Winter Outlook Part 2

In the first part of my winter outlook, I talked about how day-to-day weather is highly variable and rarely "normal". This is important to note, because long range forecasts can be deceiving. For instance, if I were to say this winter will be warmer than average, there will still be many days which are extremely cold. But when you average everything together, it would be mild compared to other winters.

In addition, it is important to remember that an "average" winter is just a calculation. It's rare to have a winter that has an exact amount of snow that matches the average. Usually you will fall on either side of the average...the real question is how far.

With all of that said, here are the average temperatures, snowfall and precipitation (snow with rain) during the winter. This will serve as a guide for the upcoming winter months. 

First I'm going to show average highs and lows during the coldest month of the year: January.

Now let's look at snow. This is an annual average because higher elevations and areas farther north can receive snow into April and possibly May.

Lastly, here are maps for total precipitation: rain and snow combined. I'm only including the months during meteorological winter: December, January, February.

Winter Outlook Part 1

The first part of my winter outlook will start off with some definitions and clarifications. I want to emphasize that both climatology and long-range forecasts are extremely complex topics. In fact, even the most seasoned meteorologist will make a mistake by saying that day-to-day weather is "normal" or "seasonal". Here is some data from this month to show you what I'm talking about.

These are the measured high temperatures in San Diego, CA and Richmond, VA for the past ten days:

San Diego
Oct 17...86
Oct 18...88
Oct 19...85
Oct 20...80
Oct 21...81
Oct 22...85
Oct 23...90
Oct 24...79
Oct 25...62
Oct 26...66

Oct 17...82
Oct 18...81
Oct 19...70
Oct 20...63
Oct 21...66
Oct 22...64
Oct 23...66
Oct 24...70
Oct 25...70
Oct 26...77

The 30-year average high for San Diego in late October is 72 while in Richmond it is 68. Notice that none of the measured high temperatures match the average high (each day is above or below the average).

So if you are a meteorologist who lived in San Diego, why would you describe Oct 24 as "unseasonably warm" if every October you see highs reaching the upper 70s? Similarly, if you lived in Richmond, why would you describe October 26 as "unusually warm" if every autumn temps rise to this level? I had a professor who said it best: "The most normal thing about weather is that it is abnormal". This is a great way to describe day-to-day weather. A 30-year average for a specific date is worthless (like when you hear a meteorologist say "Today's normal high is...)

You should only use the average over several days or weeks to describe something "unseasonable". This will be key when I talk about long range outlooks and how they compare to the average.

Ok, I'm now done with my weather vs. climate rant :)

10/6/2011 - Rain Totals From Yesterday

Isolated showers could still pop up today as the core of the storm system passes our area. Rain totals from yesterday were impressive in some areas. San Diego received 0.42". Totals were much higher in the mountains, where Julian tallied 1.49" and Palomar got 2.45". Here are the rest of the totals:

10/5/2011 - Showers Likely For Most Of Southern California

Scattered showers will move across the area this afternoon and evening. Most of the rain will taper later tonight, however, isolated showers will still be possible Thursday morning and early afternoon. Rain totals will range from .25" to 1.0" along the coast and into the inland valleys. Higher elevations to the west will pick up 1 to 2".

(Rain Totals)
Winds will remain sustained 15 to 25 through Thursday evening. Gusts will peak up to 35 to 45 mph off the coastal waters and for the western half of San Diego county (mountains and desert).

Waves will steadily increase as the core of the storm system approaches. Swells will peak out at 2 to 5 feet by Thursday morning, then drop back down to 1 to 3 feet Thursday evening.