Week 2 Debrief

While week 2 of the HWT Spring Experiment started out fairly quiet it certainly didn't end that way. Wednesday night's tornadoes in N. Texas ended up being the highlight of the demonstration so far and a lot of good feedback was collected from that event as well as the rest of the week. Check it out...

GOES-R CI
- 'On days where convection in more questionable it may be nice to have the ability to filter out the lower values to get rid of the confetti-like display, however on days where convective initiation is much more likely, those lower values provide some valuable information and help in keying in on particular growth.'
- 'Values of 57% or greater seemed to do fairly well on identifying initiation throughout the week.'

CTC
- 'The CTC is useful but does have trouble in areas of cirrus.'
- 'Most of the storms that developed did have a high POD, but also had some FAR.'
- 'In operations we're looking for which storms have potential. This is where the CTC would definitely be useful.'
- 'For situational awareness the CTC is a big thing. It identifies which storms to watch.'
- 'It would have been a better experience on Wednesday night if we'd had Rapid Scan Operations for GOES-13.'

Nearcast
- 'The CAPE field was good to compare to other CAPE fields though it can be hard to wrap your head around exactly what you're looking at and how it was computed.'
- 'The color scheme was a bit confusing. With the theta-E difference I'm used to thinking that green, yellow, and red values, are values to key in on, but in this case it was the darker blues and pinks.'
- 'The GOES-E and GOES-W images were definitely different, they didn't match, so I wasn't sure which one I should look at. It would definitely be useful to have a seamless overlap.'
- 'CAPE is conventionally what we're used to looking at, but the theta-E difference was also very useful.'
- 'Yesterday I looked at the theta-E and PW values... there were no high PW values [in west KS] and so it made sense why the storms there weren't growing. This information was very beneficial to have.'
- 'Then on Wednesday the storms in OK and TX formed right on the low-level and mid-level maximums of theta-E, so it did very well.'

RGB Airmass
- 'Yesterday the RGB showed showed drier, cooler air behind the convection which is what you would expect, but as the day went on you could see the moisture return to the area... because of this I kept my eye on what was going on there.'
- 'On Wednesday the dryline structure in OK and TX was very visible and we keyed in on this area.'
- The RGB gives you more information about the airmass source, it's composition, etc. It's very helpful information to have for situational awareness.'
- 'I liked the RGB as an overview, especially when you first sit down to see where airmasses are setting up. Though once you get into the nitty gritty of warning operations I didn't use it as much.'

Simulated Imagery
- 'We'd use it as a comparison to the actual IR to see what was influencing the model later.'
- 'It doesn't seem to handle anvils very well, but this may be a good thing because you could see where the storms were developing without the anvil getting in the way.'
- 'It's fairly remarkable what this imagery can do, giving you a satellite image so many hours in advance.'
- 'It did very well this past Tuesday in holding off on convective initiation up in the Western GL.'

PGLM
- 'Add the number or percentage of sensors currently working... for testing purposes it's crucial that we have this information so that we can use the product accurately.'
- 'Perhaps the 30 flashes/min threshold should be colored different so that it stands out more.'
- 'I used this product to identify which storms were starting to intensify and what cells I should key in on.'

Well that's a wrap for the week 2 debrief... but don't forget, our 'Tales from the Testbed' webinar will be beginning within thirty minutes and will cover the use of all of our experimental products during the N. Texas tornado event on Wednesday night. It should be a very interesting discussion!

Slow Day in CI/CTC Land

Shown below is a classic example of CI/CTC spoilage by upper level cirrus clouds. Note the rather mature convective system over the GLD CWA. All of the SPoRT CI algorithm detections (upper left) are all in the cumulus field on the outer fringe. CTC detections, when they occur (upper right), are similarly absent from the main complex. This has been the case the entire shift. Perhaps without the cirrus, we would be able to see strength fluctuations in the convective line, but the constant presence of cirrus over the top does not allow the satellite to sense updrafts. While there have been improvements to CTC over the last year to two to deal with thin cirrus, even that work would not help here. Cirrus contamination is clearly the main drawback to these otherwise excellent and useful products.

051613 2230 UTC CI (top left), Visible Satellite with CTC (top right),  NLDN lightning (bottom left), and Reflectivity (bottom right)

CL

20Z Nearcast Analysis of CAPE Trends Through the Afternoon

The 20Z Nearcast model shows slow but steady weakening of instability fields through the afternoon. Ribbon of 800-1000 J/KG along the CO/KS border between 20-22Z with a theta-e diff of 8-11K decreases through the late afternoon and evening to roughly 600-900 J/KG. There is a similar trend in theta-e difference with 6-9K theta-e difference in this region through the early evening…along with about 30kts of 0-6 km shear. Further east into central Kansas…CAPE and theta-e difference significantly drop off…so from this forecast one can expect any storms that develop within the convergence zone along the KS/CO border to move east and have some marginal strength and organization before dissipating as they approach central Kansas.

051613 2000Z Nearcasting CAPE

Sad Storms so far in SE CO/NW KS - No juice in the Nearcast

051613 22:31 Nearcast Precipitable Water Difference and Reflectivity

This image depicts CIMSS-NRE 700-300 mb precipitable water values overlaid with 0.5 Reflectivity from KDDC. These struggling high based storms are over an area with precipitable water values only 0.05 to 0.11 inch between 300 and 700 mb. It seems very unlikely these storms will do anything, unless they can quickly move east in the next few hours where much higher precipitable water values exist. 

Scotten

Struggling High-based Convection in SE CO using CI/CTC

A few high based storms have been struggling to develop across southeast Colorado due to abundant dry air and SBCAPE 500-1000 J/kg.

The first image was at 2045 UTC on May 16 where the GOESR UAH CI suggested some potential for convection with a few locations 61-78%, and the CIMSS CTC depicted a maximum of -18C/15 min. This appeared promising for deep convection.

The next image was at 2115 UTC and continued to depict a few areas 20-62% for CI as well as -16C/15 min along with a few weak cells. At this point, there still remained hope for some deep convection.

The last image was at 2145 UTC respectively with lower CI and CTC values as well as a few non-severe/rather weak cells. So far, these cells have failed to intensify or become severe. Weak forcing aloft in conjunction with the lack of low level moisture may be the main culprits for the poor development of storms.

Close... but No Cigar... Held Off SVR Based on GOES-R CI/MRMS

051613 2138 UTC MRMS fields

Held off issuing a severe thunderstorm warning for a developing storm over northern Nebraska due to MESH staying around 0.75 inch and maximum reflectivity of only 55 dBZ at the -20C level.

051613 2045 UTC GOES-R CI

In addition, the GOESR UAH Convection Initiation Products depicted a few pixels of 10-40% in the hour prior to this storm developing, perhaps suggesting that the environment may not be conductive for explosive storm development.

Flash Extent Density and Updraft Strength

Playing a bit with the SPoRT flash initiation density product and the evolution of an updraft. Although it’s not a serious storm, it represents the ongoing pulsating activity very well which could eventually gain strength when entering a more unstable air mass to the east. Below you can find the ‘Flash initiation density product’ at 2035Z and 2040Z, showing a marginal increase in lightning activity. Reflectivity at the same time showed a core with 35-40 dBz and only a few isolated lightning strikes occurred.

051613 2035 UTC PGLM Flash Extent Density

051613 2040 UTC PGLM Flash Extent Density

051613 2055 UTC Reflectivty

At 2055Z, the storm finally strengthened in reflectivity fields (the core peaked at near 60 dBz) . Although that was just a temporal strengthening trend of that storm it is great to see the lead time you get with that lightning product before the updraft eventually strengthens. 

Helge

MESH and CTC in the GLD CWA

Setting up in the Goodland KS CWA today. A small cluster of storms is ongoing and certainly producing a lot of rainfall and lightning…note the 0.5 reflectivity on the upper left. To the upper right is CTC on top of the visible. No detections here…likely due to anvil cirrus hinderance. On the lower left, we have MESH from MRMS. Nothing at one inch or above here either. Reports from the area have consisted of small hail lately…0.75″ and less. This seems to reinforce the marginal nature of the storms depicted by MESH and other experimental products.

051613 2018 UTC Reflectivity (top left), CTC (top right), and MESH (bottom left)

CL

RGB Airmass Use Over NE and KS

051613 1901 UTC RGB Airmass

The GOES Sounder Air Mass image is very useful in highlighting the different features of interest for today. First of all the compact disturbance which is about to leave NE Colorado to the east/northeast is well visualized by mid-level drying in the image. Weak forcing ahead of that feature already caused some initiation over N/NE Nebraska with another round of storms evolving over extreme NE Colorado. Of interest is a southward extending and weakening vorticity lobe which is about to enter Kansas from the west right now. Also, the dryline is well recognized by that product, showing warm/moist air ahead of the dryline advecting to the north (green-ish colour). This correlates well with mid-level moisture, seen in latest RAP output. A gradual transition from ‘green to blue’ occurs when moving westward (e.g. towards the TX Panhandle). This corresponds well with some residual low-level moisture f.ex. in the lowest 850 hPa, which gradually mixes out. We will monitor both the dryline and the eastward moving but weakening PVA lobe for some kind of interaction during the following hours and eventually for sporadic CI. 

 Helge

Daily Debrief: 5/15/13

Yesterday turned out to be the best day of the experiment thus far! Later in the evening we saw rapid convective initiation in Southern OK and Northern TX. Supercells formed just west of the Dallas-Fort Worth metroplex and produced very large hail as well as a series of strong tornadoes in the area. Check out the image below of the pair of supercells just west of DFW. Tornados from these cells caused a lot of damage in Cleburne and Granbury.

051513 0036 UTC Reflectivity (top left), Velocity (top right), CC (bottom left), and TDS (bottom right)

A lot of blog posts and feedback were collected from this event on the various experimental products. Here are some of the comments noted in this morning's debriefing:

PGLM
- 'I noticed a correlation between the MESH and the lightning data. Several minutes after there was a big jump in flashes, there was also a big jump in MESH values.'
- 'The OUN network kept losing sensors so it was hard to know what was a jump and what was data loss. It would be helpful to have the status information so we know that we've actually lost sensors and and when we've got a jump.'
- 'In my opinion forecasters won't like that you have [use the lightning moving trace tool] manually.'
- 'In real time I can see [the moving trace tool] being a little clunky to use, a little labor intensive, but for analysis of an event it would be awesome to see that trending information.'
- 'It would helpful to see the lightning data plotted with the hail/MESH information.'
- 'We didn't hardly get any lightning with the Oklahoma bow echo... perhaps this could be an indicator that it wasn't going to be as strong of an MCS.'
- 'I paid attention to the lightning cores and where it was increasing significantly. This seemed to be a good indication of a strong storm.'

GOES-R CI
- 'There were a couple of times where the CI gave us an 80/90% value that developed/initiated into a deep convective core.'
- 'Values were overall low yesterday in TX, but where it pinpointed the higher values it did a good job of indicating strong initiation.'
- 'I thought it did extremely well. We were looking at a decent sized cu field and it seemed to pinpoint on specific cu very well.'
- 'Yesterday there was enough of a difference in the CI values where you could pick out the more significant initiation, but on other days it seems to be far more confetti-like.'
- 'THe Montague storm had a CI value of 60%. An hour later it initiated. Thirty minutes later we had baseball sized hail. Fifteen minutes after that we had a strong tornado.'
- 'It seemed to do well with the clusters of strong updrafts, but had trouble in higher terrain. This may be an elevation/snow effect.'

CTC
- We had good CTC rates on a number of storms that ended up falling apart. It ended up that the storms had good initiation but were moving into an environment not conducive to further growth.'
- 'The CTC did a good job yesterday, but it's still very important to know your environment. We saw strong signals, but not all initiated because of other environmental factors not seen in the CTC.'
- 'The CTC gave consistent lead time of at least 20-30 minutes for severe storms on multiple occasions [in Texas].'

Our last day of operations this week doesn't look to be nearly as exciting as yesterday. We're currently in the Goodland, KS, and North Platte, NE CWA's where things have already began to initiate, and may move further south later in the evening. Stayed tuned for further updates as the day progresses...