ITCZ ?

Neil Roberts · Post by **Neil Roberts** » Mon Jun 19, 2006 9:12 am

Dear Paul, Could you please tell me what ITCZ stands for, as used in your latest forecast.
Many thanks, Neil Roberts.

Brian Taylor · Post by **Brian Taylor** » Mon Jun 19, 2006 11:12 am

I thought I'm just not smart enough....

feel better now, thanks neill....

so paul, what is it?

STEPHANIE

Post by **Steve Wooler** » Mon Jun 19, 2006 11:15 am

Didn't you guys go to school?

It stands for the Intertropical Convergence Zone (ITCZ) - an area of low pressure that forms where the Northeast Trade Winds meet the Southeast Trade Winds near the earth's equator. As these winds converge, moist air is forced upward. This causes water vapor to condense, or be "squeezed" out, as the air cools and rises, resulting in a band of heavy precipitation around the globe. This band moves seasonally, always being drawn toward the area of most intense solar heating, or warmest surface temperatures. It moves toward the Southern Hemisphere from September through February and reverses direction in preparation for Northern Hemisphere Summer that occurs in the middle of the calendar year. However, the ITCZ is less mobile over the oceanic longitudes, where it holds a stationary position just north of the equator. In these areas, the rain simply intensifies with increased solar heating and diminishes as the sun moves away. An exception to this rule occurs when there is an ENSO event, during which the ITCZ is deflected toward unusually warm sea surface temperatures in the tropical Pacific.

p.s. Amazing what we ignoramuses can find out through Google

Brian Taylor · Post by **Brian Taylor** » Mon Jun 19, 2006 11:21 am

I thought that does not sound like O-tone steve

more like the weatherman from channel five Pittsburgh... (Groundhog Day)
thanks for enlightening (does it spell like that? germans...!) us!

STEPH

Post by **Steve Wooler** » Mon Jun 19, 2006 11:49 am

Hi Steph

Your spelling is clearly better than your (or mine) understanding of ITCZ. Can't say I'm any clearer, myself either, even having copied the definition. Far too deep for a Monday morning.

Neil Roberts · Post by **Neil Roberts** » Mon Jun 19, 2006 12:48 pm

Well that's cleared that up then.....but what's an ENSO event!!??

Best wishes to all,

Neil Roberts.

Post by **Steve Wooler** » Mon Jun 19, 2006 1:47 pm

"cleared that up then"? What brain food are you taking Neil - I need some!

ENSO - I'll leave that one to Paul, but in the meantime try "El Niño–Southern Oscillation"

Bill B · Post by **Bill B** » Mon Jun 19, 2006 3:16 pm

I think what it all means is that if you look out the window and it's raining that means it's raining and if the sun is shining it's not raining.

Whatever the weather is on vacation in Tobago still has to be better than being at home and at work $\:D/$

Bill

Neil Roberts · Post by **Neil Roberts** » Mon Jun 19, 2006 4:00 pm

Well so far Bill's explanation makes most sense. I thought that Steve's was just a bit too silly to be believable. It's a bit like that old panel game that Robert Robinson used to compere, the name of which escapes me. I'm sure, if your from U.K., you will remember the one when someone had to guess which explanation was correct and which was a bluff. I'll wait for Paul's contribution and choose then.

Keep up the good work,

Neil Roberts.

M Canham · Post by **M Canham** » Mon Jun 19, 2006 4:27 pm

I learnt about the ITCZ at school, and had long forgotten about it until today when I checked the Liquid Sunshine update. Looks like I might get to experience it first hand later this week! Steve's copy and paste makes sense to me though, thanks to my geography teacher

I'm only going to be there for a week so obviously would prefer the weather to be glorious, but as someone posted above, rain in Tobago has got to be so much better than any weather at home/work.

Paul Tallet · Post by **Paul Tallet** » Mon Jun 19, 2006 4:42 pm

Ladies and Gentlemen (... and Steve !)

Here is the text from a post I made in Liquid Sunshine Feedback on 17th August 2005 in response to another question about the ITCZ and it's association with Hurricanes, Hadley Cells, Tropical Waves.

As all your tongues are hanging out ... I will be back to explain the mysteries of ENSO as soon as I can !!

Hi Everyone

Educational Slot … the Inter-Tropical Convergence Zone (ITCZ)

I have received a number of queries about the ITCZ and I am pleased to explain …

The ITCZ is a ‘weather area’ around the equator that is basically constant low pressure.

This area represents a band around the centre of the earth where the trade winds from the southern latitudes meet the trade winds from the northern latitudes.

Being equatorial … the air from both sides is tropical and generally this produces a lot of rainfall that manifests itself commonly from ‘Hadley’s Cells’ that I recall mentioning before.

These are the most violent types of Thunderstorm on Earth and the reason is simple … in equatorial regions the atmosphere is higher and therefore the cloud tops can reach greater heights than over regions closer to the earth’s northern and southern poles.

The more cloud, the more rain … and this explains why tropical areas suffer tremendous flooding episodes during their monsoon or wet seasons.

The ITCZ’s position would typically be between 5 degrees north and south of the equator, but this changes as the earth tilts and creates the seasons in the temperate zones (i.e.; outside of the tropics).

So, from April to October, the ITCZ is more likely to be north of the equator and from November to March it is likely to be south of the equator.

Tobago is about 11 degrees north of the equator.

Arguably, Tobago should not really have a dry and a wet season because Tobago is very close to the equator … closer than all of the other Caribbean Islands, apart from Trinidad.

This could explain why Tobago has rain all year round … there is a marginal difference between Tobago’s dry and wet seasons and this is due to Tobago’s proximity to the ITCZ.

Take January 2005, for instance. It was the dry season and it rained over Tobago almost daily throughout January. It was unseasonal and this was because the ITCZ decided to stay north of the equator when it was supposed to be further south … on this occasion the Amazon areas would have had an unusually dry season.

The only other complications that can arise is where Tropical Waves (during the wet season) move off the African Coast and these have a magnetic effect on the ITCZ.

A strong Tropical Wave can ‘kink’ (ever wondered why they are called Waves?) the ITCZ and create a depression … such depressions can develop into Storms and possibly Hurricanes.

The funny old thing is that developing Storms and Hurricanes cannot survive in an environment of low pressure such as the ITCZ and so we go back to that Wave to explain why Hurricanes rarely affect Tobago.

If you imagine a Wave/kink in the ITCZ … like a Mexican Wave. The Depression is sort of kicked away from the ITCZ and moved away from the equatorial zone.

The reason why Tobago has experienced 2 close Hurricane calls over the last year is simply due to the fact that the ITCZ was well to the south of Tobago and that there was strong high pressure to the north at the times these Storms manifested themselves … they got the ITCZ kick but the momentum was checked by the unyielding high pressure in the north … so these storms had to go west.

These are the simple basics that I use to track Hurricanes and this how I had the sense that Hurricanes Ivan (Sept 2004) and Emily (July 2005) would come close to Tobago.

Official forecasters use sophisticated models to predict Hurricane tracks.

Generally, their initial estimates are appalling but they improve as a Hurricane develops because the models are updated to take account of a Hurricane’s behaviour in it’s early development stages.

Consequently, the predictions are pretty accurate by the time these Storms reach Florida.

So that leaves me to watch over Tobago … as I do … every day.

Regards
_________________

Post by **Steve Wooler** » Mon Jun 19, 2006 4:58 pm

Come on, Paul - play fair. Before rushing off to find out what ENSO means, why not tell us whether my definition of ITCZ was right or wrong? I'm not sure whether Neil was referring to the definition of ITCZ or ENSO, but either way he's promised to treat the winner to dinner for two at the Seahorse Inn, so I'm dying to know.

Neil Roberts · Post by **Neil Roberts** » Mon Jun 19, 2006 5:01 pm

Well I don't know about you Stephanie, but I'm sorry I asked now! I think I'll go and watch football on the television....I feel that is closer to my level.
Unless of course he's bluffing too!

Thanks for the replies,

Neil Roberts.

Bill B · Post by **Bill B** » Mon Jun 19, 2006 5:03 pm

Paul,

Thanks for your explanation but personally I'm going to stick with mine as it appears yours is much too complicated for me to do anything about.

When I get to Tobago next January any possible rain means I have to do my liming on the porch rather than on the beach. Oh well!

Bill

Neil Roberts · Post by **Neil Roberts** » Mon Jun 19, 2006 5:04 pm

I fear that Steve has a way of putting his posts into the system to gain best advantage....as he has again. Call My Bluff wasn't it. I also seem to have missed this dinner offer!!

I'm sticking with Bill.

Neil Roberts

Paul Tallet · Post by **Paul Tallet** » Mon Jun 19, 2006 5:09 pm

Well done Steve ... enjoy your nosh at the Seahorse Inn !!

As for ENSO, rather than mistake this for the identity of a decent Spanish Chap ... I have a very useful link for those that are dying to know about ENSO ...

http://www.cdc.noaa.gov/ENSO/enso.description.html

Regards

Brian Taylor · Post by **Brian Taylor** » Mon Jun 19, 2006 6:48 pm

I stick with soccer on TV, too and for weather I do the simple window looking thing. since tobago is such a small island, some weather does not even manage to rain or shine while passing. every beach near here has a place to stay dry and since we are moving down to little bay soon I'm on the beach all the time

rain or shine...
just love the heavy rains coming from the forest, definately a part of gorgeous weather for me....
no more explanations for me...too hot to think!

STEPH