What happened to make Katrina come together so fast?

Kurt Wayne

She just formed as a tropical storm over the Bahamas, did she not? I'm sure she was a TD off the Cape Verde Islands at some point, but I can't find any maps (as I'm not sure where to look) showing her path from formation.

One other question, and please take no offense at my asking, but...I'm involved in a project heavily researching Kinshasa, the capital of the Democratic Republic of the Congo in central Africa. I've read an article about how the Congo basin is one of the most hot for thunderstorm activity (along with the Amazon basin and Indonesia) and that Africa has a higher "chimney" for convection than other places. I've probably asked a few questions in one, so what I'm curious on is...do these tropical depressions which come off west Africa and the Cape Verde Islands originate in the Congo basin? (Not that it will mean anything to us in our research...I'm just curious.)

Sorry to include a non-Katrina question. Thanks in advance for any help.
 
My understanding about Katrina is the very warm waters of the Gulf of Mexico acted as fuel.

Regarding your other questions... wwwaaaayyyyy over my head. :)
Maybe someone else can answer.
 
I don't know very much once you get away from mid-latitude cyclones, but I will try to answer part of your question.
I don't know precisely where tropical waves typically form over Africa, but I do know that most disturbances that grow into hurricanes originate over Africa and along the intertropical convergence zone. I also know that hurricanes are supposed to be more numerous and more intense during years that western Africa gets above average rainfall.
 
I agree with -ed. When Katrina moved into the Gulf of Mexico, it EXPLODED into this Catergory 5 monster. :( :shock: That warm water was fuel for the fire, so to speak.

I seriously thought the storm would hit with 185 mph sustained winds. :shock:
 
...

Iiiiiii take that back...looking at those Atlantic maps there was some heat action (not surpisingly, in late August) around the Bahamas.
 
Discussed in Met class

Thanks for giving me an opportunity to review my notes from my first weeks of formal study in meteorology.

The short answer would be that the tropical waves from which hurricanes form probably developed well east of the Atlantic coast of Africa, perhaps as far east as the northern or northwestern Indian Ocean. Tropical waves that often generate Atlantic hurricanes travel over Africa at 0 to 20 degrees north latitude, a region better known as the Sahel and well north of the Congo (formerly Zaire). You are right in that the Congo generally receives lots of rain; this is true of most equatorial regions.

Now for the long answer.

We'll start with the Hadley circulation. The sun shines most directly nearest the equator, and as a result the lower troposphere (less than perhaps a mile above ground level) warms most at low latitudes. Air thus heated rises, drifts toward the poles and falls toward the surface at roughly 30 degrees N and S latitude, at which point it flows back toward the equator. The Coriolis effect appears to deflects the air that reaches the surface westward; we say that these winds have acquired an easterly component. These winds are called the trade winds.

The trade winds flow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. They meet in what's called the Intertropical Convergence Zone, which moves north and south over the course of the year.

With convergence (air rushing together and getting pushed upward) and convection (warm, humid air rising), clouds and precipitation form along the ITCZ; barometric pressure is usually a tad lower in such systems than outside. This area of relatively low pressure usually extends on a NE-SW axis (in the Northern Hemisphere) and is called a tropical wave.

In late summer, the ITCZ is about as far north as it gets. If the systems drift far enough north over warm water, the Coriolis effect (in the northern hemisphere, the tendency for something moving to be deflected rightward) kicks in and the air in the system can spin. If other conditions are ideal (warm water temperature, reasonably consistent windspeed and direction over all levels of the atmosphere), such systems may spin into tropical depressions and develop further into tropical storms and hurricanes.

(Side note: a change in wind direction and/or speed with altitude is called wind shear.)

Please note that tropical waves are not necessarily confined to the ITCZ and that hurricanes forming early and late in the season may not spin up from tropical waves -- I have a feeling that this October every occluded front and thunderstorm complex that hits warm seas will be carefully scrutinized.
 
just because a storm dosent develop near Africa dosent mean it cant become a monster. Conditions were right for the storm to blow up. Andrew was a tropical storm 2 days before landfall as a category 5

Mitch developed in the carribean and became a Cat 5 also.
 
Another key component for tropical storm development is the organizaiton of the strom's outflow. Without upper level winds to vent the developing storm, the development will be very slow or not exist. High pressure aloft is a key indicator of an area ripe for tropical development.

I am no expert, but it seems to me that a surface low develops over hot ocean waters, and the low deepens when the convection continues to strengthen. Without the rotation caused by the coriolis effect, the storm would choke itself as the convected air cooled, sank, and entered the storm again. Rotation allows the cool air to be seperated from the convection, especially if there is high pressure aloft, which will vent the colder air away from the strongest convection in the storm. The only place that the upper level winds aren't strong enough to whisk the convected air away is the eye of the storm, where cool, relatively dry air sinks to the surface. Also air mass boundaries serve to guide the tropical storm, and generally, interaction with the boundary weakens a tropical storm by increasing vertical wind shear, which disrupts the convective "machine" that drives the tropical storm. Additonally, boundaries serve to directly disrupt the outflow channels of tropical storms.

Katrina moved into the Gulf where all the conditions were favorable for explosive development. Weak boundaries and high pressure aloft in addition to very high seawater temperatures.

I know my explanation isn't clear, and probably wrong. If anybody can educate me/correct me, please do!! I hope I didn't mess it up too much.

Have a great day!
Tom
 
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