Half of Indiana (shaded in dark green on the map, above-left) has a marginal risk of severe thunderstorms between 9 a.m. EDT today and 8 a.m. EDT tomorrow, according to the “Day 1 Convective Outlook” that the National Weather Service Storm Prediction Center (SPC) issued at 8:52 a.m.
The primary risks are damaging straight-line thunderstorm winds of 58 mph or stronger and hail of one inch or more in diameter. The probability of either occurring within 25 miles of any point in the slight risk area is five percent.
The normal hail probability for any May 12 is about one percent, so today’s probability is roughly five times normal.
There’s no reason to be alarmed by a marginal risk, but if you live in that half of Indiana, it’s wise to remain weather-aware today, especially if you’ll be involved in any outdoor activities (e.g. baseball games, etc.). Remember that all thunderstorms, severe or not, bring lightning, which kills people who are outdoors.
The SPC plans to update its outlook for today by 12:30 p.m. EDT.
Earlier, in commemoration of Indiana Severe Weather Preparedness Week, I wrote about the important distinctions between watches and warnings. Readers who saw that post will recall that the National Weather Service usually issues weather watches hours before severe weather develops in the watch area.
You can also know about the possibilities of severe weather days in advance, if you know where to look.
In addition to watches, the NWS Storm Prediction Center (SPC) issues convective outlooks. In this case, “convective,” refers to thunderstorm development through atmospheric instability. Convective outlooks include maps that show various risk levels for severe thunderstorms in various parts of the country as far into the future as six days.
For example, on April 27, 2014, a large, violent tornado killed 16 people in Vilonia and Mayflower, Arkansas. Five days earlier, the SPC indicated a risk of severe weather in that area on a convective outlook map (see below).
Anyone who wants an advance look at severe weather probabilities can look at SPC convective outlooks on the SPC website. During severe weather season, I review every morning at least the “Day 1 Convective Outlook” (which shows risks for the same day) and the “Day 2 Convective Outlook” (which shows the next day’s risks).
For a more localized outlook, I also view the “Hazardous Weather Outlook” that our local NWS office issues. This text-only product indicates local forecasters’ assessment of the risks of hazardous weather within their coverage area the same day (day one) and for the following week (days two through seven).
So, what can you do with this information? When an outlook indicates a risk of severe weather in a few days, you can:
Develop and/or review a plan for what to do if sever weather strikes.
Encourage others to develop a plan.
Assemble a disaster supply kit and pet kit.
Check your NOAA All Hazards radio for fresh batteries and operation.
By knowing about outlooks, watches and warnings when they’re issued, you can keep from being surprised by severe weather.
For the first time in a couple years, meteorologists from the northern Indiana office of the National Weather Service (NWS) personally conducted training of SKYWARN storm spotters in Fort Wayne Feb. 17. Warning coordination meteorologist Michael Lewis, KG4KJQ and meteorologist Michael “Skip” Skipper presented the training to an official total of 91 attendees. Approximately half of audience members raised their hands when Lewis asked hams to identify themselves.
The session included the usual information on the role of the spotter, storm development, local severe weather climatology, recognition of various weather phenomena, spotter safety and reporting procedures. A detailed description of the training is beyond the scope of this article, which will instead touch on a few of the highlights, especially those portions that were new this year. If you missed the training, NWS plans two sessions near Fort Wayne this month:
One new feature of the training this year was audience participation via electronic polling. The presenters evaluated audience knowledge before and after the training by asking them to respond to questions via text message, Twitter or Web page form. Responses appeared on the projection screen in real time.
Thunderstorm spectrum discussed
One highlight of this year’s presentation was a discussion of the thunderstorm spectrum (see figure 2). It ranges from single-cell “pulse” storms, to two forms of multi-cell storms, to the classic supercell thunderstorm. Large, strong tornadoes originate from supercell storms, but such storms are rare in the 37-county warning area (CWA) of the northern Indiana NWS office. Multi-cell storms, especially “derecho”-type squall lines can produce winds as strong as weak tornadoes, which is why spotters and the general public should not ignore severe thunderstorm warnings. It’s important for spotters to understand that, especially in the northern Indiana CWA, storms can change type one or more times during their existence.
When it comes to tornadoes, 82 percent of twisters in the northern Indiana CWA create damage at the EF0 or EF1 levels of the enhanced Fujita scale (see figure 3). Note that EF0 tornadoes can have winds as week as 65 mph. Severe thunderstorms can and often do produce much stronger winds. Also note that EF0 and EF1 tornadoes are very difficult for NWS Doppler radar to detect, sometimes developing and dissipating between radar scans. Less than one percent of storms in the northern Indiana office’s CWA reach the EF4 damage level, with wind speeds of 166 mph or greater.
Convective outlooks change
Situational awareness is an important part of spotter preparation and safety. The NWS Storm Prediction Center’s (SPC) convective outlooks are important situational awareness resources. Those outlooks look different now (see Figure 4). The new day one through day three convective outlooks have three risk categories between “general (non-severe) thunderstorms” and “moderate risk,” instead of the former single “slight risk” category. A “marginal risk” category now falls between “general thunderstorms” and “slight risk” and new “enhanced risk” category falls between “slight risk” and “moderate risk.” An SPC video briefing that fully explains the change in convective outlooks is available on the SPC’s website.
Also related to situational awareness is the announcement that the NWS office’s home page layout – and possibly navigation and URLs – will soon change. If you have bookmarked, for example, the severe weather briefing page on the northern Indiana office’s website, you might need to update your bookmarks after the change.
New spotter mnemonic: T.E.L.
This year’s training presentation uses a new mnemonic acronym to help spotters remember what the NWS needs to know (see Figure 5): “T.E.L. us.”
The “T” stands for “time.” Spotter reports should contain the clock time at which the spotter observed the event, even if it’s happening while the spotter sends the report. For example, rather than saying “now,” or “two minutes ago,” spotters should say “4:38 p.m.” or “1638 Eastern time.”
The “E” stands for “event.” This is the part of the report that contains detailed information about what the spotter saw, for example, hail (by size), a wall cloud, funnel cloud, tornado, wind or lightning damage (described), flooding, etc.
The “L” stands for “location.” This part of the report should contain a specific location, for example, “Allen County, Indiana, two miles northwest of Grabil,” or “In Fort Wayne, near the intersection of Coliseum Boulevard and Vance Avenue.”
Note that the reporting criteria are different than NWS warning criteria. For example, the NWS issues a severe thunderstorm warning for any storm that it expects to produce either winds of 58 mph or greater or hail of one inch or more in diameter. But the spotter reporting criteria are winds of 50 mph and hail of any size.
Finally, the NWS included in this year’s presentation a new reporting method matrix (see Figure 6). As in previous years, the meteorologists strongly recommended the use of the Twitter social media channel, while taking care to avoid discounting the importance of ham radio.
A primary advantage of reporting via ham radio is that others listening to the same frequency will simultaneously hear the report, aiding in the situational awareness of those who are monitoring. Another advantage is the resiliency of ham radio and the fact that it continues to work during Internet and cellular telephone failures. Disadvantages of reporting via ham radio include:
Inadequate volunteer staffing of the ham station at the NWS office often means that net control stations must re-file the reports by other means (e.g. telephone or an internal NWS Internet chat system).
When the ham station at the NWS office is staffed, the operator there must write down each report and then hand it off to a meteorologist, creating a certain amount of delay.
Until and unless the NWS issues a “local storm report” based on the spotter’s report, the information in the report is available only to those who are monitoring the frequency, which often includes few of the many spotters who are not hams and have no equipment with which to monitor.
Ham radio systems currently in use for SKYWARN provide no means of including photographic data with spotter reports.
Advantages of the Twitter social media channel include:
The channel does not rely on the limited availability of volunteer operators at the NWS.
Reports show up immediately on a computer in the NWS office, without relay or transcription.
Reports are visible immediately to anyone who has access to the Internet, including other spotters, emergency managers, members of the news media and the general public. As Lewis put it at one training session this year, “Call me and you and I know. Tweet me and the whole world knows.”
Reports can include photographs or video of events being reported, aiding in the NWS’ ability to validate the reports
The capacity of Internet channels is virtually unlimited, enabling the NWS to encourage sub-criteria reports.
Note that on the reporting methods matrix, the NWS encourages spotters to report winds of less than the normal reporting criteria of 50 mph (the approximate speed at which structural damage begins to occur) when using social media or the “mPing” app (more on that below). But for ham radio and telephone reports, the minimum wind is 50 mph. This is a sign that NWS really wants much more information from the field than it has received in the past but understands the limited capacities of channels such as ham radio and telephone.
For spotters who choose to use their Internet-connected mobile devices to file reports, a relatively new option is the Meteorological Phenomena Identification Near the Ground (mPing) app from the National Severe Storms Laboratory. The app is available for both the Andoid and iOS platforms and originally only accepted precipitation reports. The current version also allows users to send hail, wind damage, tornado, flood and other reports. Reports sent via mPing show up directly on Advanced Weather Interactive Processing System (AWIPS) terminals in NWS offices. A disadvantage of mPing is that all reports are anonymous and as such, users cannot identify reports as coming from trained spotters.
In conclusion, I encourage all hams who are spotters to become familiar with Twitter, especially those who have Internet-connected mobile devices (e.g. smart phones). At the same time, I also encourage all hams to continue to make reports via ham radio, even if they’re also reporting via Twitter. This will assist in the situational awareness of spotters who are on the ham frequency as well as those who are only able to monitor Twitter.
I have become active on Twitter (@RadioW9LW, if you’d like to “follow” me) and will be happy to provide any assistance I can to any spotters who want to know more about Twitter. You can reach me via the “Contact W9LW” form in the right-hand column of this blog.
The northern two thirds of Indiana and adjacent parts of Ohio, Lower Michigan and Illinois have a slight risk of severe weather between 8 a.m. EDT Saturday, July 12 and 8 a.m. EDT Sunday, according to the “Day 3 Convective Outlook” that the National Weather Service Storm Prediction Center (SPC) issued at 3:30 a.m. today.
This means that as Fort Wayne’s annual Three Rivers Festival gets started Saturday, damaging straight-line thunderstorm winds of 58 mph or greater and/or hail of one inch or more in diameter could threaten the festival’s mostly outdoor activities.
As you can see on the map above right, the slight risk area includes all of IMO SKYWARN quadrant two, except the Ohio counties of Putnam and Allen.
We won’t know much more about Saturday’s severe weather risk until the SPC issues a “Day 2 Convective Outlook” at around 2 a.m. tomorrow (Friday). I’ll write about that outlook sometime tomorrow morning, so check back on w9lw.farlowconsulting.com then.