Prob Severe of 99%…Three Body Scatter Spike

While monitoring the Soux Fall radar this morning, this beast developed just east of the radar site. The Prob Severe Model jumped to 99%.The hail size was predicted by the tool to be over 2 inches in diameter. A short time later a nice three body scatter spike appeared. We are still awaiting any reports from the area.

Jared Maples

1 Minute Satellite Feed

Today the GOES-14 SRSOR is updating at one minute intervals. This provides an excellent opportunity to see how quickly cloud tops develop, even well before the radar updates. In the first image you can see the void in the circled area. This general area is the same area in which clouds have already developed and are beginning to can upper level winds.

Update: Showers and thunderstorms have initiated in the same area that satellite feed was showing the high tops. The one minute feed gave great lead time in this instance.

Jared Maples

Severe convection firing near EWP WFOs

Strong thunderstorms have developed this afternoon just west of the DMX EWP domain along the dryline associated with low pressure center over the Northern Plains.  The NOAA/CIMSS ProbSevere depicted a storm near Sioux Falls, SD with strong satellite growth rates, a favorable environment and radar estimated hail size increasing with time (Figure 1).  The ProbSevere model generated probabilities in excess of 50% at 2006 UTC.  The NWS Sioux Falls WFO issued a severe thunderstorm warning on this storm at 2025 UTC, when the ProbSevere value was 91%.  As more storms develop and evolve along the dryline further south, more updates will be made.

Figure 1.  NOAA/CIMSS ProbSevere and MRMS composite reflectivity valid 2004 - 2024 UTC 8 May 2014.

-Sieglaff

CI picks up on line of initiating convection

Line of convection working through Omaha’s CWA. Initial CI hits 50-60% at the northern end of a line of cumulus at 1825Z.

At 1830Z CI probs increase to 80-90%. Weak reflectivity is evident at this point.

At 1855Z cumulus further south along the line shows CI at 60-70%. The northern portion of the line has developed into a strong shower/minimal thunderstorm.

At 1915Z the CI probs have verified – the line of developing cumulus is now a line of showers and thunderstorms.

Scott Rudge.

Early Thursday Severe Convection

While we wait within the EWP for severe storms to get going over the currently emulated WFOs (ICT and DMX) we looked north into two regions with severe thunderstorms earlier today--eastern South Dakota/western Minnesota and the upper peninsula of Michigan.  Figure 1 below shows the evolution of two storms near the Sioux Falls, SD WFO between 1644 and 1730 UTC 8 May 2014.  The western storm had ProbSevere values (with strong satellite growth rates) in excess of 50% at 1650 UTC--36 minutes prior to the storm becoming severe warned at 1726 UTC.  The eastern storm had ProbSevere values in excess of 50% at 1704 UTC--18 minutes prior to becoming severe warned at 1722 UTC.  One subtle point in this example, is the western storm had satellite growth rates, but the eastern one did not due to thicker existing cloud cover--users can expect better lead time when the GOES satellite can observe the growth of storms from the cumulus stage to the cumulonimbus stage, as is exemplified in this case.

Figure 1.  NOAA/CIMSS ProbSevere, MRMS composite reflectivity and NWS severe/tornado warnings valid 1644 - 1724 UTC 8 May 2014.

Further to the northeast over the UP of Michigan, severe thunderstorms developed associated with strong warm air advection ahead of the storm system over the Northern Plains.  Figure 2 shows the evolution of the severe storm between 1650 and 1754 UTC 8 May 2014.  The storm of interested achieved ProbSevere > 50% by 1732 UTC--22 minutes prior to the severe thunderstorm warning issued at 1754 UTC.

Figure 2.  NOAA/CIMSS ProbSevere, MRMS composite reflectivity, and NWS severe thunderstorm/tornado warnings valid 1650 - 1754 UTC 8 May 2014.

-Sieglaff/Cintineo

DSM area analysis

Models agree on low pressure lifting NE or NNE form eastern NE into MN through the afternoon.  As of 19Z, all of IA was in the warm sector, with a cold front expected to cross form the west during the afternoon/early evening.  the 12 Z NAM puts the front near DSM at 0Z; the 12Z GFS still has it just to the west.

Earlier convection is exiting stage right, and some clearing is taking place in western IA.  We’re getting rapid scan GOES data today, so we’ll be monitoring the boundary structures that are evident on the imagery.  Below is the CI product superimposed over the visible image…we’re seeing 67% probability of development of 35 dbz returns in the next hour or so along these boundaries.

As this activity develops and moves eastward, Nearcast forecast theta-e difference by 22Z would indicate pockets of instability (in an area of closer to neutral stability) moving in over the next few hours from the west.  Will be interesting to see how this translates into storm coverage, or even storm mode, as the front moves in.

And in the time it’s taken me to work on the above…we’re seeing gradually developing convection marching to the NE/IA border in an area marked by the CI earlier.  Only low to moderate hits on ProbSevere (45% or less by 1930Z).

Do have LAPS data today, but a late realignment of the domain has the model playing catch-up.  Will comment later.

Wx briefing indicated increasing chances of UH tracks in our area, especially in our northeastern counties…watching for supercells with tornadoes and hail…and some severe wind

db

EWP Day 4: Operations Update

The final day of week 1 is already in progress and a complicated forecast it is (due primary to overnight convection).  Our initial thought was to play in the moderate risk associated with the low pressure and warm front, but with the presence of ongoing convection and the desire to utilize many of the GOESR products meant for the pre-CI and CI environment we decided to shake it up. One group of forecasters (Rudge/Bickford) remains in the moderate risk in Des Moines (DMX) CWA while the other pair (Maples / Thoren) is operating in the Wichita (ICT) CWA and looking for possible development ahead of the surface cold front/dryline.  While some convection is already ongiong in the north and eastern DMX CWA, expectation is that supercell storms (and tornadoes) will develop in the area clearing farther west.  Severe activity in the ICT CWA is a bit more uncertain and timing is likely a later this afternoon and evening if it were to occur.

SPC Day 1 Outlook

Current Watches over operational domain

Super-Rapid Scan (1 min imagery) is in it’s first day of operations.  The animated gif (click to show animation) below shows the Cu development along the cold front into the ICT domain and clearing in the western DMX domain.

Super-rapid scan visible satellite on 8 May 2014

-K. Calhoun, Week 1 Coordinator

Daily Debrief (for activities on 05/07)

Forecasters operated in the Norman, Cheyenne and North Platte CWA's. Sim Sat Imagery still not available.

NearCast: 
- Convection started on gradient of highest theta-e and pw values
- A couple times i leaned on this product a little bit
- Might be helpful to overlay surface information with nearcast
- I thought it did pretty well showing where the greatest instability was and showing the moisture advection so you knew the storms would have some fuel
- Forecast worked well as well
- Gaps are a limitation, but I can mentally interpolate the data. This is where the storms are now, there headed towards this area, they could intensify.
- I would actually use this product in operations

GOES-R CI:
- This was the first day I actually could use it in a non-contaminated cu field
- It gave a good indication that further development would occur, even behind the dry line
- It was a confirmation tool maybe at best
- A lot of lower percentage CI and then there was a cluster of higher CI percentages showing up. Convection did occur here.
- It might be helpful to block out the noise (lower probs)
- I sometimes think 35 dBz is too small of a threshold
- When things started going and the sat picture got dirty, the CI probs didn't do as well

Prob Severe:
- It is my favorite tool so far
- In Oklahoma, I warned on storms based on what this was saying, and I looked in the office, and that was where all the current warnings were.
- It is nice to be able to quickly show you what is happening with a storm or group of storms, especially when I was previously paying attention to some other, already active storms
- It would be nice to figure out a way to make it work with organized convection (linear modes, etc.)

Convection develops along NearCast boundary

Severe convection struck much of the central US on 5/7. EWP participants were monitoring the nearcast instability fields (forecasts and analyses), and noticed convection was developing along a sharp instability gradient. Participants noted that this has been a common theme with the nearcast during the week (convection developing along and moving with boundaries), as it does very well with picking up on moisture gradients and their movement. The loop below is hourly NearCast theta-e difference analyses (with 00 UTC forecast at end) with IR underlaid. Notice convection initiates along the boundary in Oklahoma and continues to develop northward along the instability gradient as depicted by NearCast. Negative values (blues to purples to reds) indicate greater instability.

The NearCast system is a Lagrangian model that dynamically projects GOES Sounder temperature and moisture retrieval data forward through space and time at multiple levels of the atmosphere. This provides forecasters with hourly, rapid updating, observation-based, 1-9 hour forecasts and analyses of the vertical moisture structure of the atmosphere. The sounder observes horizontal moisture boundaries particularly well, while the NearCast system preserves said boundaries in its analyses and forecasts. NearCast products can be loaded in AWIPS-II as past analyses leading into the most recent 9 hour forecast cycle, as is done with this loop.

- Bill Line

Storms fire along and near Theta E difference boundary – Henrietta storm has tornadic tendencies

Storms initiated across far western OK along and near a Theta E Difference boundary.

At 20Z

At 21Z

At 22Z

At 23Z

At 2330Z – Henrietta Storm quickly developed a hook with a report of a rapidly rotating wall cloud.

Scott Rudge.