Models....

[Guest]

I have been attempting to understand models especially during hurricane season - its seems to be a losing battle. Anyone have any good suggestions for a amatuer to get started learning - especially for hurricane season?

[isobar]

I know what you mean, ticka. I have a number of links bookmarked, but understand very little.

[vbhoutex]

I'm not really sure where to start with something like this.

I had no idea what models were until about 4 yrs. ago and now I am becoming relatively proficient at reading and understanding what they are showing. I'm not even sure how I got to where I am with my knowledge of models.

You need to understand what you are seeing on a surface map that shows fronts, lows, highs, etc. to be able to understand the models. These features aren't just a flat circle or line on difference between weather like they look on the maps. They extend from the surface up 10s of thousands of feet into the atmosphere. This extension upwards is the millibar levels you see on the maps. The 1000mb level is the surface level, 850mb level extends to 5000 ft, 700mb is up to 10,000 ft, 500mb is up to 18,000 ft, 300mb is up to 29,000 ft., 200mb is up to 39,000 ft, and 100mb extends to 53,000 which is about tops for weather in the atmosphere. When a thunderstorm or TC extends this high into the atmosphere it is literally at a severe level.

Take a tropical cyclone for instance. As it begins to form it is a tropical wave or elongated area of low pressure which is basically riding the lower air currents that prevail from east to west during the Hurricane season. At this point the steering currents will be relatively weak since they are acting on only a low level of the forming TC. As it grows into a TS and extends further into the atmosphere it is now also controlled by prevailing winds, etc. at slightly higher levels. This is also where we sometimes see dryer air or colder air or other anamolies coming into play in what happens with a TC. As it continues to grow into a Hurricane, Typhoon or whatever it extends even further up into the astmosphere bringing into play even more levels of the atmosphere and the "weather" that is present there. Of course to understand some of this one has to understand the symbols used on the maps. I'm not sure where there is a good site that explains them. I've just learned them over the years. On a map that shows low and high pressure areas and frontal boundaries you see "circles" depicting different levels of pressure as you move out form the center of the low or high. Normally, the lower the pressure the more stormy the weather will be. And vice versa for high pressure. Fronts are boundaries between colder and warmer of air masses usually also shown as the high and lows "lines" meeting at a point where the pressures between the two centers are equal. I'm really starting to get out of my league here so I better stop and let someone else take over. Aslkahuna or Rob or Stormsfury would probably be able to explain it better than I can. I fear I have done nothing but babble and probably muddle the picture more than it might have been to start.

[Rob-TheStormChaser]

Nice way or putting it David!

[Allexpert Mike]

It may not be but I started with Winter weather forecasting and then from there got into Severe weather and half the time I don't use what models say in the middle range. Long range forecasting I never use one single model,,,,heck I dont use models I just check ensembles,,,Telocnnections and etc.

For Hurricane season you have to start with the basics. I'm no expert at it just yet but I know a good chunk thanks to Tropicalwxwatcher

Just like Dave said it starts off with knowing your surface data. From there it was all common sense for me on a computer model. But once you get into the upper levels you have to knwo your stuff and i'll give some links but basically:

H850- Used for thermal advectionand H8 temperatures and also locating barolclinic zones with tight thermal gradients.

H7- Used to see how much uplift is occuring with UVV's which high light the areas where best precipitation will fall. Usually Vorticity advection and low leevel convergence enhance strong UVV's. (Upward Vertical Velocities)

H5- Look at Vorticity advection along with MLJ structiure for Severe wx. Vortexx of an area of low presure gives you an idea,,,basically 18-25 is significant storm system aiwth values 25-30+ are major storms.

H3- For instance a strong flow aloft over a hurricane shears it apart and it will become disorganized. Also used to locate ULJ along with jet streak and flow aloft.

Theres so much more but I dont have time to get into it,heres a site which goes into more depth:

http://weather.unisys.com/model/details.html


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Once you have that down you just have to know your stuff about hurricanes,,,for ex:

1) Hurricane moving into dry air it will move into a weakening environment.

2) Slow moving hurricane may lead to upwelling weakening.

3) Flow aloft is strong shear is high not favorable for tropical development.

4) Location of ITCZ

5) At least 5° away from equator because theres no spin for a hurricane to be a hurricane!.

much much more.