Monday, September 23, 2013

Lies ... and (weather) statistics

I'm sure you've heard the old saying about the three kinds of lies, in which the third "kind of lie" is statistics.

That bit of wisdom played out during the weekend with Charlotte's weather.

If you look at the monthly statistics from Charlotte Douglas International Airport, we've had above-average rainfall for the month. The official rainfall total is 2.89 inches, and that is nearly a half-inch above average for this time in September.

As we all know, that's a deceptive number. If you look at that total, you'd think September has been a relatively wet month.

In fact, measurable rain has fallen only three days. And 2.74 inches of that 2.89-inch total came Saturday night, with the passage of a cold front. There also was .14 of an inch Sept. 1, and .01 of an inch the next day.

It has been, in short, a dry month -- despite what the numbers say.  Certainly, the heavy rain Saturday night will help bring a little life to growing things in the region, and it will give a boost to the water table.  But it hasn't been a wet month.

John Tomko, who does the number-crunching at the National Weather Service's office in Greer, S.C., is fond of saying that meteorological averages are merely the result of extremes. In other words, our annual Charlotte snowfall of about 5 inches really comes from some winters with 8 or 10 inches, averaged out with winters with an inch or less.

Incidentally, Charlotte is now 7.25 inches above average at this point of the year, with 38.21 inches. We already have received 5 inches more precipitation than all of last year, and we're approaching the average number for the whole year.

Friday, September 20, 2013

Your weekend: Wet, then nice

It looks like we'll be able to salvage one dry day from the coming weekend.

That's good news is you have outdoor plans Sunday.  If you have plans for Saturday, it's not so good.

A cold front will push across the Carolinas on Saturday. Earlier in the week, some of the computer models hinted that the front would move very slowly across the region, giving us a good chance of rain for several days.

But the models now are pretty consistent in pushing the front east of our area later Saturday night and early Sunday. So let's deal with the good parts of the weekend first.

Friday night will be great for high school football, Festival in the Park, or anything else you have planned.

Temperatures actually are a bit on the warm side, with Friday afternoon readings in the middle and even the upper 80s. Expect temperatures in the 70s on Friday evening.

Sunday also should be a keeper. A few showers might linger into the morning hours, but they should push east of the Charlotte region by sunrise, or maybe an hour or two later. That will set the stage for a very nice day, with at least partial sunshine and high temperatures climbing into the upper 70s.

If you're headed to the Carolina Panthers' game against the New York Giants, figure on temperatures around 72 degrees at kickoff.

Then there's Saturday.

It's pretty much a given that the afternoon and evening will be wet, and possibly stormy. The computer models show a fair amount of atmospheric instability, especially along and southeast of the I-85 corridor. That means a chance of thunderstorms.

The big question is when the showers and storms will arrive. In Charlotte, we might be able to salvage the morning hours, but don't be surprised if a shower arrives before noon.

Next week looks like a return to dry and seasonal temperatures.  There is no rain in the forecast after Saturday night for several days. Our afternoon highs next week will be mostly in the upper 70s.

Thursday, September 19, 2013

Wet or dry this weekend? It's still not clear

Weekend weather is a big issue in the Carolinas, and this weekend's forecast carries a lot of importance to people for many different reasons.

There are a lot of outdoor events on the schedule, ranging from football to festivals.  And while we have a slightly better idea about the weekend weather than we had yesterday, there still are some unanswered questions.

At this point, on Thursday evening, a couple things are clear:

FRIDAY EVENING ... If you're headed to a high school football game or the AutoFair at Charlotte Motor Speedway, you'll have no problems. The only exception to this is in the mountains, where showers and thunderstorms are possible Friday afternoon and evening.

For everyone else, though, the weather should be OK.  Forecasters expect a mix of clouds and sun with mild temperatures. Daytime highs should be in the low 80s, with evening temperatures falling into the upper 60s by midnight.

SATURDAY MORNING ... If your plans include children's sporting events, a golf game or tennis match, or perhaps heading to AutoFair or the Festival in the Park at Freedom Park, you're probably OK.

A cold front will be advancing on the Charlotte region Saturday, and clouds will be on the increase. On Wednesday, computer models were predicting the heaviest rainfall for Saturday night and Sunday, but the models now say the showers and storms will arrive by early afternoon.

SUNDAY ... This is good news.  Where the forecast looked very wet just 24 hours ago, it now has a drier appearance. Most of the computer models now predict the cold front will push east of the Charlotte region late Saturday night, allowing for partial clearing by noon Sunday.

That should clear the way for fans headed to the Panthers' game against the New York Giants, or for Festival in the Park and the AutoFair.

Now, for the uncertainty.  There are still some areas we're not sure about ...

HOW MUCH RAIN SATURDAY, AND WHEN? ... If your plans include attending a college football game or any of the previously mentioned outdoor events, it appears as if you'll get wet. But the computer models can't agree on whether the rain will be scattered and fast-moving, or if it'll be heavier and more prolonged.  The forecast trend over the past 24 hours has been for a faster-moving system Saturday, but it's a safe bet that you'll encounter some rainfall Saturday afternoon and evening.

RAIN EARLY NEXT WEEK?  The official forecast from the National Weather Service is for partly cloudy skies and seasonal temperatures Monday and Tuesday.  But if you look at some of the computer-generated forecasts, the Charlotte region still could be facing some very wet weather. Some of the models show a slow-moving low pressure system crossing the area, especially late Sunday and Monday.

We should have a better idea on this by Friday.

Wednesday, September 18, 2013

Gulf storm likely ... then what?

The area of disturbed weather which is meandering in the southern Gulf of Mexico is likely to become a named tropical storm within a day or two, according to the National Hurricane Center.

Even though the system might never approach our part of the world in the Carolinas, it will be something to watch.

The storm, which would be named Jerry, is expected to continue wandering rather aimlessly between the Yucatan Peninsula and the Mexican mainland for a day or two.

Then, forecasters expect a cold front to push down from the northwest. The question is:  Will Jerry link up with the front?

If so, the storm will bring gusty winds and heavy rain into the Texas coast.

At this point, it doesn't appear as if Jerry would become more than a tropical storm, and that would be good. When hurricanes are in the western Gulf of Mexico, bad things happen to our gasoline supplies and prices.

One interesting scenario concerns the possibility that Jerry wouldn't make the connection with the cold front and slide northeastward, up the front.  In that case, it would continue a slow drift in the Gulf, waiting for some larger system to provide a steering current.

I read a couple theories today that suggest Jerry might eventually push eastward next week and provide a threat to the eastern Gulf Coast or even Florida.  In that case, some of the heavy rain from the system could become a part of our weather.

As it stands, we appear likely to get a significant non-tropical rain event late in the weekend, as low pressure forms along the same cold front -- the portion in our part of the Southeast.

After several weeks of very, very quiet weather, things could begin getting noisy again.

Wednesday, September 11, 2013

A near-miss at a hurricane record

The modern record for latest first hurricane of the season has stood the test.

Tropical Storm Humberto became Hurricane Humberto shortly before 6 a.m. Wednesday, preventing 2013 from going into the books as producing the latest first hurricane since the U.S. government started tracking these storms for real in the mid 1940s.

The standing record was set in 2002, when Gustav became a hurricane about 8 a.m. on Sept. 11.

Humberto achieved that status a few hours earlier than that this morning.

Either way, it remains a very quiet year in the Atlantic and Caribbean basin. Humberto is expected to threaten only the Cape Verde Islands in the far eastern Atlantic Ocean.

An area of thunderstorms over the southern Gulf of Mexico could organize into a named system by Thursday or Friday, but all the computer models indicate that storm would push westward into the Mexican coast, far south of Texas.

There also is a disorganized area of showers and storms, a tropical wave, that will push from the northwest Caribbean Sea into the Gulf by the end of the week. But there are no indications that weather system will organize.

Friday, September 6, 2013

We're approaching a (non) hurricane record

Remember all those forecasts about above-average hurricane activity this season in the Atlantic basin?

Well, we're closing in on a very different type of record -- the latest in the season without a hurricane.

Since the U.S. government's weather agencies have been keeping tabs on hurricane activity in the Atlantic, Caribbean and Gulf of Mexico, the latest first hurricane was Sept. 11, 2002. That was Hurricane Gustav, which eventually reached Category 2 strength, grazed parts of the East Coast, and eventually hit Newfoundland.

With only a few disorganized systems in the Atlantic basin today, and conditions that are very unfriendly for hurricane development, it seems almost a certainty that we'll break the record.

The government has been watching hurricanes actively since 1944, according to what I've been able to determine. Weather records show the first hurricane in 1941 also came on Sept. 11, but there are no indications that we've ever gone later than that date without a 'cane.

The season started with a bit of a bang, with several systems reaching tropical storm status in July and early August. But over the past few weeks, the few tropical storms that formed were ripped apart by a strong westerly upper level wind flow. That's the type of situation you see in an El Nino year, but scientists say we're not experiencing El Nino conditions currently in the Pacific Ocean.

By the way, those westerly winds also insure that if anything were to form in the Atlantic currently, it would get shoved away from the East Coast.  It's a different story in the Gulf of Mexico, but there is nothing threatening the U.S. Gulf Coast at this time.

Incidentally, the second-latest date for a first hurricane in recent years was in 2001. Erin became a hurricane on Sept. 8 of that year.

Meteorologists remind us of two things, however.  First, all it takes is one strong hurricane to make it a memorable year.  Second, a series of storms can form in a hurry.  In 1941, for example, there were three major hurricanes (what we know today as Category 3 or stronger) after that initial Sept. 11 storm.