GOES-R CI Across Far Western Texas

051413 1945 UTC GOES-R CI

Shown above is the 1945Z GOES-R CI. Note the two red values of 90% or greater within the panhandle of far western Texas.

051413 1941 UTC Base Reflectivity

051413 1956 UTC Base Reflectivity

Both of the red areas, especially the southeast one, depicted an increase in 0.5 Degree reflectivity indicating developing convection. This product seems to be doing a good job with new developing convection, though much of this convection would not sustain itself likely due to a weakly sheared environment. I would like to see how this product responds to a more strongly sheared environment. 

Scotten

14May2013 Mesoscale Discussion: W Great Lakes

Monitoring the potential for convective development across W Minnesota / SE South Dakota, and across central Nebraska.

Shortwave trough currently progressing east across S Saskatchewan into E Ontario providing support for some initial development across the Canadian provinces, as seen in IR / VIS / CTC data. Large-scale lift aloft, in association with eastward progressing frontal boundary is supporting a line of agitated cumulus extending south into NW Minnesota. Nearcast difference CAPE product indicates an axis of weak-to-moderate instability (500-1000 J/kg) in front of this boundary extending south into NE and IA. WRF simulated IR fails to develop much of any activity across N Minnesota, keeping all activity developing after dark across the UP of Michigan. Farther south and west, it shows better development across Iowa and Nebraska around 00Z. However, considering best large-scale forcing exists closer to the Canadian border, and model fields were generally overestimating surface dew points farther south (forecast >60 versus AOB lower 50s being observed), thought is that best potential may exist closer to the international border over the next few hours.

If storms can develop, dry low levels and steep lapse rates support a high wind threat from higher based storms. Better wind fields farther north (0-6 km shear >50 kts) and slightly cooler temps also support an enhanced threat for marginal severe hail closer to the Canadian border.

Picca

Daily debrief: 5/14/13

Yesterday was a very quiet day in regard to convection, ending with only one issued warning for the entire shift. However this gave forecasters the chance to explore and familiarize themselves with each experimental product, and through this they were able to provide some good feedback. Comments are shown below:

- 'Cloud Top Cooling had a good day and seemed to hit most of the good storms.'
- 'The only warned storm wasn't caught by the Cloud Top Cooling due to cirrus, but it did catch the earlier ones.'
- 'The GOES-R CI was very confetti like and too noisy.'
- 'The synthetic imagery did a pretty good job of tracking the short wave on shore [in the NW US]. It was slightly faster, but really keyed in on the development of the first storm in NE Oregon.'
- 'It did a good job translating that shortwave further inland and keyed in on the other storms initializing further east.'
- 'Despite the fact that [the convective activity] was pretty unorganized, the synthetic imagery did capture the initial storm and also the second round.'
- 'Combining the forecast from the synthetic imagery with what the Nearcasting was showing gave us a pretty good idea of where to key in on.'
- 'The Theta-E difference [from the Nearcast] showed unstable air over Montana. When storms entered this unstable air they did strengthen quite a bit, several becoming severe.'

Today looks to be pretty quiet as well and in an effort to maximize our evaluations we'll be splitting our forecasters up between Texas and the western Great Lakes. Down in Texas our experimental warning operations will focus on the Midland and San Angelo CWAs, while in the western Great Lakes they will, for now, be focused on a mesoscale outlook.

GOES-R CTC Training Comments...

Location: Montana. Threat: severe hail/high winds. Soundings suggest potential for thermodynamically-driven downbursts over mountainous terrain. Question: will cloud dtop cooling (CTC) rate be applicable to hail cores that could generate wet/dry microbursts?

CTC rates have been noted to have problems in mountainous regions such as the Rockies and even Appalachians. The rates were at or below 10C/15 minutes on the first few updrafts and only one storm briefly (one volume scan) reached 50 dbz through 20UTC. A storm entering Idaho County showed cooling rates of 12.6C/15 minutes at 2015 UTC, but this storm did not intensify until after 2130 UTC. This storm was not assigned a CTC rate after 2015 UTC because of masking by cirrus blowoff. Another storm that formed on the forward flank of this storm became marginally severe but was also never identified due to cirrus.

Possible sampling issues were noted in the MRMS sfc height of 60 dbz above -20C. The levels showed big scan to scan variability which may have been a function of distance from KMSO and sparse coverage of surrounding radars. As this storm got closer to the RDA, the scan to scan variability decreased.

SPC issued a severe thunderstorm watch at 21UTC with the main threats being large hail and high winds, with a secondary threat of a tornado.

-Ostuno

14May2013 01Z Mesoscale Discussion

Best possibility for near-severe wind gusts and marginally severe hail appears to exist across the E half of Montana over next couple of hours. WRF simulated IR images and CIMSS 780-500mb difference products continue to point at this region having the best thermodynamic environment (approx 700-900 J/kg of CAPE) to maintain convective development during this time period. Regardless, severe threat still appears to be low-end.

Picca

Nearcast Vertical Theta-E Difference with Ongoing Strong Storms

Despite moving atop an increasingly dry boundary layer (ref. to dewpoint readings in the mid to upper thirties), the strong to severe thunderstorms keep their strength. The GOES vertical theta-e difference (low-mid) product highlights the moist and unstable air mass nicely with 500-1000 J/kg (another product) present. In fact the thunderstorms really increased in strength when approaching and eventually crossing that plume of unstable air. For this event, the product by CIMMS helped a lot to get a feeling about how supportive the air mass stratification would be ahead of the thunderstorm despite decreasing boundary layer moisture. In the near future we should see a potential increase of a downburst risk with inverted-V profiles to the E/SE of the storm. A marginal hail risk continues with that storm.

051313 2300 UTC Nearcast Vertical Theta-E difference overlaid with radar imagery

Helge

Simulated Satellite Comparison Across NW US

Comparing the simulated satellite from NSSL-WRF/GOESR/CIRA on the right to the actual IR on the left at 23 UTC on May 12 depicts general good agreement. The simulated satellite imagery overdeveloped isolated convection over southern Idaho, Montana, and Wyoming, and was a bit to quick/far to the east with the cooler/deeper moisture plume from far northern California to Alberta. The simulated IR verified very well with post-frontal cold air cumulus depiction over western Washington and northwest Oregon.

Scotten

13May2013 2245Z Mesoscale Discussion

A shortwave trough is moving through central Washington and Oregon with scattered coverage of storms initiating over northeast Oregon and the Idaho panhandle this afternoon.

CIMSS Nearcast Product is depicting a weakly unstable environment averaging 500 to 1000 J/KG along a corridor stretching from eastern Oregon through northern Montana with storms initiating off the higher terrain and continuing to track along the axis of instability within this corridor. RAP analysis is indicating roughly 60 to 70 kts of 0-6km shear collocated with axis of instability…which is likely inhibiting deep growth and organization at this time due to the imbalance of high shear and weak instability.

Initial look at synthetic WRF IR and WV show relatively good agreement with GOES IR/WV…albeit slightly more progressive by about 50 to 100 mi. Strongest storm so far was analyzed quite well by the WRF in northeast Oregon with only a slight southern displacement from real time location. In general though…the model captured the initiation and future trend of this storm with relatively high accuracy. Additionally…the model is showing future intensification further east off the higher terrain through the evening…although the slightly more progressive system in the model may mean a later initiation and intensification of this activity by an hour or two.

However…once the convection does initiate…slightly less shear collocated with an area of 1000J/kg could allow the storms to become better organized than current trends. The synthetic imagery portrays this situation across western and central Montana 23Z through 01Z. Current surface observations show a relatively dry boundary layer in this area with dew points averaging in the low 40s and downslope winds. Main threat from any storms in this region will be mainly downbursts but better storm organization will allow for a continued severe hail threat as well.

Mazur/Picca

Cloud Top Cooling Products and Cirrus Clouds

We’re monitoring a few showers/weakly electrified storms over N-central Idaho. Using the cloud top cooling product, the focus for cooling was found to be along the northeastern fringe of that cluster. Using VIS imagery and keeping strong SW-erly shear in mind, the northeastward blowing cirrus shield (increasing in strength due to strengthening convective activity) caused the strongest signals for cooling (e.g. -20K/15min) along the NE fringe of that cluster. However, the most healthy looking cells eventually evolved just to the south of the cirrus shield, where some clearing occurred. It seems like this “messy situation” with rapidly clustering storms may mask local areas with better conditions for initiation.

Reflectivity data beneath the cloud top cooling product

Idaho Storms Spudding Out - Low 700-300 Precipitable Water Values

Isolated to scattered high based storms are struggling to develop (with highest reflectivity cores 45-50 dBZ up to 25 kft MSL) as they move northeast across Idaho in a minima in 700-300 mb Precipitable Water Values (PW) according to CIMMS-NRW. Wonder if the storms will intensify if they moved into higher PW values.

Scotten