June 1 marks the beginning of the Atlantic hurricane season, although the most active periods typically come later, in August and September.
Despite forecasts of a below-average season, tropical storms can still impact Louisiana, and other weather changes connected to El Nino could last into the winter.
WWNO/WRKF Coastal Desk reporter Michael McEwen spoke with Jay Grymes, Louisiana’s state climatologist, about what those changes are likely to mean.
The following conversation has been edited for clarity.
MICHAEL MCEWEN:
Today is June 1st, and notoriously for us Gulf dwellers, the beginning of hurricane season. The consensus forecast for hurricane season this year is below average. What is your outlook, and what would a below-average hurricane season really mean at this stage?
JAY GRIMES:
We have to be careful of that. It's below average to near average if you listen to what the National Weather Service people have to say. And my biggest takeaway from that is that's great coffee-table banter, but it doesn't tell us anything about the threat to Louisiana. The reality is with Louisiana, if we look at the last 20 to 25 years, we've been averaging one named storm impact per year, regardless of whether it was El Nino, La Nina, or La Nada.
So the El Nino storyline here, which does typically mean a reduction in activity over the Atlantic basin as a whole, does not necessarily protect Louisiana from storms. In fact, we've had some historically large storms hit Louisiana during El Nino years. Some would argue that Betsy, for example, might be considered an El Nino year, and everyone remembers how Andrew in '92 was a very quiet year in terms of the number of storms, but it was anything but quiet in terms of its impact in Louisiana. So as I get older and crustier, I get less and less excited about the forecasted numbers at the start of the season; they just don't really give us any guidance.
The number to remember here in Louisiana really is zero or one. Are you going to prepare for hurricane season, yes or no? And the answer should be yes. Prepare for it now. My concern many times is the complacency that we see in the public, particularly since last year was a quiet year. Many times, folks have very short-term memories, and we can't afford that here in the Bayou State.
MCEWEN: You mentioned complacency — are there now risks that some folks aren't thinking of, that it might only be one named storm, but that potential of rapid intensification is still there? And could that maybe catch people off guard?
GRYMES: That's an extremely important point to think about. In El Nino years, we tend to see fewer of those long-tracking storms that we're monitoring for five, six, seven days before they get in the Gulf. What we have to worry about here in Louisiana are the homegrown varieties, the ones that pop up in the Gulf or maybe down in the Caribbean that give us three days, two days of heads-up.
And as you point out, rapid intensification. In fact, I've done a look at the last six or seven storms that have impacted the Gulf Coast region, and most of those saw some dramatic intensification in periods of less than 24 hours. So that's just another reminder about getting ready now, because you're not going to have four or five days to get ready for a storm that might be a Category 3 or stronger.
And the other thing we have to remember is just because that storm may not come through your parish or your community, doesn't mean you're still not gonna get impacted. In fact, we've been impacted by storms that have gone into Texas, but still flooded us here, putting out the lights over numerous parishes.
So it's imperative that you go ahead and just assume we're gonna get impacted by a storm, and then if we don't, you can curse me out later.
MCEWEN: For those who might not be too familiar, what is the relationship between an El Nino, or what forecasters are calling a ‘Super El Nino’ this year, and hurricanes in the Atlantic Basin? What's the connection there?
GRYMES: First off, El Nino's evil sister, La Nina, and the intermediate phase, these are all features that we look at in the central and eastern equatorial Pacific. For many people, their first thought is, "Why are we looking in the Pacific? We're in the Atlantic Basin." Well, what you have to think about here is that the ocean and the atmosphere are two fluids, one sitting on top of the other. Obviously, the atmosphere is sitting on the ocean. From a physics standpoint, these are two fluids that interact with one another.
So when you change the situation, or the circumstances in one of those fluids, some of that energy gets transferred to the other fluid. So when we talk about El Nino and La Nina, we're talking about water temperatures in the equatorial Pacific: El Nino, water temperatures are warmer than normal; La Nina, water temperatures are cooler than normal.
The atmosphere is being impacted by those water temperatures. And while the Pacific can't get into the Atlantic, air over the Pacific can travel to the Atlantic, and that's what we're really looking at. So if you think about the atmosphere flowing like a river and you change the conditions under the atmosphere, it's kinda like throwing a big boulder in a creek. Now the atmosphere has to change how it flows around that boulder.
For us, what it typically means is higher wind speeds with elevation – that creates vertical wind shear. Now, that's a good thing. That's what actually helps reduce the ability for tropical storms to develop.
But what's also important to remember is we're talking about reducing the number of tropical storms and hurricanes, not cutting them off completely. In fact, during an El Nino year, when we see that reduction, we're really only talking about an average reduction of 20 to 25% of the named storms. Well, if the average number of named storms in the Atlantic Basin is somewhere around 14 or 15, if you take off 20% of that, you're still left with 10 to 12 named storms.
So yeah, we've reduced the threat, but we haven't eliminated the threat.
MCEWEN: And even beyond the relationship between El Nino and Atlantic hurricanes, there are other climatological impacts that we can expect here in Louisiana, coastal Mississippi, and really around the Gulf of Mexico. What are those?
GRYMES: The thing is that El Nino doesn't give us any real good guidance in terms of summertime rainfall or temperatures.
But as we get into the fall and winter, if El Nino is still hanging around, and we fully expect it will be, then what we typically see is what are the normal conditions along the entire Gulf Rim, not just Louisiana, Mississippi, and Alabama, but from Texas to Florida.
Particularly, the coastal counties and parishes tend to be wetter than normal in the winter and spring, especially if El Nino hangs on that late into the year. You can kind of say it's good for us in the summer and early fall because it may reduce the number of storms that threaten us, but as we get into the winter and spring, it drives up our flood threat because it makes for wetter than average conditions.
So the trade-off there may not be a good one in the bigger scheme of things. And typically, what happens when we have a wet winter and spring, more often than not, especially for the southern half of Louisiana, average temperatures tend to be a little bit above normal in those months. And a part of what's happening is that we're getting more of the wintertime Gulf air intruding into the state. So it doesn't mean there won't be any cold spells, but it means the cold snaps tend to be a little bit shorter of duration and maybe not quite as intense as what we've seen, for example, these past two winters.”
