Figure 1 takes place at 1910 UTC and shows a 4-panel display from AWIPS II.  The lower two panels show radar observations of storm relative velocity (left) and reflectivity (right).  The top panels show two total lightning products.  The first is the source density product (left), which is used several SPoRT partners in operations.  The pseudo-geostationary lightning mapper (PGLM – right) is the demonstration product SPoRT is providing to the Hazardous Weather Testbed this year to demonstrate what the future Geostationary Lightning Mapper observations may look like.  The PGLM data are derived from the ground-based lightning mapping array data.  In this case it is from the Oklahoma network provided to SPoRT with this collaboration.  Lastly, please not the two pop-up windows.  These display the output from the SPoRT / MDL total lightning tracking tool, which is a time series of the source densities (left) and PGLM (right) observations, respectively.  Newcastle and Moore, Oklahoma are circled for reference.

Figure 1: AWIPS II four panel display from 1910 UTC that shows the total lightning source density (upper left), and pseudo geostationary lightning mapper flash extent density (PGLM – upper right), along with the radar storm relative velocity (lower left), and radar reflectivity (lower right). The pop-up windows show the total lightning tracking tool’s time series plot for the source densities (left) and PGLM flash extent density (right), respectively.

Both the source density and PGLM demonstrate a lightning jump around 1910 UTC, as shown by the spike in observations in the time series (~800 sources and 46 flashes, respectively).  Christopher Schultz’s official lighting jump algorithm supports this visual inspection as it too indicated a lightning jump.  Interestingly, the first severe thunderstorm warning was issued at 1912 UTC and based on radar observations at 1908 UTC.  Normally, we train that lightning jumps will precede severe weather, so why is the jump coincident with the initial severe thunderstorm warning?  The answer is that the environment in central Oklahoma was extremely favorable for tornadic supercells.  As such, as storms showed any signs of growth a warning was issued.  This is similar to how the Huntsville forecast office operated during the April 27, 2011 outbreak as there were so many violent storms across the region.  Given the environment, the total lightning would play a reinforcing role as the lightning jump at 1910 UTC indicates that this storm is rapidly strengthening and becomes rooted in the boundary layer.  One feature that the total lightning observations provide is a very rapid update cycle.  The total lightning data update every minute, versus the radar updating every 4-6 minutes.  This means that the total lightning observations are providing continuous updates into how the storm is evolving, allowing the forecaster to evaluate the storm’s growth in between radar volume scans.

We will next step forward to 1928 UTC, shown in Figure 2.

Figure 2: This is the same as Figure 1, but at 1928 UTC.

The total lightning observations begin to undergo a second, reinforcing lightning jump at 1928 UTC.  The time series plot is less obvious than from 1910 UTC, particularly with the source densities, but the lightning jump algorithm did flag a reinforcing jump at this time.  At this point, this is 12 minutes before the official tornado warning at 1940 UTC and 28 minutes prior to the reported touchdown time of 1956 UTC, near Newcastle, Oklahoma.  This reinforcing jump emphasizes to the forecaster that something is occurring and that the storm continues to intensify.  Given that a severe thunderstorm warning is already active, this reinforcing jump alerts the forecaster that this storm is unlikely to weaken soon.  The radar reflectivity emphasizes this as well, as it begins to take on a supercell structure and a faint hook echo may be forming (circled in reflectivity frame).

Figure 3 comes at 1940 UTC, shown in Figure 3, when the tornado warning was issued.

Figure 3: This is the same as Figure 1, but at 1940 UTC.

At this stage, the lightning activity has decreased somewhat after the initial jump at 1910 UTC and the reinforcing jump at 1928 UTC.  Radar continues to show intensification, particularly with the radar velocity couplet clearly evident to the west-southwest of Newcastle, Oklahoma.

We will next step ahead to 1950 UTC, just prior to the touchdown of the tornado at 1956 UTC in Figure 4.

Figure 4: This is the same as Figure 1, but at 1950 UTC.

At this stage, the tornado warning has been active for 10 minutes and the radar observations show the classic hook echo and velocity couplet signatures.  Both total lightning products show one final increase in activity, but given the high values for the past few minutes, this is not a third lightning jump.  The tornado would touchdown 6 minutes later just outside of Newcastle, Oklahoma before further intensifying and moving through Moore, Oklahoma.

Christopher Schultz provided an additional radar analysis that is a cross section of the radar azimuthal shear (a measure of the storm’s rotation) in time in Figure 5.  Red vertical bars show the occurrence of the original and reinforcing lightning jump at 1910 and 1928 UTC, respectively.  Of note is the large increase in azimuthal shear after each lightning jump prior to the tornado’s touchdown.

Figure 5: A radar azimuthal shear cross section plot from 1900-2300 UTC. The red bars indicate the times of lightning jumps from the lightning jump algorithm.

Once again, I would like to re-iterate that these experimental data were not available to the forecasters in real-time and that this is a post-event analysis.  Overall, the total lightning data behaved as expected, with two lightning jumps preceding the severe weather and the tornado that would later impact Moore, Oklahoma.  Based on the extremely favorable environment for tornadic supercells, the total lightning data would play a supporting role providing insight into the storm’s development for a forecaster, particularly with its one minute update times.  Total lightning typically has more utility in marginal events, but the post-analysis here shows that the underlying concepts of what drives a lightning jump are just as valid here.

Mount Pavlof, one of Alaska’s most active volcanoes, has been erupting since last week. The plume has caused some disruption of flights and ash fallout in nearby communities. The Alaska Volcano Observatory has been closely monitoring it’s activity (http://www.avo.alaska.edu/activity/Pavlof.php). The steam, ash, and gas plume is continually created as hot lava contacts snow and ice. The steam, ash, and gas plume has occasionally reached up to 20,000 ft and has been carried downwind as much as 100 km to the northeast, east, and southeast  before dissipating. This graphic from the Alaska Volcano Observatory shows the location of Mount Pavlof within the Aleutian Island Chain.

The plume can be seen in the VIIRS RGB Dust product. Let’s first look at the VIIRS true color product. Inside the red circle, you can see a faint brown plume, but it’s not easy to see (click on the images).

VIIRS True Color Image 2135 UTC 18 May 2013

Now take a look at the VIIRS RGB Dust product. On the three images below there is a pink/red streak (inside the purple circle) emanating from the location of Mount Pavlof.

This is an excellent example of the utility of multichannel RGB products to obtain a clearer view of the location and extent of volcanic plumes.

VIIRS RGB Dust Imagery 2135 UTC 18 May 2013

VIIRS RGB Dust Imagery 1138 UTC 18 May 2013

VIIRS RGB Dust Imagery 2332 UTC 17 May 2013

Many SPoRT team members have spent time in the Oklahoma City area as students at the University of Oklahoma in Norman, or through collaborations with other scientists at the National Weather Center.  Our thoughts are with our colleagues in Moore and the citizens of Oklahoma during their recovery efforts.

Day-night band imagery from the VIIRS sensor aboard the S-NPP satellite show city lights, cloud cover, and lightning during the early morning hours of May 20 prior to the storms over Moore, OK and the Oklahoma City area.

VIIRS DNB imagery during the early morning of May 21 show city lights in the Oklahoma City area, but reduced light output in Moore, OK as a result of the major tornado that occurred during the afternoon of May 20. Storms from earlier in the day had shifted eastward, still visible in the DNB imagery.

When pre- and post-storm imagery are combined in a 24-bit composite, power outages in the Moore, OK area are evident in shades of yellow. Other areas appear yellow, such as Tulsa, OK, but this is a result of changes in cloud cover between the two scenes.

Zoomed in area of the outage composite focusing on the Oklahoma City area.

Image 1. MODIS Airmass RGB valid 0716 UTC May 16, 2013.

A swath of dry air wrapping around the base of the closed low could be seen moving into the region, from Louisiana into Mississippi early on the morning of May 16th.  While this was apparent in standard 4 km GOES water vapor imagery, the MODIS Airmass RGB certainly showed more detail.  This type of imagery also has the ability to delineate airmass of differing characteristics.  Notice the warm, moist airmass across much of the Southeast, ahead of and along the cloud shield.  The Nighttime Microphysics RGB image valid at the same time below provided more detail of low level clouds upstream and in the local area, which was important for the forecast.

Image 2. MODIS Nighttime Microphysics RGB valid 0716 UTC May 16, 2013.

Since it was apparent that some clearing was indeed possible, if not likely for parts of the area during the morning and into the afternoon, I decided to increase my forecast temperatures.  With this type of imagery, it is far easier to delineate between cloud types, and makes the forecast process more efficient.  I also noticed that much of the cloud cover at the time to our west, particularly over the Arklamiss area, was mostly cirrus clouds.

This morning, the aviation forecaster and I used the imagery to distinguish between cloud types once again.

Image 3. MODIS Nighttime Microphysics image valid 0429 UTC May 18, 2013

While an area of deep convection can be seen in northern Alabama (red colors in north central AL), at the time we were actually more concerned about the low clouds and fog impacting our TAF sites.  The image above showed that the low stratus were present across much of northern Alabama and prevalent enough to keep IFR conditions in for the MSL TAF.  Additionally, a narrow line of clouds stretching from NE Oklahoma to north central Mississippi could be seen in the imagery.  This turned out to be a weak, albeit developing baroclinic boundary upon which deep convection resulted in Mississippi.  The RGB imagery above essentially make the forecast process much more efficient and were utilized in several aspects of forecasting this morning.  We are eager to get this type of imagery in AWIPS II at some point in the near future.

https://www.surveymonkey.com/s/NASA_Latency

WFO staff are using the new LMA plug-in provided by SPoRT to determine whether a lightning threat exists for the festival.  A cell developed in Lawrence County, AL, Saturday afternoon, and using the LMA data, we were able to determine that it contained intracloud lightning.  (The concentric circles indicate the 5 and 10-mile radii from the festival site.)

KHTX radar and North Alabama Lightning Mapping Array source density data, with range rings from downtown Huntsville

Fortunately, subsequent LMA and radar scans indicated a weakening trend, and it ended up posing no threat to the festival and its attendees.

Image 1. KHTX 0.5 degree reflectivity valid ~1413Z April 24, 2013, overlaid with NALMA and 1-minute NLDN data.

A little later at 1435Z, the area of convection had moved downstream to Bedford County, TN.  Intra-cloud lightning activity had been sporadic through the period, but can be seen increasing again with a forming area of deep convection in the eastern portion of the county at 1435Z.  Notice a negative cloud-to-ground strike can be seen in west central portions of Bedford County (just to the upper-left of the “B” in Bedford).

Image 2.  KHTX 0.5 degree reflectivity valid ~1435Z April 24, 2013 overlaid with NALMA and 1-minute NLDN data.

Later, at 1443Z, as the developing area of deep convection enters western Coffee County, a small jump appears in the LMA data, likely correlated with a strengthening updraft.  Still, no cloud-to-ground lightning has occurred with this storm.

Image 3. KHTX 0.5 degree reflectivity valid ~1443Z April 24, 2013, overlaid with NALMA and 1-minute NLDN data.

Finally, at 1449Z, the NLDN data indicate a negative cloud-to-ground strike in northwestern Coffee County, as seen in the image below (the negative sign may be a little difficult to see, but is located in the NW part of the county on the western fringe of the area of high reflectivity).

Image 4.  KHTX 0.5 degree reflectivity valid ~1449Z April 24, 2013 overlaid with NALMA and 1-minute NLDN data

In this case, the NALMA data showed that electrical activity was occurring in the intra-cloud region and that a thunderstorm was in progress well before (~35 minutes) the NLDN data alone would have indicated.   These data can be invaluable during real-time weather watches for our Emergency Manager partners and for the general public during outdoor events and can also alert a forecaster that a thunderstorm is indeed in progress when there are no cloud-to-ground strikes observed by the NLDN data alone.

Now, for something a little different…

I also noticed some unusual data that appeared well ahead of the line of convection yesterday in Madison and Limestone Counties.  While intra-cloud lightning could take place well ahead of the deep convection within the cirrus shield, this didn’t seem to be the case yesterday.  After some consultation with Dr. Geoffrey Stano of SPoRT/ENSCO, he believes the NALMA was detecting an aircraft traveling east to west through the region.  He wrote to me that, “the speed of the propogation in successive images and the “line” the sources make all point to an aircraft.”

Here are the images…

Image 5. KHTX 0.5 degree reflectivity overlaid with unusual NALMA signature over Madison County, AL, valid ~1326Z Apr 24, 2013.

Image 6. KHTX 0.5 degree reflectivity overlaid with unusual NALMA signature over Limestone County, AL valid ~1328Z Apr 24, 2013.

The NALMA page maintained by the lightning group showed the linear streak very well too, as seen in this image provided by Dr. Stano…

Image 7. NALMA data for the period 1300-1400Z April 24, 2013. Notice the linear streak highlighted from ENE to WSW.

Dr. Stano described this as a corona discharge that is generated by an aircraft flying through clouds that are electrically active (although not necessarily producing lightning).  The corona discharge can go into very high frequency range (VHF), which can be observed by an LMA.  We’re not sure at this point if we’re going to observe this more in AWIPS II.  Nevertheless, forecasters will have to be made aware of this type of phenomena and not be falsely alarmed by sudden increases or appearences of source data from the NALMA.

Acknowledgement:  I would like to thank Dr. Geoffrey Stano for his consultation with this post.

SPoRT has begun processing the 42-level temperature and 22-level moisture CrIMSS Environmental Data Record (EDR) data and qualitatively comparing these soundings to other hyperspectral sounders (AIRS and IASI), in situ observations (RAOBs), and regional models (North American Mesoscale (NAM) and Rapid Refresh (RAP)).  All of these comparisons are available on SPoRT’s hyperspectral sounding comparison page (http://weather.msfc.nasa.gov/sport/hyperspectral_comparisons/).

As an example of these comparisons, the three images below were taken from that webpage for soundings at Vandenberg Air Force Base (VBG) in California all valid around 2100 UTC on 31 March 2013.  Note that the CrIMSS and AIRS soundings both match very closely to the RAP temperature sounding with near-perfect agreement of tropopause height in the AIRS sounding and similar tropopause placement in the CrIMSS sounding.  Both the AIRS and CrIMSS soundings highlight a low-level moist conditions and mid-level dry conditions.  Satellite soundings in this form can be used by forecasters to gain additional confidence in their model guidance or obtain additional information in regions where there are not other upper air observations (such as over Northern Mexico and the Gulf of Mexico).

Temperature and dew point soundings at VBG at 2100 UTC on 31 March 2013.

Temperature and dew point soundings from CrIMSS at VBG at 2100 UTC on 31 March 2013.

Temperature and dew point soundings from AIRS at VBG at 2100 UTC on 31 March 2013. Thicker line indicates highest quality data.

Image 1. GOES visible imagery and METAR observations loop 2231-0045 UTC March 26-27 2013.

A few of the smoke plumes really stand out: one in SW Arkansas at site KDEQ, one west of McComb, MS and another between Jackson and Hattiesburg, MS.  Notice that the smoke plume from the fire in far SE OK was reducing visibility at KDEQ in SW Arkansas.  At times, visibility was reduced to 1 3/4 SM, which is within IFR conditions.  If this was a Terminal Aerodrome Forecast (TAF) site, this would cause potentially large aviation impacts and a forecaster would want to know about the evolution of the fire and smoke after sunset.  Granted, while only serving as a snapshot, the DNB imagery (images 2 and 3 below) show that the fires and smoke in the region had essentially dissipated by the satellite pass at approximately 0751 UTC Mar March 27.

Image 2. VIIRS DNB Reflectance image valid 0752 UTC 27 March 2013.

Image 3. VIIRS DNB Radiance RGB product valid 0752 UTC 27 March 2013.

Now, the question might remain, did the smoke actually disappear/dissipate or are the smoke plumes simply not showing up in the imagery?  It seems more likely that the smoke/fires had dissipated.  Early morning daytime visible imagery just after sunrise (not shown) indicated that the fires indeed had burned out.

Now, for another type of phenomenon…snow.

During the day, clouds may linger over recent snowfall and it can be difficult for forecasters to discern the true extent of the snow.  Sure, observations allow forecasters a sense of the extent of snow cover, but may not allow for a sufficient assessment of its true extent.  Notice in the short loop below, the clouds moving across recent snow in sections of the Midwest.

Image 4. GOES visible image loop valid 2315 – 0015 UTC March 26-27 2013.

In the imagery above, a trained eye can differentiate snow on the ground in portions of eastern Missouri and western Illinois from cloud cover.  However, forecasters and others would want to know the extent of snow cover on the ground over the area.  The VIIRS DNB Radiance RGB combined with the VIIRS Nighttime Microphysics RGB later that night after clouds had cleared somewhat helped to answer that question.

Imager 5. VIIRS DNB Radiance RGB valid 0752 UTC 27 March 2013.

Image 6. VIIRS Nighttime Microphysics image valid 0752 UTC 27 March 2013.

In the DNB RGB image above (image 5), the snow field is relatively easy to see extending from eastern Missouri into western Ohio.  Some clouds still obscure the view and SPoRT’s Nighttime Microphysics RGB product (image 6 above) makes it very easy to distinguish clouds from areas of snow.  The low/mid clouds in the area appear as yellows/oranges, while higher, colder clouds appear as deeper magenta/reds.  Toggling the two images (as shown in image 7 below) makes the ease of detecting snow vs. clouds apparent.

Image 7. Toggle of Nighttime Microphysics RGB with DNB radiance RGB, both images valid 0752 UTC March 27 2013.