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

Gap in MetOps Pass

See below for a gap in the MetOps pass earlier this morning across the northeast.

-Ironman

Simple Water Vapor and Airmass RGB

Today is the second day that I used the simple water vapor RGB. Normally, I have a 4-panel with the three water vapor bands included. I wanted to see if I can get a quick overview of moisture in the atmosphere. I surveyed the data with sampling on which helped me see the contribution in the Red, Green, and Blue. I think this RGB helps put together all 3 water vapor channels and makes an easier view of this data in one image.

Another suggestion that was given to me was to load the Airmass RGB on top of the Simple Water Vapor RGB. I toggled back and forth between the two RGBs and was able to note that the areas where it appears dry in the Jackson, MS area are actually fairly moist as there are lots of greens in the Airmass RGB. I was also able to see convective development on some of the gradients between dry and moist air.

-Ironman

Using 4 panel TPW to look for mid level dry air over tropical system

4 panel showed that there was drier air that could increase tornado chance in eastern bands of Cindy in Jackson, MS CWA.

However, so far no gate to gate winds in either Base V or SRM.

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

EWP Week 1 Day 4 Operations

Our two pairs of participants have begun operations today in the Jackson, MS and Boulder, CO CWA's. The folks in Jackson are monitoring potential severe weather in association with Cindy, while the Boulder pair is monitoring convection developing off of the high terrain.

EWP Week 1 Day 3 Summary

For Wednesday, participants began operations in the New Orleans, LA and Grand Forks, ND CWA's. The New Orleans group moved to the Hasting's, NE area midway through the shift.

-Bill Line, NWS

• GOES-16 ABI Imagery and products
• Imagery
• Improved temporal and spatial resolution makes monitoring cloud top trends easier than with the old imagery.
• It improved my SA to have two panel VIS/IR next to my warning radar display
• Derived products (CAPE, LI, winds, dsi, tpw)
• In north south dakota, could see cape gradient along wind shift line analyzed in surface obs. Nose of stronger cape coming in from south. Storms developed on the western edge of the max. Got a good sense of the progression of the northward surge of greater instability and pw. As storms tapped into that, they intensified pretty quick
• In hastings, storms were moving slow and stayed week. They didn't quite get to the greatest instability
• I do like loading VIS on top of the cape or pw to fill in data gap holes with useful data
• Derived winds weren't good again. Both speed and direction were way wrong, compared to looking at the movement of clouds and other datasets. GOES-13 winds also looked much more realistic
• Channel differences
• 
  
• RGB composites
• I didn’t really get anything unique out of the RGB’s that I could see in the raw imagery
• I like the water vapor RGB once it was explained. There is a learning curve, but can be utility to get a feel for larger scale processes/features
• GLM
• Immediate things to address with GLM data:
• Allow political boundaries to overlay gridded lightning data.
• Lightning menu’s have so much stuff in them, it is tough to quickly get, or know, what I want to and should load.
• Forecasters need to tell lightning folks what they will use, and what they will never use, in order for change to happen.
• We had a case in north dakota where glm events preceded the first CG by a few minutes
• Need to fix the geolocation of lightning data (parallax). This is very important, especially for dss purposes
• ProbSevere
• Probtor was not very helpful with storms associated with the tropical system. It would be nice if you could have it work in this situation, as these are very difficult cases to identify tor’s. One storm had probs increase, but it was very late
• In the northeast US, we dont have classic supercells, but often get quick spin ups. If probTor could key on these, it'd be very helpful.
• I did see utility in the hail and wind model. It was a little slow with catching up on hail side. Storm ref core to 30k feet, issued warning, then probsevere picked up. When we had multiple cells going, nice to have this on a display for SA as it will pick up on storms I should interrogate closer.
• At a time when probwind was at 90%, very high, we had a strong wind damage report
• On a storm I warned on, after i warned, probsevere increased. This increased my confidence in my warning.
• There are so many products, probsevere puts it all together into one  nice quick view of what's happening.
• Never tipped my warning decision, but more useful when there is a lot going on.
• Percentages seemed a little low with our storms yesterday.
• It's nice to have this second eye to give confidence in my warnings.
• I like to zoom out, get a quick look at what is going on elsewhere in my cwa.
• NUCAPS
• Looking at metop in the morning, we modified, cape was over 1000, seemed on par
• Nucaps pass about 1.5 hours before convection developed. I paid most attention to FL and -20C level. I used these levels for the whole day when looking at radar. You could verify model by doing this, or use this instead of model values. Don't have to modify soundings to get this information.
• One can use nucaps upper level info to verify how model is doing
• With tropical system, we were looking for cape in a few areas that were available. There was a bit of cape to sustain cells, this was good information
• In hastings, I was looking at core of instability, so it was nice to have here. Good confirmation that instability was there
• During 19z pass, you could see signs that a capping inversion was in place, that information was very helpful.
• If you’re concerned a model might not be verifying correctly, in any situation, I like idea of comparing the nucaps profiles to model profiles.
• There would be utility to plotting 2d plan view of critical levels (-20c, 0c)
• I’d use sounding to assess stability, dry or moist areas. Use plan views to look for/asses gradients spatially
• We’d like to get readout from nucaps availability display (cape, critical levels, etc)

Some observations and thoughts on NUCAPS Soundings and the Experimental Soundings...

New to the HWT this year is the addition of Experimental Suomi NPP NUCAPS soundings.  Data accuracy in the boundary layer of the NUCAPS soundings is generally lower than that in the mid and upper levels of the troposphere, since these are satellite-derived retrievals.  The Experimental version of the NUCAPS soundings is supposed to represent an improvement in these lower level conditions.  In the past, forecasters have typically modified the lower portions of the soundings manually by using a simple temperature and dew point adjustment based on nearby surface observations.  The Experimental data, however, automatically makes this adjustment for forecasters, by using a mixed layer growth model with Real-time Mesoscale Analysis (RTMA) data for surface winds and temperatures and GOES-16 data for skin temperatures (thanks for the explanation Jack Dostalek!).  Not only is this method more efficient for forecasters, but it represents a more robust method for sounding modification based on an increased number of observations.  Below are a couple of soundings from this afternoon in western Kansas, near the town of Syracuse.  The first sounding represents the regular NUCAPS sounding, while the second image is the experimental or modified NUCAPS sounding.

Image 1.  Soumi NPP NUCAPS Sounding near Syracuse, KS, ~19Z 21 June 2017

    

Image 2.  Experimental Soumi NPP NUCAPS Sounding near Syracuse, KS, ~19Z 21 June 2017

The Experimental sounding included here doesn't necessarily represent a drastic change to the original sounding.  But, you can clearly see the removal of the rather large superadiabatic layer in the lowest layer of the sounding (up to nearly 700mb), and its replacement with a dry adiabatic layer in the experimental sounding.  There have been a number of potential improvements noted in the soundings during the HWT so far, and forecasters are happy not to have to make these modifications themselves, although there is a bit of a delay with the Experimental soundings, amounting to another hour or two past the receipt of the original NUCAPS sounding data.  Sometimes though, the amount of "improvement" in the soundings is not always clear.

This brought up some discussion between myself and the other NUCAPS sounding representative at the HWT.  In the past, apparently forecasters have desired to make modifications to the surface data in the soundings and also to the boundary layer simply by using some nearby surface observations.  It should be understood by researchers that this is fairly normal practice...to take a forecast sounding and modify it with a more recent and perhaps accurate surface observation.  However, I think the inclusion of model data would perhaps be better in some cases.  If the model initialization/analysis or <6 hour forecast grid is ultimately the best representation of the state of the atmosphere at the time, over a simple point observation, then the model data should be utilized or at least considered.  It should probably be pointed out to forecasters that the NUCAPS soundings are volumetric soundings, not necessarily point data as represented by a point sfc ob or perhaps even RTMA data.  So, forecast data which also represent volume information may ultimately be a good choice for sounding modification in some or maybe even most cases.  Just some thoughts here.

Kris W