West Coast Storms and Hurricane #Rick #Mexico (Sunday 24 Oct 2021)

Only one tropical system of interest, Hurricane Rick (EP17) should hit the west coast of Mexico Monday (more below), but there are two big non-tropical storm systems impacting the US today. Here is the TAFB surface analysis this morning, showing Hurricane Rick off of Mexico, the tangled fronts and low pressure in the middle of the country, and the big Pacific storm system starting to stream moisture into California …

Click to embiggen

Two areas are of concern in the US – the first is in the middle of the country, where a complex system is likely to produce some strong thunderstorms today. But the big Pacific storm (just under the label in the upper left of this graphic) has been getting media attention with the usual breathless headlines like “Atmospheric river, high winds to wallop California and Pacific Northwest” and talk of “Bomb Cyclones.” The terms “Atmospheric River” and “Bomb Cyclone” both have specific meanings and really aren’t necessarily scary or destructive unless you say them in the right tone of voice.

The more accurate term for “Bomb Cyclone” is “Explosive Cyclogenesis.” There is in fact a technical definition, that a storm decreases in minimal surface pressure by at least (24 sin φ/ sin 60°) mb in 24 hours, where φ represents latitude in degrees. I never liked the term “bomb” as being overly dramatic, but it has been in used in meteorology for a long time. They do have the potential to cause a lot of damage – the one approaching the Pacific Northwest has winds of hurricane force and higher. In addition, a second phenomena called an atmospheric river (AR in NWS abbreviations) is setting up over California today. That stream of moisture will drop a lot of rain there, which has the potential to cause flash flooding and over a foot of snow at higher elevations since in combination with the approaching cold fronts (the saw-toothed lines in the upper left of the above map) there will be a big temperature drop because, well, WINTER IS COMING! This year there is another factor, the large burn scars from this year’s wild fires. That means the vegetation that normally helps slow down or hold back rain is gone, so the potential for epic mudslides is present. You can get accurate and relatively drama free (and totally advertising free since you already paid for it!) reporting on all this at the National Weather Service web site (link). The short range weather discussion is always a good place to check for the “big picture” …

Click to go to Short Range Weather Discussion.

For those in Mexico, here is the damage swath expected from Rick:

Click to embiggen

NHC’s Key Messages regarding Hurricane Rick caution that as is typical for landfalls in Mexico, inland flash flooding and mudslides in the mountains are always a risk with this storm in addition to the threat of storm surge and wind on the immediate shoreline.

Busy weather map today (21 Sept 2021)

First, those in the Coastal Georgia and Lowcountry of South Carolina, it rained yesterday. A Lot. Savannah airport hit a record 6.66 inches (ok, that’s not ominous), breaking the old record of 2.12 for this date (which was low for a record, but has stood since 1885!). In midtown Nicholas says we got 6.51 inches, so it was pretty uniform heavy rain over the area. More rain predicted for today, probably not so much as yesterday, but watch for street flooding in the usual places. Here’s the TAFB weather map for this morning …

click for the details.

The stalled front (jagged line) with a low pressure “L” symbol over Georgia is the reason for all the rain. If you follow the front around to the east (right), you’ll see it ends in the label “storm” next to a Low pressure symbol. That’s what used to be Odette, now a winter storm.

There is less going on in the tropics than meets the eye. Yes, there are two tropical storms, Peter and Rose, but both are disorganized – notice that the heavy convection (oranges on the IR satellite image) are displaced from the center (the storm symbols) and not wrapping around them. That’s a sure sign of strong wind shear, and in fact NHC says in the latest bulletins that both storms will probably be torn apart in the next couple days.

There is some angst about a wave coming off of Africa, AL98 (Disturbance #1 on the NHC Tropical Weather Outlook), which has an 80% chance of spinning up. Run to run consistency has been fairly good for the GFS model, showing this system becoming a tropical storm in the next week. The longer range (10 day) forecasts are showing it following the same trajectory as most of the storms this year, north of the Leeward Island then east of Bermuda. But that’s along way off, and again if the magic words “Interests <somewhere> should <do something>” don’t appear in the NHC messages and/or you aren’t “somewhere”, don’t worry about it. If you’re curious, here’s the image swiper comparison tools for the GFS runs initialized at 8am yesterday morning and 8pm last night … this is amazingly consistent (but, as a caution, can rapidly change given the complexity of the atmosphere – 10 day forecasts are getting better but can still rapidly change). Slide right for the old run, left for the new run.

#Tennessee #Flooding; #Henri

There was record-breaking rain event in Tennessee over the weekend, killing at least 22 and several dozen still missing (AP Article). Here is the Multi-Radar Multi-Sensor (MRMS) rain accumulation …

Click to embiggen. White area is over 12″, most of which fell in a few hours.

The point gauge readings are epic; the previous record was nine inches, so this event nearly doubled that total:

OUS44 KOHX 230839
PNSOHX
TNZ005>011-023>034-056>066-075-077>080-093>095-232045-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE NASHVILLE TN
339 AM CDT MON AUG 23 2021

...KNOWN RAINFALL TOTALS FROM SATURDAY'S HISTORIC FLOOD...

CENTERVILLE 9.5 N...17.26" (COCORAHS) 
MCEWEN..............17.02" (CO-OP) 
DICKSON 6.3 WSW.....13.76" (COCORAHS) 
CENTERVILLE 2 N.....10.71" (CO-OP) 
DICKSON 12.7 NW......9.79" (COCORAHS) 
CENTERVILLE..........9.72" (CO-OP) 
BON AQUA 3.0 ESE.....8.29" (COCORAHS) 
DICKSON AIRPORT......8.17" (AWOS) 
VANLEER..............7.99" (COCORAHS) 
BURNS................5.28" (RAWS) 
ELLIS MILLS..........5.14" (CO-OP)

$$

This rain resulted from a series of storms “training” – one after another passing over the same area. Due to the current circulations over the US, a lot of moisture from the Gulf of Mexico has been pushed up into the southeast, and the available water to fuel these storms has been at historical highs. Articles such as the AP story cited above almost always mention climate change in every extreme weather event any more. The problem is that it is difficult to ascribe any specific event to anthropogenic (human caused) climate change. However, we are seeing patterns – as predicted by the models – that reinforce the other data that we are seeing evidence of a changing atmosphere. And, yes, it’s largely cause by human activities that have changed the surface characteristics of the earth, and chemical composition of the atmosphere. What should we do? That’s a very messy question, and so far none of the proposals on the table have any realistic hope of changing the course we are on. And that’s a different post.

In the tropical realm, Henri is now a tropical depression, and is dumping rain across New Jersey this morning, with some risk of flash floods in areas vulnerable to that sort of thing. Damage seems relatively light, a review of the Boston and New York Local Storm Reports this morning indicated trees down, street flooding, that sort of thing. There are thousands of people still without power. Here is the 5am radar (left) and 48 hour rainfall accumulation (right):

Unusually, most of the rain fell in New York and on the west side of the storm. Going to be a messy day today as the remnants slowly wander towards the east, not moving a lot. So if you are in that area be careful.

Not so bad today …

Click for an embiggened viewing experience …

But still some hot spots, in mid-town Savannah, GA, 95F 58% humidity, for a heat index of only 114 F. Better than the 120+ we spiked Friday/Saturday. Nothing in the tropics, a few earthquakes (including an 8.2 in Alaska the other day, fortunately no tsunami), so using the “break” for doing some long overdue computer maintenance like vacuuming all the @#$%! cat hair out of the computer intake fans :O

It’s not a dry heat

So there’s one or two heat warnings and advisories up this morning …

(in red, click to embiggen; blue stuff are flood, fog, or coastal advisories)

… and a lot of talk about the Heat Index. Let’s take a closer look. First off while the temperatures are above normal, at least here in coastal GA/SC they won’t be threatening the historical record highs. The air temperatures are going to be high Friday/Saturday, but won’t set any records. The average for July 30th is 92, the records this time of year are over 100 (101-103), and forecast highs in downtown Savannah are 97 today and 96 Saturday. The problem is that humidity is way above normal. That is due to the pattern of air flow over the region is keeping moist Gulf and Atlantic air “trapped” over us (recall the low pressure system that NHC was looking at earlier this week, AL90, wandered over us, then off of North Florida before drifting back over us). And it’s the humidity that’s the problem.

The Heat Index has an interesting history, and there are several versions. The method currently in use by the US National Weather Service is not a complex equation, if you want to see it look here:
https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml

  The TLDR is that the “heat index” is supposed to represent how hot if feels, given that the higher the humidity, it “feels” hotter because your body can’t cool itself as efficiently.  The technical reason is because we cool ourselves by sweating (ewww), and the evaporation of that sweat cools us down, since it takes energy – heat – to convert water from the liquid to gas states.  The evaporation rate depends temperature and humidity – the higher the humidity, the less moisture evaporates, and the less heat is transferred from your body to its surroundings. Drier air means that evaporation works better, so it “feels” cooler (although that can be misleading), thus all the jokes about a Dry Heat …

You can’t talk about heat without quoting Hicks 😛

  Either way, especially if you are not adapted to it, the heat can be dangerous (and in the ranges expected today, even if you are). By the way, the NWS has different criteria for when to issue heat advisories around the country, depending on normals. So a heat advisory in Vermont is issued at much “cooler” temperatures than in Savannah.

 To sum up, technically speaking, it’s not that it’s so hot, it’s because it’s kinda hot and really humid … it would be uncomfortable at 97, but all that humidity today will make it feel like it’s well over 110, maybe as high as 120 in parts of town where the temperature and humidity gang up.  So if you can avoid working outside this afternoon, don’t, and if you absolutely have to, drink lots of fluids, protect yourself, and be careful.

Update: at 2:30pm, in midtown Savannah the air temperature was 93, the humidity 70%, which adds up to a heat index of 120F :O

Update on WP09 (#Okinawa), Floods in Germany

Tropical Depression 09W slowly organizes as it moves in the general direction of Okinawa. The Joint Typhoon Warning Center forecast today is for a weaker storm tracking further south than yesterday. Here’s the “plain language” impact estimate based on their 5am ET forecast:

click to embiggen.

The objective guidance has it barely at hurricane strength at that time at worst. So it may not be more than some strong winds and rain on Okinawa. After that, the storm is likely to head for Mainland China, but it’s too early to estimate impacts there.

Elsewhere, a big weather story are the floods in Europe, particularly Germany (this link goes to Deutsche World live updates). The Netherlands and Belgium have also been hit hard.

A lot of the bad flooding is around Bad Neuenahr-Ahrweiler, Germany. The Ahr river flows through the town. . In looking at the period where we have really solid modeling for comparison with the climate models (1980-present), the peak total rain that ended up in the Ahr River fell on July 14th, and was 31% higher than the second highest value on record (which was in 2014). Worse, the Fifth highest daily value was on the 13th – and it was only about 5% lower than 2014. So two of the five highest total rainfall amounts in the last 40 years fell on back to back days.

The totals this last week were epic – 40% higher than the 2014 floods which came in at number two. Statistically it’s a well over 100 year event, maybe pushing a 200 year event. The rains on the 13th and earlier meant the soils were totally saturated (in fact soil moisture levels were at record highs on the 13th). So all of the water that fell on the 14th just ran off into the rivers and over the landscape. Also note that long ago (say 100 years) the flooding wouldn’t have been this bad with the same amount of rain due to development, impervious surfaces, etc.

This really was an epic amount of water. Fortunately it looks like there will be several days of clear weather, hopefully things dry out some before the next rains fall in 5-6 days. You’re probably hearing a lot about this being due to climate change. We’re in a difficult place right now data-wise. We are starting to see evidence of climatic changes that we would expect given anthropogenic changes to the atmosphere. Is this particular flood caused or made worse by human caused climate change? I think that’s impossible to say based on the data we have. But these kinds of disasters (floods, heat waves such as out west) are expected to become more frequent – and by the time it happens, it’s really too late to do anything except get out of the way. More on that in an upcoming post.

System approaching #Georgia Coast today

TLDR: it doesn’t really matter much if the NHC starts advisories or raises warnings in terms of impacts, the physical effects are going to be about the same: rainy afternoon and overnight, “landfall” this evening. Maybe some localized street flooding with over an inch of rain, winds don’t look bad at all right now, maybe a bit higher in South Carolina, and you might see some gusts and branches down, that sort of thing.

Here’s the details … The system moving towards the Georgia coast hasn’t organized much overnight, so the National Hurricane Center hasn’t started official advisories or raised any warnings as of 6am. Here is what it looks like on satellite (water vapor band, with surface analysis map overlay so you can see where the “center” is located – the L symbol):

Water Vapor Band and surface analysis, 6am Monday

The Charleston radar (which is really in Hampton, SC, about half way between Charleston and Savannah) is showing the outer rain blobs (not really bands at this point if ever) approaching the coast:

Radar from “Charleston”: reflectivity on the left, velocity (wind speed) on the right,

At the moment the impacts of this thing don’t look so bad. Could get some heavy rain, totals of an inch or more in the Savannah/Hilton Head/Beaufort area. It’s moving fairly fast so while there is some potential for minor flooding, flash flooding isn’t too likely. Winds look well below tropical storm strength; if it does organize enough to reach depression criteria, the winds should stay confined to the coast (the islands) but even then not really a big threat. On the beaches there is a rip tide caution, and any time these things come ashore there is a chance of waterspouts or weak tornadoes (EF0/1). So keep your weather radio on just in case. Serious rain should kick in around noon, and be gone by tomorrow morning.

One Percent

Here is one last rant and some additional perspective on the sensationalist, fear mongering reports in several USA TODAY network newspapers this week. In 2019, 42 people died from tornadoes. That same year 47,511 committed suicide. In other words, reducing suicides by JUST ONE PERCENT would have saved ten times as many lives (475) as completely eliminating tornado deaths. On average, there are 132 suicide deaths PER DAY – more than the last two years of tornado deaths combined (117), and nearly twice the average annual tornado death rate (69/yr). Now, given that perspective, is this front page justified?

To be sure, any premature death is a tragedy, and weather causes a significant amount of death and destruction, a lot of it preventable. But we have made tremendous strides in warning and mitigation, especially in the area of hurricanes. The articles had some good points – but the melodrama and fear overwhelmed whatever valid points were to be made. I’ve made it my life’s work to try to reduce the impact of natural hazards, so obviously I think this work is important and valuable – but you have to keep it in perspective. Consider: over 6,000 Military Veterans are thought to die due to suicide every year – at least eighty six (86) times the annual average deaths from tornadoes. If I had the skills and knowledge to help reduce that horrific figure I’d drop what I’m doing in a second and change careers.

It’s important to realize that the most insidious and toxic thing about this kind of “reporting” is that factually the article is almost entirely “true” – as noted in the previous post, tornado activity might be shifting, and “The South” is more vulnerable than the Midwest. It just the reports lack context. I can do a screaming headline about “Every Surface In Your Home Is Coated in Bacteria,” show gross pictures of people with necrotizing fasciitis accompanied by sob stories from their families, and without any falsehoods make you afraid to touch your kitchen counter. But in context, all that bacteria isn’t really a major problem for most people with some common sense. I could have used many other examples of things more dangerous or impactful on everyday life than tornadoes, but I just got a note on Veteran suicide so it’s on my mind.

The bottom line is that while tornadoes are scary, by any rational measure we’re afraid of and worried about the wrong things – and “journalism” like this a big reason why.

Is “Tornado alley” shifting, and is coastal Georgia at greater risk?

Is Tornado Alley shifting, “spreading to the South, leaving a trail of DEATH AND DESTRUCTION” as this morning’s local Savannah newspaper dramatically blared? And is coastal Georgia at greater risk? Let’s see what grumpy cat has to say:

Grumpy Cat calls BS on another media scare piece …

There has been a series of articles on potential changes in tornado climatology in the last few weeks, and the local paper in Savannah, as part of the USA TODAY network, has run a couple of dramatic front page articles on the subject including a front page Sunday feature that happened to coincide with some tornado potential from the passage of Tropical Storm Claudette, and another dramatic front page spread this morning (Wednesday). As I read these articles, I saw a lot of red flags, especially for being in the local paper and not pointing out that a lot of what was said did not apply to the Savannah area (including a local supplemental article supposedly focused on Georgia). It has been about 10 years since I was involved in active tornado research, and while I do try to keep up with things, it’s always possible to miss something, so I spent a fair bit of time the last couple of days catching up before writing this post. The bottom line is that while it had some great points about changing population and demographics, the implication that tornado activity is changing in some drastic way and that the risk was dramatically changing in the south – and particularly the implication that the local Coastal Georgia/South Carolina area has changed – was simply misleading.

The biggest technical issues are around the reliability of the historical data and the way the overall scenario was presented. However there are wider issues. This kind of overly dramatic reporting isn’t helpful in providing perspective, and are fueled by wider availability of raw data sets that anyone can download and manipulate, combined with scientists who naturally want to see their research publicized but often don’t get to see the final articles before they reach the public, and a sound-bite driven culture that has permeated even what should be more thoughtful long form pieces. These articles are a (cough) perfect storm, coming together to create a misleading train wreck. This is a complex topic, so will have to take some time to work through this to get a more balanced perspective.

Continue reading

Severe weather potential in coastal GA/SC today (Sat Apr 24)

For those in the coastal Georgia and South Carolina Low Country, while there is some uncertainty there seems to be two bands of potentially severe weather on the way today. The first is a Quasi Linear Convective System (QLCS), which is a fancy term for a line of thunderstorms, interacting with a warm front late this morning. The second is a squall line that is shaping up to push through during the peak energy time, late this afternoon and early evening. Overall, heavy rain (up to 3″ in the Savannah area, maybe near high tide, so expect street flooding!), gusty winds, and according to the Storm Prediction Center a 10% chance for a tornado … so keep your weather radios on and be aware we could get some heavy weather today. You can see stuff shaping up to our southwest in this radar composite as of 7:30am …

Click to embiggen; severe thunderstorm and tornado warnings in southern AL this morning