channel (1.38 µm) in a region in the electromagnetic spectrum where strong water vapor absorption occurs; this channel is ideal for high cloud detection. (GOES-R will also detect radiation at this wavelength) The toggle below shows the Visible (0.65 µm), Cirrus channel (1.38 µm) and Infrared window channel (11.02 µm) from MODIS. The storm at mid-day on 22 January was producing an extensive cirrus shield that had the classic baroclinic leaf structure (a structure that was also evident in the infrared window channel).

MODIS Visible (0.65 µm), Cirrus Channel (1.38 µm) and Window Channel Infrared (11.02 µm) Imagery at 1836 UTC [Click to enlarge]

MODIS Visible (0.65 µm), Cirrus Channel (1.38 µm) and Window Channel Infrared (11.02 µm) Imagery at 1836 UTC [click to enlarge]

Careful inspection of the visible and near-infrared channels from MODIS reveals transverse banding (features commonly associated with turbulence) along the western edge of the Cirrus Shield along the East Coast. The toggle below of the MODIS Water Vapor imagery (6.8 µm) shows distinct transverse banding. Pilot reports of turbulence with this system are widespread.

MODIS Infrared Water Vapor (6.8 µm) Imagery at 1836 UTC along with Pilot Reports of Turbulence (PIREPS) [Click to enlarge]

MODIS Infrared Water Vapor (6.8 µm) Imagery at 1836 UTC along with Pilot Reports of Turbulence (PIREPS) [click to enlarge]

To better monitor the long-duration storm, the GOES-13 (GOES-East) satellite was placed into Rapid Scan Operations (RSO) mode for a 2-day period beginning at 1215 UTC on 22 January. During RSO, images are available as frequently as every 5-7 minutes, an improvement over the routine 15-minute image interval (note: the ABI instrument on GOES-R will be able to provide images as often as every minute, or even every 30 seconds). Animations of RSO Visible (0.63 µm), Water Vapor (6.5 µm), and Infrared window (10.7 µm) imagery during the daylight portion of Day 1 of the storm are shown below.

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Water Vapor (6.5 µm) images [click to play animation]

GOES-13 Water Vapor (6.5 µm) images [click to play animation]

GOES-13 Infrared window (10.7 µm) images [click to play animation]

GOES-13 Infrared window (10.7 µm) images [click to play animation]

Though they lack the temporal resolution provided by geostationary satellites such as GOES, polar-orbiting satellites such as the NOAA series (with their AVHRR instrument), Terra and Aqua (with their MODIS instrument), and Suomi NPP (with the VIIRS instrument) offer imagery with significantly improved spatial resolution. Shown below is a series of AVHRR, MODIS, and VIIRS Infrared window channel images (10.8 µm, 11.0 µm, and 11.45 µm, respectively) on 22 January, with the data projected into a 1-km AWIPS-I grid. Areas with cloud-top IR brightness temperatures in the -50º to -60º C range (orange to red color enhancement) can be seen as the storm moved across the eastern US.

AVHRR (10.8 µm), MODIS (11.0 µm), and VIIRS (11.45 µm) Infrared window channel images [click to enlarge]

AVHRR (10.8 µm), MODIS (11.0 µm), and VIIRS (11.45 µm) Infrared window channel images [click to enlarge]

Excellent detail can also be seen in a series of 1-km resolution MODIS Water Vapor (6.7 µm) images spanning the 21-22 January period, shown below.

MODIS Water Vapor (6.7 µm) images [click to enlarge]

MODIS Water Vapor (6.7 µm) images [click to enlarge]

One interesting aspect to note was that the cold front associated with the intensifying storm had moved southward across the Gulf of Mexico (surface analyses), crossed the mountainous terrain of Mexico, and emerged as an area of strong gap winds over the Pacific Ocean south of Mexico (in the Gulf of Tehuantepec). The leading edge of the gap wind flow, known as a Tehuano wind (or a “Tehuantepecer”), was marked by a thin arc cloud fanning out away from the southerrn coast of Mexico, with hazy plumes of blowing dust seen streaming southward off the coast as the strong northerly winds persisted during the day.

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

The hazy signature of blowing dust resulting from the strong gap wind flow was even more recognizable on Suomi NPP VIIRS true-color RGB imagery, below.

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

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

GOES-13 satellite-derived atmospheric motion vector (AMV) winds, below, were showing cloud targets moving at speeds around 30-35 knots. Unfortunately, there was no good Metop ASCAT wind coverage of the Tehuano winds (as was the case for past events such as these documented here and here).

GOES and ASCAT satellite winds [click to play animation]

GOES and ASCAT satellite winds [click to play animation]

===== 23 January  Update =====

As the surface low deepened to a minimum central pressure of 983 hPa and moved northeastward just off the US East Coast (surface analyses), GOES-13 Visible (0.63 µm) images, below, showed  the moisture — with some embedded convective elements, judging from the texture and shadowing of the cloud tops — moving inland from the Atlantic Ocean north of the storm. Thundersnow was in fact reported at a number of locations. A similar animation of GOES-13 Visible images covering the daylight portions of the 22-23 January period is available here, with the entire 48-hour Infrared window channel (10.7 µm)  animation here.

GOES-13 Visible (0.63 µm) images with surface weather symbols [click to play animation]

GOES-13 Visible (0.63 µm) images with surface weather symbols [click to play animation]

Consecutive Suomi NPP VIIRS true-color RGB images at 1652 and 1828 UTC, below, provided a more detailed view of the convective elements that were moving inland north of the storm center.

Suomi NPP VIIRS true-color RGB images at 1652 and 1828 UTC [click to enlarge]

Suomi NPP VIIRS true-color RGB images at 1652 and 1828 UTC [click to enlarge]

===== 24 January Update =====

MIMIC Total Precipitable Water product [click to enlarge]

MIMIC Total Precipitable Water product [click to enlarge]

Shown above is a 72-hour animation of the MIMIC TPW product (from 00 UTC on 21 January to 00 UTC on 24 January), which — as mentioned at the beginning of this blog post — revealed the large amount of moisture-rich air that was drawn northward and subsequently wrapped into the storm. South of Mexico, a narrow tongue of dry air (a signature of the aforementioned Tehuano wind event) was also clearly seen, moving southwestward over the Pacific Ocean.

GOES-13 Water Vapor (6.5 µm) images, with surface weather symbols [click to play MP4 animation]

GOES-13 Water Vapor (6.5 µm) images, with surface weather symbols [click to play MP4 animation]

The entire 48-hour period of Rapid Scan Operations GOES-13 Water Vapor (6.5 µm) imagery with plots of surface weather symbols (above; also available as a large 66 Mbyte animated GIF) depicted the evolution of the storm as it moved across the Eastern US from 1215 UTC on 22 January to 1215 UTC on 24 January. The storm produced widespread heavy snowfall, areas of freezing rain and sleet, hurricane-force winds (peak gusts), and coastal flooding (WPC storm summary | NWS impacts statement | Capital Weather Gang blog) — it was ranked a Category 4 on the NESIS scale, and the 4th most intense since 1950 (NCEI overview). Features seen on the water vapor imagery included the development of a well-defined dry slot, cold conveyor belt, and elongated comma head / deformation zone that helped to produce the prolonged period of heavy snow. Interesting gravity waves were also seen within the offshore dry slot on 23 January, which appeared to be propagating westward back toward the coast. Larger-scale GOES-13 animations covering the entire 48-hour RSO period are also available [Water Vapor (6.5 µm): MP4 | animated GIF ; Infrared window channel (10.7 µm): MP4 | animated GIF].

The illumination of a Full Moon helped to provide a vivid “visible image at night” using the Suomi NPP VIIRS 0.7 µm Day/Night Band (below), highlighting the clouds associated with the departing storm along and just off the US East Coast, as well as the vast areas inland that were snow-covered. In the toggle between the corresponding Infrared window (11.45 µm) image, cloud streets due to cold air streaming southward and southeastward across the Gulf of Mexico toward Cuba were also seen.

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared window channel (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared window channel (11.45 µm) images [click to enlarge]

With the arrival of daylight on the morning of 24 January, the expansive area of snow cover was very apparent on GOES-13 Visible (0.63 µm) images, shown below. Snow depth values (inches) are plotted in cyan — 12 UTC depths for the earlier images, and 18 UTC depths for the later images.  The 18 UTC snow depth values were a bit less at many locations (due to compaction and/or melting), and parts of the extreme southern and southeastern edges of the snow cover were seen to melt away during the late morning hours.

GOES-13 Visible (0.63 µm) images [click to play animation]

GOES-13 Visible (0.63 µm) images [click to play animation]

False-color Red/Green/Blue (RGB) images made using Terra MODIS Visible (0.65 µm) and Snow/Ice (1.61 µm) images, below, showed how such RGB images can be useful for the discrimination of snow/ice (shades of red) vs. supercooled clouds (shades of white). Bare ground appears as shades of cyan.

Terra MODIS Visible (0.65 µm) and False-color RGB images [click to enlarge]

Terra MODIS Visible (0.65 µm) and False-color RGB images [click to enlarge]

The full-resolution Terra MODIS true-color RGB images viewed using the SSEC RealEarth web map server, below, showed even better detail, including the very sharp northern edge of the snow cover from New York and Connecticut to Massachusetts.

Terra MODIS true-color RGB iimage [click to enlarge]

Terra MODIS true-color RGB iimage [click to enlarge]

Terra MODIS true-color RGB image [click to enlarge]

Terra MODIS true-color RGB image [click to enlarge]

The wider swath of the VIIRS instrument on the Suomi NPP satellite provided a good true-color vs false-color image comparison, shown below. In this particular RGB image, show/ice (and glaciated ice crystal clouds) appear as shades of cyan, while supercooled water droplet clouds appear as shades of white.

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

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

Even greater detail could be seen in a 30-meter resolution Landsat-8 false-color RGB image, centered over the Washington DC area (below). Snow and ice also appear as shades of cyan in this image — ice can be seen in parts of the Potomac and Anacostia Rivers. The partially-plowed runway network of Reagan National Airport appears at the bottom center of the image.

Landsat-8 false-color image of the Washington DC area [click to enlarge]

Landsat-8 false-color image of the Washington DC area [click to enlarge]

A close-up Landsat-8 view of the Baltimore, Maryland area (below) also showed some ice forming in a few of the rivers.

Landsat-8 false-color image [click to enlarge]

Landsat-8 false-color image [click to enlarge]

Table of Maximum Wind Gusts [click to enlarge]

Table of Maximum Wind Gusts [click to enlarge]

Widespread strong gusts occurred with this storm, as shown in the Table above (from the National Weather Service). The hourly animation, below, of GOES-13 Water Vapor (6.5 µm) with Wind Gusts superimposed, shows that the strongest gusts occurred as the storm’s dry slot, depicted as darker shades in the water vapor imagery and a region which is often associated with strong subsidence, was nearby.

Hourly GOES-13 Infrared Water Vapor (6.5 µm) and surface reports of Wind Gusts (knots) [click to play animation]

Hourly GOES-13 Infrared Water Vapor (6.5 µm) and surface reports of Wind Gusts (knots) [click to play animation]

Suomi NPP VIIRS Visible and Near-Infrared imagery, below, shows the extent of the snowcover on 25 January. The benefit of multi-spectral imagery (as is available today from Suomi NPP, and will also be available from GOES-R) appears by comparing the 0.64 µm, 0.86 µm and 1.61 µm channels. For example, regions of snow vs. no snow are less distinct in the 0.86 µm (over northwest Connecticut, for example), but land/water differences are accentuated. Comparing the visible and the 1.61 µm brings out snow/ice features. The band of snow over southern New England is dark in the 1.61 µm because snow/ice absorbs radiation at that wavelength. Snow is highly reflective in the visible, however, and it appears bright white on that image. This comparison of visible and 1.61 µm can also be used to highlight ice clouds (as noted higher up in this blog post).

Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared (0.86 µm and 1.61 µm) imagery, 1753 UTC on 25 January 2016 [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared (0.86 µm and 1.61 µm) imagery, 1753 UTC on 25 January 2016 [click to enlarge]

RGB Imagery allows a one-image perspective (vs. an image toggle) to highlight features. The RGB image from Suomi NPP VIIRS imagery (0.64 µm and 1.61 µm) below shows snow cover (shades of red) over the Northeast. In the mid-Atlantic states, thin patchy clouds are present. The brightness of these clouds in the 1.61 µm channel suggests they are composed of supercooled water droplets.

Suomi NPP VIIRS RGB Imagery showing snow/ice features (red), water droplet cloud features (white) and bare ground (cyan), 1753 UTC on 25 January 2016 [click to enlarge]

Suomi NPP VIIRS RGB Imagery showing snow/ice features (red), water droplet cloud features (white) and bare ground (cyan), 1753 UTC on 25 January 2016 [click to enlarge]


===== Added 28 January =====
Rich Grumm, the SOO from the WFO in State College, discussed this storm as part of VISIT’s Satellite Chat series.

GOES-14 SRSO-R Imagery over North Carolina

May 21st, 2015 |



 

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).

Day 1 Outlook for Convection from SPC, issued at 1300 UTC 21 May 2015 [click to enlarge]

Day 1 Outlook for Convection from SPC, issued at 1300 UTC 21 May 2015 [click to enlarge]

==================================================================================

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

==================================================================================

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.

GOES-13 Sounder DPI values of Lifted Index, 1600 UTC 21 May 2015 [click to enlarge]

GOES-13 Sounder DPI values of Lifted Index, 1600 UTC 21 May 2015 [click to enlarge]

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.

Suomi NPP VIIRS 11.45 µm infrared imagery and NUCAPS Sounding Points (in green), ~1730 and ~1900 UTC 21 May 2015 [click to enlarge]

Suomi NPP VIIRS 11.45 µm infrared imagery and NUCAPS Sounding Points (in green), ~1730 and ~1900 UTC 21 May 2015 [click to enlarge]

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.

Suomi NPP VIIRS 0.64 µm visible imagery and 1.61 µm near-infrared imagery 1903 UTC 21 May 2015 [click to enlarge]

Suomi NPP VIIRS 0.64 µm visible imagery and 1.61 µm near-infrared imagery 1903 UTC 21 May 2015 [click to enlarge]

Severe Weather over the Southern Plains

March 25th, 2015 |

The Storm Prediction Center in Norman issued a Moderate Risk of severe weather over the Southern Plains on March 25, 2015. Convective products were available in AWIPS to help monitor the evolution of this event.

Cloud-Top Cooling (10.7 µm imagery) for GOES-13, 1907-2000 UTC on 25 March 2015 (Click to enlarge)

Cloud-Top Cooling (10.7 µm imagery) for GOES-13, 1907-2000 UTC on 25 March 2015 (click to enlarge)

For example, the Cloud-Top Cooling product, above, monitored rapid development of convection over eastern Arkansas just between 1915 and 2000 UTC (the 10.7µm imagery for about the same time is here). Cloud-Top Cooling depicts where the strongest vertical cloud growth is occurring and is most useful for the initiation of the convection (or subsequent re-energized growth). The NOAA/CIMSS ProbSevere product, below, can also monitor the evolution of the storm from initial growth through maturity and beyond.

NOAA/CIMSS ProbSevere Product, 1900-2028 UTC on 25 March 2015 (Click to animate)

NOAA/CIMSS ProbSevere Product, 1900-2028 UTC on 25 March 2015 (click to animate)

The NOAA/CIMSS ProbSevere product gauges the likelihood of a storm first producing severe weather (of any kind) in the next 60 minutes. It combines information about the environment (Most Unstable CAPE, Environmental Shear) from the Rapid Refresh Model, about the growing cloud (Vertical Growth Rate as a percentage of the troposphere per minute and Glaciation Rate, also as a percentage per minute), and Maximum Expected Hail Size (MESH) from the MRMS. The storm over east-central OK, crossing over the border of Arkansas, showed a ProbSevere value of 45% at 2004 UTC and of 87% at 2006 UTC; 1-inch hail was reported with this storm (in Roland, OK) at 2005 UTC, and a Severe Thunderstorm warning was issued at 2026 UTC. AWIPS-2 imagery that includes readouts for this storm are below.

NOAA/CIMSS ProbSevere product, 2000-2026 UTC on 25 March 2015 (Click to animate)

NOAA/CIMSS ProbSevere product, 2000-2026 UTC on 25 March 2015 (click to animate)

Suomi NPP overflew the region shortly before convection developed, and the NUCAPS soundings in the clear pre-convective air described the thermodynamics of the environment. The location of the NUCAPS soundings are shown below, overlain on top of the Suomi NPP VIIRS visible imagery. The Red and Yellow stars show two sounding locations to be discussed. It’s helpful when using NUCAPS soundings to know surface values of temperature and dewpoint, because it can be helpful to adjust the NUCAPS soundings so that surface values are more in line with observations as reported by METARS. Accordingly, the VIIRS visible image with surface METARS plotted is here. Dewpoints in eastern OK and western AR are close to 60 F/15 C.

NUCAPS Sounding Locations at 1833 UTC on 25 March 2015;  Red and Yellow Stars indicate sounding locations described below (Click to enlarge)

NUCAPS Sounding Locations at 1833 UTC on 25 March 2015; Red and Yellow Stars indicate sounding locations described below (Click to enlarge)

The soundings from the two starred sites are below. In both cases, the original sounding and a sounding that has been modified by increasing the lowest dewpoint by 2 C are shown. Most Unstable CAPE for the plotted soundings (original and modified) are indicated. NUCAPS Soundings suggest greater instability over west-central/northwest Arkansas than over southwestern Arkansas.

NUCAPS Sounding at the red star location, both original and modified (Click to enlarge)

NUCAPS Sounding at the red star location, both original and modified (Click to enlarge)

NUCAPS Sounding at the yellow star location, both original and modified (Click to enlarge)

NUCAPS Sounding at the yellow star location, both original and modified (Click to enlarge)

A short (1900-2015 UTC) GOES-13 visible image animation as the convection started is shown below. Click here for a longer animation (1300 – 2345 UTC); Click here for a faster version of the 1300-2345 UTC animation.

GOES-13 Visible 0.65 µm Imagery (Click to animate)

GOES-13 Visible 0.65 µm Imagery (Click to animate)

[Added: This severe weather outbreak caused the first tornado fatality of 2015, in Tulsa County, OK. Satellite imagery of those storms can be found here. ProbSevere product animations from 2024 to 2230 UTC on 25 March and also from 2206 UTC on 25 March to 0012 UTC on 26 March are shown below]

NOAA/CIMSS ProbSevere product, 2024-2230 UTC on 25 March 2015 (Click to animate)

NOAA/CIMSS ProbSevere product, 2024-2230 UTC on 25 March 2015 (click to animate)

NOAA/CIMSS ProbSevere product, 2206 UTC on 25 March 2015 to 0012 UTC on 26 March 2012 (Click to animate)

NOAA/CIMSS ProbSevere product, 2206 UTC on 25 March 2015 to 0012 UTC on 26 March 2015 (click to animate)

Convection Returns to the central Great Plains

March 24th, 2015 |
Suomi NPP VIIRS 11.45 µm infrared channel images (click to enlarge)

Suomi NPP VIIRS 11.45 µm infrared channel images (click to enlarge)

The ongoing change in seasons was accompanied last night by a round of convection over the Missouri River Valley. Suomi NPP 11.45 µm imagery from overnight shows scattered convection over Kansas, Missouri and Iowa at 0728 and 0909 UTC. Coldest cloud tops are around -65 C. The Day-Night band showed lightning streaks at both times as well, over east-central Kansas at 0728 and north-central Kansas 0909 UTC.

Suomi NPP VIIRS 0.70 µm Day-Night band visible channel images (click to enlarge)

Suomi NPP VIIRS 0.70 µm Day-Night band visible channel images (click to enlarge)

GOES Sounder DPI Lifted Index, times as indicated (click to enlarge)

GOES Sounder DPI Lifted Index, times as indicated (click to enlarge)

The GOES Sounder showed the unstable air that was feeding into this convection. Imagery at three-hourly intervals, above, shows values between 0 and -4 persisting over the central Plains. Plots of 850-mb data on top of the GOES Sounder DPI Lifted index, below, shows the development of strong warm advection over the central Plains that helped feed moisture into the developing convection.

GOES Sounder DPI Lifted Index and Radiosonde data at 850 hPa, times as indicated (click to enlarge)

GOES Sounder DPI Lifted Index and Radiosonde data at 850 hPa (click to enlarge)

NUCAPS soundings, created from both CrIS and ATMS data on board Suomi NPP, below, showed steepening mid-level lapse rates over/near Kansas. This convection likely was not surface-based.

Suomi/NPP NUCAPS Soundings near Kansas City (07z) and over Eastern Kansas (09z) with an individual sounding from the starred point plotted (click to enlarge)

Suomi/NPP NUCAPS Soundings near Kansas City (07z) and over Eastern Kansas (09z) with an individual sounding from the starred point plotted (click to enlarge)