PTC#9 Mid-day “nothing has changed” report

Not too much changed with PTC#9 at the 11am advisory … will do a full update on the blog later today. Here’s the latest TAFB analysis … two things to note if you embiggen is the sort of oblong shape to the system, and the big high pressure system to the north.  That high pressure ridge (think of the “H” as the top of a hill) is causing the storm to move around the left hand side – that is what is guiding the storm right now.  So at the moment, the thinking is still that the system will stay weak, and should track south of Puerto Rico (but that may not help much if the winds and rain cross the Island).  After that, hard to say at this point … stay tuned!


AL092020 – Still “Potential” (Wed 29 July AM)

Rules! We’ve got some rules around here”  And so it is with what is and isn’t a Tropical Cyclone (the technical name for depressions, tropical storms, and hurricanes).  The system NHC is tracking as AL09, “Potential Tropical Cyclone Nine,” doesn’t meet the formal criteria to be a tropical storm, even though it is producing tropical storm force winds in places.  As of this morning though there are thunderstorms (convection) flaring up near the center, indicating better organization.  It will likely be declared Tropical Storm Isaias later today.  Here is what it looks like at sunrise … left is infrared, right is visual (still a bit dark).  Click to embiggen:

So what does that mean in practical terms?  It means the wind field is broader than a typical tropical storm – but not as strong in the core.  It is slower to organize even with somewhat favorable conditions. It also makes forecasting much harder because we don’t have a good center fix and motion.  Depending on where the center finally coalesces,  On the current track across the Greater Antillies (Puerto Rico/Hispaniola/Cuba), the high mountains should inhibit much strengthening.  The official forecast keeps AL09 as at best a middling tropical storm.  But that can still cause a lot of misery, especially in Puerto Rico, as they have are still struggling to recover from Maria or the recent earthquakes.  Beyond that, it is likely the storm will curve north into Florida.  But it wouldn’t surprise me if it doesn’t survive the trip over Hispaniola and Cuba intact, or enters the Gulf of Mexico and strengthens.  Or something else (yeah, that’s a lot of help).  That’s how it goes with disorganized storms …

On this track it would cause upwards of $100 Million in damage across the Caribbean, and maybe $700 million in impacts in Florida.  A big question is if it triggers evacuations and shelters – that has major implications for the COVID19 pandemic we will look at later today …

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AL092020 and Chaos … (5pm Tue 28 July 2020)

So … I wasn’t planing on doing this quite so soon, but with Potential Tropical Cyclone #9 threatening the viral encrusted southeast, I’m doing a mega-juggleing act and trying to fire up the Patreon site, as well as do some much needed computer infrastructure rearranging.  So please be patient with the chaos … and the brevity of this post.  As for PTC9, nothing too much changed since NHC started advisories.  Here’s the latest “core” track models that NHC is having to work with.  I didn’t put GFS in here because the 12z run was way off and the 18z run isn’t up yet:

As for impacts, the current thinking is that this thing will remain a tropical storm until Florida landfall – but there is a yuge amount of uncertainty in that until it spins up better, so it may not even go to Florida.  Way too early to freak out if you are on the mainland US.  PR does need to prepare for a tropical storm, as do the USVI and northern Caribbean.  More in the morning …

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NHC now issuing advisories on Potential TC #9 (Tue 28 July)

There is a lot of uncertainty in this, but NHC has started advisories because there are some readings indicating the system is already producing near tropical storm force winds … here is the forecast impact swath based on the 11am advisory.

Much more around the afternoon (5pm) forecast cycle … here is an exerpt from the NHC  forecast discussion:

It cannot be stressed enough that since the system is still in the
formative stage, greater than average uncertainty exists regarding 
both the short-term and longer-term track and intensity forecasts.  
A subtropical ridge that extends westward from the central Atlantic 
is expected to be the dominant steering mechanism over the next 
several days, and the flow around this ridge should steer the low 
pressure area generally west-northwestward.  However, the details in 
the track forecast could change depending on exactly where within 
elongated circulation the center forms.  Regardless of the exact 
track, the system is expected to bring locally heavy rainfall to 
much of the Lesser Antilles, and tropical-storm-force winds to 
portions of the Leeward Islands, the Virgin Islands, and Puerto Rico 
within the next 24-48 hours.  After that time, a general west- 
northwestward heading should continue but as mentioned before, 
uncertainty exists as to how close the system tracks to  
Hispaniola, Cuba, the Bahamas, and Florida. The NHC track forecast 
is in best agreement with the HFIP corrected consensus model.  It 
should be noted that a stronger cyclone is likely to favor a more 
northern track, while a weaker system is likely to remain more 
equatorward.  Users should remember that the long-term average NHC 
track forecast errors at days 4 and 5 are 140 and 175 n mi, 


Finding the storm (#AL92, Wed. 28 July 2020)

First a quick review – Douglas skimmed just north of the Hawai’ian islands, causing much less damage than anticipated as only the weak side of the storm swiped them.  In Texas, as anticipated Hanna caused power outages, scattered damage, and some flooding.  As for the “investigation area” in the Atlantic, 92L, it continues to move across the Atlantic as an elongated tropical wave.  Here is what it looks like this morning, with the Tropical Analysis and Forecast Branch surface analysis as an overlay.  As usual, click to expand and see the details …

NHC still gives the system a 90% chance of becoming a storm in the next 5 days, with a completely unpronounceable name (Isaias) unless you are a fluent Spanish speaker.  So of course the usual suspects are sifting the entrails and trying to see where the computer model tracks are going.  Here is the track model map as of 6am this morning:

When looking at these maps it is vital to realize that they are lumping together models that probably shouldn’t be put together (like purely statistical models, as well as individual ensemble members).  You will hear terms like “ensemble runs” and “ensemble members”.  Just what does that mean?  Here are two examples.  The problem with a storm is that even in a stronger storm the exact position, and the surrounding environment, isn’t perfectly known (much less an invest area – look at the satellite map above and pin the fix on the storm!).  What an ensemble run does is start the storm in slightly different positions and intensities (perturbed initial positions is the technical term), and re-runs the model to see what happens.  Here is one example, the US Global Forecast System (GFS) run:

Notice the initial position for each track line is different.  The blue line is the “main” GFS forecast run, while the brown line is the average of the ensembles.  Notice how much variation there is?  (Actually, this isn’t bad for a weak system!).  Now, let’s look at another example, the Canadian model:

Again, for AL92, these are really rather consistent, which indicates a more stable environment (or, which is possible, they are all wrong in the same way!). The European model looks similar (but because of licensing restrictions I can’t show you that map) as do the Navy’s model and others.  The key point is to again reinforce the fact you can’t just pluck one model track – even a good model – out and get terribly excited about it (much less bet your life on it one way or the other).  This data has to be properly interpreted, and by far your best bet with respect to publicly available data is the official NHC forecast.

Administrative note:  As previously noted, I don’t have funding to do these posts and commentaries.  The last couple of months I’ve been trying to figure out how to do them that covers the costs – and even expand the features.  I don’t want to run advertising, so on August 1st I’m going to start a Patreon page where those of you who read all the way to the end can contribute to keeping these things running and help support the research work we do here, and get extra information including site specific forecasts from our commercial system.  I think we can do some pretty cool stuff, especially trying to get “plain English” no-hype forecasts for hurricanes and eventually other severe weather.  I hope you’ll think about contributing.


#Hurricane #Douglas, #Hanna, #Gonzalo, and that thing off of Africa

The TLDR is that Hanna is making landfall in Texas today.  May technically be a hurricane at that point but almost everywhere in the impact zone will experience tropical storm conditions.  Gonzalo is crossing the southern Windwards, but is barely even a storm at this point, with heavy rain the only threat.  Douglas is now aimed at Kaua’i as a hurricane – high surf (not the good kind), wind, rain are all in store – but a wobble puts Maui/Moloka’i/O’ahu in play.  There is a storm coming off of Africa that may spin up, or may do a Gonzalo and flare and fade.  Here’s the details and pictures …

Tropical Storm Hanna is making landfall in southern Texas today.  As always your best source for the official word are the NHC “Key Messages” products:  Key Messages regarding Tropical Storm Gonzalo (en Español: Mensajes Claves).  With Hanna, as with Texas, while much is made of crossing the arbitrary threshold between a tropical storm and hurricane (74 mph, 64 knots maximum winds), it is important to remember that for any given storm, the hurricane force winds may cover only a small area – or, for some storms, a much broader area.  The amount of damage depends on lots of variables.  So focusing on the track is a bad idea.  Here is the damage swath with “plain English” impacts using my TAOS/TC model, based on the official NHC forecast track:

Hanna is looking a lot better organized on both Satellite and Radar.  Here’s what it looked like just before 8am ET this morning from the Corpus Christi WSR-88 NEXRAD radar … the left hand side is the reflectivity, the right hand side is the Doppler velocity.  If you embiggen and look carefully you can see the winds in the nascent eyewall are on the order of 65-70 knots.  HOWEVER: that at 10,000 feet (the further you get from the radar the higher up in the atmosphere you are looking because the radar beam is going straight – but the Earth is curved).  So the surface winds are lower.

A third of the world away, Douglas too looks to be a minimal hurricane as it impacts Hawai’i.  The track has shifted north a bit since yesterday.  Here’s the swath map:

In both cases economic impacts are expected to be under $100 Million USD.  Normally, especially for Hawai’i, they would be higher, but the extremely depressed tourist season means many businesses are already closed or reduced operations.  Damage is expected to be somewhat light as long as nothing breaks that shouldn’t and the forecast intensities hold true.

Gonzalo has faded to a minimal tropical storm, and unless a flash flood causes some damage, shouldn’t be so bad.  There is a system off the coast of Africa that some are talking about, currently with the Invest code AL92.  It’s way early to get excited about it – some of the models spin it up, many do not.  Here’s the available forecast tracks.  A lot of the GFS and ECMF ensemble runs dissipate the thing before it even gets started.  So don’t worry about it – plenty of other stuff to keep your BP and heart rate elevated these days …

#Douglas heads towards #Hawaii, Hurricane #Hanna?

The tracks and intensity estimates for Douglas still have it headed to the State of Hawaii, making “landfall” sometime Sunday.  Here is an animation of the GOES West visual imagery (note Tropical Storm Hanna approaching the Texas coast in the upper right).  Also notice the sun reflecting off of the ocean … click to embiggen.

Douglas is starting to weaken, but the big question now is how fast.  It will probably be just below hurricane strength as it hits the islands.  The worst of it looks to be centered on O’ahu, Moloka’i and Maui, but higher elevations on all of the island could see hurricane force winds.  Rain, flash flooding, and mudslides are always a risk on the islands.  Here is what CPHC has to say, and here’s my TAOS/TC impact map based on their forecast track:

Speaking of Hanna … NHC now forecasts it making landfall as a minimal hurricane (en Español: Mensajes Claves).   I’m not sure I buy that – the impacts for most people will be tropical storm conditions.  Here’s the impact map:

If the NHC forecast holds up, Hanna could top $200 Million, but I think it’s more likely that any high winds will be restricted to over water or right on shore.  Rain and flash floods, and maybe coastal flooding on the immediate shoreline are the biggest risks.  It looks like only voluntary evacuations are being ordered. Shelters are trying to do social distancing, but that’s always iffy.  If you are in a sturdy structure and not in a place that floods regularly, best to stay put – but if at risk of flooding, or in a weaker structure like an unsecured mobile home, the virus is the least of your worries: find someplace safer.

Whats in a name: Gonzalo, Douglas, and TD8 (23 July 2020)

After a long boring spell, the tropics got “interesting” all of the sudden.  Two storms in the Atlantic, and one headed to Hawai’i, so will be lot to cover today! But first we’ll start with a brief overview of how storms are tracked and named.

Last night the US National Hurricane Center started public advisories on the suspicious (investigation) area in the Gulf of Mexico.  As a reminder, tropical systems (Hurricanes, Typhoons, Cyclones, etc) are given unique formal identifiers when the reach a certain level of organization and intensity.   The first two letters are the Basin (area of world’s ocean – AL for Atlantic, EP for east pacific, CP for central pacific/Hawaii, WP west pacific, IO Indian Ocean, SH southern hemisphere).  The next two digits are the storm number for that year, followed by the year.  Storms are also given informal names to help in public awareness and watch/warnings. The number codes (called ATCF identifiers) are important since names are reused unless a storm causes a lot of damage and the name retired.  In the Pacific it is also important since some weather agencies (The Philippines for example) use their own names that are different from the other regionally accepted names.  Investigation areas are given temporary storm ids  in the 90 to 99 range, which are reused during the year since most of these don’t spin up.  So the system in the Gulf that had been given the temporary ID of AL912020 now has the formal tracking ID of AL082020.  In advisories it is being called “Tropical Depression Number Eight or TD8.  If it reaches tropical storm force intensity, it will be given the informal name Hanna.  But you will always be able to find it as AL082020.

So what is TD8 up to?  I again want to push the NHC’s “Key Messages” summaries.  They are a great, minimal hype, one-stop official summary of what you need to know about a storm, at least in the National Weather Service area of responsibility (Atlantic and East/Central Pacific regions). They are also available in Spanish, for those serving  Spanish speaking communities.  TD8 still isn’t that organized, but conditions aren’t unfavorable, so NHC is still thinking it will become a minimal tropical storm  before landfall.  Economic impact/damage should be minimal as well, under $10 Million if this forecast holds.  The key question is if significant evacuations become necessary.  Only those at risk from flooding, or in weaker structures like mobile homes should be seeking shelter – we really don’t need lots of people congregating in Texas right now with the COVID19 causing virus in uncontrolled community spread … here’s the impact swath:

The second storm out in the Atlantic is Tropical Storm Gonzalo (AL072020).  Gonzalo has expanded and intensified, and is expected to pass south of Barbados and across the Windward Islands in about two and a half days.  It is forecast to become a hurricane by late this afternoon, and maintain that strength as is crosses the Islands.  After that is a bit uncertain – there is a mass of unfavorable dry air in the central Caribbean that should knock Gonzalo down pretty quickly before it reaches Jamaica.  Impacts are estimated at under $5 Million on this track.

Finally we have Major Hurricane Douglas.  Douglas is an impressive Category 3 hurricane, but fortunately no where near land at the moment.  It is forecast to hold this strength today, but should begin to decay as it approaches the islands of Hawai’i in about 3-4 days and should be just below hurricane strength as it passes over the islands.  Here is the TAOS/TC “plain English” impact map:

The main risks from Douglas at this point seem to be heavy rainfall, but winds could still be over hurricane force along higher elevations and ridgelines.  We’ll know more in a day or so once it starts to decay.

Geology and Meteorology tired of Biology getting all the attention (22 July Review)

We have small tropical storm in the Atlantic headed towards the Windward Islands, a  hurricane (expected to weaken) headed towards Hawai’i, and we had a big earthquake off the coast of Alaska last night, so finally something to discuss other than the pandemic (which has become a political story more than biology or public health at this point, but I’ve ranted about that enough already).

Let’s start with the earthquake.  There was a M7.8 Earthquake off the coast of Alaska overnight (and a bunch of aftershocks, which are always expected after a big quake).  Damage on land should be light, it did cause a tsunami warning that was later retracted.  Here’s a quick look map of the impact area:

The Atlantic has finally dusted itself off and figured out it’s hurricane season.  Last night NHC started tracking TD#7, and this morning it was organized and intense enough to get the name Gonzalo.  As of 11am they have started the key messages product.  Here is the impact swath from my TAOS(tm)/TC model:

NHC substantially changed their intensity philosophy as of the 11am advisory, and now forecasts Gonzalo to become a hurricane.  The guidance is split – the major global models like GFS and the ECMRWF models kill off the storm in a few days because there is some dry air ahead; specialized hurricane models like HWRF intensify it.  NHC is sort of splitting the difference with a bias toward the high end.

Economic impact should be in the low millions of US dollars, but as in many areas of the world, any economic stress is unwelcome at this point.  The Caribbean is especially dependent on tourism, so this hurts more than the raw numbers might seem.

Another island is at potential risk half a world away: Hurricane Douglas is strengthening in the open waters of the east Pacific, and on the current track should be passing near or over the Islands of Hawai’i as it decays.  If the current NHC/CPHC track holds, it might cause a few million USD of disruption to the big island.  Here’s the current forecast impact:

Last and probably least, there is an invest area moving into the Gulf of Mexico, bound for the Texas/Mexico border.  NHC gives it a 50/50 chance of becoming a depression or greater by then.  Given the spread of the virus in Texas, hopefully it won’t spin up and trigger any evacuations …



Doomwatch, 20 July 2020 (Tropics and Pandemic)

There are a couple of weak tropical systems that the US National Hurricane Center is watching in the Atlantic and East Pacific, but nothing in the West Pacific this morning.   Here’s the view from GOES East of the Atlantic:

The only actual system (EP072020, East Pacific TD#7) is in the shadows as of 10am, off the Pacific Coast of Mexico, no threat to land.  The two “watch areas” have low formation probabilities; the mid-Atlantic invest area (AL99) perhaps a bit more, but still low over the next 5 days at 20%.  If you just need a spaghetti map, here’s an early look using the shallow (TABS) and mid level (TABM) steering currents, as well as some statistical models.

In viral doom, the data hasn’t really shifted that much over the last few days – as previously ranted, pandemics move slowly, with time scales in weeks.  Since we’re coming off a weekend and the data is catching up from that, I won’t post a plot, but the trends haven’t really changed much.  The precentage of people testing positive per test (the positivity ratio) as well as raw total positive patients showing up for treatment are still increasing far faster than anybody wants to see, mortality is up, not as much as the pessimistic predictions but worse than the optimistic scenarios.  Despite the Sturm und Drang, political posturing, and cultural gamesmanship, it is increasingly clear that masks outside the home are probably the best tool we have right now, especially if we want to resume something like normal lives.  So please just do it.