Dorian, Tuesday 27 August morning update

Dorian is now just past St. Lucia/St. Vincent.  The storm is still hovering around 50mph wind speeds, a middling tropical storm, and from the current (6:30am ET) high resolution satellite image showed some big thunderstorms are passing over Martinique.  The dry air in the mid levels of the atmosphere in the Caribbean is keeping the storm suppressed, and development seems to be stalled.  The present National Hurricane Center forecast has  backed off on forecasting the storm to become a hurricane before it reaches Puerto Rico and the Dominican Republic (the eastern half of the island of Hispaniola), although there are still hurricane watches up for both.  Preparations in PR and the eastern DR for a strong tropical storm or minimal hurricane make sense at this point, especially for the inevitable localized flash flooding that accompanies these storms.  Wednesday will likely be a wet and blustery, but hopefully not catastrophic day for them.

As to what happens next, it depends on some subtle wobbles and not so subtle mountains.  If the storm threads the Mona passage between the islands of Hispaniola and Puerto Rico, it could maintain its circulation enough to rebound in the warm waters of The Bahamas. This is the scenario NHC is showing.  Butf it wobbles either left or right of this track, it could well be shredded, and the islands and Florida just get a messy tropical rain system.  Hard to tell at this point, but by tomorrow we will have a better handle on this since we will know how much the dry air inhibits (or even decreases) the storm, and if is going to run aground on Hispaniola.  The obligatory “spaghetti map” shows the primary dynamic models taking the storm as the NHC has it, mostly towards the Dominican Republic. This map is showing all of the available tracks … for those of you in Georgia/SC/NC, don’t freak out about the lines headed up towards your area.  Those are mostly ensemble track members that are low probability outcomes, and often represent tracks where the storm is little more than a big thunderstorm.  They are designed to help understand the uncertainty in the forecasts.   It is pretty irresponsible to cherry pick from those tracks, as some local weathercasters and amateurs do.  The colored lines are the “primary” model tracks that are the ones to examine – but that red line is the Official NHC Track that is the one to care about.


Here’s this morning’s Haetta/TC impact map, based on the official forecast …


Evening Update on Tropical Storm Dorian (and TD#6)

The National Hurricane Center started advisories on the low pressure system off the Southeastern US Coast as Tropical Depression Number 6.  They are expecting it to become a minimal tropical storm before skimming the coast and impacting Nova Scotia and Newfoundland …

Dorian is an interesting storm, very compact, and hard to forecast the intensity since there are evenly balanced factors for and against.  So far, “for” is winning.  Here’s an animation of the last 30 minutes or so (4:00 to 4:30pm EDT) visual band one minute GOES images (click to embiggen/animate):

That central cloud feature is called a “central dense overcast” or CDO.  The National Hurricane Center is sticking with a forecast taking the storm over Western Puerto Rico and Hispaniola as a minimal hurricane. The island is now under a tropical storm watch, and will likely get hurricane watches/warnings.  That’s a smart bet, given how the storm is behaving.  The dynamical intensity models are really mixed: some virtually kill the storm, some spin it up.  The big factor, as noted this morning, is the very dry air in the lower and middle atmosphere.  Some is getting pulled in to the storm, but not as much as if it were bigger.  The track isn’t in much doubt: they all pretty much go up towards the Mona Passage (between Puerto Rico and Hispaniola).  Here is the HWRF model, which clearly oscillates in intensity and never brings it up to hurricane strength.

But NHC has good reasons to be cautious with this one.  Here is the official forecast track and intensity impacts:

On this track, the worst impacts would be over western PR, damage could be upwards of $500 million, but the fragile infrastructure of Puerto Rico really doesn’t need this additional insult.  Rain and flash floods, and electrical system problems are the most likely impacts.  As for The Bahamas and Florida, it’s a touchy (but not panic time) situation.  If the storm is a little weaker than the NHC forecast, and gets shredded by the mountains of Hispaniola, then it might just be a wet tropical low.  But the water in The Bahamas is very warm, and upper air conditions favorable – if Dorian can survive to reach that area somewhat intact.  if so, bad news for them and potentially Florida, with a real Hurricane landfall possible.  As for Georgia/SC/NC, the more likely scenario is for the storm to cross Florida (assuming it survives), based on the longer range models. But is something we won’t have a handle on until Thursday, so if you have a plan plenty of time to wait and see.  As always, for the official word check the NHC Key Messages graphic!

Nuking hurricanes?

The US President is alleged (he vehemently denies it) to have suggested on more than one occasion that we use nuclear weapons to disrupt hurricanes.  This has received a lot of attention in global news sources the last 24 hours; as with virtually all issues in the US what people think generally breaks on tribal (political party) lines. I won’t take sides on that aspect.  Many people have a gut reaction one way or another to the substance of the idea, but there is a long history to this idea, as this 2016 (pre-Trump) National Geographic article shows.  In fact, I can’t recall a lecture on weather, climate, or hurricanes that I’ve given to the general public where it didn’t come up.  So what is the reality of using a nuke specifically, or other modifications generally?

Trying to diminish the power of hurricanes has been around since at least the 1940’s.  The first practical project was to use cloud seeding as part of Project Cirrus in 1947, then more systematically in Project Stormfury in the 1960’s.  The 1947 Project Cirrus illustrated a key problem: during the seeding process the storm, which had been headed out to sea, turned around and made landfall near Savannah, Georgia.  America being America, lawsuits were started, but were ultimately thrown out.  Later attempts had mixed results, but the consensus was that the project was a “successful failure”: a failure, in that hurricane modification didn’t work, but a success in that it greatly improved our understanding of hurricanes.

Castle Bravo test, 1954. USDOE Photo.

The idea of using nukes also dates back to the late 50’s and early 1960’s, and was suggested by no less than the head of the US Weather Bureau (predecessor of the National Weather Service) in 1961.  The idea is that the thermal effects of the detonation would disrupt the thermodynamics and circulation of the storm.  In one sense it’s not a completely insane idea; megaton class nuclear weapons have a dramatic impact on the atmosphere.  Some argue (like in the NOAA page devoted to the question) that because a mature hurricane dissipates on the order of a megaton nuclear blast of energy per minute a nuke is pointless.  I think that misses the point somewhat because a megaton class blast in the eye or eyewall would have disruptions to the convective processes far out of proportion to the average energy.  Unfortunately that discussion edges into classified modeling and data, and besides misses the point that you can’t use a nuke in a hurricane for one very important reason that was overlooked or dismissed in the discussions of the early 1960’s.

Of course, bottom line is that even if it “worked”, it’s pretty dumb to nuke a hurricane due to one key side effect of nuclear weapons: radioactive fallout.  Before you laugh too much at that, recall that in the late 1950’s and early 1960’s we were just coming to terms with the long term radiation impacts of nuclear weapons, and many of the worst effects were still classified and suppressed to reduce the fear of nuclear power.  At the time Project Plowshare was proposing all kinds of uses that, today, we would call “crazy”  like widening the Panama Canal (this as late as 1970) or creating harbors.  Twenty-two bombs were even seriously proposed to create a road cut through the Bristol Mountains to facilitate Interstate 40!

So while folks are making a lot of political hay over this because of the latest source of the idea, it’s not a new idea, and wasn’t considered all that crazy maybe as little as 40 years ago.  For a lay person with minimal understanding of science, I can see how it might seem an attractive idea.  There are lots of very bad, scientifically unsound ideas and the policies they drive floating around across the political spectrum.  It does highlight a key problem, that major world leaders and most of the people they lead often don’t have a very sound understanding of science and engineering that are so vital to our modern world.  (Or economics.  Or …)  So I’m not at all surprised that a President (especially this one) asked the question.  I just hope his advisers took the time to explain to him why it’s not a great idea, rather than do what I think many advisers to world leaders do all too often: just nod and say “we’ll look into it.”

Tropical Storm Dorian, Monday, 26 August 2019 (updated noon)

Note that while Dorian is in a mixed environment, seems to be slowly intensifying and organizing.  NHC has increased their forecast intensity, and upgraded the tropical storm watch for St. Lucia to a Hurricane Watch.  That said, bottom line for the Windard Islands hasn’t really changed much, the main risk is flash flooding, with perhaps a bit more risk of isolated wind damage.  For the Puerto Rico/Hispaniola, NHC is hinting at hurricane watches later.  That is a reasonable precaution; as always, use NHC’s “Key Messages” graphics for a good summary of actions you should be taking.

Dorian (AL052019) continues to wander towards Barbados and the Windward Islands as a very small tropical storm.  Warnings are up for Barbados, St. Lucia, and St. Vincent.  The main threat to these islands is localized flash flooding on the steep slopes of these islands; unless something breaks that shouldn’t, winds and waves should not cause extensive damage.

The official NHC forecast brings the storm to near hurricane strength as it approaches the Mona Passage (the gap between Puerto Rico and Hispaniola (Dominican Republic).  That is at the extreme upper end of the intensity forecasts.  I understand why NHC is doing that – they want people in those areas to pay attention and to be prepared just in case, and if you live in those areas you should certainly check your plans and be ready.  But it is pretty unlikely the storm will be that strong when it gets to the Puerto Rico area.  There is a lot of dry air over the region (click to embiggen)…

So what does that mean?  Again, if you are in the Windward Islands, you should be wrapping up preparations for a tropical storm.  If you are in Puerto Rico or on Hispaniola, and you have a plan, watch and be ready, but no reason to get too worried at this point.  The dynamical models like the new GFS/FV3 and the sainted ECMWF decay Dorian fairly quickly.  Normally I avoid showing individual model outputs, but will make an exception here given the situation.  Here are the forecasted impacts based on the GFS Ensemble blend, using my Haetta/TC model …

For those in Florida, definitely don’t freak out that the storm seems to hit you in 6 days: just because the line comes your way doesn’t mean it will have significant impacts, in this case, look at the color key: “Small Trees Sway” and “Large Trees Sway” (30mph winds or so).  That and rain: no big deal.  Kite flying weather.  Well, except the lightning.  So don’t do that.

But for watch and warning purposes, and taking action, the official NHC forecast is what you should be using.  It’s almost always the conservative (safe) choice, and if you follow it you will rarely be caught off guard.  Here is the same impact map using the official forecast:

Note the official forecast only goes out five days.  There is a very good reason for that: beyond that time frame the forecast accuracy reaches the point the forecast is virtually unusable, and five days is more than enough time to prepare (and three days is really enough, assuming you’ve made your pre-season plans appropriately).

Tropical Storm Dorian Update, Sunday Morning 25 August 2019

Tropical Storm Dorian (AL052019) is a small, weak tropical storm about 900km (that’s 560 miles for you backwards ‘Muricans!) east of Barbados. A tropical storm watch has been issued for that island since most of the objective track models take the storm near or over the island by late Monday, and the official forecast track shows a direct hit.  As usual, there are two questions: where is it going to go, and how bad will it be when it gets there?

Two key tools are used for the “where”: objective track models, and forecaster experience to create the “official” track.  In this day with dozens of tracks (if you include individual ensemble members, which you shouldn’t in and of themselves) to choose from, amateurs often overlook that second bit and spend a lot of time arguing over this or that individual track model. The Official NHC forecast incorporates a third component: watch and warning considerations.  In this case, Dorian is a small storm, in a mixed environment.  The present track has the storm crossing Barbados and the Windward Islands as a small but mature tropical storm, briefly hit hurricane strength in the mid-eastern Caribbean sea, then weaken as it approaches the island of Hispaniola (Dominican Republic/Haiti).  The tracks are fairly well grouped for a weaker storm …

For Puerto Rico: the forecast track has shifted away, and will probably shift away more later today. It’s a good ways away – unless it speeds up it looks like a Wednesday event for PR, and while the infrastructure is still (resisting the urge to rant) weak, and the rain potentially a problem, it doesn’t look like it cause significant problems.  But it might be a close call.  Also, even if the storm gets a bit stronger at first, it will be entering a pretty dry mass of air that should inhibit strengthening (or even cause it to decay).  Here’s the latest water vapor band image; all that orange is dry air that can choke off a storm:

As for “how bad”, the main threat to Barbados and the Windward Islands is rain and flash flooding.  But it’s a small storm in dry air, so that may be pretty localized, so if folks button up they should be ok.  The big question is more if it can intensify later and threaten the Greater Antilles (PR/Hispaniola or, if the track shifts further west, Jamaica).  As for The Bahamas and Florida, that’s at least a week away and too far out to forecast, but if it survives passage over the Caribbean (and isn’t shredded by Hispaniola) it could reform/rebuild, but that’s absolutely not worth worrying about at this point.  Here’s the forecast intensity …

Still threat condition “yawn” in the Atlantic …

Update at 1pm ET: we’re now at “Meh” for sure: NHC has started official advisories on Tropical Depression number 5 (AL052019).  I’m surprised at how aggressive they are in the initial advisory, taking the storm up to hurricane status in 5 days.  But this means folks in the Caribbean should pay attention now.

The main tropical story is in the West Pacific, Tropical Storm (Tropical Cyclone) Bailu is making landfall on southern Taiwan.  Main risk is flash flooding and landslides, estimated impacts in the low hundreds of millions of USD.

The Atlantic might look interesting at first glance, but if you have your hurricane plans in place, it’s more of a yawn at this point.  There are two “invest” areas in the Atlantic –  Chantal (AL042019) is no more, fading out in the North Atlantic.  The first area, AL982019 (recalling INVEST areas get temporary ID’s so you may see that code again!) has moved inland over Flordia.  It is causing rain in that state as well as over The Bahamas.  This is the expected scenario, that it will drift out to sea and head northeast away from land (either Florida or the northern Islands).  At that point it has a good chance of becoming a depression or storm, but by then it won’t be a problem except maybe for Bermuda.  Here’s the full track map for this morning (Saturday 24 August) … there is no official forecast yet, but I think the most likely track is like the red line (the GFS Ensemble).

Further south, over the mid-Atlantic, the system tagged AL992019 in the Automated Tropical Cyclone Forecast System (ATCF) is lurching towards the Caribbean and almost rises to the “meh” level.  NHC gives it a 70% chance of becoming a minimal tropical storm, but conditions are unfavorable once you get close to the Islands, so it’s not likely to get strong enough to cause much damage.  Still, worth paying some attention to, given the risk of flash flooding to cause localized damage on many Islands, and there is a small chance it could spin up more than expected..  Still to far to anticipate impacts to Puerto Rico, should know more by Monday.  Again, still just an invest, so no official tracks yet. (OK, now there is at 11am, as AL052019).  Highlighted red line is the GFS Ensemble, which at this point is as good a guess as any.


Tropical system passing over Florida

There is a tropical system passing over South and Central Florida this weekend (23-25 August 2019).  Not very unusual – Florida gets systems like this just about weekly during the summer!  But this one does show some signs of organization, and once it moves back out to sea might cross the threshold to become a system officially tracked by the US National Hurricane Center.  Before they are “officially” tracked (in other words, with formal 6 hourly public advisories), these systems are called “Investigation Areas” or INVEST areas. It’s not too likely this thing will be strong enough over land to cause problems, and any strengthening shouldn’t happen until after it moves away from the US or Islands.

Right now, this system is called “AL982019”.  What does that mean? All tropical systems are given tracking codes in the form BBNNYYYY where BB is the basin, NN is a number code, YYYY is the year.  The basin codes are pretty straightforward: AL is the Atlantic, EP is the East Pacific (off of Mexico), CP is the Central Pacific (Hawai’i), WP is the West Pacific (Asia), IO the Indian Ocean, and SH the Southern Hemisphere.  The number codes are a little tricky.  Numbers 90 and above are reserved for INVEST areas and are reused during the season.  This bears repeating:

Be careful searching on teh intertubs for invest areas by the codes:
they are re-used during the season!

If the system meets the criteria to become a system with advisories, it is given a “permanent” code, the next in line starting at 01 for each year (January 1st in the Northern Hemisphere.  In the Southern Hemisphere, the year starts September 1st of the previous year, so a tropical storm forming off of Australia in November this year might have the code SH032020! ).  Note this is different from the name of the storm.  The criteria for a storm being “tropical” and being “named” are different!  So AL03 may not be the “C” named stormed.  In fact, the presently active Chantal is AL04 because there was a previous system that was organized enough to start advisories, but did not meet the criteria to become a “named” storm.

Here’s the track map as of 7am this morning.  Some models kill it off, some spin it up after it moves off shore into the Atlantic.  NHC is saying 30% chance of it meeting the criteria to be a minimal tropical system in the next two days, and 60% in the next 5.  Again, even if it does, this system is not likely to have any significant impacts.

Why you shouldn’t get excited about long range forecasts …

I ran across a weather blog yesterday (sadly, by someone with an AMS seal) playing up a possible hurricane hitting New Orleans next week, based on the GFS model forecast.  Here’s the forecast map in question, the 225 hour forecast from the 18z GFS/FV3 run on Tuesday, August 13th (the Tuesday Afternoon run).  Looks bad for the sweltering, drunken masses on Bourbon Street …

But, as a reader of this blog, I know that while the new models are better, global weather models still have a tendency to spin up vortexes, so I waited to see what the next run on Tuesday night showed before freaking out …

Oh, now it’s just a tropical depression or storm, and not a problem for the weekly NOLA Friday Night Bacchanalia.   But, what does that mean for my oil and cattle futures?  Lets look at the early morning (06z, Wed. 14 August) for the same time (03z Friday, August 23rd, now “only” 213 hours away) …

Hey, where’s my storm?  Now it’s just a blob of rain on the Alabama/Louisiana border?

Forecast tracks from the global models have improved a lot in recent years, once a storm spins up, and are better at forecasting formation in the short term (0-5 days).  But this example is why these long range models are not that useful for long range hurricane forecasts, and why the National Hurricane Center only does outlooks out five days.  These models just aren’t designed for it, and this far away, the uncertainty is so great you can get exhausted tracking every little vortex that, over the life of the model, will spin up, but don’t even exist in the “real” world (not to mention the systems that spin up in the real world).  So anybody talking about storms forming a week away is probably just phishing for clickbait.  Now, talking about those who talk about them, that’s a public service and perfectly ok …

NOAA’s Atlantic Hurricane Season Update

Last week the US National Oceanic and Atmospheric Administration (NOAA) released an updated seasonal forecast, and due to the waning El Nino has increased their forecast for the number of storms expected this year, now saying there is an increased chance for an “above average” season.  What does that mean to you, the huddled masses cowering in fear along the shoreline, waiting for your inevitable doom?

Exactly nothing (assuming you have a hurricane plan already, which you should no matter what the seasonal forecast says).

First, even if you knew *exactly* how many storms were going to form in a year, it tells you nothing about how bad the season will be.  There have been above average years in raw numbers with no hurricane landfalls.  1992 was a below average year – well, except for Hurricane Andrew.  So unless you know where they are going to go, even one hurricane can ruin your day, and 20 can be no big deal if they are all fish storms.

Second, the numbers used to compute the averages are becoming more and more suspect.  This year’s “hurricane” Barry more than likely would not have been classified as a hurricane in past years for a number of reasons (before anyone yelps, no, this isn’t part of the Vast Global Warming Conspiracy(tm), it’s because of better observation systems that can see small patches of possible hurricane force winds, and different classification criteria).

I really don’t like the hype around seasonal forecasts and their updates.  Dr. Mark Johnson of UCF and I used to do them (including something NOAA doesn’t do, landfall probabilities), but the media circus and subsequent fear mongering were just a bit too much.  We still generate them, and they have decent enough skill, but they aren’t really “actionable” except for narrow applications.  About the only thing they are good from a public safety standpoint is “awareness,” but there are other ways of doing that than shoveling out the statistical stables …

So if you haven’t put together a plan yet, slap yourself and go to visit the FEMA web site and get some checklists to think about, consult your local EMA for risk maps for your risk of flooding (which is by far the major threat to life; the golden rule is shelter from wind, evacuate from water), and put together a plan.  Then don’t worry about it.