What is now Tropical Storm Ida impacts our area later today and tonight. Here is what to expect.
After a historic landfall and a devastating impact to southeastern Louisiana, once Hurricane Ida has been downgraded to a Tropical Storm early on this Monday morning as the center of circulation moves into southwestern Mississippi. As of the time of this writing, maximum sustained winds on the latest advisory are down but still at 60 mph, and the pressure is 990 millibars. Ida's circulation is projected to be moving north at 8 mph, and Ida will be moving into our area later today and through the overnight and Tuesday morning.
All of the Tennessee Valley Weather Channel's viewing area remains under a FLASH FLOOD WATCH through all of today, tonight, and into tomorrow for the expectation of widespread heavy rain moving into the area in association with the remnant circulation of Ida. An average of 2 to 4 inches of rain is projected, but isolated areas under training heavy rainbands could definitely see more than that. The national-level Weather Prediction Center office of the National Weather Service has placed all of our area in at least an Elevated Risk of excessive rainfall and flooding for today and tonight, with portions of northwest Alabama and northeast Mississippi being placed in a Significant Risk of excessive rain and flooding (somewhat rare to be placed in this risk level).
Ida will be a multi-faceted system for our area. In addition to the risk of heavy rain and flooding / flash flooding, there will also be an elevated risk of high wind gusts on the order of 30 to as much as 50 mph possible. We can't even rule out an isolated gust or two being higher than that. With the heavy rain incoming and with the recent heavy rains and flooding the last few weeks, wind gusts like this will make it easy for trees to come down, and these gusts are also high enough to knock down power lines or cause trees to fall onto them. That means there will be an elevated concern for power outages. These wind gusts will be widespread across the entire area for several hours. This will be a long duration wind event for our area.
Wind gusts as high as 20-30 mph could start as early as the mid afternoon with the initial rainbands. In addition to tornadoes being possible with these initial rainbands (and we will detail that in just a moment), this potential is the reason why we have the general start time for our impactful weather at roughly around 3:00 this afternoon (don't interpret that as exact, but rather a general guideline). However, the widespread long-duration wind gusts of 30-50 mph really crank up during the late evening and overnight hours, lasting toward Tuesday morning.
As is natural with ALL landfalling tropical systems, there is a threat of tornadoes across our entire area from maybe even as early as midday today, but more likely by mid afternoon... lasting all the way through the overnight into Tuesday morning. Tornado threats with tropical systems are usually long-duration threats lasting several several hours, compared to "typical" tornado threats with spring, fall, and winter frontal systems that usually only have you in a tornado watch for 4 to 6 hours. Tornado watches with a tropical system can last 12 hours or longer.
Based on the current expected track of Ida's remnant circulation and where that sets up the more convective rainbands and higher instability versus a more steady rainshield, it appears that, although a few tornadoes are possible areawide, there may be a slightly better chance of them over northern Alabama in comparison to Tennessee, especially the parts of north Alabama that are south of the Tennessee River. These areas are a little farther away from the track of Ida's remnant center of circulation. For a higher tornado threat, you usually want to be in the outer rainbands, where there is the potential for sun breaks and higher instability, and where the structure of the rainbands contain thunderstorm cells instead of there being a steady shield of rain. Still, it looks like there will be a few of those cells embedded within the rain shield as far north as middle Tennessee, and even here, we sure can't rule out a tornado or three.
For the most part, tornadoes with tropical systems are shorter-lived and are usually on the lower half of the intensity/damage scale. The vast majority of tornadoes from tropical systems are in the EF0-EF1 range. There can definitely sometimes be tornadoes from tropical systems that are stronger than that though. Our particular area has had its fair share of EF2 intensity tornadoes from tropical systems over the years, and we have even had them as strong as EF3 intensity before. One such event was with the remnants of Hurricane Danny in 1985, where there was a swarm of EF2-EF3 intensity tornadoes across north Alabama and southern middle Tennessee. So, strong tornadoes can occasionally happen. Once you get above that level of intensity, while we can never rule out anything, "violent" tornadoes (EF4 and greater) almost never happen with tropical systems. In United States recorded weather history, there have only ever been two (E)F4 intensity tornadoes associated with tropical systems. One of those was an F4 tornado that hit near the Galveston, Texas area in association with Hurricane Carla in 1961. The other was an F4 tornado that hit Larose, Louisiana in association with Hurricane Hilda in 1964. There has never been a recorded (E)F5 intensity tornado associated with a tropical system in United States weather history. Still, when it comes down to it, it doesn't really matter. A tornado of ANY intensity is danger. An EF0 tornado can take your life if you aren't doing the right think and seeking shelter in a safe place. So, it is really important to take ANY tornado warning seriously if we have them later today, tonight, and into Tuesday morning.
The other thing about tropical-related tornadoes that we have to strongly caution is their overall behavior. Tropical related tornadoes generally move faster than their mid-latitude counterparts because of the intense wind fields aloft in association with the tropical system's remnant circulation, even days after landfall. These tornadoes often don't approach from the "typical" direction you would expect either. These form in convective cells in the outer rainbands that are rotating around the tropical system. Because of that, many of them may approach from the due south or even the southeast, instead of the west or southwest that you typically expect with a cold frontal system. Tornadoes from tropical systems also spin up very fast and are usually on the ground for only a short period of time. That makes them VERY difficult to warn for, even with the best radar technology and the best meteorologists watching those radar screens. They often also spin-up very shallow and close to the ground and not even show themselves on radar until after they have been on the ground and causing damage. You will have to be more alert to changing weather conditions than you usually are during a severe weather threat. However, with advances in radar technology, skycams, and storm spotters out in the field, the vast majority of these tropical tornadoes ARe caught and warned for in time. And the stronger ones are just like the stronger ones ahead of a cold front. They ARE more obvious looking on radar and make themselves easy to spot.
Our high-resolution Futurecast model from Baron gives a good timeline for how everything evolves over the next 24 or so hours. A few showers are possible this morning, but the more steady rain in association with Ida begins spread in from the southwest during the midday and afternoon hours. By the mid to late afternoon, it looks like an initial feeder band of convective cells moves northward into the area. Notice how the thunderstorm elements in this band are cellular. These will have to be vigilantly watched for a tornado threat. As we head into the evening and lose daytime heating, those convective cells may gradually weaken, but they won't completely go away, and the risk of a few tornadoes will continue. Later in the evening and the deep overnight, heavier rain in association with the core remnant circulation of Ida overspreads the area. This is when the highest risk of flooding and damaging wind gusts will be, and it may be a long-duration event that lasts 6-9 hours across the area. By the mid to late morning on Tuesday, the actual low pressure circulation with Ida moves overhead, but the heavier rain and higher winds will be shifting out of the area to the east and northeast. Toward the late morning and midday on Tuesday, the tornado risk will likely flare up again east of Ida's circulation. For now, it looks like this happens to our east over east Tennessee, east Alabama, and into Georgia. However, if Ida is just a few hours slower than projected, that may move the western fringe of that tornado threat back into our eastern counties for Tuesday. We will need to watch carefully.
Both the Baron model and the HRRR model show a widespread 1.5 to 3 inches of rain across the area. However, models notoriously underdo the actual rain totals in the training rainbands of tropical systems. This, when combined with precipitable water values of 2.5 to over 3 inches, rain totals should be a bit higher, and that is why we are forecasting an average 2 to 4 inches with isolated higher amounts being possible.
We are going to post a timeline of the wind gusts from both the Baron model and the HRRR model to give an idea of the overall evolution there.
Our in-house Baron model shows widespread wind gusts as high as 15 to 20 mph being possible as early as the morning and midday hours. Even before Ida's direct impacts move in, we expect breezy east to southeast winds today. As we head into the afternoon and that first rainband moves into the area, it has the potential to carry 20 to 30 mph wind gusts with it. It's as we head deeper into the overnight that the more steady, long-duration wind event moves in. The Baron model here shows widespread 25 to 35 mph gusts (with isolated gusts over 40 mph) moving in after 10 PM and lasting through daybreak on Tuesday. This model is on the lower side with the gust projections compared to ALL higher-resolution models. But even if this is correct, this would be more than enough to cause the potential for widespread trees to come down, possibly on power lines, with the heavy rain and recent flooding causing tree roots to be weaker.
Other models, such as the HRRR model here, are stronger with the wind gusts, but they all generally agree with the Baron model on the timing aspect of the evolution. The HRRR shows widespread 40-45 mph wind gusts being possible tonight, with a few spots here and there seeing isolated gusts as high as 50, 55, maybe even 60 mph. Other models like the GFS, Euro, and the various high-resolution WRF models agree with these higher wind gusts. Based on previous similar systems over the years and the winds we have seen well inland so far with Ida, there is a good amount of credibility in the idea that the higher wind gusts are correct.
So, now that you know what to expect, what do you do with all this information? Take the time this morning to go over and finalize your severe weather safety plans. Make sure you have multiple reliable methods of hearing watches and warnings, even if the power goes out. Two great ways to stay informed are our FREE Tennessee Valley Weather App and a NOAA Weather Radio. You can scan the QR code above with your mobile device to be taken right to the download link in your app store where you can pick up the Tennessee Valley Weather App. In addition, if you happen to lose power, we will be carrying any live coverage via simulcast on our WLX / Radio 7 Media family partner stations. Those include WLX 97.5 (southern Tennessee) / 98.3 (north Alabama), 106.1 / 93/1 The X, The Legend WDXE, and WKSR in Giles County. Should any of the counties in our viewing area be issued a Tornado Warning, we will be on air LIVE with NON-STOP coverage until the warning is expired, cancelled, or the danger is otherwise over. We will also be having other frequent live updates through the storm as conditions warrant, even when tornado warnings are not in effect.