simonjk
Well-Known Member
Hi All,
I've been noticing an interesting phenomena over the last few weeks, all related to the sea surface temperature anomaly in the Atlantic west of the British Isles.
Now, I know this is of no use at all when you're deciding what to do tomorrow, but I thought you might be interested to look at the chart yourself and perhaps consider the implications of what is happening.
Take a look at the chart at https://www.fnmoc.navy.mil/products/NCODA/US058VMET-GIFwxg.NCODA.glbl_sstanomaly.gif
This shows the areas where there were warmer than normal, or colder than normal water conditions. Think of the ocean as a huge heat sink, slowly absorbing and releasing heat into the atmosphere. There will be those receiving this email, many of whom are eminent scientists who will now be yelling "NO IT DOESN'T!", well guys, sorry, I know my explanation isn't strictly true, but that's how most of us think of it.
Back to the chart. Firstly, see all the yellow colours around the UK, Ireland and western Europe, with some really warm water in the Mediterranean. No, look in the central western Atlantic, a real cold pool of cold water in there. Next, to the tropical Atlantic. although not as well defined, there's a definite warm signal here, whilst off the coasts of western Africa we've a cooler than normal region.
What on Earth can all this mean though? Well, and these are only my ramblings late one evening, here's what I suspect.
The warmer water around the UK and western European coasts could aide convection. Remember the Musing I sent through earlier this week with the convection cloud over the Bay of Biscay in the developing low? Well, that could only get going because of convection forcing the ascent of the air into the atmosphere. So, we know that around the UK the tendency for convection is there. Of course, with the winds coming in off the sea, warmer than normal air is crossing the land mass, increasing the tendency for convection over land too. Heavy thunderstorms? Well, we've had a few of those haven't we?
Now, the west central Atlantic cool spot. This should stifle convection, with colder air having a greater density than warmer air, it could encourage the development of high pressure in this zone. What does that mean? Well, if we've got high pressure in the western Atlantic, they'd be a tendency for the jet to form further north, this would pass through the UK bringing predominately westerly winds, a more mixed direction. It would put most rainfall to west and north Scotland and western Ireland, but less for the southern UK over the coming weeks.
Onto the tropics. It's been an early start to the season here. Again the warmer water east of the Caribbean could aide convection needed to drive tropical storms and hurricanes. Could this mean things before active here for the next few weeks? What about the cold water west of Africa? Well, this may be due to cold upwelling caused by low pressure passing over the area, and so may not give us too much of a clue about the development of tropical storms. These tend to form over the African land mass and then move out to sea. What it might mean is that the storms develop, then have a "cap" put on development as they pass over cooler water, before reinvigorating as the approach the central tropical Atlantic.
Just a few ideas, but the sea surface temperature anomaly is always an interesting one to watch, especially when major storms have passed through as you can sea the cold water "dragged" up from the depths!
Hope you aren't asleep now!
Simon
I've been noticing an interesting phenomena over the last few weeks, all related to the sea surface temperature anomaly in the Atlantic west of the British Isles.
Now, I know this is of no use at all when you're deciding what to do tomorrow, but I thought you might be interested to look at the chart yourself and perhaps consider the implications of what is happening.
Take a look at the chart at https://www.fnmoc.navy.mil/products/NCODA/US058VMET-GIFwxg.NCODA.glbl_sstanomaly.gif
This shows the areas where there were warmer than normal, or colder than normal water conditions. Think of the ocean as a huge heat sink, slowly absorbing and releasing heat into the atmosphere. There will be those receiving this email, many of whom are eminent scientists who will now be yelling "NO IT DOESN'T!", well guys, sorry, I know my explanation isn't strictly true, but that's how most of us think of it.
Back to the chart. Firstly, see all the yellow colours around the UK, Ireland and western Europe, with some really warm water in the Mediterranean. No, look in the central western Atlantic, a real cold pool of cold water in there. Next, to the tropical Atlantic. although not as well defined, there's a definite warm signal here, whilst off the coasts of western Africa we've a cooler than normal region.
What on Earth can all this mean though? Well, and these are only my ramblings late one evening, here's what I suspect.
The warmer water around the UK and western European coasts could aide convection. Remember the Musing I sent through earlier this week with the convection cloud over the Bay of Biscay in the developing low? Well, that could only get going because of convection forcing the ascent of the air into the atmosphere. So, we know that around the UK the tendency for convection is there. Of course, with the winds coming in off the sea, warmer than normal air is crossing the land mass, increasing the tendency for convection over land too. Heavy thunderstorms? Well, we've had a few of those haven't we?
Now, the west central Atlantic cool spot. This should stifle convection, with colder air having a greater density than warmer air, it could encourage the development of high pressure in this zone. What does that mean? Well, if we've got high pressure in the western Atlantic, they'd be a tendency for the jet to form further north, this would pass through the UK bringing predominately westerly winds, a more mixed direction. It would put most rainfall to west and north Scotland and western Ireland, but less for the southern UK over the coming weeks.
Onto the tropics. It's been an early start to the season here. Again the warmer water east of the Caribbean could aide convection needed to drive tropical storms and hurricanes. Could this mean things before active here for the next few weeks? What about the cold water west of Africa? Well, this may be due to cold upwelling caused by low pressure passing over the area, and so may not give us too much of a clue about the development of tropical storms. These tend to form over the African land mass and then move out to sea. What it might mean is that the storms develop, then have a "cap" put on development as they pass over cooler water, before reinvigorating as the approach the central tropical Atlantic.
Just a few ideas, but the sea surface temperature anomaly is always an interesting one to watch, especially when major storms have passed through as you can sea the cold water "dragged" up from the depths!
Hope you aren't asleep now!
Simon
