My love for weather is a passion, but no BIGGER passion is sharing the Gospel of Jesus Christ to every person!

Welcome fellow bloggers to this hurricane forecasting tutorial!

I will be using this site along with other tools(such as Jeff Haby & WU graphics) and my knowledge to put this together....All sources will be properly shown or implied(quotations)......Some sites offer techniques that are too complex for the layman to understand, and I will attempt to make it clearer....

This is ONLY meant to be a basic tutorial in which I will try and make my discussions as clear as possible.....You MUST be familiar with basic meteorology 101(concepts such as high pressure, sinking air, ideal gas laws, etc which can be found in my "weather/hurricane 101 series" blog)....You must also be familiar with basic hurricane 101 physics, structure, formation,etc and climatology which is explained in my previous blog(even though I'll be reiterating some of it in places here)....See immediately below for link to this blog...

I will leave my weather/hurricane 101 series blog up indefinitely......

This will be my last blog series....I hope you all learn the art of forecasting hurricanes, and it's my pleasure to share with you all the techniques I've acquired through the years....
-When I had more time to blog earlier this year, I predicted around 13 named storms for this season in April.

I split this tutorial up so it would be formatted more user friendly.

The topics to be covered in this tutorial include:

1)This blog-The art of forecasting, quickscat interpretation
2)Satellite interpretation
3)Forecasting intensity, track, size of tropical cyclones, Fujiwhara conditions(still under construction)
4)Using computer models, forecasting forward speed, understanding gradient concepts, forecasting near land
5)Jetstream mechanics
6)Forecasting wind shear, SSTs
7)Interpreting weather maps and understanding important climatological signals to forecast long term hurricane behavior
8)Understanding extratropical, subtropical, tropical storms and what they mean in terms of forecasting

A good place on WU to keep track of tropical activity is weatherguy03's blog. He updates his blog with informative descriptions of the situations in play and is another great place for hurricane forecasting....


HURRICANE FORECASTING TUTORIAL TO IMMEDIATELY FOLLOW:

I STRONGLY recommend you review the "hurricane section" on my previous blog before continuing this series(almost all the way down the page). Some of this will reappear here for emphasis purposes.

Also, general discussion composes the first half of this series. Maps tutorial will be the 2nd half of the overall tutorial....

Understanding weather requires the individual to be able to model the atmosphere in 3D and visualize how it will evolve with time. The most frequent mistake made by weather enthusiasts is focusing on one weather chart and basing their reasoning on one layer of the atmosphere. Hurricane forecasting boils down to understanding hurricane structure, hurricane physics, and the environment around them. Hurricanes exhibit very unpredictable behavior especially when the synoptic environment becomes very complex. The big questions many raise is WHEN to use one technique over another. The tools I will explain, require you to both understand what the graphic represents and how to interpret that graphic....Again I will be emphasizing this throughout the tutorial, you must understand the atmosphere to be fluid, ever changing in 3D....It changes differently depending on scale....The larger the scale of motion, the smaller a change you will expect over a period of time. The smaller the scale(such as eyewall physics) the more rapid a change can be expected....

WHAT ARE LONG/SHORT RANGE FORECASTS?

Already familiar with what a tropical cyclone needs to have, the next question is how can I incorporate this knowledge into a forecast? For long range forecasts, we dont have the luxury of interpreting satellites and many observations, so we must base this on climatology and computer models(which I will explain later)....A big part of this comes from understanding the many climatic variations in weather patterns on earth.....

WHAT FUNDAMENTAL ENVIRONMENTAL CONDITION FAVORS INITIAL FORMATION AND HOW DO WE RELATE THIS TO FORECASTING?

When assessing tropical cyclone formation, there is one factor that MUST be in place(in a list of other "requirements", this one's the most important). Vorticity(fancy term for "spin") describes the circulation of a fluid about an axis. We can define this as POSITIVE vorticity, or NEGATIVE vorticity.....By convention, positive vorticity is cyclonic, while negative vorticity is anticyclonic. Keep this in mind when looking at weather maps...What causes vorticity? In meteorology, there are MANY reasons, but the chief reason when analyzing hurricane formation is coriolis. Coriolis is caused by the rotation of the earth and is what causes a cyclone to get it's "spin" or positive vorticity....A better way of putting it is that coriolis is essential for hurricane formation.....A common misconception is that coriolis is zero at the equator....No this is not true....It is a minimum there and is the reason why you wont find hurricane formation in those areas(about 5 degrees on either side of equator)....Knowing this, you will not expect formation in the short/long term for such areas any time of the year. For all the reasons listed in my hurricane section in previous blog, this is how we get the general June-Nov hurricane season in the regions explained......The north pole is a region of maximum coriolis....But the SST's and synoptic environment is extremely hostile to formation....


Notice on the graphic above, there is very little deflection at the equator and the maximum deflection occurs at the poles.....The dashed lines represent the initial direction of flow, the solid lines represent what the coriolis force does to the flow in each hemisphere...

In summary, the regions of formation, and the expected seasons of formation occur because the HIGHEST potential of the "ingredients" coming together are at a maximum...Therefore we can expect and forecast with a high level of certainty that hurricanes form in selected regions for reasons explained and that hurricanes will not form in certain areas...

CONCEPTS TO KEEP IN MIND WHEN MAKING A HURRICANE FORECAST

1)Conservation of energy and Newton's 1st/2nd/3rd laws-Conservation of energy states that energy cannot be created or destroyed. In essence, there's no such thing as runaway winds, runaway temperature, runaway pressure because this violates Newton's 3rd law.....If we did not have this conservation and Newton's laws, winds could blow at infinite speeds, pressure could become infinitely large enough to kill the life out of our planet, temperatures could increase indefinitely. There are LIMITS to hurricane strength, limits to temperature maximums given certain conditions, limits to other variables....Why is this? Because considering a stable environment, a force exerted upon the atmosphere will be countered by another force to maintain equilibrium......Energy can change forms to help maintain equilibrium....A deep understanding of the Ideal Gas Law is imperative to understanding pressure/temperature/etc relationships...A big area in energy conservation and relationships is in the area of radiation and atmospheric waves......Atmospheric waves transport energy THROUGH a medium, not the medium itself......This is beyond the scope of this tutorial but you can read more on my previous blog under the associated topics....

Newton's 1st law-"A particle will stay at rest or continue at a constant velocity unless acted upon by an external unbalanced net force."
Newton's 2nd law-"F=ma: the net force on an object is equal to the mass of the object multiplied by its acceleration."
Newton's 3rd law-"Every action has an equal and opposite reaction." With this law, in regards to the atmosphere, shows why pressure, temperature, winds, etc...cannot individually approach infinity values...In other words, pressure will not increase indefinitely, because other forces will oppose this pressure increase and try to maintain equilibrium....

2)Ideal gas law. Yes there is an equation you should know!LOL But the only one you need for this tutorial. The ideal gas law is the equation of state in a hypothetical ideal gas(you really should have this concept down, many sources on the internet available by googling "ideal gas law")....There are many forms of this equation but I'll give you a relevant form here.
The equation: PV=nRT
Explanation:P=pressure, V=volume, n=# of gas moles, R=gas constant, T=absolute temperature...

Ok....We're going to focus on pressure, volume, and temperature......The equation itself represents an equilibrium state. The terms on the left are balanced by the terms on the right.....Understanding that n and R are constants we wont bother with them. Only look at P,V, and T......Here is the equation w/o the constants:
PV=T

Now here comes the trick......If we cause an imbalance to one side of the equation, the other side MUST respond to keep equilibrium. Lets assume we are dealing with an isobaric surface(holding pressure constant). If we increase temperature, holding pressure constant, volume must INCREASE in order to make this system get into equilibrium. Lets assume we hold temperature constant. Increasing pressure, holding temperature constant, volume must DECREASE.....


3)Uncertainty. Uncertainty in regards to hurricane forecasting is a function of time, number of data sources, and the reliability of the data.....As time increases, the number of sources available decreases,so naturally uncertainty increases.....

Also, from the surface up into the atmosphere, the number and frequency of weather data decreases, leading to more uncertainty with the upper levels(in time especially)...

4)Sources of information....Ok, this really isn't a concept but more of a warning. It is absolutely crucial that you use as many sources as possible.....From reputable sites(like CIMSS)....Because the atmosphere is difficult to measure in many layers, dont expect all the techniques to yield the EXACT same conclusions...But most likely, these sources will reveal information close enough for one to build a forecast...

5)Integration. Having all the weather knowledge is wonderful but not practical in forecasting purposes.... Understanding how 3D weather evolves in time requires one to synthesize the data, interpret what's going on, and how this will play out in the future...

Visualization in 3D is key here.



TROPICAL CYCLONE FORMATION GUIDELINES:

Because tropical cyclones in their formation stages are more fragile to adverse environments than to preexisting
storms, expect hostile upper level conditions to have a bigger role in PREVENTING hurricane formation, than the demise of one......If this weren't the case, every tropical wave would develop(only about 10 storms on average form in a season full of hundreds of tropical waves)......

Zehr provides a conceptual model of what a developing system should look like.

stage 0("pregenesis")- occurs when a cloud mass of convection persists for at least 24hrs or more which fails to diminish in convection from morning to evening according to a typical diurnal pattern.

stage 1("suspect area")- occurs when systems are detected with LLC's(low level circulations) that have persisted(12-24 hrs). Convection pattern is not as important in this stage. A typical trademark of LLC's is the formation of curved banding, but one must be careful of using satellites to diagnose this(as a thick cirrus structure can give the illusion of system organization without there being any LLC)...

A great source in detecting LLC's is the quickscat storm page.....Quickscat is a complex system of measuring winds speeds/directions near the surface of oceans using satellite techniques.....The downfall to this technique is rainfall contamination regions(shown as black barbs)....What you are looking for is a region showing a completely closed off cyclonic wind pattern(a circular orientation of the wind barbs)...Note that a healthy LLC will have wind barbs VERY circular in structure...See diagram below for an example of a closed off circulation:


Image below shows a quickscat image showing a tropical wave's axis:


Here is an example of a quickscat image where there is no defined LLC-link

Here is a quickscat image below where there is an axis of convergence along a tropical wave axis....Notice the elongated structure.....You want a much more symmetrical structure to the wind directions for healthy development:


Elongated wind barb structures are indicative or poorly organized LLC's or a lack thereof....Also, these wind speeds must fit in the general guidelines in classifying tropical systems...See graphic below for a streamline visual:

The above photo describes the initial wave structure, before they become closed off...Notice, the tropical wave is an inverted trough. Even though the height pattern looks like the configuration of ridge, it is not....Remember, troughs/inverted troughs have cyclonic circulations associated with them. Troughs tend to have corresponding westerly winds with it, while inverted troughs correspond with an easterly wind flow....Why is this? Well, tropical waves usually situate themselves south of mid-latitude high pressure systems(which is in a region of easterly wind flow around the sides of the high)..Inverted troughs for this reason bulge to the north.....See diagram below credited by Jeff Haby:




stage 2("Incipient Tropical Cyclone")-This occurs when previous conditions are met in addition to convection increasing in the area of interest relative to the diurnal cycle in its vicinity...


A way to diagnose the health of a potential formation area and the potential for it to become more healthy is to stack the low level circulation center under the most intense ball of convection.......Balls of convection directly over a LLC indicate a healthy structure, while convection maximums occurring not directly over the LLC indicates shear in many cases....Of course we must look at more than just satellites to assess the health or potential health of a system....Many times, an intense ball of convection will associate itself with a MLC(mid-level circulation), and we need mid-level circulations to be be vertically aligned with LLC's for a system to intensify.....Mistaking a LLC and a MLC is a common occurrence, and I'm going to show you how to better your odds at making the correct interpretation...This involves understanding satellite interpretations(the next topic)...