Lubbock, TX Mesoanalysis

Operating in the Lubbock, TX CWA to start today. At 2100 UTC, GOES-16 upper-level water vapor imagery (Fig 1) indicates a weak shortwave lifting to the northeast across SE Colorado/N Texas this afternoon, rounding the base of a broader upper trough over the western US. For viewing synoptic scale trends in water vapor imagery, I prefer to load the full disk imagery with CONUS imagery as an overlay. Time match to the full disk imagery allows for 15-min imagery which, for me, is ideal for longer term water vapor analysis. Meanwhile, loading the CONUS imagery allows for the full resolution (2km) to be displayed over the CONUS (full disk imagery has reduced resolution).

Figure 1

A GOES-16 1-min mesoscale sector was available over the forecast area today. In 0.64 um visible imagery (Fig 2), high to mid cirrus clouds mask much of the scene. A cu field has established itself across much of the southeast half of the state, on the eastern half of a dry line.

Figure 2

With the cloud cover in place, the LAP thermodynamic fields were missing significant data. The all sky products are useful in  filling in the cloud-induced gaps in data. The cloud type all sky product tells us whether a given pixel is derived from the GFS, cloudy sky retrieval algorithm, or clear-sky retrieval algorithm, allowing for comparison between the different algorithms and GFS first guess. Comparing adjacent pixels of different types for CAPE, the cloudy and clear sky pixels have lower values (~1800 j/kg) than the GFS first guess (~2400 j/kg). Comparing both with HRRR model runs and the SPC mesoanlysis, the lower values in the satellite retrievals seem to be more on par than does the GFS first guess. This leads one to believe the satellite is providing a correct adjustment to the model first guess. The LAP data indicates a max in instability through the center of the CWA along the dry line, decreasing east. LI values were also slightly lower in the retrievals compared to the GFS first guess, while TPW values were similar.

Figure 3: cw from top left: CAPE, LI, Retrieval Type, TPW. Sampling for clear sky pixel

 

Figure 4: cw from top left: CAPE, LI, Retrieval Type, TPW. Sampling for cloudy sky pixel

 
As for trends, the half-hourly all-sky LAP data indicates CAPE increasing steadily from around 1000 j/kg at 1728 UTC to around 1800 j/kg at 2028 UTC. A half-hour temporal resolution is adequate for analyzing trends in thermodynamic fields.

- Bucky

Forecast Update - Bismarck CWA

Currently watching developing cumulus field behind first area of convection along and east-west oriented stationary front near Montana/South Dakota border.

Daytime microphysics RGB indicating glaciation taking place in this area and with GOES-16 derived Lifted Indexes suggesting this area most unstable would expect storm growth to continue. Intensity of storms further east in line with previous stability analysis as storms appear to be moving into less favorable environment.

A fairly rapid glaciation  of the storm was noted between 1927 UTC and 1957 UTC.

 -JRM

Bismark CWA - Derived Stability/Moisture Data Analysis

Quick look at some of the derived parameters sat 1857 UTC prior to expected storm initiation today.  Following image has the following parameters from upper left to lower right : Total Precipitable Water, CAPE, K-Index, Lifted Index.

TPW fields indicate some moisture pooling to the west of ongoing convection, with a similar trend in the instability fields. Drier, more stable air in place upstream of developing storms. Unsure if this just indicates where current forcing/ascent is and this will translate eastward or if current storms moving into less favorable environment.

CAPE values continue to be significantly lower than numerical model analysis, but LI values much closer and seem reasonable given the pattern.

-JRM

South Dakota

-tvguy

Looking at atmosphere in wake of ongoing MCS which is moving to the east, trying to use tools to determine whether atmosphere will recover in time for a second round of severe weather later today.

SBCAPE from the sectors reporting in south central South Dakota ranges from 500-1000 j/kg along the Nebraska border, to 1000-1500 north of I-90 at 1830Z. A moment ago, a couple of bins in excess of 2000 j/kg emerged along the Missouri River north of Pierre.

On the downside of recovery, heights are slightly rising in south central SD. At 1913Z, the area of 2000 j/kg was reduced under 1500, presumably because a broken cloud shield went through that area. Don't think there was much else going on that would have caused the SBCAPE to diminish.

NUCAPS grids arrived about 1945Z, and we were able to determine what kind of cap existed. We knew there was warm air, but we did not know how warm. We have been seeing a slight increase in towering Cu, but our hopes and dreams were dashed after seeing NUCAPS grids, which reported temps >13C at 700 mb behind the anvil shield of the departing MCS. Not sure what the convective temperature is, but it must be really high.

But when NUCAPS sounding came in it told a scary story, producing SBCAPES >5000 in south central SD. I did a cross section of temperatures in NUCAPS grid. Drew a line A across a thin line of towering Cu. In the middle of the cross section, I could see a thermal boundary right were the line of Cu had developed. (I was unable to use the drawing tool, but the gradient is seen a the bottom of the screen about halfway between the bottom left and bottom right edge of the image.

Convection quickly popped up along that boundary, and so did ProbSevere product, with 80% ProbHail. The object appeared immediately next to the SFD METAR plot, which was 103/65. Immediately to the SW, the measurement at VTN (Valentine, NE) was 109/52.

Thunderstorms grew quickly along that boundary over Winner, SD...

and the strongest core almost certainly produced large hail. Seemingly the only forcing was because of the subtle boundary we had observed earlier. ProbHail was 99%.

Isolated thunderstorm was amazingly resilient, and continued to produce significant lightning as detected on GLM. Since storm now crossing border into Gregory Co (my FSD CWA) I chose to issue a warning for the hail/wind threat. Am concerned about hail size being suppressed by very hot environmental temps, but any melting would also contribute to the wind threat.

ProbSevere developed a second object south of NE border which moved north. It treated the two cells as two different objects. Figured they would be a line, and previous warning expired, grouped them together and formed SVR for the line in Gregory Co.

About 15 minutes later, the dominant part of the storm (highest reflectivities, overshooting top) dropped south across the border into Nebraska. Left the warning expire on schedule.

But as the strongest cell moved down into Nebraska, a trailing cell strengthened, with reflectivities and ProbSevere both increasing. Had to issue a new warning for the cell which followed the Missouri River toward the Nebraska border.

We were watching that part of the storm on satellite, but our viewing appeared to hampered by anvil of the Nebraska storm, which covered up our few of the new updraft. That is unfortunate, because this area is nearly in a NEXRAD void, with beam heights very high from all three of surrounding 88-D's.

Had an interesting event pop up a short time later, as the cluster of thunderstorms was in Nebraska. We saw flashes show up well downstream from the storms, at the edge of the anvil in Yankton, South Dakota. The lightning is not in a place we would have expected, but GLM picked up on it, and then there was also a single NLDN CG (+ charge) just SW of Yankton on the Nebraska side of the border. This, where the FSD NEXRAD was only reporting 20 dbZ. Station plot also reported TR.

Forecast Discussion Flagstaff CWA

Main concern will be severity of convection across bulk of cwa through the afternoon. Shear profiles overall weak as large ridge dominates the area with light easterly flow aloft. While SPC and RAP analysis indicate 1500-2500 J/KG CAPE present, GOES 16 Derived CAPE values much lower, generally a third or less what other analysis provide (See below images)

GOES 16 Total precipitable water was useful in identifying plume of moisture advecting into the southern CWA.

A loop of water vapor imagery indicated a short wave trough drifting east into the area, it showed up most apparently in the simple water vapor RGB :

RAP 1.5 PVU pressure fields supported a PV anomaly/trough in this area as well

JRM

OAX

Just doing a quick analysis of OAX area. Departing MCV leaving the CWA to the east, so looking at how/when atmosphere will recover. Looking at GOES16 stability indices, seeing that much of the CWA lacks data due to clouds associated with convective debris. Looking at advective area to the south, see a huge difference in CAPE along NE-KS border... with GOES giving us 600-700 j/kg, while GFS model give us 200-3000 j/kg, a huge disparity.

NUCAPS soundings arrived over the CWA at 1848Z. Wanted to sample point nearest Beatrice in the far SE corner of Nebraska, since warm moist parcel was advecting from that area, and NUCAPS point was very near the Beatrice surface ob, which was reporting 89/74. NUCAPS sounding underreported skin conditions as 81/65. Manually edited T and Dp to match Beatrice ob, resulting in SBCAPE of 3883. Experimental NUCAPS came in a few minutes later, reporting SBCAPE as 3883 j/kg, probably closer to reality, although the sounding did not look much like the real world.

Mount Holly, NJ CWA - Starting to See Development

Over the last 13 minutes, we are starting to see development in the Mt. Holly CWA.  At 1918Z, there were a few showers but at that time, no lightning present.

1918Z - Little to no lightning in the Mt. Holly CWA

Just a short 13 minutes later (1931Z), two storms have developed in the unstable air mass and are producing a decent number of GLM Flashes.

1931Z - Two storms have intensified in the CWA

Unfortunately, the existing cloud cover has limited the use of the Derived Stability products today.

1917Z - GOES-16 Derived Parameters (UL - CAPE, UR - LI, LL - PWAT, LR - Sandwich)

Looking at the SPC Meso page, there is decent MLCAPE and Effective Bulk Shear over the CWA.

19Z MLCAPE & Effective Bulk Shear

-GOB

GOES-16 Precipitable Water

Looking at PWAT trends across the central United States. As GOB said yesterday, the Full Disk may be a better way to view trends of the derived products over longer time frames, several hours vs minutes, given the 15 minute updates. The PWAT values are well represented on GOES-16 when investigating areas outside of cloud development for convective initiation. Compared to the RAP, HRRR, and SPC Mesoanalysis page (influenced by the RAP), GOES-16 does very well and likely very representative. From the GOES Experts, this is likely due to the multiple water vapor channels.

Clockwise: GOES-16 Red Visible & PWAT, Low Level Water Vapor, HRRR PWAT, RAP PWAT.

SPC Mesoanalysis PWAT

Dale Doback

Getting Setup in BUF CWA

The group that is in the BUF cwa is starting to look at the environment for convection in the region. After a couple days of being to use the GOES Derived Stability data, the clouds over the region are inhibiting being able to use it for the BUF cwa.

1857Z GOES Derived: UL - CAPE, UR - LI, LL - PWAT, LR - Clean IR

In cases like this, I like to underlay the Visible (Red) data to fill in the blank areas.

1857Z GOES Derived: Same as above with Visible underlayed

-GOB

GOES CAPE: Leveraging Full Disk Data for Trends

One thing that was helpful in monitoring trends in the GOES Derived Parameters was to switch over to the Full Disk data, which provided 15 minute intervals.  The next two loops use the same 40 frames.

GOES Full Disk CAPE - 15 minute

GOES CONUS CAPE - 5 minute

Note how the reduced temporal resolution helps you visualize the change in the CAPE values through the afternoon.  While you could increase the frames on the CONUS version, you may not have enough to display the trends you would like to see.

Would it be possible to have a 30 min or 1 hour derived stability parameters for monitoring trends?

-GOB

GOES Derived CAPE: Decreasing Instability in Eastern SD

One item of note in the FSD CWA is the recent decrease in the GOES Derived Stability parameters over the eastern part of SD.

GOES Derived Stability is in the Upper Left panel.

This is significantly different than the SPC Meso Analysis page which still has MUCAPE values well above 3-4k J/kg and the CAPE gradient farther to the west.

We have seen the initial development near Huron, SD dissipate, but surface obs still indicate a very moist low levels and starting to see additional development to the southeast of the first cell.

-GOB

CU developing along CAPE gradient

Bubbling Cu field developing along the gradient of higher CAPE in the FSD forecast area. Initiation should be pretty close as CAPE values continue to rise across the area.

-Michael

GOES-16 Agitated Cumulus Developing in northeastern ND

Cumulus development becoming more agitated across northeastern North Dakota. Boundary layer winds are more convergent across the western portion of the Grand Forks CWA, west of Maysville to near Devils Lake. A fine line is visible on KMVX, with some slight backing of surface winds at Cooperstown in response to the eastward push of the surface trough. Looking at the Day Cloud Phase (RGB), the composition of the cumulus is becoming more attributed from the Green and Blue, signifying more vertical development, and more cloud ice.

Dale Doback

GOES Derived Stability in Eastern SD

The GOES Derived Stability parameters are highlighting the gradient along the surface trough/low over central SD.

GOES Derived Products: Upper Left - CAPE, Upper Right: LI, Lower Left - PWAT, Lower Right - GOES-16 Sandwich Product.

Comparing the values to the RAP forecast, the values are much lower, but still show a similar gradient.

19Z RAP run valid at 21Z.

This will be the area of focus for the initial development over the next hour or two.

-GOB

GOES Derived Instability Limitations

Interrogating the warm sector across the South Dakota/Minnesota into southeastern North Dakota. GOES derived instability is ~1000 J/Kg lower than model derived surface based instability. However, the placement and plume of instability is in the proper location. Visible imagery reveals an increasingly agitated cumulus field along the western edge of the strongest surface based CAPE axis. This is also where low level winds are converging ahead of the broader surface trough/850mb trough swinging across the Dakotas. 

Dale Doback