Poster Chirimoya posted this in the Noel thread a few days earlier and I thought to wait awhile before I tried to explain. Now that relief efforts are underway, here is an explanation. It is neither technical, nor does it make complete sense, as weather forecasting is not an exact science.
Quote:
Originally Posted by Chirimoya
Diario Libre is criticising the Met. Office for not providing enough warning, but my impression is that this was not forecast by international meteorologists either, so the DR weather people should not be singled out, or anyone for that matter, because of the way the storm developed. Do the weather pundits agree?
|
No-one can be criticized for not seeing the way that this storm was going to develop. Tropical storms are a regular occurrence in the Caribbean. This one did not show any of the normal tropical storm tendencies, like, it had little steering currents and the darn thing did not move.
Saturday night before the storm, Noel was churning around in a shearless environment - what this means, is that there were no steering currents, i.e., winds. This is not usual for a tropical system in our area. They usually move, they have winds and they rain and move off. It was an excruciatingly slow moving system, at slower than 5 miles per hour. When it got close to the DR, it was not even a tropical depression. At this point the meteorologists were taking cursory notice ... a late season tropical depression, so what. But what no-one knew is that it was going to stop, strengthen and rain and rain and rain.
So, it arrived on our south side doorstep on Sunday. There were no signs that it was going to be anything more than a simple, normal, everyday Caribbean weather system - here today and gone tomorrow.
But, it sat itself down and kept dumping rain .. and strengthened to a tropical depression. Now the meteorologists started taking notice, although there were hardly any winds, no significant weather systems nearby that one could try and draw conclusions from and it gave every sign that it was going to dump some rain and move off as normal.
Except it did not. It sat itself down, making more and more rain, and developing a longer and longer tail end.
Guidance that we had then, was ... with weak steering currents, the movement could be erratic on Monday and Tuesday. Note, we're talking about movement. Not a dead stop. Caribbean storms don't stop, they move (or so I thought before Noel). But what we knew, is that if a tropical system stops or pauses, it strengthens. So, Noel strengthened to a tropical storm. But again, oh heavens, very little wind, none of the usual indicators so, the guidance that we had was that it is not going to develop into a full blown hurricane here on our doorstep. And it did not. But this was 'negative guidance', i.e., not what it was going to do, but what it was not going to do.
With no appreciable winds, the track was highly uncertain and the intensity was impossible to forecast, but, it sat down and continued to pour down rain ....
So, the center of the storm moved by us and moved by Haiti at the dizzying speed of perhaps 5 miles per hour. And then the tail end did not leave. It kept making more and more rain - it was like a locomotive falling off the tracks and all the other cars behind it, piling up.
Meteorological guidance was ... various possibilities, including a split of the mid-level and low-level centers ... doubt on the forecast track ... doubt on the intensity ... further west, more intense ... etc., etc. In other words, the meteorologists were flummoxed and flabbergasted and their data did not support anything (and I include this poor hobbyist). The words used for Noel in the meteorological circles, was meandering, spinning, splitting, perhaps this way, perhaps that ... no-one knew.
The center was near the southeastern peninsula of Haiti early Monday. And still the tail end bucketed down, and grew and grew. Reminded me of Pinocchio's nose! At this time we had some tropical storm force winds extending up to 115 miles out from the center. This thing was growing and take into account that we all were guessing where the center really was.
It rained for a number of days. It soaked the DR. It soaked the people, created floods, mudslides and caused all kinds of miserable suffering.
So, now that the storm is off of our coastline, I have a theory. It is not a scientific theory but it is something that I mentioned before in my time on the weather forum. It is normal for the Caribbean to have hurricanes. Hurricanes bring fresh water in order for the islands to save up a fresh water stock and replenish ground water. The DR has not had a hurricane for a long time. So, Noel came along, noticed that the ground water in the DR is depleted, and sat around trying to address the balance.
In conclusion, with all of our excellent coverage, satellites, remote weather sensors and monitoring stations, radar etc etc., there is no way that we can accurately predict to 100% certainty what the weather is going to do. Sometimes we're lucky and a system follows a path and shows indicators that we've learnt to interpret. Sometimes a weather system simply does what it wants to do.
Or, are we dealing with extraordinary circumstances? The floods in Tabasco in Mexico, the floods in the midwest of the US, the melting of ice on both the North and the South pole, wildfires in Canada and atmospheric carbon dioxide increasing much faster than expected. What are we really dealing with?
Tropical Storm Noel - Why?
(663)
