Monitoring Severe Weather Outbreaks Online

Fair warning; this is a VERY lengthy post. However, the information within this post is EXTREMELY important, especially for those who live in areas that are prone to severe weather. I do ask you to read through this post, as it breaks down the steps taken to monitor severe weather; using today’s (11/17/13) severe weather outbreak as an example. Additionally, some of the links may change following today’s event (they are “live” pages) – however, archived information can be pulled from the links by entering the date for Nov. 17, 2013.

First of all, in order for chasers and spotters to be activated by National Weather Service officials, there must be a considerable chance of severe weather. Many spotters and chasers analyze model imagery for elevated chances of severe weather. When the models begin to come into agreement, the potential of an event arises and usually, the Storm Prediction Center (SPC) issues a statement on the threat. These statements can be found on the SPC’s Convective Outlook, which are detailed for days 1 through 3, and threat areas mentioned for days 4 through 8. At the bottom of each image is a synopsis and analysis of the threat (although with the extensive meteorological jargon, it may be hard to understand for some). Today’s Convective Weather Outlook is a prime example of what the product looks like for an outbreak.

With today’s event, many NWS offices have activated their storm spotter networks. The individual NWS offices release statements, commonly in their Hazardous Weather Outlooks, that have a statement regarding spotter information. For an example, here is the Hazardous Weather Outlook for today’s event from the NWS office of Lincoln, IL. Additionally, the SPC will issue Public Severe Weather Outlooks (PWO) which is aimed at state and local emergency managers, along with spotters, chasers, and the general public. The information within a PWO is explained in terms that are easier to comprehend compared to the convective outlook discussions, and also provides a statement of precautions for the public to follow. I suggest to take the time to compare today’s PWO with the discussion of the convective outlook hyperlinked in the prior paragraph; can you tell the difference? Additionally, Severe Weather Specialist Dr. Greg Forbes of The Weather Chanel updates his Tor:Con for events such as these, with today’s highest Tor:Con value as a 9 for central and eastern Illinois and Indiana.

Now for the day of the potential severe weather outbreak, Mesoscale Discussions (MDs or MSDs) are issued by the SPC regarding the threat and potential for watch issuance. A national list of MSDs can be found on a branch of the SPC’s website. To view the MSD, simply click one of the red areas or one of the items on the list below. For an example of a MSD, here is MSD #2011 that was issued for much of IN, central/lower MI, and northwestern OH. Within the MSD discussion, the threat is listed and described (meteorological jargon, yet again), along with the probability of watch issuance and sometimes, even the specific type of watch (which for #2011, was 95% for a tornado watch).

Continuing on from Mesoscale discussions are the watches that are often issued shortly after the issuance of a MSD. Watches mean that conditions are favorable for the occurrence of a specific weather event. For this example, I want to focus on the tornado watches that have already been issued for today’s event. Additionally, I can take you a step further by introducing you to a rare form of a watch; a PDS. First, all active convective watches can be found on another branch of the SPC’s website. First example is of a regular tornado watch, TW #563; along with an evaluation of the threat, there are many other sections of information along with safety precautions within the watch page. I also suggest taking the time to flip through the different tabs at the top of the watch image to familiarize with the different information.

Now, for the introduction to the PDS watch. A PDS watch is issued when the threat is extremely high for significant severe weather and/or tornadic activity. PDS stands for Potentially Dangerous Situation, and although it can be issued as a severe thunderstorm watch (usually for a high probability of damaging winds or extremely large hail), it is most commonly seen as a tornado watch. For this example, I will use PDS TW #561 (which was the resulting watch issuance of MSD #2011, linked above). The information within the watch is similar to that of the normal tornado watch. However, there is a considerable difference regarding the risk evaluations.

Following the development of a thunderstorm, there is the potential for a warning to be issued. Warnings mean that the event is imminent or already occurring. Although you can find a list of warnings on a branch of SPC’s page, I prefer the self-updating warning page from the College of DuPage’s Meteorology department. Within the warning texts are reports, radar information, hazard information, location of threat, path of threat, and precautions for the public to follow. Something to always remember is to heed all warnings issued by your local NWS office!

The last topic I wish to touch is storm reports. Storm reports are very important when it comes to producing new warnings or analyzing an event. Even though most storm reports are relayed by emergency managers, state/county officials, and trained storm spotters and chasers, the public is also encouraged to make reports to their local NWS offices. The SPC keeps a current list of storm reports, which are separated into unfiltered and filtered categories. Often times, there is a statement within warning text on how to make a report to your local NWS office. First of all, here are the guidelines, events, and criterion for making a report. Additionally, if there is no information regarding how to make a report, different methods and instructions for making a report can be found here.

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Derecho: Becoming the Most Widely Used Meteorological Term

Before the North American Derecho of June 2012, very few outside of the meteorological world knew what the term “derecho” meant. However, after the night of June 29th, “derecho” would quickly become one of the most used meteorological terms thrown at any kind of storm system. The reasoning for the constant use of the term could very well be attributed to fear caused by the initial occurrence of the June derecho. However, I’ve also seen the term thrown around to give ratings a healthy bump over the past year.

First of all, let’s classify a derecho. According to the Storm Prediction Center’s Facts about Derechos page, a derecho (pronounced “deh-REY-cho”) is a “widespread, long-lived wind storm” known for producing severe straight-line wind damage. In order to be classified as a derecho, there must be wind damage over a swath of at least 240 miles, include wind gusts of at least 58mph along most of its length, and have several 75mph or higher wind gusts within the swath. By reading down further on the SPC’s Facts about Derechos page, there is much more information regarding derechos than I’ll be posting here.

Derechos are not uncommon in the United States as shown by the SPC’s Derecho Climatology map. They are most common in the Midwest and Mississippi River Valley and mainly occur during the peak severe weather season (May-July) as shown by this graph. Regarding the occurrence of derechos throughout history, we can see just from a small compilation from SPC’s Derecho Facts page that there are many other derechos that have affected the Mid-Atlantic region just in the past 45 years. With proof that other derechos have occurred in the same area, why is there such a reaction following a single occurrence? Quoting the infamous Tootsie Pop commercial, “The world may never know.”

Let’s go back to the day of June 29th, 2012 by looking at some of the following images (via. hyperlinks). As shown by the SPC’s Surface Analysis map issued 1pm CDT on June 29th, it was a hot and humid mess throughout most of the Eastern half of the US. However, what caught many off guard was the failure of forecasting the event. As shown on the NWS’ assessment of the event (p.10-12), there was inadequate model data capable of forecasting more than a day out. The inadequacy of the model data is portrayed through the Convective Outlooks (p.12-15). By looking through the rest of the assessment, the discussion about the overriding of warning systems and the issuance of severe weather watches and other texts unfold as the derecho powers through the Appalachians. Even though the mountains weaken the derecho, it does not completely “kill” the storm as meteorologists and forecasters assumed. As shown in the radar loop, the derecho flares back to almost full strength as it moves into the DC/Baltimore area, leaving behind it massive amounts of damage.

Now let’s tie in the title of this post to the content. Ever since the June 2012 derecho, I have heard the term smeared and slathered onto everything that even looks the slightest bit similar. Amateur forecasters, along with those who love the publicity on social media, clamored at the term the very second a model run showed the possibility for thunderstorm development. Although I understand that such events help with the ratings (or amount of “likes” in current situations), instilling a fear in your followers that such an event is coming four days to a week out is NOT acceptable. Hyping up the public because one model run showed something that looked the slightest bit similar to a derecho is not good forecasting. If the slight possibility must be mentioned, do so in a manner and tone that portrays the inaccuracy and variability of a single model run.

Meteorological technology is not even coming close to the pinpoint accuracy we so desperately desire, so it should never be treated as such.  However, it is the responsibility of meteorologists, forecasters, and the general public to monitor each plausible situation that may threaten their areas. Even though there was poor forecasting in advance of the Mid-Atlantic derecho, as that afternoon and evening of June 29th, progressed, it became clear that those in the Mid-Atlantic were going to have an *electrifying* night.

Links for further reading:

“The Ohio Valley/Mid-Atlantic Derecho of June 2012” (SPC)

“Derecho of June 29, 2012” (Capital Weather Gang, The Washington Post)

Service Assessment of “The Historic Derecho of June 29, 2012” (NWS)

Event summary of “The Derecho of June 29, 2012” (NWS Baltimore/Washington, KLWX)

“Ring of Fire Derecho (Ref + Velocity Two Panel)” (Daryl Herzmann, YouTube)

“About Derechos” (SPC)

“Satellites Examine a Powerful Summer Storm” (NASA)