How dangerous is COVID? How about the COVID Vaccines?

We’re starting to get enough data to draw some conclusions. TLDR: COVID is dangerous – 4.5 times more deadly than the 2017 Influenza strain, which was a bad one. With the caveat that the long term studies are still underway for a lot of at-risk populations, COVID itself is about 215 times more deadly than the vaccine. The COVID vaccine isn’t really significantly more dangerous than the Influenza vaccine. Here’s a bit more detail and context …

You can’t get this vaccine for some reason.

There is a lot of argument and discussion over the relative risk of COVID vaccines, especially in Europe with the reports of the AstraZeneca/Oxford vaccine potentially causing blood clots in some people, and the Polyethylene Glycol (PEG) in the mRNA vaccines causing anaphylaxis (allergic reactions) here in the US. Both are concerning – and there is an urgent need to figure out why certain people are more vulnerable to adverse reactions than others. Certainly those with known allergies should be very careful to check the components of each vaccine before receiving it – the CDC publishes guidelines for this, and if you have sensitivities check with your Doctor before getting a shot (or any) procedure. This is the dilemma of vaccination: it’s best for the vast majority of people, but can be dangerous for a few. But care must be taken not to blow that true statement out of proportion.

What are the overall risks – in context with other risks? Lets take a closer look at the data from the FDA’s Adverse Event Reporting System as well as the CDC’s National Center for Health Statistics data bases and a few other data bases at CDC, NHTSA, and the FBI for context. Here is what your chances of dying this year look like:

  • Chances of dying from COVID: 1 in 163
  • Chances of dying from COVID Vaccine: 1 in 35,000
  • Chances of dying from Influenza (2017 H5N1 strain): 1 in 740
  • Chances of dying from Influenza Vaccine: 1 in 100,000
  • Chances of dying in any Accident: 1 in 1,350
  • Chances of dying from Gun Violence (you are a criminal): 1 in 3,000
  • Chances of dying from Gun Violence (you are not a criminal):1 in 220,000
  • Chances of dying from a Weather or Earthquake Hazard: 1 in 2 million or so

So in context, the vaccines are not risky compared to the disease – and certainly not compared to dying in a car accident (1 in 6000 or so). There has been some reports and talk that the COVID vaccines are significantly more dangerous than the Influenza vaccines. That’s a bit hard to judge. For one thing, the COVID vaccines are being scrutinized in a way the Influenza shots have not been. But even given that, the raw numbers show that the potentially associated mortality rate is about 2.8 times higher. It’s likely that difference would disappear if similar tracking were in place, but even if true isn’t bad. So the “50 times more side effects” stuff you see circulating is overblown.

Hope that helps put things in perspective …

Seasonal #Hurricane #Forecasts and ENSO

Like a bad remake of Groundhog Day, it’s that time of year when the various research groups emerge from their ivy covered lairs and issue forecasts for the upcoming Atlantic Hurricane season. I used to play that game, with the annual press conferences, media interviews, and associated tabulation of number of articles and citations to go into the next annual report and round of funding requests. But the last decade or so I have given up on the annual media circus as NOAA has started issuing its own estimates, and our research has moved on to site specific seasonal impact estimates rather than simply counting the number of storms. After all, having 20 storms doesn’t matter if none of them hit you; likewise, one storm can ruin your decade. So while this post does end with a suitably depressing outlook for 2021, it is more about the influence of the big driver of storm activity in the Atlantic: the ENSO or El Niño cycle.

CFS2 ENSO Forecast this fall from the NOAA Climate Prediction Center

The El Niño-Southern Oscillation (ENSO) has a huge impact on global weather. Although the usual way of measuring it is in terms of East Pacific sea surface temperatures, ENSO is a complex phenomena that changes both oceanic and atmospheric circulation patterns worldwide. The Wikipedia page has a nice overview of the system; what concerns us here is the impact on hurricanes. In the Atlantic, the warm phase of ENSO (El Niño) typically depresses hurricane activity; likewise, the cold phase (La Niña) tends to result in more and stronger storms. Periods in between are called “ENSO Neutral” or neutral. The reason ocean temperatures in the Pacific influences Atlantic hurricanes (in another ocean thousands of miles away) are complex, but mostly have to do with wind shear over the Atlantic and the so-called “steering currents” that push storms around as they move across the ocean. Don’t confuse these Pacific SST’s with ocean temperatures in the Atlantic – that is a separate cycle and phenomena. Normally we associate warmer oceans with more hurricanes, but in this case, a warmer Pacific during a El Niño phase means the Atlantic becomes less favorable (at least from a wind shear perspective)! The worst combination is a cold Pacific (La Niña) and a warm Atlantic: the cold Pacific is cold because winds are favorable over the Atlantic, and the warm Atlantic means more energy for Atlantic storms. Confused yet? Don’t be – in this case it’s simple, we’re just looking at how the three phases of ENSO correlate with hurricane landfalls and damage since it is such a big factor.

Let’s take a look at the peak of hurricane season, the month of September to see what impact the contrasting ENSO phases have on the number of storms, as well as on damage. Using data since 1871, it’s pretty even split between the two contrasting conditions. About 25% of Septembers are El Niño, 24% are La Niña, whereas 51% are neutral. But in terms of total numbers of storms, 30% occur in La Niña years, whereas 22% occur in El Niño. That doesn’t seem like much on the surface, but it actually translates in to a significant difference in the number of storms between the two years – an El Niño September typically has one third fewer storms than either a neutral or La Niña year. The number of people impacted by hurricane conditions also reflects this difference in a similar way. About a third fewer people are impacted by hurricane conditions in an average El Niño September than in other kinds of years. Damage basin-wide is not quite so dramatic, with damage during La Niña years only about 25% higher than in El Niño. But … there are regional twists to this story.

The biggest driver of the economic impact of hurricanes in the Atlantic is of course the mainland United States. The US experiences nearly DOUBLE the economic impact of hurricanes in an average La Niña September as compared to El Niño years (33% vs 17%)! This is partly due to the higher intensity, but more importantly due to the landfalls in La Niña years being closer to high value exposures (cities, or targets if you prefer 😮 ) in the Northeast and Atlantic coasts. Looking at the other two active months, La Niña Augusts tend to have more storms – but those storms stay offshore, so the damage actually tends to be less than in El Niño years, but in October the impacts are dramatic. A La Niña October tends to generate three times the damage as an El Niño year.

If you look at individual states there are also dramatic differences. In Florida, La Niña Septembers have generated FOUR TIMES as much damage as El Niño years! In New York, New Jersey, and Massachusetts there have been so few El Niño losses the computer said “Fuhgettaboutit” when I asked, they are so rarely damaged during those years, and La Niña years are so bad. The Gulf Coast isn’t quite so dramatic, but still Louisiana has had just under twice as much damage during La Niña.

Another interesting area is the Georgia/South Carolina Lowcountry coast (south of Edisto Isl). The unusual shape of the coastline, combined with being at the latitude where storms begin to recurve to the northeast means that for hurricane damage, the difference between La Niña and El Niño isn’t quite so dramatic – only about a 30% difference. However, unusually, activity is depressed in ENSO Neutral years, and elevated in both La Niña and El Niño Septembers.

What can we expect for this year? The current ENSO forecast for August to October is that we will almost certainly be at least neutral, and there is around a 50% chance of being back into La Niña conditions by September, and a higher chance for that in October. While not as favorable as last year, that’s Not Good for hurricane season, as it means higher than average activity. Therefore, I expect the hurricane forecasts coming out over the next few weeks to reflect that. Not likely as many storms as last year, but very likely to have multiple threats over the season. But there are a lot of other factors that go in to how many storm form in a given year, much less where any individual storms goes once it forms. The atmosphere is a very complex beastie.

So let the scare mongering begin … or, you could just enjoy the beautiful spring weather, the flowers blooming, and consider that as bad as hurricanes are, and unlike tornadoes that give you little warning, or earthquakes that give you almost none at all, you can see them coming days away, and have time to get out of the way. So as a reminder, this is the time of year to revisit your hurricane plans, especially insurance. There is a “lock out” period for changes prior to a storm and if you wait until one is headed your way, it’s too late. Check out for checklists and advice.

Sound Tracks for the Apocalypse

Since absolutely no-one has asked, here is a sample of what I listen to while working. I hope you find it an interesting mix … A lot of recent listening has been to metal bands from northern Europe. As an intro, hard to go wrong with Nightwish, Amorphis, Delain, or Within Temptation. Nightwish has had three lead singers – fans get in to flame wars over who is best, but each is good in their own way and worthy to listen to (even there is no doubt as to who is best, as this live clip proves 😛 … be sure to hang in there for the finale at the 9 minute mark):

After Forever, Floor Jansen’s previous group, disbanded but it has some great songs out there – “Equally Destructive” is a go to song for climate change, and “Discord” is just a great song. Look for other songs she’s done with various groups or solo – amazing vocalist and range.

I suspect that my two current second-most favorites (favorite is below the fold) are Amorphis and Sabaton. Amorphis has a variety of songs ranging from very heavy growls to near ballads. Here’s something in the middle …

Some people who don’t know any better think the Swedish metal band “Sabaton” glorify war. They’ve obviously never actually listened to most of the lyrics – even the songs that emphasize the heroic aspects of the military and war have an underlying message of “WTF was this really for?” that anyone who has lived that life will recognize. In any event, the song “En Livstid i Krig” (a Lifetime of War) is unmistakable. Here it is in Swedish …

… but as an accommodation to the few folks out there who don’t understand Nordic languages 😛 , here is a version in English. I think the Swedish lyrics are more poignant, it’s worth listening and have a translation of that version handy even if you don’t understand much. Sabaton’s music is a lesson in history, and they are fantastic live. Be sure to hack off Joakim and listen to “Swedish Pagans” from Wacken 2019 – this version with Tina Guo on Cello :O ! (it’s one of their most popular songs, and it’s a running joke that it’s never on the playlist and he hates it, but somehow gets played at every concert).

Continue reading

Thinking about weather/#climate #records

People love sports analogies. Maybe that’s why talking about weather records – be it record lows, record snow, whatever – gets a lot of press and attention. Sometimes it’s warranted, a lot of times it is (Surprise!) exaggerated and, almost always, reported out of context. The series of winter storms causing so much disruption across the US right now are certainly severe … here’s the current snow cover map, and forecast additional snow over the next 48 hours …

Snow Cover (blue) as of this morning (16 Feb 2021)

But just how “record breaking” is it? Let’s take a quick look at one weather station in Texas and try to get some context. Since we’re talking about the US, we’ll use medieval measurement units related to the FFF system 😛 …

Here is an excerpt from the official daily climate report from the NWS office in Houston, for Houston International Airport yesterday (Monday the 15th):

 CDUS44 KHGX 160849
 249 AM CST TUE FEB 16 2021
                 VALUE   (LST)  VALUE       VALUE  FROM      YEAR
   MAXIMUM         25   3:10 PM  83    1962  66    -41       67
   MINIMUM         16R  7:26 AM  18    1905  47    -31       40
   AVERAGE         21                        56    -35       54

That “R” next to the minimum means it is a new record. So … using the period 1892 to 2021 as the period of reference, the low temperature Monday set a new record for the 15th of February at 16 degrees. The old record was 18. In media headline terms, RECORD LOW IN HOUSTON!!! LOWEST TEMPERATURE IN OVER ONE HUNDRED YEARS!

But … if you read down a bit you will see the record for the 16th is 13 degrees, and if we check the 14th, the record was 10 degrees F (yes, ten!). So in that context, 16 is really cold but not so bad. Plus or minus a day in climate terms is no big deal, so for context you have to look at a couple of days either side of a record to see. In my global data archive I have daily records for thousands of stations since the mid 1970’s (that is the beginning of somewhat regular satellite data which is important in my research). Looking at Houston Intercontinental, we see that the twenty coldest temperatures since 1973 are:

     dtg         | lotempf 
  1989-12-24 00:00:00 |       7
  1989-12-23 00:00:00 |       7
  1983-12-25 00:00:00 |      11
  1989-12-25 00:00:00 |      11
  1983-12-26 00:00:00 |      11
  1982-01-11 00:00:00 |      12
  1985-01-22 00:00:00 |      16
  1985-01-21 00:00:00 |      16
  1989-12-22 00:00:00 |      16
  1979-01-03 00:00:00 |      17
  1979-01-02 00:00:00 |      17
  1983-12-27 00:00:00 |      18
  1983-12-31 00:00:00 |      18
  1977-01-20 00:00:00 |      18
  1977-01-11 00:00:00 |      18
  1977-01-10 00:00:00 |      18
  1983-12-24 00:00:00 |      18
  1977-01-19 00:00:00 |      18
  1983-12-30 00:00:00 |      19
  1976-11-30 00:00:00 |      19
 (20 rows)

So a low of sixteen is in fact pretty cold – now in the top 10 years since 1973, and the coldest mid February temperature since 1981 when there were a couple days that hit 20F.

In technical terms, this is the danger of looking at the tails of distributions, because of the way weather works with systems spanning several days, there is correlation between days, and gaps in the extremes.

So, yes, it’s cold. Yes, it’s disruptive (even though it shouldn’t be, but that’s a different rant). It’s hazardous or even dangerous if you don’t exercise some common sense and take some precautions. But while extreme, I think calling it “once in a lifetime” is probably a bit overblown, given the 1989 Christmas cold snap with a week of lows below 20F. As with most things, context is everything.

Final note – during these kinds of extreme weather events, especially with power outages, please keep an eye on your neighbors (especially the elderly and those with health issues or disabilities) to make sure they are safe. Bring animals in for sure, and consider helping with projects that try to shelter strays. Given icy roads, DON’T DRIVE ON THEM IF YOU DON’T KNOW WHAT YOU ARE DOING! And if you grew up in the south, be realistic: you don’t know what you are doing!!


Jupiter and Saturn

Conjunctions (the close approach of two objects) happen fairly frequently on a cosmic scale – Jupiter and Saturn pass one another about every 20 years, but today Jupiter and Saturn are the closest they have been in the sky since the year 1226, almost 800 years ago! This is one of those events that sounds a lot more spectacular than it looks. What you will see is one bright and one less bright star-like object in the sky that are less than the width of the full moon apart. The real show was in slow motion over the last couple of weeks as the two moved closer to one another. Here’s the view on the 13th and 18th (same focal length lens, slightly different times and camera position as you can see from the Spanish moss hanging down …). You can grab the slider (<>) and move it from side to side to see how much difference a week made …

Jupiter and Saturn, 13th and 18th of December

Through a small telescope you can see that these are not stars but planets … here is a view using a 400mm lens …

Saturn (top) and Jupiter. You can just make out the rings of Saturn and the cloud bands of Juipter in a small telescope. Although not visible in this shot you would also see several moons of each planet.

The real magic in this event is that you are seeing something that won’t be seen again in several lifetimes. People today are less attuned to the sky, especially given the lights in most cities block out the stars. Besides the sun, the only object most people see is the moon – and that often only when it’s full. But our ancestors watched the sky carefully, and noticed that some of the “stars” moved, and thought them to be special, perhaps messengers of the Gods or even the Gods Themselves. Those who watched the sky and interpreted the motions of the sun, moon, and stars noticed that in the years leading up to the year 750 AUC (Ab Urbe Condita, after the founding of The City – Rome) that there were a series of conjunctions between Jupiter, Venus, the Moon, and Saturn in auspicious constellations that may well have indicated to them that a new King would be born in Israel. That is one theory as to what the Christmas Star might have been, but there are others. From a theological standpoint seeking a naturalistic explanation seems to miss the point a bit since it is one of those things that probably isn’t going to convince anyone one way or the other. Besides, the Nativity was almost certainly in the Spring anyway … In any event, if you are a Christian or not, this is a window to a past where the majority of humans lived outside and were much more connected to the sky and their environment. So take a few minutes right after sunset and try to imagine what it was like thousands of years ago with no city lights, watching these mysterious objects majestically dance through the heavens …

The Coming Storm

No, not that one. Or that one. I mean the literal one, this one, the first big winter storm of the season. Here is the situation as of this morning (map forecast for 8am ET Wednesday, the storm is the “L” off the Georgia Coast):

Winter storm forming over Southeastern US … GFS model of precipitation type and moisture transport.

Like hurricanes, winter storms have to have a mix of conditions come together to cause them to grow and evolve. The key to weather on the earth is the need to balance the warm, moist air from the tropics with the cold, dry air over the poles. This happens in a number of ways, but in the summer the most dramatic are of course hurricanes. In the winter, it’s nor’easters. A classic nor’easter starts out as a low pressure system just off the coast of the Southeast. It moves northeast along the coast, carrying with it the warm moist air of the Gulf of Mexico and Bahamas, pushing that air inland where it meets cold polar air. It is along that swath where the air masses collide that the potential problems for Humans comes in. The danger this morning lies Appalachians and western North Carolina where the precipitation may be in the form of freezing rain, as well as inland in Kentucky (on the map, the red/purple area). Here is what things should look like this evening around 7pm. Notice that the low is deeper (stronger), the blue moisture transport vectors are longer (stronger), and across the New York/Pennsylvania area snow will be falling. The zone of freezing rain will by then have shifted to western Virginia.

The situation tonight …

By tomorrow morning the Low should be more elongated and off the Massachusetts coast, still pumping moist, snow-laden are into the NorthEast. The storm should be off the Canadian Marine Provinces by Friday.

Thursday Night

In terms of impacts, again the big concern is the area where freezing rain and ice will be falling. For the Northeast, snow could be fairly deep in places – some forecasts are for up to 24″ – but it’s more likely to be disruptive rather than truly dangerous, and again conditions should clear out by this weekend. For the Deep South (GA/SC), this will be a rain event, even for North Georgia. As things continue to cool off with the approaching winter season, the risk for ice storms will move further south … but the impacts of this event will be in North Carolina and the NEUS. How should you prepare for winter storm season? Take a look at the FEMA/DHS Winter Storm page for tips …

Yet another rant about COVID data

It’s one thing for the media to have “death counters” and for talking heads to spend 15 minutes an hour talking about the COVID statistics. Sure, it’s overly dramatic, misleading, causing a lot of unnecessary FUD (Fear Uncertainty and Doubt). But … entertainers are going to entertain. However, an awful lot of people are making life and death decisions based on week to week (even day to day!) fluctuations in COVID19 statistics. Does that make sense? Let’s take a look …

For a start, lets take a look at US Death reports, comparing the estimated numbers with the “final” totals for the latest reporting period, the week of September 12th:

Oops. Looks like there is a problem. First, (looks at calendar), it’s the 28th. The data for the week of the 19th is so incomplete it isn’t even showing up yet, only 25% or so of jurisdictions nationally have submitted data. Let’s put this in bold: we don’t really have solid numbers ( say, no more than 2% missing) for SIX WEEKS. Not six days, much less six hours (or, for TV folks, six minutes!). Here is a CDC paper describing the lags in the reporting system.

Now, let’s look at the reported deaths vs. the expected deaths. For expected we are using the average deaths in the US over 2000-2015, adjusted for current population. It varies from week to week during the year, more people die in winter than summer (mostly due to Influenza and Pneumonia). Here is the plot since February 1st of this year …

Two things are obvious from this plot: first, there is drastic under reporting in the most six to eight recent weeks (but we knew that from the previous graph). The second is that something out there is killing lots of Americans. So those saying COVID-19 isn’t that big a deal, well, that’s not what the numbers are showing – that’s not really the point of this graph, which is to show that the rapid tail off in recent weeks is probably due to reporting issues. We won’t have a good idea of what the data is for this week until November. That’s insane for a so called developed country with computers and telephones and stuff, but there it is.

Essentially all of the numbers you are seeing reported on a daily basis are ESTIMATES – not actual data. Now, the CDC, NCHS, Johns Hopkins and others doing the estimates are trying to do their best, and everyone is trying to get COVID data expedited through the system, but that’s actually a problem because now COVID confirmed deaths are being treated differently than other cases. and due to inconsistent testing and reporting it’s clear that we are missing a lot of COVID related deaths. Why do I say that? Take a look at this:

In other words, either there is another respiratory virus out there killing folks (very unlikely), or we are under counting COVID-19 deaths by around 20% (5 or 6% of total deaths).

And remember anything since week 28 or 29 (Mid August) is incomplete … so don’t get duped by the apparent tailing off since week 29 or so in this graph.

I could grind through this on a state by state basis; some are doing better, others worse, but you get the picture: the data isn’t timely or accurate. This is why (much to the annoyance of some) I don’t get bogged down in what this or that article (or even specific credible study in isolation) is arguing, trying to use the COVID-19 statistics to prove masks don’t work, or do work for that matter, or if the mortality rates are going up or going down or reopening is or isn’t working. Because to be blunt, the data sucks and we just don’t really know other than generally or anecdotally. That’s not to say the data is worthless – certainly we can see trends, and professionals can extrapolate a good bit from incomplete data, but this obsession with the death statistics isn’t healthy. Cases? Forgetaboutit. That’s even worse due to testing, reporting, and societal issues.

All this noise is why you can find an “analysis” out there (some credible, some not) that supports just about any point of view you want to try to flog. But if you take a step back and aren’t trying to make some political point, the picture is relatively clear: the SARS-COV-2 virus that causes COVID-19 is killing a lot of people who wouldn’t have otherwise died, we aren’t counting everyone who is being killed by it, and it isn’t going away.

Data Sources:
Excess Deaths Associated with COVID-19 (CDC).
Provisional COVID-19 Death Counts by Week Ending Date and State (NCHS).

#Sally landfall forecast impacts

Hurricane Sally should make landfall late tomorrow, with the US National Hurricane Center warning of “historic flooding.” Here are their Key Messages regarding Hurricane Sally (Spanish wasn’t available at 5:30am). But you may well ask, how is that possible given it’s not a very strong storm – only a middle Category One hurricane. Let’s take a closer look …

Here is the current infrared satellite view (the sun has not yet cast its baleful eye upon the Gulf). There are cold, dense overcast in the center, and as we can see on radar an eyewall keeps trying to form, but just can’t quite pull off a full eyewall or clear eye.

IR Satellite, 5;30am ET Tuesday; all graphics can be embiggened by clicking
New Orleans Radar at 5:25am Tuesday

And here is the MRMS radar composite for the bigger picture of the structure of the storm:

MRMS at 5:50am Tuesday

Aircraft data backs this up as well. All this means that contrary to the brief scare last night, rapid intensification and a Cat 3 landfall are just about off the table. Even Cat 2 seems a stretch. Sally is a solid Cat 1, and will remain so until landfall.

Here is the TAOS/TC impact map based on the 5am NHC forecast track:

Sally impact forecast

So why the “historic flooding” warning? The problem is that the steering (upper level winds that push storms around) is very light and changing slowly. So Sally is just drifting northwest at the moment at about 3-4 mph. As you can see from the regional radar, a lot of rain bands are pushing their way onto the MS/AL/FL Panhandle. So that is going to continue all day today and well into tomorrow. The rain totals just inland are in the neighborhood of 20 inches according to the latest HPC 5 day forecast:

HPC Rain Forecast

Because the winds aren’t that high, the surges would normally be somewhat nominal, but there are two aggravating factors. Storm surge depends on intensity, direction, and duration. Intensity isn’t so bad, but direction and duration are certainly favorable for high surges in some places. Ordinary we would expect a Cat 1 to product storm surges in the 6-8 foot range, but Sally will likely product surges on eastward facing shorelines of up to 12 feet such as parts of Mobile Bay and in the Delta. Overall, water levels will be at 4 or 5 feet above normal across the entire region from Panama City to the tip of the Delta. That, combined with all that rain, means the water has no place to go, and rivers, streams, and streets will have to deal with potentially a couple of feel of water. That is the reason for the inland rain warnings, especially in Alabama and the Pensacola area. Impacts will likely extend far inland, potentially to Montgomery. And speaking of inland, the rain swath is shown extending across North Georgia, and it is possible that the Atlanta metroplex will get dumped on later in the week with up to 8″ of rain. Atlanteans know what that means: grow gills, and prepare for epic traffic jams and stupidity. At least things look ok for New Oleans; it’s outside the excess rain swath, and while winds are blowing into the city off the lake, they should be light enough to not cause a big enough surge. As long as the city defenses work as designed.

Economic impacts are probably going to be in the neighborhood of $5 Billion, but that could easily double depending on where the rain ends up falling. Or, if the rains stay mostly offshore, impacts may be only $1 Billion or so. Ran is just about the hardest variable to forecast in these things …

#Sally Update, #Paulette, at 11am Sunday

The scary scenarios some of the high resolution hurricane models like HWRF were throwing up overnight have backed off somewhat, and in the 11am advisory the National Hurricane Center is sticking with around 85 knots (about 100mph, or Category 2) intensity at landfall. Key Messages regarding Tropical Storm Sally (en Español: Mensajes Claves). Thats “good” in a relative sense, but there are still circumstances around this storm that while not panic inducing, certainly keep it in the “be careful and be prepared” realm. Anything that dumps a lot of rain and storm surge in the New Orleans area is a worry. It is important to realize that the worst of Katrina was well west of the city, on the Mississippi coast; NOLA just caught the fringes. In terms of wind, despite being 100 knots (126mph) at landfall, winds in New Orleans itself were probably only in the neighborhood of category 1 sustained (80-90mph). The problem was the levee system failed and caused catastrophic flooding. Despite a weaker storm we are potentially facing something similar here for two reasons: first, lots of rain, with a slower storm. Katrina produced 10-12 inches of rain around NOLA. Sally’s current forecast is getting close to that:

NCEP 5 Day Rainfall forecast through Friday, 18 September

Notice New Orleans is right on the 8-10 inch range; it wouldn’t take much to kick it into the over 12″ range. A bit of a catch-22 is that when the storm surge protection masures are in place, it’s harder to pump rainwater out. Which raises the other big issue, storm surge from Lake Ponchartrain. New Orleans is essentially a big bathtub with a stopped up drain. The storm surge is extremely sensitive to the duration, direction, and speed of winds. This is a nice diagram from Wikipedia showing a cross section from the lake across the city:

Cross section of New Orleans (from Wikipedia)

Some of the storm surge scenarios for Sally put a lot of stress on the system due to the storm slowing down. If anything breaks it could get ugly fast. Again, this isn’t inevitable, but everything needs to work well to avoid a very bad situation. Currently on the Mississippi River side things look ok – the forecast is for a peak of around 10 feet, flood stage is 17 feet, so that side is probably safe (note the gauge stages are different from the elevations in the diagram). The lake side is forecast to reach at most 12 feet on the current forecast track and intensity – but 15 to 18 feet is not out of the question if Sally stalls out and the winds blow over the lake for a bit stronger, or a bit longer, than forecast. The good news again is that the duration of the “stall” seems tot be less and more importantly southwest of NOLA rather than south or over water, meaning the winds won’t be blowing water directly against the levee for so long. In any event, hopefully the storm will keep moving. That will reduce both rain and surge levels.

This isn’t intended to be scare mongering or alarmist, but to point out that New Orleans is a very vulnerable place. Right now the odds are definitely in their favor and a rapid intensification scenario is less likely. That said, it only takes a relatively small change in the scenario to narrow those odds (insert gamemaster comment here), and as I often point out, NOLA is one of those place where if something breaks that shouldn’t, the consequences are severe … so preparations are absolutely essential.

Out in the Atlantic, Paulette is still on track to hit Bermuda fairly hard tomorrow. Key Messages regarding Hurricane Paulette. They should be “hunkered down” at this point, tomorrow could be rough. Swells are reaching the US and Caribbean; if you go to the beach, beware of rip currents (or safely enjoy the surf if you are experienced and enjoy that sort of thing!).

The #Invest Thing Off Of #NorthCarolina #AL94 (8 Sept 2020)

Aside from Tropical Storms Paulette and Rene (note that’s a dude’s name in this case), there is an Invest (potential disturbance) area just off the coast of North Carolina that is getting some attention. It was designated as an invest area overnight, and is being tracked as AL942020, with a 40% chance of becoming a disturbance over the next five days by NHC. No watches or warnings. Check back in this evening or in the morning. That’s the official forecast. Let’s take a closer look at it since it is close to shore, and there is some probably misplaced angst over it.

Here is the infamous objective track model forecast map, aka “spagetti map”:

Available track models as of this morning; click any graphic to embiggen …

As a reminder, these maps are essentially useless and misleading. You have to cook the spaghetti and season it with experience (ack, that was bad). To start with, let’s get rid of all of the ensemble runs and just look at the prime track models:

prime model tracks, AL942020

OK, that’s not so bad – and in fact, for a weak disturbance without much definition, at first glance this is awfully good. If we look at the GFS model run and ensemble members (remember that the ensemble members are simplified runs of the prime model designed to assess the uncertainty in the main run), we get this:

GFS Ensemble Members from 00Z run

So … this thing will be moving towards the Southeastern US coast over the next five days. Of course, the track is just half of the story: how strong will it be when it gets wherever it is going? The ensemble members, as well as the prime runs that are truncated, are a bit of a clue: many of them die out before reaching the coast. But let’s look at this in a bit more detail. Here is what the last two intensity forecast cycles looked like for some representative techniques:

Intensity Guidance, 00Z Model Runs
Intensity Guidance 06z Model Runs

So you might think the trend is for stronger intensity, but beware: the ones trending higher are statistical models; the physics based (dynamical) models are for the most part not yet trending higher, and be especially aware that even the higher trending techniques are as of yet still only showing a minimal tropical storm. Looking at a solid dynamical track and intensity model, HWRF, here is what the overall picture looks like. Note that this does become a depression – then dies before landfall …

ohh, that’s not very doomy …

It is vital to remember that just because something might become a tropical disturbance or even tropical storm doesn’t mean it is an existential threat. Risks have to be kept in perspective. I try to categorize things as an inconvenience (windy, wet, rainy day with maybe some scattered power outages), hazardous (you shouldn’t go out in it, but if you are sensible will be ok), dangerous (lots of trees down, flooding), or life-threatening (winds high enough to seriously damage normal buildings, flood waters over a foot or two). This thing is likely to fall in to the “inconvenience” category for the vast majority of people in the “target” ‘area of the upper South Carolina/North Carolina/Virginia coasts, with perhaps some hazardous areas right on the coast or, as is always the case with tropical systems that produce lots of rain, hazards in low lying areas that can flood. Keep an eye on it? Sure – check back this evening or in the morning and see if it is developing. Wear out your refresh key? Not unless you just need the exercise … it is forecast to be slow moving, and so assuming you have a plan, nothing to get excited about yet.