Preconvective Environment in Wichita

Below you can see VIS imagery of the Wichita CWA (in yellow).  The dry line is clearly seen to the west.

If you look at GOES-East derived CAPE (below), it's missing data over most of KS.  This is to be expected due to the clouds over the central and eastern portion of the state.  But why is the seemingly clear sky western portion of the state missing data?

Looking at the Cirrus band, you see thin high clouds blocking the western portion of the state retrievals.

This missing area is filled in with the AllSkyLAP layer CAPE.

It matches up fairly well with the SPC Mesoscale Analysis MLCAPEs.  The AllSkyLap layer CAPE is only a little underdone.

-Kevin

Derived CAPE shot

Look at Prob. Severe image and those storms moving into initial area of increased CAPE within hour or so.  Moisture continues to surge north into that area of the eastern NE panhandle.

Low level moisture ahead of the cold front will continue to pull dew points in the mid to upper 50s into the Dakotas through late this evening. An upper level short wave axis moving across MO/WY will move to the east and increase chances for severe weather development within the next few hours and continuing late evening. Large hail likely to be the main severe weather threat at first and then large and damaging win gust as the evening approaches.

Derived Sat Products

Tracking the return of moisture with surface dew points and using the derived TPW image. Some masked data with TPW but enough upstream to see the progression of higher PW airmass.

Original NUCAPS vs Experimental NUCAPS in Dodge City, KS Area

A NUCAPS pass over the Dodge City, KS area occurred around 18 UTC on June 22, 2017. Here is a sounding from this region.

The experimental NUCAPS came into AWIPS about 30 minutes after the original data. Here is the sounding from the same location.

The original profile had limited CAPE, around 500 J/KG.  The experimental profile had much more when the surface observations were included. The CAPE value was around 3,300 J/KG. This value was much more comparable to what was seen on the SPC mesoanalysis in the Dodge City region.

One other quick note: The Baseline Derived CAPE at the same time as the NUCAPS pass was also much lower than the CAPE derived from the experimental sounding.

It appears the reason why the original NUCAPS sounding was more stable was because the surface dew point was in the mid 50s where as actual obs and the experimental sounding had dew points in the mid 60s.

Lastly, I noted there was a gap in the experimental data points with this pass, that was not seen in the original NUCAPS.

Experimental 

Original

-Ironman

BOU: Meso-Analysis: GOES-Derived Stability

Main Points:

• GOES-16 derived CAPE shows data gaps across most of the CWA, but does reveal modest instability across NE CWA. Filling this gap would be ideal.
• Simple WV RGB:
• May be useful for identifying moistening mid-level, less steep lapse rates, and perhaps slightly less convective outflow threat. 
• SW and SE corners of CWA show dry mid-levels so will watch these areas for faster convective growth (dry-adiabatic lapse rate) and better convective outflow and hail threat. 
• Update: Cell propagating into the SE CWA did show intensification as it entered the potential steeper lapse rate region.

A quick analysis of the 12z KDNR sounding reveals a relatively dry yet sufficient amount of column moisture (0.56") and steep mid-level lapse rates(8.5C/km).  Convection has initiated but cloud see some dry air inhibition.

 

GOES-16 derived CAPE and LI fields show a substantial data gap across the BOU CWA (another example of have a synthetic blend might be useful).  The areas across the NE CWA do show areas of 300-600 j/kg.

There is evidence on using the RGB: Simple Water Vapor that there is an increasing presence of mid to upper level moisture particularly around the convection in the central CWA. This moistening aloft may push upper lapse rates towards the moist adiabatic rate which could reduce instability aloft and slightly reduce wind outflow threat versus the convection across the southwestern CWA.

The convective cell approaching the SW CWA (pink) appears to be entering a region of dry mid/upper levels so will be monitoring this area along with the SE corner for higher convective outflow potential.     Forecaster: Tahoe

Assessing Why Convective Clouds are Struggling to Grow Deeper Across Eastern Mississippi

There are several broken bands of heavy showers and embedded thunderstorms moving NNE across Mississippi in association with Tropical Depression Cindy.  East of the KDGX radar across eastern Mississippi, a few showers have developed, but are weak and seem to be struggling.

Here is an animation of 1-minute 0.64 um data across the Gulf Coast region. The deeper convective clouds can be clearly seen across the western and eastern part of the imagery, with a narrow corridor of more shallow cumulus.  There are even a few locations where there are no clouds.

When placing the baseline derived total precipitable water on top of the 0.64 um imagery, you can see there is a relative minimum (values around 1.6 inches). Values to the west and east of this drier corridor were on average around 2.2 inches.

Looking at the airmass RGB within this narrow corridor, there appears to be some upper level moisture with the deeper convection ongoing to the west and east.

Some of this upper level moisture can also be seen on the 6.19um.

However, very dry air is observed in the middle levels on the 7.34 um channel noted by the deep orange colors.
 

There was a NUCAPS pass at 1836 UTC. The cursor on the image is the location of the sounding below.

This sounding confirms how dry the middle and upper levels are in this region, which is very likely chocking off convective development. 

I also looked at a sounding in the location shown below by the cursor in this screen capture. 

 

 

This sounding revealed more moisture below 500 mb, which supports why there is deeper convection to the west. 

In summary, I was able to use an assortment of 1-minute GOES-16 data, the airmass RGB, baseline derived total precipitable water, and NUCAPS sounding data to assess why the cumulus field was struggling to develop into deeper convection. This was an area of interest because of more significant heating in a region with high levels of low level shear. 

-Ironman

Colorado Convection Moving Toward More Favorable Environment

Using the GOES-16 derived CAPE and precipitable water, it can be determined that convection developing off the higher terrain is moving toward a more favorable environment.

Note: On the images below, visible satellite overlaid on the derived products. This allows the "blacked out" areas to be filled with information. 

Preciptable water values are increasing to nearly an inch across northeast Colorado, which is favorable for convection in higher terrain. The convection is moving toward higher CAPE as well.

-Lost Met

Baseline Derived Products within Tropical Cyclone

Due to extensive cloud cover, the baseline derived products did not have much information over the JAN CWA. However, we could still sample some of the pixels that were available to get a quick idea of instability and moisture.

CAPE values are very low with Lifted Index values -1 to -2. Highest TPW values range from around 2.1 to 2.2 inches across western portions of JAN with drier TPW further east with 1.6 to 1.7 inches.

There were no MetOps or NUCAPs passes at the time of this analysis. 

-Ironman

GID: Axis of instability analysis from SPC Analysis vs GOES-16 derived and LAP.

Convection has been struggling with development this afternoon but has shown signs of improvement as the cells track eastward toward the CAPE gradient. SPC's meso-analysis depicted that these cells were approaching a tighter gradient in instability which would make sense given the increase in activity.

 ML CAPE from SPC Mesoanalysis

GOES 16 derived CAPE had a gap in data in the critical area where the gradient is expected to exist. (Having an option to fill in data was valuable here). As such, added in the LAP to see if this gradient jived with the mesoanalysis. They in fact did, so as a result confidence is increased that convection should intensify through the evening as these cell move east. Forecaster: Tahoe

GOES 16 derived CAPE and LAP CAPE

Derived CAPE & IR10.3 during warnings

Derived CAPE:
In our per-analysis there was a nose of stronger CAPE moving NE through E Nebraska, W Iowa towards the southern part of our CWA (Grand Forks).

During our warnings, around 2342Z, our southernmost cell was the strongest.  We went back to Derived CAPE and observed that nose of higher CAPE was finally intruding into our southern sections, and hence starting to affect that storm.

IR 10.25:
Simultaneously, IR 10.35 was showing that storm was the one with the coldest top.

IR 0.64:
Showed the updraft very well.

Davis Nolan
WKRN Meteorologist

GID: Environmental Analysis (NUCAPS (non-experimental) and GOES-16 Derived CAPE)

NUCAPS and GOES-16 Derived Stability Comparison.

• Notable CAPE gradient across GID with CAPE values below 300-400 j/kg across the far western CWA. 
• 19z NUCAPs soundings revealed MLCAPE higher and around 1700 j/kg along the far western gradient when modified to sfc obs. Using the modified NUCAPS sounding was beneficial in that it looked like mid-level cap would be able to be overcome with continued daytime heating which would allow for deep convective activity.
• 1st cells developing in this area but haven't shown deep growth as of yet. As of 0030z the cells have been slow moving and are just starting to approach the CAPE gradient. Cell have been noticeably been starting to trend stronger and 2 severe thunderstorm warnings have been issued in western CWA.

-Tahoe. 

Convection Approaching Higher Instability

By overlaying visible satellite with derived CAPE, it's obvious that the convection is approaching higher instability across central and eastern Nebraska:

There, we would expect thunderstorms to intensify as they shift east into higher instability.

-Lost Met

GOES-16 TPW Comparsion

GOES-16 TPW has done a good job capturing the general trends of preciptable water.  Here is a comparison of GOES-16 TPW and SPC Mesoanalysis:

Both should very moist values in association with tropical storm Cindy (>=2.2") and then a dry corridor across central Texas into southern Oklahoma.

-Lost Met

Pre storm analysis with Derived Products and METOPS sounding

The Grand Forks CWA was recovering from a previous line of showers.  The sun was returning and heating the environment.

Temps were recovering into the mid 80s with DPs in the low to mid 60sby 20z.
Metars showed a wind shift line SW/NW right on the border of our CWA.

Derived Cape at 1902z ran from 450-500 in our northwest counties to 175-200 in the southwest. There was a gradient that lined up with the wind shift line (west of wind shift line dropped  to zero).  Animation showed the gradient moving with the wind shift.

Derived TPW ran in the 1.2-1.3" range on the average.  Animation showed a gradient moving from west to east with the highest values along the wind shift, dropping to 0.6" behind  the wind shift. 

Conclusions of Derived Cape and TPW:

It was fascinating to see the satellite derived CAPE and TPW oriented to the wind shift line as it moved from west to east (whether the numbers are exact or not, the relative orientation was there).  We expect initiation along that line.

We also picked a METOPS-A sounding in the far southwest part of the CWA where instability looked the highest.

The original METOPS-A sounding was from 1647z, and we were now at 20z.  CAPE was zero, not very unstable.
The original is below:

Modifying it to 20z ob T=84F and C=63 we got SB CAPE 1443.  I used the method I learned yesterday of following mixing ratio to modify DP up from surface.  Also modified T a little bit above the surface to look more like reality.
Edited METOPS-A Sounding below:

Conclusion of METOPS-A:

Modifying the sounding was necessary since 2 hours had elapsed from 1706-1902 and heat and moisture had jumped considerably.

Davis Nolan
WKRN Meteorologist

Our environment is not overly unstable.

Pre-Storm Analysis Across FGF Area

During pre-storm analysis over the FGF CWA, I looked at baseline derived products from GOES-16 in a 4 panel as shown below, which included the moisture difference product. 

There is a tongue of slightly higher CAPE values, approximately 500 J/KG, entering the western portion of the CWA. This coincides with a tongue of higher TPW, around 1.2 inches and better LI values (-3 to -5). The better moisture can also be seen in the moisture difference panel on the better right.

I also looked at a 4-panel water vapor procedure, which included the upper, mid, low, and simple water vapor RGB. This was mainly to get a feel for the larger scale moisture and flow pattern. Once some instruction on the RGB was given, I found it useful in assessing where the moisture contributions were coming from.

A look at radar data from both KMVX and KMBX reveals a fine line or surface boundary approaching the FGF CWA from the west. This line is the leading edge of the drier air, which means the focus for convection is generally going to be along and east of this boundary. The CAPE and TPW gradients were generally along and east of this line as well above in the derived products.

I also looked at a modified MetOps sounding in the western part of the CWA. The modified sounding had CAPE values around 700 J/kg.  Before modifying the sounding, there was little to no CAPE. These values were generally consistent with the baseline derived, although slightly higher.

-Ironman

GOES-16 TPW Near Cindy

On 21 June, Tropical Storm Cindy approached the Louisiana Gulf Coast. The main threat with this system was heavy rain and flooding. The GOES-16 TPW baseline product provides forecasters with rapidly updating information about how much moisture is available in the atmosphere. Widespread TPW over 2.0" was sampled in the vicinity of Cindy, with some localized areas over 2.5" (Fig 1). These observations agree with nearby radiosonde data (LIX), which measured 2.36" of PW  (Fig 2).

Figure 1: 21 June 2017 GOES-16 TPW (color) and IR (gray).

Figure 2: 21 June 2017 LIX 12z radiosonde.

- Bill Line, NWS