Summer ends how it started in the Tri-State, with sun and dangerous surf

The summer season unofficially comes to an end on Monday, with the Labor Day holiday signaling to Tri-State kids that it's time to trade the beach and boardwalk for the school bus. This year, the final weekend of summer also coincides with the start of meteorological fall, which is from September 1st to November 30th. For this final weekend down the shore, the weather forecast bears some similarity to the weather we had to kick off the season. Memorial Day weekend was mostly sunny and pleasantly warm, and we're expecting lots of sun and seasonal warmth this weekend, too (check out the forecast here). 

The holiday weekend unfortunately includes another element from Memorial Day weekend as well- deadly rip currents. So far this year, the National Weather Service attributes 70 deaths to rip currents, four of which happened in New York and New Jersey. Sadly, many people underestimate the power of rip currents, or are unaware of the visual signs of a dangerous rip. My blog post previewing the MDW forecast discusses rip currents in detail, including the weather setup causing the risk, what to look for, and how to stay safe. This weekend's weather setup has a similar look to Memorial Day weekend's map: 

Forecast surface map for Friday from the Weather Prediction Center

Notice the area of high pressure to our north; that's what will bring us lots of sunshine. The airflow around the center of high pressure is clockwise, so our winds will be mostly from the north. That means lower humidity, since the northerly breeze pulls down drier continental air from Canada. On Memorial Day, a strong area of low pressure was stirring up the seas off the coast of North Carolina: 

Tropical outlook from May 25th, 2023, from the National Hurricane Center

The current tropical outlook map is much busier, but the big similarity is the placement of Idalia's remnant low:

Tropical outlook from September 1st, from the National Hurricane Center

It's this feature that's primarily responsible for the rip current risk this weekend. Unlike high pressure, Idalia's circulation is counterclockwise, and it's pushing ocean water onto the Tri-State's Atlantic-facing beaches. So along with dangerous rip currents, minor coastal flooding  is also likely with the next couple of high tide cycles. 

This is the final weekend for lifeguards at most of our local beaches. With water temperatures in the 70s, the ocean will certainly look inviting this weekend, but even the strongest of swimmers will struggle with this surf. Instead, wade in until you're knee-deep into the water, and if you feel a strong undertow, walk parallel to the shoreline to find a calmer spot. And, as always, obey the lifeguards and pay attention to any signs of caution you may see at your favorite beach spot. You can learn more about beach weather and other summer weather phenomena from this post I wrote back in June. 

More "I" named storms have been retired than any other. Will Idalia be next?

The hurricane season typically peaks right around Labor Day in the Atlantic basin, and this year appears to be following that trend. As of Monday night, Hurricane Franklin was a powerful Category 4 storm, with winds sustained at 150mph at its center. Thankfully, the National Hurricane Center predicts that the strongest winds and heaviest rain from Franklin will remain over the Atlantic Ocean. That said, all eyes in the continental United States are trained on Tropical Storm Idalia, which is also forecast to become a major hurricane before making landfall in the Gulf Coast. The current forecast track of Idalia takes it into the "Big Bite" on Florida's west coast, an area with a lower population density than the major city of Tampa to the south. But given the recent history of storms beginning with the letter "I", forecasters are not letting their guard down.

Forecast track of Idalia as of 7PM CDT on Monday, August 28th.

(NOAA National Hurricane Center)

As I mentioned in my hurricane season preview blog post back in May, more "I"- named storms, the ninth position in the naming order, have been retired than any other letter. Thirteen "I"- named storms have been retired since name retiring began in 1954 (I'm not counting Iota, since that is a Greek letter, not the ninth named storm of the season). Though it makes sense that more intense and destructive storms would happen later in the year as the ocean heats up, "I" still stands out. The chart below shows all the retired names, broken down by letter. The next highest, "F", has been retired 10 times. "I" truly is an oddity.

However, the timing of the retired storms beginning with the letter "I" is much more intuitive. The Atlantic tropical season peaks on or around September 10th, statistically speaking. Six of the retired "I" storms' lifespans overlap with September 10th, and all but two of the retired storms, Iris (2001) and Irene (2011), were active during the month of September, which by far the most active month of the year. 

Hurricane and Tropical Storm climatology, from the National Hurricane Center

But, to an extent, it's a coincidence; just because Idalia begins with an "I" doesn't mean it will be more dangerous than an "H" or "J"-named storm. The more important factor is Idalia's environment- and unfortunately, that environment is primed and ready for strengthening. 

You might have seen headlines earlier this summer about hot tub-temperature water in the Gulf of Mexico. Those supercharged sea surface temperatures (SSTs) are still in place, setting the stage for a process called rapid intensification, or RI. A tropical system is deemed to have undergone RI when the central pressure drops by at least 24 millibars in 24 hours or less. Why is that important? The central pressure of a storm is almost directly linked to its maximum wind speed. The lower the pressure is inside the storm, the faster the winds tend to be. Super-warm water is the key ingredient for RI. The other elements, wind shear and dry air, are actually detrimental to storm development if they're present. 

ECMWF forecast model depiction of 500mb winds, about 20,000ft above ground level.

Winds in the Gulf of Mexico are weak at this level, except surrounding the area forecasted to include Idalia. 

(College of DuPage Weather)

Wind shear is any change in wind speed or direction with height. If winds are getting stronger through the vertical column of the atmosphere, they disrupt a tropical storm's intensification process. (The opposite is true for midlatitude cyclones, such as Nor'Easters. We'll talk about that after hurricane season!) The subtropical jet stream is the most common source of wind shear during hurricane season.

Forecast animation of near-ground aerosols, such as salt and Saharan dust.

The dust, in red/orange, is not reaching the Gulf of Mexico.

(NASA's Scientific Visualization Studio/NASA Center for Climate Simulation)

Dry air, however, most often comes all the way from the Sahara Desert to impact the Atlantic basin. If the trade winds blow in the right speed and direction, they can inject desert dust into the tropical Atlantic. In the late Spring, Saharan dust was observed as far west as the Florida Keys! But today, neither wind shear nor Saharan air are present over the Gulf of Mexico. And that's why forecasters think that nothing is stopping Idalia from reaching major hurricane status. 

You can get the latest information on Idalia and its forecast path from the National Hurricane Center. For detailed information about impacts to your neighborhood, I recommend finding your local trusted information source, like a local TV station. Most TV meteorologists will answer your questions directly on social media, too. And finally, get tips on hurricane preparedness from start to finish from NOAA's Weather Ready Nation site. 

How can they say that? Discussing the claim of hottest July on record

The devastating headlines have been all over the place this summer. Heat records on land and in the ocean are being set in multiple locations around the globe. Unusually large, long-lasting, and deadly wildfires in Canada and Hawaii, along with mass coral bleaching events off the coast of Florida, add tangible consequences to the otherwise abstract concept of record-breaking heat. 

Bleached and diseased coral in the Cheeca Rocks Marine Sanctuary, off the coast of the Florida Keys.
Photo from NOAA AOML.

A report released by NASA on August 14th states that last month was the hottest July in recorded history, and that it will likely go down as the hottest month ever measured, with records dating back to 1880. The map below shows temperature departures with a 30-year average used as a baseline. The corresponding graph shows that same anomaly, with the same baseline, plotted through all the years in NASA's period of record. 

The return of El Niño last Spring (which I discussed in this blog post) may have exacerbated the temperature spike this summer. But it doesn't explain all the extra heat. After all, there have been many El Niño events before this one, and the ENSO cycle creates temperature swings of less than 5°F, even in the most extreme cases. NASA GISS's analysis shows that July 2023 was .43°F hotter than any other July on record, including all the previous El Niño episodes since 1880. But still, how can scientists be sure that these temperatures are unprecedented? It's a question that climatologists take very seriously, and they use rigorous processes to ensure their analyses are trustworthy and reliable. 

A Cotton Region Shelter at an official National Weather Service observation site

In the 19th Century, before remote sensing existed, all our weather observations were in situ, or taken on site. These observations primarily came from thermometers near the ground (the proper way to measure temperature at ground level is through a Cotton Region Shelter, often referred to as a Stevenson Screen), and in buoys and ships on the water. To ensure that modern temperature records are consistent with previous methods of measuring temperature, NASA's temperature analysis includes a quality control process to account for the Urban Heat Island effect and other possible impacts, like inconsistent spacing of observation sites; for example, there are fewer weather sensors in Siberia than in the Tri-State area, and NASA GISS's analysis corrects for these differences. The areas that have experienced the most warming, as it turns out, are not in major metropolitan areas like NYC. Instead, NASA's report shows that nearly uninhabited reaches of the Arctic and Antarctic are among the areas that have warmed the most. 

Other reports earlier this summer indicate that we may be experiencing the hottest summer in human history. This claim is understandably tough to comprehend. How can scientists know the temperature records of the past if no one had a thermometer? As it turns out, some plants and animals can only survive in very narrow temperature ranges, and they have left clues behind in layers of rock and sediment. Climatologists utilize these ancient climate records to calculate climates of the past. They also utilize resources like ice cores, tree rings, and even fossilized pollen to create a full picture of past environmental conditions. You can learn more about the fascinating science of paleoclimatology here.

Scientists at Woods Hole Oceanographic Institution examine an ice core containing paleo climate artifacts 

such as ancient air samples, pollen grains, and ash particles.
Photo from WHOI

In this blog post from June, I talked about the difference between daily heat records and those records that have a longer time span. A more consistent, steady heating process will produce warmer years, not just warmer days. After all, the term "average" means that any extremes within the dataset are being evened out. And the same is true on a spatial scale, not just a time scale. It's easier for a heat record to be broken in one individual city than it is for the entire Earth to reach a new temperature extreme. And yet, that's exactly what we saw in July, and it's an ongoing trend in the 21st Century. 

The Perseid peak is coming! Here's how to enjoy the show

The Perseid meteor shower, an annual display that lasts about a month every summer, is expected to peak early on Sunday morning. In recent years, the meteor shower has been hard to see in the NYC metro area; last year's peak coincided with a full moon, and in 2021, the shower peaked on a day with heat, humidity, and clouds. This year, the predicted peak coincides with a chance for thunderstorms in the Tri-State, but that doesn't mean we're out of luck! Meteors may still be visible at a rate of around 30 per hour on Sunday night. Here's why you should try to view the Perseids on both Saturday and Sunday:

- The moon will be in the waning crescent phase. Just a small sliver of the moon will be visible, reducing the amount of light it will reflect back to Earth. A less-bright moon means less interference with the light display of each meteor.

- On Saturday, the current forecast from the National Weather Service office in Upton, NY calls for thunderstorms, so don't venture outside if you hear thunder (more on lightning safety here). But mostly clear skies are predicted on Sunday night into Monday morning. If the clouds stay away, we should be able to glimpse a few meteors, even in the metro area. One year, I saw a Perseid meteor while walking my dog in Central Park! 

- The humidity will drop on Sunday, too. Muggy air is not just uncomfortable for standing outdoors and stargazing, it can also impede your view of the heavens. Water vapor scatters light more efficiently than dry air, so if it's less humid as it's predicted to be, then the view of the stars should be better. 

This dramatic image is a composite photo from the Perseid meteor shower. 
With the right conditions present, we can expect to see about one meteor per minute.
Photo from skyandtelescope.org

Even with favorable weather and moon phase, it's still tough to see the Perseids in the Tri-State area due to all the light pollution. Follow these tips to maximize your chance of seeing the meteor shower:

- Get as far away from city lights as possible. If it's safe to do so (and if you're allowed), you might want to try the roof of your house or apartment building. 

- Look for meteors after midnight and before dawn. This is when the sky is usually darkest. 

- While Perseid meteors may appear anywhere in the sky, they will likely be concentrated at the shower's radiant point. Look toward the north and northeast and elevate your gaze away from the horizon. The meteor shower will rise higher in the sky (from our perspective) as the night goes on. 

Where to look for the Perseid meteor shower this weekend.
Graphic courtesy of skyandtelescope.org

You can find more facts about the Perseid meteor shower at Sky & Telescope's website, which has a wealth of easy-to-read information about other celestial events as well. This article also includes a great explanation of the reason meteor showers exist and why we can see them as bright shooting stars. And, check out more Perseid photos on this site. Enjoy the show!

Learn in a flash: seven fast facts about lightning

Earlier this week, a young man in Alabama sadly lost his life after being struck by lightning. According to John Jensenius and the National Lightning Safety Council, eight people have died as a result of lightning strikes so far this year. Though this is not a large number of people- and in fact, it's half the number of lightning fatalities we normally see in the USA by this time of year- the sad truth is that almost every single lightning death is avoidable. 

So far in 2023, eight people have succumbed to injuries following a lightning strike. 

The 10-year running average by August 7th is 16 lightning fatalities.
Image and information courtesy of the Lightning Safety Council

In these final days of summer, it's understandable that we want to maximize our time on the beach, at the ballgame, or whatever is driving out into the great outdoors. But if you hear thunder, it's not worth the risk. NOAA developed an adage to address this concept: "When thunder roars, go indoors".  Below are some more facts and myths about lightning:

2022 AMS Weather Band Photo Contest winner: "Lighting Up the Tower" by Laura Hedien

- Lightning does not always strike the tallest object in an area. This is a common myth. What's actually happening is that lightning always chooses the path of least resistance. And while that path is often the tallest object in the immediate area, it's not always the case. And along those lines...
- Lightning is not attracted to metal. Most metals are excellent conductors of electricity, and many are easily ionized, which puts them in the "path of least resistance" category. But strictly speaking, metal does not attract lightning bolts.
- Standing under a tree will not keep you safe from a lightning strike. People can easily be electrocuted by lightning that travels through a tree and the ground below. Water is a very efficient conductor of electricity, and trees are loaded with water.
- Wearing rubber-soled shoes will not keep you safe from lightning. While rubber is an insulator, the soles of our shoes are not thick enough to protect from electricity in the ground after a lightning strike. Which leads to the next myth...
- You're not safe from lightning in a car because of its rubber tires. Instead, it's the metal frame of the automobile that protects you. But didn't I say that metal is a conductor of electricity? Absolutely. But when metal is fashioned into something called a Faraday Cage, and an insulating material is added (think of all the plastic and fabric elements inside a car), then lightning can't penetrate into the cabin of the vehicle. Importantly, the windows must be rolled up to ensure your safety in a thunderstorm. 
- Lightning can, and does, strike the same place twice. I do not understand where this myth came from! On average, the Empire State Building is struck 25 times every year.
- While you can count the number of seconds between seeing a flash and hearing thunder to estimate the distance of a lightning bolt, this estimate is irrelevant to your safety. If you can hear thunder, you can be struck by lightning. Head inside immediately.
- And finally, "heat lightning" is not generated by heat! This moniker probably arose because distant lightning, out of earshot of the thunder, is more commonly seen in the summertime. More on heat lightning can be found in my June blog post about summer weather phenomena.

If you missed this great webinar from the AMS Weather Band, which is also the source of the spectacular photos in this post, you can watch the recording by becoming a Weather Band member. And get more lightning safety tips here.

WHEN THUNDER ROARS... GO INDOORS