Tuesday, September 12, 2017

Horseshoes and Hurricanes

Several folk - half the world to be precise- have been going too and fro about the role that climate change has played in the latest weather catastrophes.  Eli had a say yesterday, and some of the Friends of the Bunny chimed in.  Perhaps Izen had the best tweet comment about cause and effect

To stretch the metaphor, many things can light a fire, but the size depends on how big the pile of fuel it can burn.
and Bernard J pointed out that the nature of the beast of chance is that when the statistics become strong enough so a single event can be unequivocally attributed to the changes we are making in the atmosphere, oceans and soil, then it is already too late and a considerable amount of pain has already been absorbed with more and worse to follow.  It may not be a good idea to be living on such a planet.

This, of course, raises the question of the skill in hurricane track forecasting  A difference of 70 km or so yesterday saved Miami and by an even smaller margin Tampa.  Others may debate to the value and duration of such a reprieve.  There are lots of folk who know more about this than Eli, and one of them pointed him to those who really care, the US National Hurricane Center page on Forecast Verification.  

Turns out there are multiple models from many places and a scorecard is for sure needed. NOAA provides one for the models it uses  Forecasts are done on a three hour cycle with the forecast due three hours after the start of the cycle.  Models are divided into early or late, depending on when in the cycle (or afterwards) they are available.  Early models which start to run at the beginning of the cycle and are available before the end are called early.  Those which take longer are called late.  The output of the late model is adjusted so that it feeds into the start of the next occurring cycle becoming a psuedo very early forecast for that cycle. 

Models can be statistical, depending on historical data, these tend to be early, or dynamical, at some (varied) level doing physics based climate modeling.  The most complex of these are pretty obviously late models.  Models can be dropped from the ensemble when they don't perform well or something better comes along.

That being said, how are the models doing.  Data goes back to the 1970s.

Things are improving, perhaps also because tracking is improving.  At early times the ensemble was heavily weighted to statistical models, dynamical models rose to the fore in the 1990s

There are multiple models and combining them into a single forecast has a bit of magic about it where the forecasters weigh the combination of various models.  This can be seen in the 48 hour forecasts from the "early" models and the official NHC (dark line) forecast,  The dotted line is a combination of two statistical forecasts (see links for details)

Anyhow the Florida peninsula is about 150 miles at the widest down to about 100 just north of Orlando.  You can get lucky at horseshoes.


lifeisthermal said...

Still denying the physics of heat engines, huh? Bad move.

You actually beleive that a cold fluid makes it's own heat source hotter? And that increasing amounts of heat absorbers in a constant limited heat flow, increases the average kinetic energy per molecule?

I repeat, Prevost said that the emission from a body depends on the internal state only. Yet you continue to say that it depends on the external atmosphere. Doesn't that make you a denier of proven physics? Yes it does.

There is no greenhouse effect.

lifeisthermal said...


thefordprefect said...

lifeisthermal said...
Still denying the physics of heat engines, huh? Bad move.

You actually beleive that a cold fluid makes it's own heat source hotter?

Using whatever version of physics you believe in please explain how a room temperature thermal imaging camera can take thermographs of objects down to -50C
There are no "cold rays" so how does focusing a object at -50C onto a microbolometer at 25C change its temperature compared to a microbolometer at 25C with an object at -49C focussed onto it?

thefordprefect said...


This shows a thermal image of sky and clouds (in winter). The camera body was approx. 15 to 20C and the sensor was uncooled and there at a similar temperature.

If you are correct and cold objects cannot cause warmer objects to warm then this picture should effectively be an even black. All objects in the field are less warm than the sensor and in your physics cannot change the temperature of the sensor.

However you can see temperatures down from -2C to -35C. This is because the cold clouds are providing energy to the sensor changing its temperature.
If the object in the field of view were at abs zero then no heat would be transferred to the sensor and the sensor would be in equilibrium with its camera environment.
At -50 (approx.) the heat from the object adds sufficient energy to the sensor for detection and the sensor warms until the energy OUT to the camera environment equals the energy IN from the camera environment plus the energy in through the lens.
This additional heat is detected as a change in microbolometer resistance.

thefordprefect said...

You should also be aware that the germanium lens used on thermal imaging cameras acts as a bandpass filter.
So most radiation from CO2 and water vapour is not passed to the sensor. Hence no back radion seen from water vapour or CO2. Clouds of course are not water vapour but a cloud is an aerosol comprising a visible mass of minute liquid droplets (wiki) and hence thermal radiation is more like a black body hence the camera sees the radiation.

CapitalistImperialistPig said...


Alas, there is never a spoon big enough to empty the ocean of stupid. There are none so blind as those who will not see - but good try anyway.

Martin said...

Lifeisthermal, have you ever thought about how a sweater can make you warmer? Must be fake news because it appears to violate the laws of thermodynamics.

Unknown said...

Unfortunately some physics teachers talk about heat flowing from warm bodies to cooler bodies to simplify matters. If they want to keep things simple but more accurate then they should be saying that it flows in both directions, but the flow from the warmer body is greater than that from the cooler, so that there is a net flow from the warmer to the cooler.

Bob Loblaw said...


Lifeisthermal is a Sky-Dragon-class physics denier. (S)he will just continue to thread-bomb anywhere (s)he can, and is immune to any arguments. Use your troll-food sparingly.

CapitalistImperialistPig said...

@Bob L - Yes indeed.

EliRabett said...

Nigel - Eli's take on this is that thermal energy can flow in both directions, but heat only from warmer to cooler. The reason for this formulation is that thermo developed in the early 1800s before the molecularity of matter was firmly established and radiation was not a well described phenominon but they could observe the net flow of heat.

With the coming of statistical mechanics and E&M to retain the concepts of heat inherent in the early Clausius second law a separation between heat and thermal energy became necessary. Fortunately there is a simple definition of thermal energy, e.g. energy whose distribution among the carriers can be described by a single temperature.

Thus the Stefan Boltzmann and Planck laws can be used to describe the radiative energy emitted from a body. The rate of emission of thermal radiation from a hotter body exceeds that from a colder one and the net exchange describes the heat flow.