As of 1834z (not shown) the updrafts on the SW flank of the line continue to become dominant, and ProbSevere has increased to 76%.
Tuesday, June 4, 2019
All Sky LAP CAPE and convective trends
Thunderstorms continued to strengthen in the MPX CWA after 18z. The All Sky LAP CAPE indicated instability building over Kandiyohi County as of 1728z (note some latency). There is a line segement of tstms moving into this area, and a SVR has been issued as of 1821z for the SW part of the line as it moves into the region of higher instability. Note, this development likely triggered along outflow from an earlier complex. The SVR polygon was edged to the SW closer to the higher instability.
As of 1834z (not shown) the updrafts on the SW flank of the line continue to become dominant, and ProbSevere has increased to 76%.
As of 1834z (not shown) the updrafts on the SW flank of the line continue to become dominant, and ProbSevere has increased to 76%.
AllSky TPW better feel for moisture in atmosphere
Noticed the AllSky TPW had a seemingly better handle on moisture over western MPX area than the more blotchy Merged TPW. Looking at other instability parameters, the TT were in the mid 50s over western MPX, lifted index, K index upper 30s, CAPE mid 2000s. Eastern storm following the gradient of the CAPE to the southeast. AllSky has shown the CAPE increasing rapidly ahead of our storms.
Severe Threat over Minnesota This Afternoon
Ongoing complex of thunderstorms pushing into south central MN this hour. Have a new set of thunderstorms forming in what AllSky is showing as a higher CAPE environment along the outflow pushing out from this complex. ProbSevere has picked up on this cell as well (near Milan)...showing a Hail chance of 55% now and growing quickly. Will monitor the downstream growth of both systems.
Today's Experimental Operations - Tuesday, June 4, 2019
Today's operations will be begin with their focus over the Twin Cities/Chanhassen (MPX) county warning area. Severe storms have already developed and are approaching the Twin Cities area from the northwest. The Storm Prediction Center current has a mesoscale discussion out for the area highlighting potential watch issuance within the next few hours with the main threat being damaging winds but large hail is also possible.
Other potential regions of operation include the low-country region of South Carolina, where there is currently a severe thunderstorm watch, and extreme west Texas into southern New Mexico. We'll monitor the weather situations in these locations and adjust our operations area as needed.
Other potential regions of operation include the low-country region of South Carolina, where there is currently a severe thunderstorm watch, and extreme west Texas into southern New Mexico. We'll monitor the weather situations in these locations and adjust our operations area as needed.
Tuesday, May 28, 2019
Wild weather weekend
Severe weather abounded this Memorial Day weekend, punctuated by a strong tornado in Dayton, Ohio. Tornadoes were observed in 13 states over the three days, from Idaho to Pennsylvania and from Texas to Minnesota. The Dayton storm emerged on the south end of a cluster of severe storms entering Ohio from Indiana (Figure 1), with nothing in its way from ingesting air parcels in an excellent environment (~1800 J/kg MLCAPE, ~55 kts eff. bulk shear, ~300 J/kg 0-1km SRH, ~40 kts 1-3km mean wind). This storm rapidly increased in ProbTor and produced its first tornado at 02:35 UTC, right after ProbTor exceeded 85%. The storm exceeded 90% ProbTor for almost an hour (see Figure 2), during which time the Dayton area suffered extensive damage. A tornado emergency was also issued for Dayton by the NWS at around 03:00 UTC. See the archived time series of ProbSevere products and predictors here and here (the storm merged with a storm to its north, prompting a change in ID).
A handy feature on the ProbSevere webpage is the "ProbSevere Accumulation" tab, which allows users to get a quick-look at the severe weather for a day and check out ProbSevere's performance. Once clicking the tab at the top, users can set the date using the UI on the left. Each day is considered a "convective day", starting at 12Z and going to 12Z the next day. For example, 2019-05-26 12:00 UTC is the start time and includes reports, NWS warnings, and ProbSevere objects from that time until 2019-05-27 11:59 UTC.
You can see the extent of the storms for the convective days 05-25, 05-26, and 05-27 in Figures 3 through 5. The green, blue, and red circles are preliminary LSRs for large hail, severe wind, and tornadoes, respectively. The orange and red polygons are NWS severe thunderstorm and tornado warnings, respectively. The white and pink boxes are centroids for ProbSevere objects at each valid time (every 2 min), colored by the probability of any severe value. In this way, a user or researcher can quickly see which areas ProbSevere 'hit' on, 'missed' on, or had 'false alarms' at the 50% threshold.
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| Fig. 1: A cluster of storms with ProbSevere objects, MRMS MergedReflectivity, and NWS severe weather warnings. The Dayton storm is highlighted. |
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| Fig. 2: Time series of the ProbSevere products in relation to severe LSRs and NWS severe weather warnings. |
A handy feature on the ProbSevere webpage is the "ProbSevere Accumulation" tab, which allows users to get a quick-look at the severe weather for a day and check out ProbSevere's performance. Once clicking the tab at the top, users can set the date using the UI on the left. Each day is considered a "convective day", starting at 12Z and going to 12Z the next day. For example, 2019-05-26 12:00 UTC is the start time and includes reports, NWS warnings, and ProbSevere objects from that time until 2019-05-27 11:59 UTC.
You can see the extent of the storms for the convective days 05-25, 05-26, and 05-27 in Figures 3 through 5. The green, blue, and red circles are preliminary LSRs for large hail, severe wind, and tornadoes, respectively. The orange and red polygons are NWS severe thunderstorm and tornado warnings, respectively. The white and pink boxes are centroids for ProbSevere objects at each valid time (every 2 min), colored by the probability of any severe value. In this way, a user or researcher can quickly see which areas ProbSevere 'hit' on, 'missed' on, or had 'false alarms' at the 50% threshold.
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| Fig. 3: An accumulation of severe LSRs (circles), NWS warnings (orange and red polygons), and ProbSevere centroids, colored by their probability of any severe value (boxes) for 05-25. |
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| Fig. 4: An accumulation of severe LSRs (circles), NWS warnings (orange and red polygons), and ProbSevere centroids, colored by their probability of any severe value (boxes) for 05-26. |
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| Fig. 5: An accumulation of severe LSRs (circles), NWS warnings (orange and red polygons), and ProbSevere centroids, colored by their probability of any severe value (boxes) for 05-27. |
April and May have seen above average tornado activity nationwide, with the U.S. inflation adjusted number of tornadoes at 794 through yesterday, at about the 90th percentile for this time of year (Figure 6).  |
| Figure 6: U.S. inflation adjusted cumulative annual distribution of tornadoes. |
Thursday, May 23, 2019
NUCAPS Procedures Usefulness
The NUCAPS Quick Guide from JPSS includes a few procedures. Here I show the utility of a few of those procedures for combining GOES Satellite data and NUCAPS data.
This procedure plots 400-200mb relative humidity and GOES-16 water vapor. You can see the representation of the dry air across the northern US and the systems in the Plains & southeast.
Another procedure compares GFS, HRRR, and NAM lapse rates with the NUCAPS lapse rate info. This is a good check to see if model lapse rates are performing well or where they need to be taken with a grain of salt.
Another procedure plots 850-300mb RH and low-level water vapor. The product shows the system in the Plains and the system in the Ohio Valley. Drying is also obvious in the southern Great Lake and North Dakota.
I like the procedures provided in the JPSS Quick Guide. I am starting to understand the applicability of the NUCAPS data little bit more. These procedures are helpful in contextualizing the provided data fields.
-Atlanta Braves
This procedure plots 400-200mb relative humidity and GOES-16 water vapor. You can see the representation of the dry air across the northern US and the systems in the Plains & southeast.
Another procedure compares GFS, HRRR, and NAM lapse rates with the NUCAPS lapse rate info. This is a good check to see if model lapse rates are performing well or where they need to be taken with a grain of salt.
Another procedure plots 850-300mb RH and low-level water vapor. The product shows the system in the Plains and the system in the Ohio Valley. Drying is also obvious in the southern Great Lake and North Dakota.
I like the procedures provided in the JPSS Quick Guide. I am starting to understand the applicability of the NUCAPS data little bit more. These procedures are helpful in contextualizing the provided data fields.
-Atlanta Braves
Decrease in GLM lightning activity coincident with 2 inch hail report
A storm just northeast of Amarillo developed quickly along a frontal boundary, and quickly showed supercellular characteristics with mid level rotation and a 65+ dbz core reaching about 35 kft MSL. 2 inch hail was reported with this storm during this time. GLM data again shows a decrease in both Flash Extent Density (top right) and Event Density (top left) show a notable decrease in GLM lightning activity while ground based radar remains fairly unchanged, and both the IR satellite presentation (bottom right overlaid on visible imagery) and radar data (not shown) indicate the storm maintained intensity and if anything, had strengthened a bit.
-64BoggsLites
-64BoggsLites
Comparing NUCAPS Modified Soundings and 18Z RAOBs
A satellite pass at around 19Z allowed us to compare NUCAPS modified soundings with 18Z RAOBs. A comparison of a NUCAPS sounding near Amarillo seemed to reasonably represent the mid and upper levels with the 18Z KAMA RAOB. The NUCAPS sounding had slightly lower freezing level and -20C and -30C heights compared with the RAOB (10.9, 19.0, and 23.2 kft vs 12.2, 20.8, and 25.4 kft, respectively). The midlevel lapse rates were comparable at around 8.0 C/km. However, the NUCAPS sounding appeared to struggle with the lower levels, not representing the subsidence inversion evident on the RAOB, and being too cool and dry at the surface (T/Td of 20/17C on the NUCAPS compared with 24/19C on the RAOB). This led to lower CAPE estimates from the NUCAPS than were observed by the RAOB.
Similar results were seen in a comparison of the 18z KLMN RAOB with a NUCAPS Modified sounding near Lamont, OK:
Ron Dayne
Similar results were seen in a comparison of the 18z KLMN RAOB with a NUCAPS Modified sounding near Lamont, OK:
Ron Dayne
AllSky as a good proxy for dryline location and CI
The AllSky Layer Precipitable Water product showed utility in identifying and tracking the dryline as it moved into the Lubbock CWA. The dryline entered the CWA at about 1930 UTC.
Coincidentally, the KLBB radar shows convection initiation around 19:30 UTC as well.
And the convection continues to develop:
The AllSky product remains a very useful tool for situational awareness and 2-D environmental familiarization.
-Atlanta Braves
Coincidentally, the KLBB radar shows convection initiation around 19:30 UTC as well.
And the convection continues to develop:
The AllSky product remains a very useful tool for situational awareness and 2-D environmental familiarization.
-Atlanta Braves
Comparing the modified and unmodified NUCAPS sounding from Western Oklahoma on May 23
While waiting for any convection to develop in PA, I ventured into western Oklahoma to do a comparison of unmodified and modified NUCAPS soundings in an area under an enhacned risk of severe weather. The soundings examined were near the Texas border (point E below).
We'll first look at the visible satellite and observations at 19Z.
Notice that point E is near a WSW/ENE oriented boundary. Obs near the point show temperatures in the mid 70s, with dew points in the mid 60s. So let's take a look at the unmodified NUCAPS sounding first.
It uses a surface temperature of 63F, and a surface dew point of 50F, both more than 10 degrees below the nearby observations. These inaccurately low values give, as one would expect, no sign of instability (CAPE=0). Looking at the modified NUCAPS gives a different picture, however.
In the modified sounding, the surface temp is 69, and the dew point is 65, which is much closer to the observed surface obs. This changes your surface-based CAPE to 2055 J/kg, vs. 0 from the unmodified. It also has a sharper low level inversion, which one wood expect based on the stratus deck in place.
To "verify", let's look at the SPC mesoanalysis.
Sure enough, the mesoanalysis shows CAPE at around 2000 J/kg. Clearly, this is another case where the modified NUCAPS sounding is a noticeable improvement over the unmodified sounding.
Thorcaster
We'll first look at the visible satellite and observations at 19Z.
Notice that point E is near a WSW/ENE oriented boundary. Obs near the point show temperatures in the mid 70s, with dew points in the mid 60s. So let's take a look at the unmodified NUCAPS sounding first.
It uses a surface temperature of 63F, and a surface dew point of 50F, both more than 10 degrees below the nearby observations. These inaccurately low values give, as one would expect, no sign of instability (CAPE=0). Looking at the modified NUCAPS gives a different picture, however.
In the modified sounding, the surface temp is 69, and the dew point is 65, which is much closer to the observed surface obs. This changes your surface-based CAPE to 2055 J/kg, vs. 0 from the unmodified. It also has a sharper low level inversion, which one wood expect based on the stratus deck in place.
To "verify", let's look at the SPC mesoanalysis.
Sure enough, the mesoanalysis shows CAPE at around 2000 J/kg. Clearly, this is another case where the modified NUCAPS sounding is a noticeable improvement over the unmodified sounding.
Thorcaster
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