Convection in the heart of Texas

An amplified trough and associated lee cyclone developed in west-central Texas Sunday afternoon, with a dryline generating strong supercell thunderstorms. The Storm Prediction Center upgraded their outlook to a moderate risk at 16:30 UTC for mainly large hail and strong tornadoes.

The NOAA/CIMSS ProbSevere model was able to capture the strong initial convection along the dryline, with GOES East IR observations, as the satellite transitioning to rapid-scan operation.

In a very unstable and moderately sheared environment, a strong normalized vertical growth rate and less than 0.5" of MESH gave the first storm of the day a probability of severe of 34% at 17:32Z (see animation below). Ten minutes later, MESH was 0.65" and the probability accordingly rose to 58%. By 17:50Z, MESH was 0.85" and the probability was 81%. The first severe thunderstorm warning was issued at 17:52Z, 10 min after the first probability ≥ 50%.

Two counties to the south, strong vertical growth and moderate storm-top glaciation rate, along with 0.52" of MESH, combined for a 55% probability at 17:58Z. Four minutes later, the probability jumped to 72%, and 6 min after that (18:08Z) it increased to 80%, as MESH increased to 0.8". This storm was first severe-warned at 18:21Z. Softball hail was later reported from this storm, in Shackelford County.

Further south along the dryline, another storm had very strong satellite growth rates, and probability of severe of 83% by 18:26Z (MESH = 0.62"). This storm was warned at 15 min later at 18:41Z. This storm would go on to produce grapefruit-sized hail and large tornadoes SW of Forth Worth, TX.

ProbSevere was able to highlight the severe potential in these storms up to 20 min before the first warnings were issued. It should be noted that ProbSevere is meant to be a 'quick-look' additional guidance to forecasters, and not provide a warn/no-warn decision at some magical probability threshold. Future development of ProbSevere will incorporate other NWP, radar, and possibly satellite fields to hone in on a probability of tornado in the very short term.

John Cintineo

UW-CIMSS

Elevated September Storms

Thunderstorms developed in southern Iowa early Monday morning along a warm frontal boundary. The MLCAPE was 0 J/kg, while the MUCAPE across the baroclinic zone was 800-1000 J/kg, indicating that these storms were not rooted at the surface. The effective bulk shear was also considerable, at 45-50 kts. The storm featured below had strong satellite growth rates at 11:15 and 11:30 UTC, which contributed to an elevated probability of severe (44%) when the MRMS MESH was less than 0.5". The ProbSevere model showed probabilities increase to 84% (12:04 UTC) and 96% (12:14 UTC), as the MESH increased to 0.81" and 1.27". This storm was never warned, while one-inch diameter hail was recorded in Appanoose county, IA at 12:55 UTC, 51 minutes after the first probability of severe greater than 80%. This example demonstrates the utility of the ProbSevere model in perhaps giving forecasters a "heads-up" on storms to watch in a set-up where severe weather was not expected.

John Cintineo

UW-CIMSS

NOAA/CIMSS Prob Severe Examples from September 9 2014

A strengthening frontal boundary extended from Lake Superior to the western High Plains on Tuesday, September 9th, while a surface warm front extended east from developing low pressure in Kansas east to central Illinois.  A vigorous mid-level short wave was moving across western and central Nebraska at the time resulting in the strengthening low pressure and cyclogenesis.  Deep column moisture was located to the south of the warm front with surface dewpoints in the lower 70s and precipitable water values of 1.5 to 2 inches.  Moderate to strong instability was in the frontal zone along with moderate effective bulk shear.  

Several strong thunderstorms developed during the early afternoon in the vicinity of the warm front. A line of thunderstorms moved across southwest Iowa toward Des Moines during the early afternoon. The below image from 1816z shows this line of thunderstorms to the southwest of Des Moines.  The CIMSS Prob Severe product was indicating a 69 percent chance for this line of thunderstorms to become severe in the following 60 minutes.  The thick cirrus anvil from this thunderstorm prevented the Vertical Growth and Glaciation Rate information from being determined.  

An examination of the KDMX all-tilts products and digital VIL indicated more of a threat of strong winds over large hail.  However RAP forecast soundings showed a strong thermal inversion around 1500 feet.  The KDMX velocity imagery indicated approaching 50 to 60 knot winds approaching Des Moines along the radial.  However, the CIMSS Prob Severe product lowered the severe probability to around 30 percent as the line of storms approached Des Moines.  A severe thunderstorm warning was issued for the counties to the west of Des Moines. The thunderstorms moved through the Des Moines area around 1915z uneventfully as the inversion prevented the strong winds aloft from mixing down to the surface. 

Another batch of thunderstorms strengthened over eastern Nebraska during the early afternoon. These thunderstorms approached the Omaha area and produced a wind gust to 55 knots at Fremont Nebraska (KFET) at 1955z which is about 30 miles west of KOMA.  The CIMSS Prob Severe product from 1948z indicated only an 8 percent chance for this thunderstorm to become severe in the next 60 minutes.  Again, the Growth and Glaciation Rate information was not available.  

The above two examples illustrate how the CIMSS Prob Severe product is geared more toward forecasting a large hail threat using available instability parameters, especially when satellite information is not available.

Marc Kavinsky
NWS Milwaukee/Sullivan

John Cintineo
UW-CIMSS

Upper Midwest storms and NOAA/CIMSS Prob Severe Model Demonstration

The GOES-R PG CIMSS/MKX shift focused on the Upper Mississippi Valley on Thursday, September 4.  Ongoing convection existed over far northern Wisconsin early in the morning on Tuesday.  The storms were discrete, elevated supercells that eventually congealed into a linear convective system.  While the NOAA/CIMSS ProbSevere model is designed to increase lead-time to the initial severe warning/hazards, this case demonstrates what others have noted during the spring and summer this year, that the ProbSevere model performs well with discrete mature convection.  Figure 1 below is shows the Green Bay 0.5 degree reflectivity with NOAA/CIMSS ProbSevere model output in the shaded contours around storm cells valid at 1452 UTC 4 September 2014.  These two storms with high ProbSevere values (> 90%) produced golf ball sized hail around this time.

Figure 1.  KGRB 0.5 degree reflectivity and NOAA/CIMSS ProbSevere output valid at 1452 UTC 4 September 2014.

Not shown was the progression of these storms across northern Wisconsin in the morning hours on Thursday.  During this time the ProbSevere values were consistently high (> 85%) with sporadic severe reports across the rural Northwoods.

Additional elevated storms developed over western and southwestern Wisconsin during the early afternoon hours, fueled by warm air advection.  These storms struggled to develop as the atmosphere was strongly capped.  The ProbSevere values associated with these storms remained (correctly) quite low over southwestern Wisconsin.  The storms over west-central Wisconsin did exhibit higher probabilities, as much as ~60% (largely due to much higher values of effective bulk shear and MRMS MESH values approaching 0.75"), but as of this writing have yet to produce severe weather.

The strong cap in place is likely to inhibit surfaced based convection along the cold front in Minnesota through the duration of the shift.

-Justin Sieglaff (UW/CIMSS)
-Ben Herzog (NWS MKX)

Severe Hail in Texas Panhandle

All day we were watching weak convection along a cold front in the Central Plains and ProbSevere as expected with these weak storms was no higher than 5 percent. Later in the afternoon, a few isolated cells in the Texas Panhandle rapidly developed. One storm, the Clarendon storm, became severe within an hour of initiation. We utilized ProbSevere as guidance in determining which storms to focus on for potentially severe hail. ProbSevere made it easy to see the evolution and intensification of the individual cells. Eight minutes before the Clarendon warning, ProbSevere was 43%, two minutes later it was up to 72%, another 4 minutes later it was up to 96%. At warning issuance another 2 minutes later it was 98%. ProbSevere performed well with regards to hail size. During this 8 minutes the MESH increased from .71 to 1.8 inches. After the warning was issued, it continued to increase to 2.4 inches. Local storm reports of 1 to 2.5 inch diameter hail were received.

Nearby cells that were developing around this time had a ProbSevere of 80-98%, however none of these cells had a warning except for the Clarendon storm during the initial time period studied. A half hour later the warning over the Clarendon storm was expanded to include most of the nearby cells that ProbSevere had high probabilities for earlier. There were no storm reports issued as of 15 minutes into the warning for the other cells but regardless there was a warning consistent with the ProbSevere guidance.

Sarah Marquardt and Sean Miller
NWS Milwaukee/Sullivan

ProbSevere in SE Missouri

A high CAPE, low shear environment fueled convective development in southeastern Missouri during the early to mid afternoon on 6 August 2014. Rapid convective development was captured using the ProbSevere function as can be seen in this image.

Convective development over SE MO at 1936Z. ProbSevere values of first warned storm are shown. 0.5 degree reflectivity was captured from KLSX.

This image shows the visible satellite imagery of the same storms in southeastern Missouri. The storm had plenty of lightning associated with it as it tracked to the southeast.

Visible satellite imagery of SE MO. Note the numerous lightning strikes over this area.

At 1936Z, the severe probability was nearly 100% for the northeastern most cell. The MESH value was 1.84. The high CAPE environment allowed these thunderstorms to develop quickly (storms had moderate to strong satellite growth rates), and ProbSevere did a good job in diagnosing the cell as ProbSevere had severe probability values jump from 26% at 1930Z to 81% at 1932Z. Shortly after this spike, the NWS in Paducah issued a Severe Thunderstorm Warning at 1936Z.

At the time of this post, there were no severe storm reports that came out of this cell. This might be contributed to the environment not being as favorable for severe weather (the area was in a See Text severe category from the Storm Prediction Center). SPC did issue an MD for the area for sporadic microbursts shortly after the initial warning, and there were a few penny sized hail reports for a cell that developed over Poplar Bluff. The ProbSevere MESH value for that cell was ~1.14, with a ProbSevere value of 90%. The ProbSevere value was at least 90% for that cell for about five minutes prior to the first report of penny sized hail.

Schultz NWS-MKX
Cintineo UW-CIMSS

ProbSevere MRMS fields vs. Single-source radar fields

NOAA/CIMSS ProbSevere display with kapx 0.5-degree Base Reflectivity, 1744 UTC on 22 July

Note the radar object above, enclosed in purple, from the MRMS (Multi-radar, Multi-sensor) fields, differs from the 0.5 Base Reflectivity field from the Gaylord, MI radar displayed.  This is to be expected because the MRMS is composite reflectivity from a variety of radars (in the case above, likely Gaylord, Marquette (MI) and Green Bay (WI)).  Do not expect a field from a single radar to overlap the MRMS fields.

(Scott Lindstrom, Ben Herzog)

Severe Storms in Northwestern Arkansas

As the CIMSS/MKX GOES-R Proving Ground shift wound down Tuesday afternoon, severe thunderstorms rapidly developed over northwestern Arkansas.  This region was supportive for strong to severe thunderstorms with MUCAPE between 2500 and 3000 J/kg and effective bulk shear 20-30 kts.  Figure 1 below shows the NOAA/CIMSS ProbSevere Model overlaid on MRMS composite reflectivity.  Of note is the rapid increase in the ProbSevere values over the course of 6 minutes between 2032 UTC and 2038 UTC 08 July 2014.  At 2032 UTC the ProbSevere value was 8%, then at 2034 UTC the ProbSevere value jumped to 56%.  This jump was attributed to more intense satellite growth rates (the normalized vertical growth rate went from 1.4%/min (strong) to 2.6%min (quite strong) and the glaciation rate increased from 0.02/min (weak) to 0.06/min (strong)) as well as a jump in the MRMS MESH associated with this storm 0.35" to 0.52".  Another four minutes later at 2038 UTC the probability jumped again to 95% as the MRMS MESH approached 1.00".

Figure 1.  NOAA/CIMSS ProbSevere Model and MRMS Composite Reflectivity over northwestern Arkansas during late afternoon of July 8 2014.

This example illustrates the increase in lead-time to severe hazards as well as severe thunderstorm warning issuance that is possible by quantitatively using satellite growth trends with environmental information and radar observations of a storm's precipitation core.  In this example, the initial severe thunderstorm warning was issued at 2059 UTC--20 to 25 minutes after the significant jumps in the NOAA/CIMSS ProbSevere output.   More storms continued to develop further west during late Tuesday afternoon, most of which became severe thunderstorm warned after reaching high levels of NOAA/CIMSS ProbSevere values.  Only one severe report was received with these thunderstorms, but one wonders if this is more related to the population of very rural northwestern Arkansas--with much of this region covered by state and national parks (Figure 2).

Figure 2.  Google maps showing the one severe hail report received with these storms (green 'H').  The very rural nature to the area inferred by this map makes one wonder if more severe weather occurred than was actually reported.

-Justin Sieglaff, UW/CIMSS
-Steve Hentz, NWS MKX

Low Topped Wisconsin Storms

The synoptic setting for Wisconsin July 7th 2014 featured a small shortwave in a mid level trough over the upper Great Lakes.  MUCAPE values ranged from 300 to 800 j/kg with 0-6 km shear around 25 to 30 kts.  Scattered thunderstorms developed by noon.  SCAN max hail values were from 0.50 inch to 0.75 inch.  The CIMSS probabilities over severe were mainly in the single digit to around 25%, but many storms did have strong vertical and strong glaciation rates.  One storm did approach severe criteria. Using FSI with the Donovan technique a narrow core of 50dbz did just reach severe criteria.  The CIMSS Probability of severe was low at 49% , with the MESH value around 0.50 inch,   giving confidence that the storm was not severe.

-Steve Hentz

ProbSevere over the Mid-Atlantic and Southeast, 11 June 2014

We lost the NOAA/CIMSS ProbSevere feed at the National Weather Sevice (NWS) Milwaukee/Sullivan, Wisconsin (MKX) at 1742 UTC 11 June 2014. This was due to a communications failure at the National Weather Service Central Region Headquarters. So, we could not use and save the AWIPS II radar imagery with the CIMSS ProbSevere product.

However, we were able to save the images below from the ProbSevere website. These images were of convection in the Mid-Atlantic and Southeast U.S. from the early afternoon hours on 11 June 2014. We could not zoom in on the individual storms to get actual values from the ProbSevere product, so I'll just give some general trends on how it performed. Scattered convection developed across the region in a moist, unstable environment with 1000 to 2000 J/kg of MLCAPE, and 0 to 6 km shear of 20 to 30 knots. 

Convection developed fairly rapidly, and the ProbSevere values increased quickly as well. They seemed to show the rapid intensification of these storms well. Several Severe Thunderstorm Warnings were issued (yellow polygons) after the ProbSevere values increased rapidly. The ProbSevere product seemed to show some lead time to the issuance of the Severe Thunderstorm Warning products.

I have used the ProbSevere product in a couple of convective events in 2014 across the MKX forecast area. It was a useful situational awareness tool when convection first developed, until the anvils overspread the area. After then, it seemed to show more false alarms.

I would like to see an option to show the probability of tornadoes, severe hail, severe wind and flash flooding, if possible. Anything to help with situational awareness with flash flooding situations would be very helpful. It would also be good to try and keep the readout from the ProbSevere product from getting too cluttered with information. The color scale may need to be modified to one that has more colors at the higher end of the ProbSevere spectrum. This would help with seeing how high the value actually is.

This was a helpful learning experience, and look forward to more in the future!

Thanks,

JJW, Forecaster

NWS Milwaukee/Sullivan, WI

Contour colors: Blue - 1-9%; Cyan - 10-29%; Green - 30-49%; Orange -  50-69%; Red - 70-89%; Pink - 90-100%.
Polygons: Yellow - severe thunderstorm warning; Red - tornado warning; Purple - special marine warning.

Evaluating the ProbSevere Model in a Moderate Risk Event

The ProbSevere model was evaluated for a moderate risk situation on June 3, 2014. Storms across southern South Dakota and northern Nebraska were interrogated for severe potential, comparing warning timing and storm reports with the ProbSevere output. Overall, the ProbSevere model performed very well for the period of time that storms were analyzed. Storms consistently reach a ProbSevere level of around 90% around the time a warning was issued and well before reports were received.

Below are a few examples of how ProbSevere performed during the evaluation period.

The first storm that was analyzed ramped up quickly, reaching a ProbSevere level of 94% and maximum estimated hail size of 1.5" by 1407Z. The satellite growth rates were in the moderate to strong categories. This storm eventually dropped severe hail, with reports of 1" received at 1430Z and 1445Z, well after the model indicated a high probability of severe.

The second storm that was analyzed reached a ProbSevere level of 92% at 1456Z, holding around that level through 1520Z. The maximum estimated hail size generally ranged from 1.5" to 2.0" through the storm's peak intensity. A hail report of 1.75" was received at 1520Z, quite a bit after the model first indicated a high probability of severe.

The last storm that was analyzed intensified quickly. At 1412Z, the storm had a ProbSevere of only 14%.

By 1524Z, the ProbSevere had reached 90%, generally holding at that this level through 1610Z. The maximum estimated hail size ranged from 1.5" to 2.5". Severe hail reports of 1" were received at 1555Z and 1610Z, yet again well after the model first indicated a high probability of severe.

DDV
Forecaster
NWS Milwaukee/Sullivan

JLC
Researcher
UW-CIMSS

Day/Night Band Provides Better Detail of Low Clouds

During the overnight hours of 23-24 November, 2012, persistent stratus and flurries lingered over much of Wisconsin in the wake of a strong cold front which had swept through the previous day.  As indicated by the below Green Bay 00z sounding, the stratus was shallow and only several hundred feet thick.  Cloud bases were 2 to 3 thousand feet. 




















The short-term forecast concern was timing of the cloud erosion.  The below CONUS wide view 11-3.9 micron imagery from 08z 24 Nov indicated widespread clouds blanketing most of Wisconsin and the western Great Lakes. 


0758z 24 NOV 2012 11-3.9 micron imagery

   At about the same time, the below NPP VIIRS Day/Night band CONUS view indicated thin spots and breaks in the cloud cover across Wisconsin and the western Great Lakes. 


0758z 24 Nov 2012 Day/Night Band

Taking a closer view of the 11-3.9 micon imagery below, the clouds appear to shroud all of Wisconsin except for the far northwest corner. 



11-3.9 micron imagery - closeup

But a closer view of the Day/Night band showed more breaks in the cloud cover across Wisconsin as well as thin spots.  The clearing over northern Lake Michigan and Door County was much more discernable using the D/N band. 

Also, the illumination (reflectance) from the metropolitan areas highlighted the thinness of the clouds as well as helped make the breaks more discernable. 

Day/Night Band Closeup

By using the Day/Night band, a clearer picture of the cloud cover covering Wisconsin was determined.  This better understanding would allow the short-term forecaster to make a more reliable forecast of clouds and timing of low cloud erosion. 

The moon was in waxing gibbous and was 85.3% lit on 24 Nov 2012.  

Marc Kavinsky
National Weather Service - Milwaukee/Sullivan

Using GOES-R IFR/LIFR Probabilities for TAFs

Tracking areas of stratus and fog can be somewhat difficult using traditional satellite images along with METAR observations...particularly on a day with a variety of low and high level clouds. Sky conditions across the Great Lakes during the afternoon of November 6th is a good example. Below are infrared and visible GOES images along with plotted METAR ceilings and visibilities:

GOES Infrared

GOES Visible

Note how conditions are evident at point locations, but it is difficult to discriminate areal coverage across the region. For the purpose of issuing and updating TAFs, it would be very useful to better visually display areas of lower ceilings and visibilities, increasing situational  awareness and improving the ability to track and forecast improving or deteriorating conditions. Fortunately, GOES-R fog and low clouds products are proving quite useful in filling this need. Below are images of GOES-R IFR probabilitly and LIFR probability:

GOES-R IFR Probability

GOES-R LIFR Probability

The IFR product does a very good job of showing the area of ceilings that are less than 1000 feet, particularly for values above 60 percent. Though LIFR percentages are not very high, the highest percentages do coincide pretty well with some of the lower ceilings and visibilities in the region. Something that was immediately useful was observing a loop of the IFR image, which showed that the eastern edge of the lower ceilings had temporarily stalled across eastern Wisconsin. This might lead to delaying the arrival of IFR ceilings in eastern TAF sites.

Another likely use of the GOES-R fog and low cloud products would be tracking stratus or fog advecting into Wisconsin off of Lake Michigan. Using an example off the California coast, note that GOES infrared and fog images will give you an idea of where there is cloud cover, but will not give and immediate idea of what type of conditions are moving into the area:

GOES Infrared

GOES IR Fog

While the traditional fog product above does give a clue that you're looking at either fog or stratus...the GOES-R IFR and LIFR products confirm this and also give an indication of how low the ceilings and/or visibilites are:

GOES-R IFR Probability

GOES-R LIFR Probability

It is immediately clear the conditions are at or below IFR for much of the area of fog/stratus...with a pretty good probability of LIFR conditions over a large portion of the area. This is quite useful...as ceiling and visibility observations are very limited over bodies of water. Hopefully the use of this product will help in troublesome situations where poor conditions can sneak onshore... particularly when somewhat obstructed by other cloud decks.

In summary, GOES-R fog and low cloud products can be very useful in tracking areas of fog and stratus. In contrast to using a combination of surface observations and traditional visible/infrared products, the GOES-R products can give a very quick and fairly accurate representation of where IFR or worse conditions are located. Being able to track these areas will hopefully lead to improvements in TAFs.

Denny VanCleve
NWS Milwaukee/Sullivan

GOES-R AWG Fog/Low Cloud Products

Conditions across the middle of the U.S. were ideal for assessing this product. Strong low pressure was forming over the High Plains while high pressure was situated along the Atlantic Coast of the southeast U.S.  Warm air and copious moisture were flowing north up the Mississippi Valley. This morning we focused on the southern coast of Louisiana.  The Louisiana case looked almost completely radiation induced.

When I was introduced to this product during the GOES-R proving ground activities of 2011, I was, to be honest, rather underwhelmed.  Back then, this product used satellite interrogation coupled with boundary layer RH from the GFS.  No observations were included in the assessment and therefore it didn't seem to perform any better than my simply using available satellite imagery and surface obs (and experience.) This year, it appears there has been significant improvement to the inputs of this product.  The boundary layer RH now comes from the Rapid Refresh Model.  Not only is the RH data resolution improved both spatially and temporally, but the Rapid Refresh incorporates the latest surface observations into its output fields.  From the few examples I saw, it is apparent this product will sometimes highlight an area, showing increased probabilities of IFR/LIFR, before these conditions appear in the observations.  This appears to be the strength of using the high resolution Rapid Refresh output.

Anyway, here is the example down along the southern coast of Louisana:

The forecaster working on the 06z TAFs would have used the GFS and NAM MOS (MET/MAV) as part of the decision aid on ceiling and visibility.  In this example, we'll look at the observation in far southeast TX, MTRJAS. See location in image below:

 Here are the METJAS and the MAVJAS products respectively at 00z Oct 23rd, 2012:

 _________________________________________________________________________________

Note the ceiling prediction shows VFR conditions dropping to MVFR from 06z-12z Oct 23rd.  No real hint of IFR, though the temp/dewpoint spread does get pretty tight in the morning.

Below are a series of 4-panel images running from 04:02Z-09:15Z Oct 23, 2012 showing a combination of GOES-R and heritage products.  See caption on first image for details. Note the GOES-R IFR probability is beginning to highlight far southeast TX with increasing probabilities of IFR at 04:02Z. MTRJAS at this point is indicating clear skies and 10 mile visibility.


GOES-R IFR Probability upper left, LIFR probability upper right, heritage brightness temperature difference product lower left, visibible image lower right

 The following image is an hour later at 05:02Z:  MTRJAS is still clear and 10 miles, but note the increasing probabilities of IFR.

At 06:15Z:  MTRJAS is now indicating Clear and 5 miles in fog...probabilities continue to show a trend toward IFR

At 07:15Z:  MTRJAS is Clear and 7 miles visibility.

At 08:15z:  MTRJAS has now gone down to a 200ft broken ceiling and 7 miles visibility. 

And finally at 09:15Z: MTRJAS dropped to as low as 200ft overcast and 2 miles, before seeing improving conditions after about 09:30Z.

In summary, it is clear that, in this case, the GOES-R IFR probability products can give the forecaster an early heads-up that conditions are on their way down to IFR conditions, despite the traditional MOS products from the GFS and the NAM indicating no IFR conditions for that METAR site. 

Steve Davis
CIMSS-MKX

Cloud Top Cooling Skillful before Severe Storms

Today's severe thunderstorm warnings were preceded by cloud top cooling rates of around 30 degrees Celsuius per 15 minutes -- around 30 minutes before warnings were actually issued!

Here is the time series of cells that developed over Winona County, Minnesota.  They produced golf-ball size hail.  The panels, from upper left to upper right and lower left to lower right, are:  cloud top cooling with visible satellite image background, convective initiation categorical classification with visible satellite image background, IR window satellite image, and radar base reflecitivity.

2002 UTC 4 September 2012

2015 UTC 4 September 2012

2032 UTC 4 September 2012

Here is the time series of cells that developed over Barron County, Wisconsin.  There were several reports of large hail over an inch in diameter.

2015 UTC 4 September 2012

2032 UTC 4 September 2012

2045 UTC 4 September 2012



It was exciting to see the performance of this algorithm in real-time.

J.J. Wood, General Forecaster, Milwaukee/Sullivan WFO

Jordan Gerth, Meteorologist, CIMSS/SSEC Madison, WI

Aug 9, 2012 CTC & Radar Comparison

Given active weather pattern (deepening upper level trough over Great Lakes) with showers and storms over Wisconsin, it wasn't hard to find quick growing cells with at least moderate Cloud Top Cooling (CTC) rates.

There were some breaks in the cloud field over northwestern Wisconsin.  Perhaps this helped oen cell in a line to pulse up.  We were able to spot CTC rates in the moderate range with a value of 17 to 18 over northwestern Washburn County.  Further north in St. Louis County of northeastern Minnesota we observed a CTC value of 12 to 13. See Figure 1 below.

Figure 1. Maximum CTC rates of 17 to 18 over Washburn County.

 We then compared the cells with decent CTC rates with what the WSR-88D Radars depicted.  SEe Figure 2 below for the radar image which corresponds to Figure 1.

Figure 2. Radar image at 1643Z August 9, 2012.

The decent CTC rates would imply an increase in cell intensity observed on radar.  This intensity increase is noted in Figure 3 below, especially in the St. Louis cell which had a 60 dBZ signature.  Of course, these storms were not severe, but it was nice to see that the CTC rate idea enabled us to anticipate an increase in cell intensity.

Figure 3. Radar image at 1706z August 9, 2012.

Rusty Kapela - MKX
Ed Townsend - MKX
Justin Sieglaff - CIMSS