What are the Ides of March and Why Should Anyone Beware Them?

The Murder of Caesar (1865) - Karl Theodor von Piloty

The Murder of Caesar (1865) – Karl Theodor von Piloty

March 15 is the “Ides of March”, which we know from the phrase “beware the Ides of March”.  But what are “ides” and why should anyone worry about them?

Under the old Roman calendar, the Ides of March was the date of the first full moon of the year.

March was important as the first month of the year for the same reason January is important on our modern calendar. The beginning of a week, month or year always always holds some psychological (and frequently, legal) importance.

Ides was an important day because it was one of three fixed points in each month of the Roman calendar.

Kalends was the first of the month, the day of a new moon. About a week later came Nones, the day of a half moon (or the “first quarter” as you’ll usually see it on a calendar). Another week later came Ides, with the full moon.

The Romans counted towards these marker days. So March 14 would be “the day before Ides”.  March 21 would be “7 days before Kalends”.

It sounds complicated, but remember that long before there was writing, people around the world could see the moon, and could accurately predict its phases. Many of us do the same thing when we count down the days before Christmas or New Year’s Day.

(By the way, our word “calendar” comes from Kalends.)

The only person who was ever warned about the Ides of March is long-dead: Emperor Julius Caesar. Caesar was assassinated on March 15, 44 BCE.

According to Greek historian Plutarch’s biography of Caesar, a seer warned the emperor that he would come to harm by the Ides of March.

That rather vague prediction is likely to be Plutarch’s romanticized fiction, although there is historical evidence that Caesar had been warned of an impending assassination attempt, even if it were not as specific as Plutarch’s version.

The phrase we know comes from Shakespeare’s 1599 CE play about Caesar’s assassination.

More than 400 years later, the phrase is still part of our cultural landscape, although most of us think it’s a general warning about a day that is unlucky, on par with Friday the 13th.

So what are “ides” and why should anyone worry about them? They’re a bit of historical trivia that should give no one any cause for worry.

The “Warmest Day of the Year” – Summer 2014 Recap

US-Warmest-Day-of-the-Year-MapEarlier this year, the National Oceanic and Atmospheric Administration (NOAA is the parent agency of the National Weather Service) released a map showing when each area of the U.S. typically sees its “warmest day of the year”.

The map reflects averages of 30 years of data, from the years 1981 through 2010.

NOAA’s map show that the metro Memphis area’s hottest day of the year usually comes during August 6-10.

This is toward the end of the six-week period when we experience our hottest average daily high temperatures. From July 5 to August 18, our daily highs average 92ºF.

Averages being what they are, we occasionally see midsummer days that come in several degrees higher or lower than that average.
—In July 2012, we had 7 days that reached 100ºF. (July 5, 2012 reached 103ºF!)
—In July 2014, we had two days that had daily highs that set records for being unusually cool. On July 18, we only reached 69ºF and the following day we only reached 79ºF.

Our hottest days for summer 2014 came during August 20 – 25. Usually, this is a period when we see some break from what is typically several weeks of dry, hot weather that begins in late July.

This year, we reached 96ºF for the first time on August 20, with temperatures peaking at 100ºF on August 24.

So August 24 was our “warmest day of the year” for 2014.

Despite this, we’ve generally had a slightly cooler, somewhat rainier summer than on average. (This in a year in which much of the U.S. was deep in drought and the world as a whole was experiencing the hottest July on record.)

For meteorological summer (June 1 – August 31) we saw only of 33 days (of 92) exceed their daily average high, and only 22 days exceeded 92ºF.

June July August
June 21 – 93ºF (90ºF avg.) July 12 – 94ºF (92ºF avg) August 5 – 94ºF (92ºF avg)
June 22 – 94ºF (90ºF avg.) July 13 – 93ºF (92ºF avg) August 6 – 94ºF (92ºF avg)
July 14 – 95ºF (92ºF avg) August 10 – 93ºF (92ºF avg)
July 23 – 94ºF (92ºF avg) August 19 – 93ºF (91ºF avg)
July 26 – 93ºF (92ºF avg) August 20 – 96ºF (91ºF avg)
July 27 – 93ºF (92ºF avg) August 21 – 96ºF (91ºF avg)
August 22 – 97ºF (91ºF avg)
August 23 – 99ºF (91ºF avg)
August 24 – 100ºF (91ºF avg)
August 25 – 97ºF (91ºF avg)
August 26 – 93ºF (91ºF avg)
August 27 – 94ºF (90ºF avg)
August 28 – 95ºF (90ºF avg)
August 29 – 95ºF (90ºF avg)

Long Range Forecast for March 9, 2014 – A Case Study (Conclusion)

On Sunday, March 9, 2014, the Memphis area National Weather Service recorded the following weather observations:

  • Sunrise — 7:19 AM (DST)
  • Sunset — 7:03 PM (DST)
  • High Temperature — 53 (1:54 PM DST)
  • Low Temperature — 41F (11:54 PM DST)
  • Conditions/Precipitation — Overcast, cloudy. No precipitation

45 days ago, AccuWeather forecast was: Rain – High 53 / Low 35

Ultimately, AccuWeather got the day’s high exactly right in that initial forecast on January 23.

However, it significantly underestimated the day’s low by 6 degrees. (I use “significantly” because temperature differences of 5 or more degrees are noticeable, the kind of difference people will comment on.)

It also incorrectly forecast rain. Although the day wasn’t rainy, it was overcast. Combined with the cooler-than-typical temperature, AccuWeather’s initial forecast was a pretty good indicator of the day: not great for outdoor recreational activities.

In that regard, I’d grade AccuWeather’s 45-day projected forecast to be a B+ effort: Correct in most of the essentials.

Still, AccuWeather offered so many different forecasts over the six weeks that this seems to be more a matter of random luck than accurate forecasting…more like getting the answer right on a multiple-choice exam.

Over the 45 days, AccuWeather’s forecast high ranged from 53F to 67F. The forecast low ranged from 35F to 48F.  Weather conditions ranged from “windy with rain” to “sunny” and every variation between.

It might have been more impressive if AccuWeather had made the forecast and then stayed with it more consistently. If it had made only minor adjustments, or deviated once or twice before returning to the same forecast, there might be a more compelling case for the 45-day forecast’s value.

The only way to more scientifically assess the value of AccuWeather’s 45-day extended forecast would be to repeat this exercise on a recurring basis.

Since the Washington Post and the meteorological community of professionals have already done that, I’ll trust their assessment that the forecast is unlikely to be accurate any other educated guess. (That is, combining historical averages with recent climate conditions…weather that’s been cooler or wetter than typical.)

Here are the essential previous entries in this study:

Long Range Forecast for March 9, 2014 – On The Day Itself…

For 45 days, I’ve been tracking AccuWeather’s long-range forecast for Sunday, March 9. The day itself has now come and gone. So what kind of day was it?

The actual weather on Sunday, March 9, 2014 was:

Mostly cloudy — High of 53 / Low of 41

Most of the day was overcast, gray and gloomy.  Morning fog and haze gave way to a heavy blanket of clouds as the day progressed. There was a burst of sunlight around 11:30 AM but it was short-lived.

There was no rain recorded in the area.  There were a few scattered sprinkles around the evening before, but no precipitation was officially recorded by the National Weather Service.

Sunday’s high of 53F occurred at 2PM DST.  The day’s low of 41F occurred Sunday evening near midnight as temperatures continued to fall to 39F at 2AM Monday morning.  Sunday morning’s low was 42F around 7AM DST.

Both AccuWeather and the National Weather Service expected the day to be partly sunny, which is an over-estimate of the amount of sun the day experienced. The day’s actual temperatures were 4-5 degrees cooler than the 57-58F highs the two services forecast.  The day’s low was also 4-5 degrees cooler than the NWS forecast of 46. AccuWeather’s forecast of a low of 42F was arguably accurate (within one degree of actual).

As an aside, our local Memphis WeatherNet, which I did not track during this exercise, also forecast the warmer temperatures.

Overall, this was one of those days when the weather forecast wasn’t very accurate. The slight chance for early morning rain didn’t pan out. But there was enough moisture in the air regionally to prevent the skies from clearing and the day from warming as much as expected.

I’ll put this day in the category of “disappointing”, but probably no more unusual than those days when it warms more than anticipated.

I’ll wrap up with one more entry in this series, recapping how well AccuWeather did over the 45-day period.

Long Range Forecast for March 9, 2014 – Sixth (and Final) Weekly Digest

Long-Range Forecast for Sunday, March 9, 2014 – A Study (Part Nine)

This is my sixth and final weekly recap of AccuWeather’s long-range forecast for Sunday March 9, 2014. For an overview about how weather forecasts are developed and why such a long-range forecast is unlikely to be accurate (and is controversial), see the previous posts in this series.

Historical average temperatures for the day in the Memphis area are High 62 / Low 42. While the NWS maintains historical data for other conditions on the day (precipitation, cloud coverage, wind speed, etc.), it’s not readily available to public.

On January 24, AccuWeather’s local forecast for March 9 was: Rain – High 53 / Low 35 (about nine degrees cooler than historical averages). In the weeks since, the forecast has suggested every combination of cool and warm, rain, clouds and sun. In the first four weeks of the period, forecasts were revised about every three days. In the final two weeks, the forecasts were revised daily, sometimes twice a day.

Here’s a breakdown of AccuWeather’s forecast revisions for the past week:
March 2: Cloudy with a Little Rain — High 54 / Low 40
March 3 (AM): Sunny — High 51 / Low 31
March 3 (PM) Sunny and Cool— High 51 / Low 31
March 4 (AM): Mostly Sunny and Cold — High 48 /Low 35
March 4 (Noon): Mostly Sunny and Cold 51 / 41
March 4 (PM): Mostly Sunny and Cold — High 48 / Low 35
March 5 (AM): Partly Sunny — High 54 / Low 38
March 6 (AM): Partly Sunny — High 61 / Low 45
March 7 (AM): Partly Sunny  — High 55 / Low 47
March 8 (AM): Parrtly Sunny — High 57 / Low 42

Beginning March 3rd, the National Weather Service began providing forecasts for Sunday, March 9.  (For reasons stated earlier in this series, the NWS only publishes projections six days in advance.)  Over the week, the NWS revised its forecast a couple times a day. (I misplaced two days of data, for March 5 and 6, but they were in line with the forecasts immediately before and after the missing days.)

Here’s a breakdown of the NWS forecast revisions for the past week:
March 3 (AM): Sunny, with a high near 55.
March 3 (PM): Partly sunny, with a high near 63.
March 4 (AM): Partly sunny, with a high near 61.
March 4 (PM):  A 20 percent chance of rain. Mostly cloudy, with a high near 61.
March 7 (AM):  A 20 percent chance of showers. Mostly sunny, with a high near 60. Evening: Clear, with a low around 46.
March 7 (PM): A 20 percent chance of rain. Partly sunny, with a high near 58. Evening: Clear, with a low around 46.
March 8 (AM): Partly sunny, with a high near 58. Evening: Mostly clear, with a low around 46.

While both services start with the same data, the difference in their forecasts indicate some difference in how they interpret the data.  Certainly, a for-profit company like AccuWeather is not going to share their forecast algorithms, but this week they have consistently forecast a slightly cooler day than historical averages.

Both services also forecast a chance of rain Saturday night that will continue into Sunday morning.  AccuWeather doesn’t mention it unless you drill down into the day’s forecast details, while the NWS gives the details on the forecast home page.

Monday I’ll post a recap of the day itself, followed by one more post that evaluates how well AccuWeather’s attempt at predicting the weather 45 days in advance turned out.

In the meantime, catch up on previous entries in this series: