Convective Initiation Product over eastern West Virginia

Click the image for an animated loop of GOES East visible imagery between 16z and 1745z along with the Convective Initiation product.

The color scale on the convective initiation product has been adjusted to three colors to simplify identification of the various probabilities. Blue is a 0-30% probability, Yellow is a 31-70% Probability and Red is 70% to 100%. I feel this helps to show increasing probabilities better than the standard multi-color scale. In the looping image notice the outlined area over eastern W. Virginia to the west of the Shenandoah Valley. Watch how the CI product shows increasing probs starting at 1615z along a ridge top 30 to 45 minutes before a line of thunderstorms exploded along the ridgeline. This product also highlighted these storms about 3 hours before a Satellite Precipitation Estimate message was issued by NESDIS. (1907z)

Shawn Smith

Tuesday 2030Z – NearCast Analysis

This post shows how the Nearcast model did well in depicting a weak north/northwest moving boundary that initiated convection in southwestern WV.  In a rather “pulsey” environment, the ability to pick out this boundary aided in confidence as to where convection was going to form.  Definitely a good tool to use in conditions where forcing is subtle and there is uncertainty on location on CI.

-Deitsch

Here is the 2030Z forecast from the 20z Nearcast model. White line represents a weak boundary

Here is the same image with current radar overlaid.

Appalachian pulse storms

ProbSevere has picked up on pulse convection in West Virginia (figure 1). A storm in a very weakly-sheared environment in eastern WV exhibited strong and moderate satellite growth rates and increasing MESH. It had a probability of severe of 70% by 1:30pm, about 25 minutes before the first NWS warning was issued. The storm later produced 1.75" diameter hail at 2:11pm.

Figure 1: Pulse convection in WV.

On the east slope of Tennessee, three storms that had moderate to strong satellite growth rates and MESH around 0.5 to 1.5" also had strong probabilities of severe (> 60%) prior to being warned. So far, the northernmost and southernmost storms were reported to have 1" hail.

Figure 2: Pulse storms in eastern TN.

-Cintineo/Sieglaff

NearCast – Decreasing 780 mb Theta E = Weakening Storms in NW OH

CIMMS NearCast 780mb Theta E product depicted decreasing values from 15 UTC (first image – around 329 K in NW OH) to 19 UTC (second image – around 327 K in NW OH)  on May 13.  Storms seemed to decrease in coverage and intensity 18-20 UTC in NW OH.  The decrease in mid level moisture around 780 mb may have caused the decrease in storm coverage and intensity.

The GOES Vertical Theta-e Differential Mid-Low product showed an increase 15 to 19 UTC from -5 K to +1 K, which may have helped to cause the decrease in storm coverage and intensity.

Michael Scotten

Convection in the Hoosier state

During day 2 of the HWT this week, the forecasters are tracking a line of storms heading through Michigan. Further south, however, storms fired along the cold front prior to our shift (~11:00am on May 13) in Indiana. In figure 1, we see part of the line with an elevated probability of severe (from the NOAA/CIMSS ProbSevere model). A strong satellite normalized vertical growth rate and moderate glaciation rate contributed to probabilities in the 45-55% range. The environment was marginal, and the MRMS MESH started to increase in the 0.6-0.7" range. When the NWS issued a severe thunderstorm warning, the MESH spiked to 1.84" and the probability increased to 96%. This storm later produced wind damage in northern Indiana.

Figure 1: Early convection over northern Indiana.

Further south, more storms developed on or ahead of the cold front. You can see that for the featured storm in eastern Indiana (figure 2), the strong satellite growth rates jumped the ProbSevere probability from 4% to 51%. MESH was only around 0.3". The NWS did issue a warning on this storm at 2:30pm (figure 3), 16 minutes after the first probability of over 50%. No reports have been recorded yet.

Figure 2: Convection in eastern IN. Satellite growth rates contribute to elevated probability of severe prior to NWS warning. MESH was very marginal.

Figure 3: NWS warning that came out at 2:30 PM.

-Cintineo/Sieglaff

GOES-R Convection Initiation NW OH

The 1930 UTC GOES-R Convective Initiation image on May 13, 2014 depicted yellow  (65%), green (58%), light blue (46%), and several darker blue pixels (less than 40%) across northwest Ohio ahead of a line of storms.  There was a small cell that developed near the green pixel at 1945 UTC (third image below) moved northeast at 1958 UTC (fourth image below).  A cell developed and moved into the yellow and light blue pixel areas at both the 1945 UTC and 1958 UTC images below.

This product seems to do a good job highlighting higher potential areas for convection initiation (if 50% or greater) compared to lower chances (50% or less).

Michael Scotten

Tuesday 19Z – NSSL WRF Simulated Imagery

Just a quick blog update to show how the NSSL simulated satellite imagery is behaving.  It is not doing all that well, unfortunately.  It seems well overdone across central Indiana, where outflow from earlier storms has undercut convection and largely caused it to die out.  In our area of the day (Detroit CWA), the convection is well underdone.  We have ongoing strong to  locally severe storms, that the model does not have a handle on at all.

The simulated imagery is on the left-hand column, with the observed 19Z imagery on the right.

-Deitsch

NOAA/CIMSS Prob Severe Model – Idea for Improvement for Linear Storm Modes

The CIMSS Probability Severe Model indicated low probability for severe storms 5-10% for a fast moving line of storms over eastern Michigan (northern part of line moving 50-60 mph) at 1928 UTC on May 13.  It seems to be a good idea to include DCAPE as a displayable variable in addition to MUCAPE, EBShear, MESH, Vertical Growth Rate, and Glaciation Rate and use this variable for calculating SVR PROBs.  The low probabilities are likely due to MESH values well below 1 inch (closer to 0.25 to 0.50 inch) as well as EB Shear generally 20-25 kt.

Michael Scotten

EWP Status for 12 May 2014: 12:30-8:30 pm Shift

Today, the threat for severe weather appears to be quite marginal, the bulk of which will be forced by the eastward propagating cold front. We have two forecasters operating in the Detroit CWA, and two in the Cleveland CWA. Similar to yesterday, convection was already ongoing this morning when participants began operations. However, there has been some new development out ahead of the front.

Today's domains were chosen in part based off of input from the EFP. You can see from the image below, the EFP expects the greatest likelihood for severe weather to be in eastern Michigan south into western Ohio.

- Bill Line, SPC/HWT Satellite Liaison and Week 2 EWP coordinator

Daily Summary: Week 2, Day 1

Much of the focus for day one was hands-on training for each of the evaluation products. After some initial familiarization with AWIPS-II, the various PI's worked with forecasters on how to interpret the products, and what to look for during the week. Forecasters also became familiar with saving images, and posting to the blog. By the end of the day, participants had already made several informative blog posts.

Today we operated in the Davenport and St. Louis CWA's. Since many of the products being demonstrated have their greatest benefit in the pre-storm environment, forecasters were unable to experience their full potential given the ongoing convection at the beginning of operations. The Prob Severe and Overshooting Top Detection products seemed to have the most utility in this situation. Additionally, forecasters appreciated the availability of the GOES-14 1-minute imagery.

Tomorrow, we will start activities at 12:30 in the Dev Lab for the daily debrief before moving to the HWT for the EFP briefing. Operations will likely take place somewhere in the Ohio Valley region.

NearCast

• I worked a lot with the theta-e difference field. I focused on a line of storms in central Missouri, theta-e difference in front of storms was -20 K. That was consistent through the forecast as storms moved forward. A bow echo formed, pop up storms filled in the area where high instability was, then the line accelerated.
• There was a lack of data in the area today

GOES-R CI

• There was a differential heating boundary in northern Illinois. CI did provide lead time to a few isolated showers and storms (45 min) around 22Z. 
• So much high level cloud cover along and ahead of front prevented usefulness
• Pop up short lived pre-frontal showers. In SW Missouri I saw 90%, storms popped up and then fizzled. Then more development and more fizzle.
• CI did not pick up on a storm near Chicago

Prob Severe

• Large cell kept maintaining a high prob (>80%), and stayed severe.
• 50 to 60 to 77, then storms produced severe weather
• I liekd having CAPE and shear output. It gave me good situational awareness about the environment.
• It would be great to use SPC mesoanalysis data
• In a field where there is a lot of storms popping up, it does well at highlighting ones to watch

Tracking Tool

• I like the trends, but getting the storm motion was difficult (it was intensive to move each circle for each time).

Overshooting Top Detection

• I liked it, but I found that it was more useful just to examine the one minute data with the human eye during the day
• Might be good for flash flood situations, providing lead time
• I liked looking at it for the overall trends. Cold pool developed that overran front, OT's went away, then storm weakened. 

GOES-14 SRSOR (1-minute imagery)

• I don't know anyone who wouldn't like this
• Removed from wow factor, the things you see makes it worth it
• Around great lakes looking at advection fog, I wish we had 1 minute updates so we could see how much fog is spreading inland.
• I see value especially in radar sparse areas
• Examples of features seen in 1 minute that you didn't see in 15 min?
• Watching a storm with an enhanced V and OT, the OT collapsed, and I issued a warning. This had positive lead time to hail reports
• I was looking at a differential heating boundary. North had cirrus, south had a lot of bubbly.  As soon as the cu moved into the cirrus, it died off. It is something that in 15 minute scans you just couldn't see. 

- Bill Line, GOES-R SPC/HWT Satellite Liaison and Week 2 EWP Coordinator