Why does the path keep moving east?

Forecasters were talking Sunday about Hurricane Irene slamming into south Florida. By Monday morning, it was north Florida. Later in the day, it was Charleston, and then Myrtle Beach.

Tuesday morning, it was Wilmington, then Morehead City. Now it looks like the Outer Banks -- or maybe not at all.

The continued eastward adjustment of Irene's predicted path has frustrated those responsible for planning emergency preparedness, although I'm sure nobody in south Florida is complaining about not being hit by a big hurricane.

But why the continued adjustments?

For starters, forecasting the path of a hurricane is not an exact science. You already knew that. Fifty years ago, meteorologists were hard-pressed to forecast the path 48 hours in advance. Now, they almost always get it right within 72 hours. It's the predictions beyond 72 hours that cause the problems.

As you might know, the path depends on a lot of factors.

In Hurricane Irene's case, the storm is expected to move into a weak area between two strong high pressure systems -- the "Death Ridge" over Texas (so named because it has been absolutely immovable this summer and has been death to any cold front or storm system that approaches), and the Bermuda high in the Atlantic.

Frequently this summer, circulation around the eastern side of the Texas Death Ridge has sent cold fronts into the Southeast. That's why we've had a lot of rain this summer and a few episodes of below-average temperatures.

That "weakness" between the two highs is called a trough, or a dip in the atmospheric flow. Hurricanes usually follow a path into such a weakness, and what happened with Irene is that computer models had a difficult time several days ago predicting how far south that trough would expand.

Imagine the trough as a roller-coaster, with the low end of the ride along the East Coast. Small low pressure systems riding along that trough can help steer a hurricane up the right side of the trough's path -- northeast, away from the U.S. coast.

Actually, we've seen this happen frequently in recent years. The last year I can remember when hurricanes barreled directly into the East Coast was 2004, when Frances and Jeanne pummeled Florida's Atlantic coast.

Some meteorologists think that as long as the Texas Death Ridge is in place (and who knows when that will break down!), the East Coast will have some built-in insurance against tropical storms and hurricanes.

Bill Reed, director of the National Hurricane Center, said in a morning news conference Tuesday that it's been tough, predicting exactly when Hurricane Irene will get caught in the upper-level flow, forcing a turn to the north and eventually the northeast. He's still not certain about the path, saying it could move back to the west or to the east.

I'm betting the east, because of the old weather saying, "The trend is your friend." And in Irene's case, the trend has been eastward.

Irene and the Carolinas ... Monday AM outlook

Hurricane Irene is leaving Puerto Rico and moving toward the north coast of the Dominican Republic on Monday morning, and while meteorologists now have a few more answers about the storm's future, there are still many questions.

As of now, the National Hurricane Center's official forecast for Irene calls for it to have nearly 120 mph winds when it makes landfall early Saturday morning between Savannah and Charleston.

Under that path, the remnants of Irene would have a major impact on the Charlotte area Saturday, with the threat of tornadoes and flooding rain, plus a chance of damaging winds.

But that is merely one of many, many possible scenarios.

First, here's what we DO know this morning that we didn't know Sunday night:

1. Irene is a hurricane, not a tropical storm. Its top sustained winds reached 75 mph overnight, while it crossed Puerto Rico. It's rather impressive that the storm strengthened despite crossing a land mass.

2. National Hurricane Center forecasters now think Irene will only graze the northern part of the Dominican Republic, rather than go over the center of the island of Hispaniola. This means the mountainous terrain of the island is not expected to affect the hurricane's circulation. And that means a stronger Irene down the road.

Then what?

Irene is predicted to move northwest, crossing the Bahamas as a hurricane. The computer models all agree with that.

By Thursday, however, the forecasts get uncertain. A trough is expected to move into the eastern United States. If the trough is deep enough (far enough south) and strong enough, it could curve Irene back out to sea. In other words, the hurricane's track would look like the tee shot of your golfing buddy with a bad slice -- off to the right.

And some computer models predict that.

WBTV meteorologist Al Conklin noted that this morning, saying that trends mean a lot in forecasting. And the trend in the predicted path of Irene for the past 24 hours has been eastward. With each adjustment from the National Hurricane Center, the storm's forecast track has been nudged a little farther east.

Conklin noted -- and he's right -- that when this happens, it tends to continue happening. If so, Irene could become an issue only for the Outer Banks. And should that happen, Charlotte and the rest of the Piedmont would get no impact from the storm.

But to be fair, it's also important to note that a few computer models actually show the storm moving farther west than the Hurricane Center's predicted path -- into south Florida and then up through Georgia and the western Carolinas.

Joe Bastardi, a former Accu-Weather meteorologist now with Weather Bell, is predicting landfall in the Carolinas, perhaps near Charleston or Myrtle Beach.

Larry Cosgrove, another private meteorologist with a big following, is pointing toward Myrtle Beach. And, he adds, "The hurricane will trigger almost biblical amounts of rain, with lots of wind, across parts of Appalachia and the entire eastern seaboard."

Dan Kottlowski of Accu-Weather says, "A look at track forecasts suggests a higher chance of Irene tracking along or just off the coast of eastern Florida and making landfall along the Carolina coast."

Something to note ... hurricanes almost never make landfall between Daytona Beach and Savannah. That's because of the curvature of the coast line.

More later.

Sunday night Irene update

There are no major changes in thinking tonight about the future of Tropical Storm (and eventual hurricane) Irene.

The National Hurricane Center's five-day forecast calls for Irene to pass near or over Puerto Rico tonight, then cross the northern part of the island of Hispaniola, before taking aim at the Bahamas and eventually Florida.

The bottom line: Nearly every forecaster agrees that the Carolinas should pay close attention in coming days to Irene.

At 8 p.m., the center of Tropical Storm Irene was at 17.8 degrees north and 64.9 degrees west. That's about 10 miles northwest of St. Croix, in the U.S. Virgin Islands; and 90 miles east-southeast of San Juan, Puerto Rico.

Irene's top sustained winds were 60 mph, and the storm is expected to strengthen into a hurricane Monday before hitting the Dominican Republic, which occupies the eastern half of Hispaniola (Haiti is on the west).

Hurricane warnings are in effect for Puerto Rico and the Dominican Republic, with tropical storm warnings posted for the Virgin Islands, Haiti and a few islands east of Puerto Rico. Tropical storm warnings also are in effect for the Turks and Caicos islands and for the southern Bahamas, with a tropical storm watch posted for the central Bahamas.

The computer models on Sunday afternoon shifted the predicted path of the storm a bit east. Some of the models show it staying east of the Florida coast and then curving out to sea. One of the highest-regarded models, the European, shows a direct hit on the South Carolina coast (possibly as a strong hurricane).

The National Hurricane Center is sticking with its forecast of a Florida landfall Thursday, and then the storm is predicted to move northward through Florida, headed for Georgia and the Carolinas.

I'll repeat what I said this morning ... a lot depends on how much interaction Irene has with Hispaniola's mountains. If the storm passes directly over the island, it will be weakened considerably as it heads toward Florida or the Carolinas. If it stays north, then look out!

Another player in this situation is a trough (weakness in the atmosphere) predicted for the East Coast late in the week. If the trough deepens and pushes a cold front south of the Carolinas, it could force Irene out to sea. If the trough is not that deep, then the Carolinas are in play.

On Sunday evening, Irene is lashing the Virgin Islands.

I received this YouTube video a short time ago from some Concord residents who are in St. Croix in the Virgin Islands. It gives you an idea of conditions there earlier this evening. http://bit.ly/oaFWGi

Very heavy rain is moving into Puerto Rico at 8 p.m. Sunday, and that island is in for a rough night.

Throughout the day, I've been monitoring messages from amateur meteorologists in Puerto Rico. About an hour ago, one of the more reliable weather watchers messaged that the winds are picking up and electricity is flickering on and off.

This could be a nerve-wracking week on the Southeast Coast.

It's Model-Watching Time for Irene

Anyone with an interest in meteorology is watching models today -- computer models.

The future track and strength of what is now Tropical Storm Irene is of intense interest across the Southeast, as forecasters and weather geeks try to determine if Irene eventually will threaten the U.S. mainland -- and how much of a threat it will be.

For the most part, the models agree on the track.

They carry the storm near Puerto Rico, across the Dominican Republic, and then brushing (or missing) eastern Cuba, before heading toward the Bahamas and Florida. Most of the models predict Irene will move into southeast Florida or along the east coast of the Sunshine State.

And after that? Will the storm curve back out to sea, or will it keep moving northward, on a collision course with coastal South Carolina?

The short answer is that nobody knows.

A trough will be setting up across the eastern United States by late in the week, when Irene approaches. How deep (how far south) will the trough extend? And will it get here before Irene does? It's too early to tell.

And it's definitely too early to tell about Irene's strength.

If the storm brushes the Dominican Republic and misses Cuba, it could be a major hurricane when it approaches the United States. But a direct assault on the Dominican Republic's 6,000-foot mountains could seriously weaken Irene, which is expected to be a hurricane when it reaches the island of Hispaniola.

We do know this is the first threat of the year for the Caribbean and the United States, but it will be early or mid week before we have a better idea on Irene's strength and course.

Tropical Storm Irene forms in Atlantic

Well, that didn't take long!

Less than an hour after writing that a tropical depression or storm could form this evening, the National Hurricane Center began issuing advisories on Tropical Storm Irene.

At 8 p.m. Saturday, its ill-defined center was at 14.9 degrees North and 58.5 degrees West. That puts it about 200 miles east of Guadeloupe and Dominica. The storm has top sustained winds of 50 mph.

Meteorologists say one key factor will play a huge role in whether Irene becomes a strong hurricane and whether it will directly impact the United States -- the track.

The National Hurricane Center's initial track carries the storm over the island of Hispaniola (Dominican Republic and Haiti), and that's usually death for a tropical system. The mountains on that island tend to disrupt the circulation in a tropical system.

What's left of Irene also would brush the north coast of Cuba, and the Hurricane Center's initial prediction shows a tropical storm -- not a hurricane -- approaching south Florida on Thursday afternoon.

What everyone will be watching over the next 24 hours is exactly where the storm's center forms, and which direction it goes.

If the center forms a bit north of where it is now, or if Irene tracks a bit farther north than expected, it would miss the big islands and have a clear aim at the Bahamas and the Southeast coast. The reverse is true -- a track farther south would carry the storm into the Gulf of Mexico.

One thing is for sure -- Irene is a big storm, and Puerto Rico will take a pounding Sunday, with flooding rains and gusty winds.

Beyond that, we shall see.

Here Comes Tropical Storm Irene

For several days, professional meteorologists and weather geeks have been watching an area of disturbed weather moving westward in the Atlantic Ocean.

The scary thing about this system is the way that most computer models have agreed on the future of the area of showers and storms -- which was given the designation a few days ago by the National Hurricane Center of "Invest 97L." That means it's an area of bad weather that the Hurricane Center has been watching.

The system is about to become designated a tropical depression, or even Tropical Storm Irene. But more about that later.

Why is this system important?

Most of the computer models have agreed that 97L (or Irene) will become a hurricane -- or major hurricane -- and make landfall next weekend somewhere in the eastern Gulf of Mexico or Southeast Coast. That means somewhere between New Orleans and the North Carolina coast. Florida has been the bulls eye for most computer model forecasts.

The National Hurricane Center sent a plane into the system late Saturday afternoon, and on its final pass, it appears as if meteorologists found a closed circulation.

The plane sent back, via radio, a Vortex Data Message (VDM), which means they found a closed storm system. And that means 97L will become designated a tropical depression or tropical storm this evening.

Once that happens, the National Hurricane Center will begin issuing forecasts on the storm's track.

It likely will have an impact on Puerto Rico and the Virgin Islands within the next 48 hours. After that, we shall see.

I'll update the blog later Saturday night, should the National Hurricane Center declare 97L a depression or tropical storm.

Some forecasters see 'Hurricane Express' coming

By any definition, the early part of the 2011 hurricane season has been quiet for the mainland United States.

Granted, there have been seven named storms, which is a large number for mid-August, but only one has affected the United States. The others were "fish storms," carving out tracks across the open waters of the central and north Atlantic.

Some meteorologists think it's about to get more active.

Granted, some meteorologists always seem to think bad weather is about to get more active, whether it's hurricanes, snowstorms or whatever.

But there's a bit of science behind the prediction of increased tropical storm activity in coming weeks, and satellite images from Africa are also rather ominous.

Leading the band for those forecasting a busy late August and September in the tropics is Joe Bastardi, who is one of the nation's best-known (and most controversial) long-range meteorologists. Bastardi worked with Accu-Weather for years but moved earlier this year to a new company, Weather Bell.

In recent days, Bastardi and others have been talking about an upcoming development in which cyclone formation decreases in the southwest Pacific basin and increases in the southeast Pacific. Some meteorologists tour the "tele-connections" theory, in which weather developments upstream -- in this case, the Pacific -- can point to changes in our part of the world.

The idea is that increased southeast Pacific tropical weather means the same thing in the south Atlantic and Caribbean. It's related to the Madden-Julian Oscillation (MJO), for those of you who are really into this topic.

Bastardi is predicting seven named storms (five reaching hurricane strength) in the next 30 days, with three to five storms affecting the United States.

Of course, there are plenty of critics out there who are probably armed with a list of the times when a Bastardi forecast went bust.

I'll offer this satellite photo today, showing a line of storm systems moving across Africa, headed for the eastern Atlantic Ocean. Is this a sign of increased activity, and are these some of the future tropical storms and hurricanes of the next 30 days?

We shall see. Here's the link: http://bit.ly/rcYScf

Low 60s at night ... can we take this?

Nobody is suggesting we haul out the sweaters and coats, but meteorologists are predicting morning temperatures Tuesday and possibly Wednesday in the lower 60s across the Charlotte area.

And it will be in the mid 50s across the mountains.

Such is our weather for the foreseeable future, as the upper-air pattern across the United States spells an end to the torrid temperatures of June, July and early August. Will the upper 90s return this summer? Chances are they will, but not in the current forecast period of seven days.

Computer models indicate our weather during the next week, and perhaps longer, will be dominated by a trough over the Northeast or eastern Canada. That counter-clockwise flow in the atmosphere will bring air that is somewhat cooler but definitely drier.

Dew point temperatures will be in the 50s and low 60s for the next few days, and that means even the daytime forecast highs of 89 and 90 degrees Tuesday through Thursday won't seem bad at all -- especially with the cool morning weather. Today's high will be 86 degrees in Charlotte, with low humidity.

"Today will feel more like mid-September than a dog day of August," said Justin Lane, of the National Weather Service office in Greer, S.C.

While it seems too early to write off a return of really hot weather, I'll remind you that it was six months ago -- almost to the day -- when the atmospheric pattern changed, and our steady stream of cold weather came to an abrupt end. After mid-February, we never dealt with cold weather again last winter.

The new pattern over the Eastern United States will bring another cold front into the area this weekend, reinforcing our milder conditions into the early part of next week, at a minimum.

Watching the tropics: So far, the 2011 tropical season is resembling the last two years, in that named storms are being steered away from the United States. For that matter, this year's storms aren't impacting land masses in the Caribbean either.

The sixth named storm of the year, Franklin, formed and dissipated over the weekend in the central Atlantic. Now we've got No. 7, Gert, and it's passing southeast of Bermuda.

The National Hurricane Center is watching another area of disturbed weather in the eastern Atlantic, and it's in an area that could pose a threat to the Caribbean. But it is merely a disorganized area of showers and thunderstorms -- hardly a threat to anyone, for now.

A cool-down, of sorts ... but for how long?

A couple readers have noted in the last week that we seem headed for another run at Charlotte's all-time record for 90-degree days. That's 88, set in 1954. We had 87 last year.

We've had 60 so far this year, which means we'll need a hot September to threaten the mark again.

I mention this because we're apparently headed for a break from the 90-degree weather for several days.

The jet stream in the eastern United States will take a dip, with a trough establishing itself along the East Coast. That will bring a cold front -- a bit stronger than usual -- into and through the Carolinas this weekend. And it will bring temperatures that actually will be a bit below average for a few days early next week.

We're talking about high temperatures in the middle 80s for a few days, before a return to average (about 88 degrees) by the end of next week. But there is no sign of 90-degree weather for the next week, except perhaps for today.

(By the way ... that cold front arrival late Saturday and Sunday will be accompanied by some strong thunderstorms, and the earlier storms could have an impact on the Panthers' preseason game against the New York Giants on Saturday night.)

I heard a meteorologist the other day surmise that the cooler weather next week might mark an end to the summer heat. Such a back-breaking event is not unheard of. If you remember, our nasty streak of cold weather last winter ended suddenly on Valentine's Day, and it never really got chilly again during the winter.

But I wouldn't bet on it.

The 6-10 day outlook from NOAA's Climate Prediction Center calls for below-average temperatures in the Charlotte region, and that's mostly because of the cool-down early next week. The outlook for 8-14 days calls for average temperatures (but below average in eastern North Carolina). That indicates a return to hotter weather around the 25th of the month (which, incidentally, happens to be the start of the school year for most N.C. public school students).

Accu-Weather, the Pennsylvania-based private weather company, is predicting highs in the upper 90s in two weeks.

Next week's cooler weather will put a dent in Charlotte's chances of breaking the record of 90-degree days, but it probably doesn't mark an end to the torrid heat of Summer 2011.

Tropic Outlook: In case you haven't noticed, it's getting busy in the Atlantic. A pair of Cape Verde systems are getting most attention from the National Hurricane Center. Check out the activity on the National Hurricane Center's website -- www.nhc.noaa.gov. That circle farthest to the right (farthest east) would seem to have the best chance of impacting the United States down the road.

90 degrees vs. 98 ... a big difference

A weak cold front is forecast to cross the Charlotte area at midweek, and it'll drop our daily high temperatures into the range of 90 to 92 degrees.

Some of you might be saying that's not a big deal, but I think it is.

There's a big difference between 90 degrees and 98 degrees.

I've heard a lot of complaints about the heat this summer, and it didn't make a lot of sense at first, because we've only had two days of 100 degrees or higher, and that's certainly no record.

The number of 90-degree days is a bit above average, but we don't seem to be headed toward the record of 88, set in 1954.

But I might have found the answer when I went looking at the exact nature of the 90-degree days we've had so far this year. We've had a lot of days when it was 95 or hotter -- more than any year in the last decade, except last year.

An air conditioning mechanic told me last year that heating and air conditioning systems are built to work efficiently to certain temperature limits. He said it's the same story with the way houses are insulated. I forget what he told me about the heating systems, but I remember him saying that when temperatures got above the mid 90s, a lot of systems simply can't cool a house very well.

So here's the total for the past decade (through Aug. 7 each year):

2011: 20 days

2010: 24

2009: 2

2008: 14

2007: 5 (although there were 16 days of 95 or hotter after Aug. 7 that year, including six 100-degree days; August was nightmarish).

2006: 15

2005: 4

2004: 0

2003: 0

2002: 9

Adios, Emily ... probably

Tropical Storm Emily met its demise Thursday afternoon south of Haiti, its closed circulation torn apart and its thunderstorms scattered over a wide area.

The National Hurricane Center downgraded Emily to a tropical wave.

One of the computer models, the European, correctly predicted Emily would not survive its trip past the island of Hispaniola. National Hurricane Center meteorologist Lixion Avila noted that in his 5 p.m. tropical weather discussion.

From the start, Emily was difficult to predict. Most of the computer models forecast the storm to strengthen, once it cleared Hispaniola, and possibly reach hurricane status off the U.S. coast late this weekend. That doesn't seem likely now.

What does this mean for the Carolinas coast?

Smooth sailing, probably.

Stacy Stewart of the National Hurricane Center said Thursday evening that there is a 60 percent chance of Emily regenerating within 48 hours. That likely would happen Saturday, when the storm's remnants move over the very warm water near the Bahamas.

By that point, though, Emily's remnants -- or an Emily II -- is expected to be caught in the westerly atmospheric flow, which would steer the system quickly out to sea.

Bottom line: Chances are good you'll have a quiet weekend and start of the next week at the beach. Just keep an eye on the forecast, to make sure this unpredictable storm doesn't surprise us again.

And it'll be interesting to see how the European computer model fares when the next tropical system looms.

Will Emily threaten the Carolinas coast?

Sometimes weak tropical weather systems can be nightmarish to predict, and such is the case with Tropical Storm Emily.

But since some of you are headed to the beach this weekend or next week, here's the latest thinking on how Emily might impact the Carolinas coast.

First of all, at the time of this writing (1:15 p.m. Eastern), it looks as if Emily is dying. The closed circulation has opened, and it appears as if the mountains of Haiti and the Dominican Republic are bashing the storm. In a few hours, it's possible Emily could be history.

If that's so, ignore the rest of this.

But if it should survive, what happens?

The majority of the computer models continue to insist that Emily will make a northeast turn away from the U.S. mainland, once it moved north of about Daytona Beach, Fla. A trough in the western Atlantic is predicted to bring Emily's path from west-northwest to north-northwest, and then the system is expected to get caught in the westerlies.

The National Hurricane Center's predicted track for the storm carries it about 200 miles east of the Carolinas coast, which means beachgoers probably won't have to worry about rainy weather.

However, they will have to contend with rough surf and rip currents, from about Sunday until Tuesday.

Let's see what happens over the next few hours.

The mess that is Emily

National Hurricane Center meteorologists are earning their pay, trying to make sense of Tropical Storm Emily.

Let's review what's happened so far:

-- The tropical wave failed to develop into a tropical storm when predicted. Low-level and mid-level circulation centers wouldn't line up properly, so the system kept spinning blobs of thunderstorms in a elliptical path.

-- Finally, on Monday evening, the National Hurricane Center's jet found enough of a center to give the system a name (Emily).

-- Late Tuesday morning, Emily came to a standstill. Some meteorologists think it might be reforming its center, south of where it previously was.

Sometime later Wednesday, Tropical Storm Emily will cross Hispaniola, and it certainly seems as if the system will have a very tough time surviving that trip across the rugged mountainous terrain. By Thursday, we might be looking at a mere tropical wave again, bringing showers and thunderstorms later this week to Cuba or the southern Bahamas.

This is only the first real formed-in-the-Atlantic tropical system of the season, and odds are there will be several more to go.

Emily looks like one of those storms that gives hurricane forecasting a bad name.

More later today.

Texas heat: I noticed that today will be the 32nd consecutive 100-degree day in Dallas. The forecast high today is 108. That's simply not right. And remember -- that's a place where snow fell last winter during Super Bowl week.

This is the second-longest streak of 100-degree days in Dallas history, and it's another sign of how truly hot the summer of 2011 has been for Texas, Oklahoma, Arkansas, western Tennessee and other parts of the Midwest and South.

Emily forms ... now what?

The mass of showers and thunderstorms that had defied forecasters' predictions for a day or two finally organized into a tropical storm Monday evening, and hence, we have Tropical Storm Emily affecting the eastern-most Caribbean islands.

Emily has top sustained winds of 40 mph, and the National Hurricane Center expects intensification over the next day or so, until the storm makes a predicted encounter with the island of Hispaniola (Dominican Republic and Haiti).

If it survives moving across that mountainous island, Emily could be a threat to the Southeast coast of the United States.

Some of the computer models are predicting the storm will make a run at Florida's Atlantic coast, but another school of thought has Emily being grabbed by a trough over the eastern United States and curved up the coast.

It's possible Emily could repeat the path of Earl last year -- a storm that stayed a few miles off the coast of the Outer Banks.

Then again, it's also possible Emily could be destroyed over Hispaniola.

Here's the point ... for the first time this year, we have something to watch in the Atlantic and Caribbean.

Some of you have asked for Internet sites to get more information. If the storm seriously threatens the U.S., I'll list some of those. For now, I suggest the Storm 2K website (www.storm2k.org). Click on "Forums" and then "Talkin' Tropics." You'll find a mix of comments, computer models, and even live reports from islands in the Caribbean.

Of course, there's the National Hurricane Center site, at www.nhc.noaa.gov.

More to come on Tuesday.