Articles tagged as: John Nielsen-Gammon
Q: It’s in the news that an El Niño may form this summer. What is the difference between an El Niño and La Niña?
A: The main difference between the two involves water temperature, explains John Nielsen-Gammon, a weather expert at Texas A&M University. El Niño and La Niña – Spanish for “the child” – both occur in the central Pacific Ocean. “During an El Niño event, which can last almost a year, the waters in that region are warmer than usual,” he says. “The opposite occurs during a La Niña – the waters tend to be cooler than usual. But the important thing is that both events can affect weather patterns in the United States and around the world.”
Q: How do they change our weather?
A: In years when a La Niña occurs, there are often warmer and drier conditions in many areas, including Texas, Nielsen-Gammon says. “In general terms, a La Niña period means drier weather patterns for Texas. There have been numerous studies on how El Niño and La Niña affect weather patterns, and specifically, hurricanes and their intensity. Some research indicates that the sorts of hurricanes that affect Texas are more common during La Niña periods than during a neutral or El Niño year. We do know that an El Niño can last up to 18 months and it can influence weather everywhere, so when one forms, there is naturally a lot of interest in what will happen.”
Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University.
The worst drought ever to hit California could rival the historic 2011 drought that devastated Texas, says a Texas A&M University professor.
John Nielsen-Gammon, professor of atmospheric sciences who also serves as Texas’ State Climatologist, says the current drought in California is so far comparable in many ways to the 2011 Texas drought, the worst one-year drought in the state’s history that caused more than $10 billion in damages and led to numerous wildfires and lake closings.
“This is the third year of California’s drought and it is on pace to be as dry as Texas was in 2011,” Nielsen-Gammon, a California native who grew up in the San Francisco area, explains.
“However, because our severe drought year came at the beginning of the drought, reservoirs across much of the state were full. In California, reservoir levels were low to begin with.
“In addition, they are dealing with environmental flows through the Sacramento Delta that weren’t explicitly laid out until a few years ago.”
Weather patterns for both states appear similar, he adds.
“The same ridge that has kept California dry has also been keeping Texas dry,” he notes. “As the pattern changes, California is finally getting some rain and snow and the chances for precipitation in Texas are increasing as well.”
California’s drought is especially worrisome because the state produces about one-half of the country’s fruits, vegetables and nuts. It is the No.1 agricultural state in the U.S.
The 2011 drought devastated Texas farmers and ranchers, and lake levels were down as much as 50 feet in some lakes while several West Texas lakes completely dried up.
Numerous Texas cities set heat records in 2011, such as Wichita Falls, which recorded 100 days of 100-degree heat, the most ever for that city. Dallas also set a record with 70 days of 100-degree heat.
Texas’ drought is now in its fourth year, Nielsen-Gammon says, and about 52 percent of Texas is still in some form of drought status, ranging from moderate to exceptionally dry.
“January was unusually dry with an average of only about one-half an inch of precipitation statewide,” he adds.
“Reservoir levels have actually declined at a time when they should be rising. So the drought is still here. In fact, the prevalence of drought in Texas has not dropped below 40 percent since 2010 when this drought first started.”
The Texas Panhandle area has been especially hard hit.
“The past three calendar years have been among the driest three on record for the Panhandle,” he notes. “Dalhart shattered its record with just 20.54 inches total in 2011-2013.
“This current drought started with more intensity than the drought of 1950-56, the driest on record. We again have a generally warm Atlantic Ocean, and that tends to mean dry conditions. An El Nino (warmer water in the tropical Pacific Ocean) might develop later this year, but it’s still a little too early to say.”
Q: Is there a relationship between global warming and hurricanes?
A: That’s a question that a lot of people are asking, says John Nielsen-Gammon, professor of atmospheric sciences at Texas A&M University who also serves as State Climatologist. “There were more hurricanes and tropical storms in 2005 than any year in at least 70 years,” he explains. “A lot of fingers are being pointed at global warming for the rise in severe storms. There are a lot of studies being done in this area, and global warming appears to be at least a strong contributing factor. We know that some areas of the oceans are warmer than in years past, and this can contribute to more intense storms.”
Q: What specific areas of water are warmer?
A: The Atlantic Ocean, Nielsen-Gammon says, is scientifically proven to be warmer than normal. “Large areas of the Atlantic are at least one degree warmer than in years past, and this goes back to 1995,” he points out. “So we have had a decade of warmer water there, and that’s where hurricanes form. The long-range outlook tells us that this warming trend could continue another 5 to 20 years. Since warmer water means stronger storms and hurricanes, it could mean stronger storms in the future. Back in 2005, there were three hurricanes that reached category 5 status — the strongest level — but it remains to be seen if that will happen in the years to come.”
Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University
Despite recent rains, the historic Texas drought is still alive and well and about 93 percent of the state remains in drought conditions ranging from dry to exceptionally dry, says a Texas A&M University expert.
John Nielsen-Gammon, professor of atmospheric sciences who also serves as State Climatologist, says that although some much-needed rainfall covered most of the state last week, most of Texas is still unusually dry and water levels are below normal.
“Part of southeast Texas and far west Texas are in pretty good shape and have had normal or above normal rain this year,” he notes. “But those are the exceptions. The hardest hit areas are those around McAllen, west of San Antonio, the Vernon-Wichita Falls area, south of Lubbock, near Midland and Dalhart and around Bryan-College Station. Most of these areas are anywhere from 10-15 inches below normal in rainfall.”
He notes that long-range forecasts tend to be neutral since there is no La Niña or El Niño in the Pacific Ocean this year that normally affects weather patterns and rainfall.
“For its combination of intensity and longevity, I consider the current drought to be the second worst drought in Texas history,” Nielsen-Gammon says.
“The worst drought ever – the drought of record – remains the drought of 1950-57. This drought still has a few years to go to catch up.
“The other rivals in the climate record, which goes back to 1895, were the droughts of 1917-18 and 1961-66. The 1917-18 drought was intense but shorter, and the 1961-66 drought was long but milder.
“The long-term Pacific and Atlantic Ocean temperature patterns still favor drought in Texas, and probably will continue to do so for another 5-15 years. Whether this drought will last that long or whether Texas will have an occasional wet year within that stretch is impossible to say.”
He notes that many reservoirs range from low to extremely low, while many Texas lakes have still not recovered from the 2011 conditions, the worst one-year drought in the state’s history.
“Until the rain event on Sept. 19-20, Texas reservoirs were one or two days away from setting an all-time record for the gap between the amount of water stored and the storage capacity,” he notes. “Our reservoirs were essentially storing 18 million acre-feet of water and 13 million acre-feet of air.”
One acre-foot is the amount of water needed to cover one acre of land to a depth of one foot. The present record was set in 2011, “but without more rain, the record might still fall in another or month so.”
The forecast of near-normal rainfall this winter is good news for water supplies, but Nielsen-Gammon notes that the benefits will be uneven.
“Normal rainfall can fill up East Texas reservoirs, but normal rain in Central and West Texas is too little to make up the gap,” he says.
Sept.13 marks the fifth anniversary of the landfall of Hurricane Ike on the Texas coast, a date for many that will live in infamy. Despite its Category 2 ranking when it hit, Ike caused more than $30 billion in damage and the lessons learned from it could be crucial ones for future preparedness, says a Texas A&M storm expert.
John Nielsen-Gammon, a professor of atmosphere sciences who also serves as State Climatologist, says Ike was not your normal storm. It was far more powerful than many believed at the time.
Ike made landfall at 2:10 a.m. on Sept. 13 over Galveston. Winds were clocked at 110 miles per hour, putting it into the Category 2 ranking, one reason why many people did not heed warnings to leave.
“Ike was a big storm that almost filled the entire Gulf of Mexico,” Nielsen-Gammon explains.
“But it was not especially an intense storm. What made Ike so dangerous was the huge storm surge it created. It was a Category 2 storm that produced Category 4 storm surge. The storm surge began earlier than forecasted, and it took a lot of people off guard.
“That has to be one big lesson we learned from Ike: a moderate storm can still pack a very big punch.”
Storm surge reached a record 22 feet at Sabine Pass and was 15-20 feet at numerous other locations.
More than 100,000 homes and businesses were flooded, most of them in the Galveston area. The small towns of Crystal Beach and Gilchrist were virtually destroyed.
Despite repeated warnings from officials to leave, it is estimated that as many as 40 percent of residents in the mandatory evacuation zone – most of them in Galveston – decided not to evacuate. Even an unusually harsh statement from the National Weather Service that said people who remained “would face certain death” failed to motivate many residents from leaving.
“One reason many people probably decided not to leave was that they remembered Hurricane Rita a few years earlier in 2005,” Nielsen-Gammon said.
“Rita came just a few weeks after Katrina, and was also a major hurricane. Many people evacuated who would have been safer staying put, and those that did evacuate were caught up in huge traffic jams. Close to 100 people were killed by the evacuation.
“With Ike, the pendulum swung the other way,” he recalls. “Many people stayed put who wished in retrospect they had evacuated. The storm took out power lines throughout the region, and lots of people were unprepared for several days without power. No electricity means no air conditioning, no functioning refrigerator or freezer, and no gasoline at the pump.”
In the final analysis, Ike did at least $30 billion in damages and killed 112 people in the U.S., at least 37 of those were Texans. It was the third costliest storm in U.S. history.
“As bad as Ike was, it could have been much worse,” Nielsen-Gammon adds.
“If the storm had tracked a little more to the west, Galveston would have been hit much harder than it was. We do have better evacuation plans today, such as contra-flow traffic and even our advance warnings have improved. Before Rita, the worst storm was Alicia in 1983, so the Houston-Galveston area went a long time before residents had to deal with one.
“But the bottom line is, be prepared. Know whether your home is vulnerable to storm surge, and expect that the next storm could be better or worse than the forecast.”