Analyzing CI Via Multiple Datasets

[20:30 UTC] Convective initiation has begun across central and eastern portions of the Billings CWA. Decided to take a look at some low-level WV imagery in conjunction with the CI product to monitor development underway in extreme northern portions of WY (in an area of poor radar coverage) as of 20:00 UTC. These supplemental datasets are very valuable in areas where radar coverage is sparse and/or non-existent.

Fig. 1: Marked increase in low level WV being shown on Ch. 10 that is associated with agitated cu field blossoming in northern WY.

Fig. 2: The day cloud convection RGB showing the cu field becoming more agitated with a gradual transition from liquid to ice phase as the development increases

Fig. 3: CI shows this cluster as a 40% of convective initiation (which is by far the highest of any "area" within the region of developing cu field). Initiation appears to be just starting following the capture of the above image.

Rosie Red

MAF - Convective development associated with increasing all-sky CAPE

1945Z: Convection continues to develop over the Davis Mountains of SW TX. Some mid-level clouds/supercooled water droplets are being identified on the Simple Water vapor & Day Cloud Distinction RGBs as the cu over the mountains continues to develop. CI prob values continue to remain around 50%.

Simple WV RGB:

Associated with this developing CU was a large increase in CAPE according to the all-sky LAP CAPE product where values increased from 200-300 J/kg to 800-900 within the hour. I expect this trend in increasing instability to continue into the afternoon.

All-Sky CAPE:

Peter Sunday

Forecast 5/17/18

A strong shortwave trough will continue to move across the Great Basin this afternoon, providing increasing southwesterly flow aloft downstream over the High Plains. The water vapor loop implies increasing forcing for ascent across the Southern Rockies with increasing mid/high clouds approaching the TX/OK Panhandles. Strong diabatic heating will allow scattered strong to severe thunderstorms to develop this afternoon and evening.

Fig 1. Increasing forcing for ascent noted over the Southern Rockies.

Rapid surface destabilization is taking place this afternoon with 18z KAMA RAOB indicating 700-500mb lapse rates of 9.1 C/km and surface temperatures near 90 degrees. The AllSkyLAP product suggests CAPE near 2500 J/kg with model progs increasing to near 3500 J/kg by peak heating. Deep-layer shear is a bit strong than previously anticipate with 0-6km BWD generally between 35-45 kts. This will be sufficient to sustain organized updrafts with some storms becoming supercellular initially before growing upscale into linear segments.

Fig 2. AllSkyLAP CAPE of 2000-2500 J/kg as of 1830 UTC.

Storms are expected to initiate along the dryline on the Caprock, moving in a general eastward direction. Lift may be enhanced across portions of the Panhandles by an outflow boundary originating from the ongoing convection over northwest OK. The Bunkers RM storm motion from the W and NW only 5-7 kts, suggesting a potential for heavy rainfall with any right movers. The very steep lapse rates and strong instability will support a large hail threat, with isolated sig hail reports possible this afternoon. There is also a potential for isolated damaging wind early in the storms' lifecycles, becoming more widespread as storms grow upscale.

wall_cloud

RGB of convective initiation

I found this capture of convective initiation to be interesting and cool to watch. As dry air on the south side of the MCV advected east into far western AR, storms would fire near the state line. The Day Cloud Phase Distinction shows this cycle very well and provides a nice optical depth to the satellite loop.

Fig 1. Mid-level water vapor loop showing dry air advecting into western Arkansas on the south side of the MCV.

Fig 2. Day Cloud Phase Distinction RGB depicting convective initiation on OK/AR state line on the leading edge of the dry punch.

I was looking for any obvious signal in the lightning data for that point but nothing significant seemed to stand out for this case. That said, it is producting consistently high Flash Event Density with relatively high Total Energy values and low to moderate Average Flash Area.

Fig 3. Clockwise beginning with upper-left image:  Flash Event Density 2 minute data (1 minute update), Average Flash Area 2 minute data (1 minute update), Total Power 2 minute data (1 minute update), ENTLN 5 minute data (1 minute update).

It was interesting, however, that the AllSkyLAP CAPE for this area was quite muted. Makes me wonder if this isn't a function of the model first guess. Since the sky was cloudy and the satellite data relied more heavily on the GFS (which was convectively contaminated), I didn't find this data particularly useful.

Fig 3. AllSkyLAP CAPE product showing CAPE values < 350 J/kg over eastern OK and western AR. This is using primarily the GFS background information.

Fig 4. GFS QPF for 18Z. The convective contamination likely resulted in erroneous CAPE values on the AllSkyLAP product.

wall_cloud

Forecast 5/16/18

An MCV from overnight convection is located over northeast OK and will drift eastward over the Ozarks later this afternoon. Moderate instability is observed over much of AR with AllSkyLAP CAPE values on the order of 1000-1500 J/kg.  The 12z raob from LZK indicated a fair amount of instability aloft, aided by relatively steep lapse rates from near 700mb through approx 550 mb. The AllSkyLAP PWAT was ~1.3" at 12z which compared very nicely to the 1.33" observed by the raob. Relatively dry air was observed aloft per the AllSkyLAP 0.7-0.3 sigma PWAT.  MLCAPE is progged to increase to around 2000 J/kg this afternoon with a DCAPE just over 1000 J/kg.

Fig 1. Split Water Vapor depicting MCV over northeast OK.

Fig 2. MCV evident in the high-level water vapor imagery.

Storms are ongoing over the Ozarks, but are expected to increase in coverage across the state throughout the afternoon in the weakley capped, low-shear environment. Shear will be limited today given the overall weak synoptic flow and vicinity of the aforementioned MCV. In general, anticipate strong to marginally severe, pulse ordinary cells but a few multicellular clusters are possible should storms develop strong enough cold pools. The primary hazards will be hail up to 1 inch in diamter and localized damaging winds.

wall_cloud

Mesoscale Analysis in Des Moines

GOES-16 upper-level water vapor imagery reveals a closed upper low advancing east across southern Nebraska early this afternoon.

Visible imagery shows low clouds across much of the CWA, with cu beginning to develop across the far southern portions in the warm sector of the storm system

Morning GOES-16 Derived Motion Winds revealed a 110+ knot 300 mb southwest to northeast oriented jet core across Iowa. This agrees with the GFS depiction of the jet in that area, which has that jet exiting and a jet entrance region poking into southern Iowa later today. Winds in the 750 mb to 850 mb layer are generally 15-25 knots from the south/southeast, with slightly stronger winds advancing towards our south implying increasing LL WAA.

The default LAP products have very little data given low cloud cover over the region.  However, the all-sky LAP products have a lot of cloudy sky retrieval pixels, filling in those gaps, in addition to some clear sky pixels moving north into the CWA. From 1730 to 1900, all sky LAP CAPE has increased from 500 to 700 j/kg, and TPW has increased from around 1.32" to 1.36". CAPE over 1000 j/kg reside just south of our warning area. These trends imply the atmosphere is becoming more favorable for the development of severe storms.

 The LAP Layer PW product, comprised mostly of clear sky and cloudy sky retrievals across the domain, shows some significant features. Clockwise from top left PW sigma layers: sfc - 0.9, 0.9 - 0.7, TPW, 0.7 - 0.3. The two lower layers show fairly high levels of moisture, while the upper level reveals a nose of dryer air advancing toward the CWA. This trend would imply increasing convective instability as we advance through the afternoon.

- Bucky

OUN Mesoscale Analysis

GOES-16 water vapor imagery reveals a broad closed mid-level low advancing into the 4-corners region with energy rounding the eastern side of the trough through west Texas.

GOES-16 Derived Motion Winds show the southwest to northeast oriented upper-level jet shifting east into west Texas, OK panhandle, and western Kansas. Diffluent flow is apparent in the winds over south-central Kansas into the Texas panhandle on the east side of the jet where convection is already ongoing and initiating. As the upper forcing shifts east, so will the convection. Given the high cloud cover, mid-level winds are not available over the region. Winds in the 850 mb to 950 mb layer are available over much of central Oklahoma, indicating 25-35 knot low level southerly flow advecting moisture into the region. Some of the lowest level winds, below 950 mb, are indicating more backing toward south-southeast, which would imply a favorable shear environment for supercell thunderstorms.

Given the cloud cover, the LAP fields have very limited data across much of OUN. However, the all-sky product does have many cloudy sky pixels, a benefit of this product over the operational LAP product. Within these pixels, CAPE ranges from 1500 to 2000 j/kg across the CWA a reduction of close to 1000 j/kg over the GFS first guess. SPC meso-analysis indicates MLCAPE between 2500 and 3000 j/kg, implying LAP CAPE is too low. Boundaries are not easily identified in the retrieval data given the cloud cover.

MetOp-A NUCAPS soundings were available over the region for the 1630 UTC pass. The surface was adjusted to match the conditions present in the NWS Norman special 18Z sounding (surface of 78F T and 68F Td). Comparing the two, the NUCAPS sounding captures the EML, though it is with much less detail. NUCAPS tries to represent the temperature inversion, but it is too coarse to be operationally useful. The drying aloft is also present, though too high, with moistening above. The general shape of NUCAPS is on par with the raob. As for the CAPE fields, NUCAPS is a little hot with MU and SB CAPE compared to the raob, while MLCAPE is slightly too low.

Expecting all three severe threats today with convection moving through the area.

- Bucky

Moisture with LPW

Similar to yesterday (blog post), I'm seeing increasing low-mid level moisture just to the east of the dryline, and we're reaching a point where convection is firing on the strengthening gradient.  RAP forecast moisture cross section suggests the increasing moisture, especially in what should be the 0.7-0.9 layer, before the dryline begins moving east today.  Already seeing that underway.  Will be watching evolution today using LPW...

(RAP moisture forecast cross section W to E from Panhandle, across C Oklahoma, to western AR)

(Above:  LPW, full column, and each layer + composite radar)

(Above:  ABI Water Vapor channels + cirrus)


Just like yesterday (blog), convection is developing over the panhandle along the dry line as 0.7-0.9 PW gradients quickly increase.

-Forrest

UNR Satellite Analysis

A loop of upper, mid, and lower level water vapor along with a simple water vapor RGP indicates an area of potential lift crossing south central MT (top right). The RAP indicates a 50kt 500mb wind maxima lifting through this area, and GOES-derived winds suggest the core of this wind maxima may be displaced a bit further north and east in the model. The wind barbs do seem to drop in and out with each frame. Not sure if this is a sampling issue or what.

Visible imagery (not shown - CAVE is locked up) shows an area of convection over south central MT associated with this jet streak, and the day cloud phase RGB indicates this area has become glaciated.

Anticipate this activity will continue, and likely grow in strength as it moves into deeper moisture further east.

-64BoggsLites

JAX Pulse Storm

In the JAX CWA, a storm seemed to intensify along a shear zone which was detected well in the upper level water vapor imagery. The intensification was noted mostly via rapid cooling of the cloud top temperatures seen in the IR imagery as well as the 1 min update of the GLM flash density at 8km. I forgot to load the PROBSevere before saving this image, but PROBhail did increase to 30% for a scan or two (which was very good for us today)

Airmass Storms in FL

Focused on airmass thunderstorms this afternoon in Florida (Melbourne CWA) with the main threat being downburst winds. Took a quick glane at upper level water vapor imagery to analyze the synoptic environment. Noticed a shear axis between the drier air from the upper low moving south and the moist air moving west from Bermuda. Can also see some outflow from an airmass thunderstorm along the eastern coast of the CWA. The shear axis could help enhance lift over the next few hours (have noticed this feature over FFC quite often and it often enhances convective coverage.

GRB satellite trends.

The Sandwich display (Vis with transparent IR overlay) depicts a quick increase in convection and cooling cloud tops across southwestern GRB's area

This is along an advancing boundary associated with a shortwave trough noted in all 4 water vapor images approaching western WI.

The interpolated 8km GLM data depicts an increase in this activity well, and seems a little more intuitive than the grid box/flash display.

-64BoggsLites

DMW with 4 panel Water Vapor

I was looking at the GOES-16 derived motion winds alongside a 4 panel of the 3 water vapor channels and the simple water vapor RGB with another forecaster. A few thoughts: First, for the most part, the winds seem to match up pretty well with the motions observed on the three different water vapor channels. Looking over north central Missouri, we notice the anticyclonic motion in the mid and upper level water vapor channels. Looking closer at the low-level water vapor loop there is evidence of some more cyclonic motion due to a remnant MCV from morning convection. The winds pick up pretty well on these differential motions. Some thoughts for improvement from me and the forecasters here at the experiment are that it would be nice to first see the winds time matched to each other at the same time. Some levels of winds show up at different times than winds at other levels and makes looking at a loop of winds very difficult. Also it would be good if the winds stay on the screen the entire time until a new update comes in. Just keep the previous barb up until a new update instead of the winds just flashing on and off as the loop rolls. Lastly, it would be more helpful to see the wind barbs color coded by level instead of speed. The barb already has the speed on it and when multiple levels are loaded it is tedious and difficult to tell what level you are sampling.

-Michael

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

Omaha 19Z Satellite analysis

A 4-panel water vapor loop containing upper level (top left), mid level (top right), low level (bottom left) and the simple water vapor RGB (bottom right) depict a remnamt MCV from overnight convection making its way across the lower MO river valley, exiting the Omaha/Topeka CWAs. One interesting thing to note is the upper level anticyclonic rotation in the upper and mid level WV, while a cyclonic low level circulation is evident in low level WV imagery crossing northern MO. This gives a nice 3-dimentional picture of the MCF throughout the depth of the atmosphere.

Red-vis imagery shows a lingering boundary extending from central WI back through northern IA and into far northeast NE around 1930Z.

Comparing this with the day cloud phase RGB (above) shows only isolated cases of glaciation along this boundary across northern IA, and no glaciation noted across northeast NE. Will keep an eye on this product to see if an increase in glaciation can be noted across NE over the next couple of hours.

-64BoggsLite

Evaluating storms across the Albany WFO this afternoon. Convection was already ongoing at the beginning of this evaluation, namely in a linear fashion. GOES-R satellite imagery proved to be useful in the initial analysis of synoptic scale features. A shortwave was noted to the north/northwest of the CWA via upper level water vapor, indicating that large scale forcing will likely aid in buoyancy. The 4 panel WV loop was very useful in an quick top down analysis, particularly moisture. Upper level shows the wave very well, mid level shows where deepest moisture resides and the lower level shows where the frontal boundary resides (taking this a step further we can also see convection generated right along the front vs the convection out ahead in the deeper moisture).

As for lightning, it was overall useful in helping to quickly address where the
stronger, more mature convection was at, however almost right away i found myself more drawn to watching the ENTLN trend because the GLM was displaced out ahead of the convection and seemed a little distracting. Top right shows the ENTLN and the top left shows the GLM.

As the line began to evolve, the NUCAPS sounding data came in. The original SNPP NUCAPS data seemed to largely underestimate the amount of instability (it was showing 100-200J/KG MLCAPE). Although I did not look at any model or SPC mesoanalysis data, based on the season, the forcing, and the amount of clearing ahead of the convection, this seemed very unrealisitic. I plotted the experimental SNPP to compare and this data seemed MUCH more reliable, showing over 2000J/KG of MLCAPE. I felt more comfortable using this data.  I then completely discounted the original SNPP data.

I find the PROBSevere to be very useful as an aid to the real time meteorology. It, for me, was more of a reassurance product as I noticed cloud tops cooling or lightning increasing, radar imagery changing, etc. I normally do not like to use derived products such as this, but I REALLY like the fact that I can see the values of each parameter that goes into it (which is probably a big reason why I decided to use it in the first place). I think almost all of the forecasters at FFC would love to use this product.

As the storms continue to evolve over the course of the afternoon, the evolution of the clouds really show up well in the IR imagery. However, it is frustrating when the last frame in my loop doesnt load the full image. Sometimes the loop can be jumpy too, which is really annoying

When looking upstream the "sandwich" imagery proved very useful in revealing some merging outflow boundaries across PA. This alerted me to the possibility of strong convection moving in later this afternoon. Will continue to monitor trends

Watching the evolution of the storms across NE PA, The IR still seems to be doing a good job of showing how the storms are evolving/which ones are strongest. This really coincides well with where the PROBSevere is showing the highest threats. PROBSevere is quicker to analyze find trends than looking for increases in lightning.

Storm evolution overall in the Albany WFO has been of the pulse-variety today, with really two strong/severe storms. This is similar to what we see at FFC this time of year, so I'm really enjoying testing all of these products. Towards the latter portion of the afternoon, convection weakened, with most storms back building from NE PA into central PA.

Grand Forks 19z Satellite discussion

Simple water vapor imagery depicts a weak shortwave trough lifting through eastern ND this afternoon, and although this feature is noted in the low, mid, and high level WV imagery, it's much more subtle in appearance in these 3 channels.

Visible imagery shows a boundary dropping south through central MN currently, and there has been an increase in CU along this boundary as it pushes south. This area in far southeast ND into northeast SD and west central MN seems primed for surface based convection within the next couple of hours.

Also noted in the airmass RGB were differences between the the more moisture rich airmass within the warm sector, which appeared with more of a green hue, while the airmass further west across the western Dakotas is drier based on surface observations, and had more of a red hue.

-64BoggsLites