Liam Dutton's Blog

Bank Holiday Weather - Getting better, albeit gradually...

2010-08-26T20:12:00.003+01:00

There are certain times of year when being a weatherman can be more testing than others.

My fellow weather people and I are usually loved when we bring news of fine weather.

However, when the weather isn't so good, then popularity tends to take a dive, at least until the sun shines again.

As you can imagine, every time a Bank Holiday approaches, the burning question on most people's lips will be, "Is the weather going to be nice?"

No doubt this is probably the exact reason for which you're reading this blog post!

Well, in a nutshell, the main message is that it will be mixed... BUT, it will gradually improve, so that by Monday most of us will be looking at something a little more pleasant.

Low Pressure versus High Pressure

You're probably thinking, why is the weather looking so mixed? Well, for the past week the weather across the UK has been dominated by areas of low pressure bringing wet and windy weather to England and Wales in particular.

Through the Bank Holiday weekend, an area of high pressure will build in from the west, but at the same time an area of low pressure is reluctant to 'take the hint' and move away.

This is where the word 'mixed' comes into things. For as long as low pressure remains close to the UK, the air will be unstable enough to rise upwards in the atmosphere and form clouds, which will in turn produce showers or rain.

As high pressure builds in from the west, the air will become more stable and the ability of the air to rise upwards and form shower bearing clouds will diminish.

So as would be expected, with high pressure building in from the west, it will be western areas seeing the weather improve soonest, with other places following early next week.

Cool Wind

Another thing to note about the forthcoming weekend is that there will be quite a fresh and noticeable wind from a rather cool north or northwesterly direction.

So even when the sun is shining, it will feel quite cool in the wind.

You often hear forecasts refer to how close the isobars (continuous lines) are on a weather chart when it is going to be windy.

As the high pressure comes up against the low pressure this weekend, it will cause the isobars to be pushed closer together for a time, hence an increase in the strength of the wind.

Once the low pressure eases away early next week and the isobars space out again, the wind will ease down.

So what's the weather going to be like then?

Well, during Saturday and Sunday there will be sunny spells and showers, with showers most likely and frequent in the north and east of the UK, where the cool wind will be most noticeable.

As high pressure drifts in further during Bank Holiday Monday, showers will become fewer and confined to the far east of the UK. Also, sunshine will be more prevalent for most of us, with the wind easing down.

Where can I stay up to date with the latest forecast?

As always there are regular updates on the BBC and Met Office websites. It's worth staying in touch with the forecast as sometimes there can be minor changes to detail for where you are.

USEFUL LINKS

Met Office News Release - Weather set to improve next week

BBC Weather - Latest forecast

Met Office - Latest forecast

Storm Watch Round Up

2010-08-08T20:26:00.000+01:00

After a quiet few weeks on the tropical cyclone scene, it seems as though someone has flicked a switch and things are now starting to look a bit more active.

I thought that I'd take the opportunity to give a little round up of the various potential tropical cyclones in each of the ocean basins, where they may go and any possible impacts.

Whilst at the moment none of the potential storms look that strong, things can change quickly, especially when looking beyond the next 36-48 hours.

Atlantic Ocean

At the moment there are three notable areas of interest in the Atlantic Ocean on the infrared satellite picture (figure 1). There's Tropical Depression COLIN, a disorganised area of thunderstorms close to Florida, and an area of low pressure in the mid-Atlantic Ocean.

Figure 1 - Image courtesy of NOAA - Shows three

notable areas of interest in the Atlantic Ocean.

After developing as a tropical wave off the west coast of Africa, COLIN became a tropical storm for a short while, before temporarily weakening.

It has since gained strength and is currently a tropical depression, with sustained winds of 35mph (55km/h). After passing very close to Bermuda through the weekend, COLIN is forecast to drift northeastwards across open waters, without any impact upon land (figure 2).

Figure 2 - Image courtesy of NOAA - Shows the

current forecast track of COLIN.

The area of disorganised showers and thunderstorms affecting Florida at the present time isn't expected to develop into a tropical cyclone, but it will enhance the risk of some places seeing torrential downpours over the next couple of days.

At the moment, the most interesting area is the low pressure system in the mid-Atlantic. With favourable environmental conditions, this has a high chance (70%) of becoming a tropical cyclone in the next 48 hours. If this does develop further, it will be named DANIELLE.

Eastern Pacific Ocean

So far this season, there have been quite a few tropical cyclones in this area, but most of them have stayed across open waters with little impact upon land. Although Tropical Storm AGATHA did cause some serious problems, with widespread flooding in some parts of central America.

Figure 3 - Image courtesy of NOAA - Shows the

current forecast track of ESTELLE.

At the moment, Tropical Storm ESTELLE is around 400 miles (645km) off the coast of Mexico. This storm is expected to drift around across open waters (figure 3) and gradually weaken during the next 48 hours.

Pacific Ocean

Following a tropical formation alert on Saturday, Tropical Depression 05W formed to the northeast of the Philippines. The current forecast suggests that it isn't expected to become any more than a tropical storm.

What it will do though, is drift northwards over the next few days, with a threat of heavy rain, strong winds and rough seas to South Korea and western Japan (figure 4).

Figure 4 - Image courtesy of Joint Typhoon Warning Center - Shows

the current forecast track of 05W.

Given the fact that this storm is in its infancy, its forecast track may change as the week progresses.

As always, the National Hurricane Center and Joint Typhoon Warning Center will continue to update their forecasts for each of these storms.

If any of them develop further, I'll try to do an update in a few days time!

USEFUL LINKS

Met Office - Tropical Cyclones

National Hurricane Center

Joint Typhoon Warning Center

BBC Weather - Weather News

Tropical Storm Bonnie Affects Southern Florida

2010-07-23T18:43:00.017+01:00

So far, the Atlantic hurricane season has been quite quiet, despite the major forecasting centres of the world predicting an active season.

To date only one named storm has formed in the Atlantic Ocean basin and that was Hurricane ALEX around three weeks ago.

Since then, there have been numerous tropical waves (areas of showers and thunderstorms) which have meandered around the Caribbean, but none have had favoured conditions to become named storms.

The silence has now been broken with the formation of Tropical Storm BONNIE, which first showed signs of circulation on the 22nd July.

It was at this point that the National Hurricane Center (NHC) classified it as a Tropical Depression whilst located over the southeastern Bahamas. Within 24 hours, it had gained sufficient strength to be upgraded to a Tropical Storm.

During Friday, BONNIE is drifting across the southern tip of Florida (figures 1 & 2), with the potential for 1 to 3 inches (25 to 75mm) of rain, with some places seeing more.

Figure 1 - Image courtesy of NOAA - Shows Tropical Storm BONNIE

on a visible satellite picture across southern Florida.

Figure 2 - Image courtesy of NOAA - Shows Tropical Storm BONNIE on a radar picture

across southern Florida. Brighter colours indicate heavier rain.

Winds aren't particularly strong, but still averaging 40mph (65 km/h) with stronger gusts. Accompanying the wind and rain is the threat of isolated tornadoes, as well as a potential storm surge of 1 to 2 feet (0.3 to 0.6m). These factors combined bring a risk of flooding and some disruption to travel.

Figure 3 - Image courtesy of NOAA - Shows forecast track for

Tropical Storm BONNIE for the next 5 days.

The next 24 hours will see BONNIE move into the Gulf of Mexico (figure 3). Whilst there may be a slight strengthening of the storm, the conditions are not favourable due to strong wind shear.

What this means is that the winds at different levels of the atmosphere are going in different directions. This has a tug of war effect on the structure of the storm, effectively trying to pull it apart and make it less organised.

After moving across the Gulf of Mexico, BONNIE will arrive along the northern Gulf coast late on Saturday, with the states of Louisiana and Mississippi bracing themselves for heavy rain, gusty winds and a risk of flooding.

BONNIE's forecast track has also caused work to be halted on the BP spill site, with an evacuation on the cards before the storm's arrival.

At the moment, there are no other potential storms brewing in the Atlantic, but the National Hurricane Center has regular updates with the latest information.

USEFUL LINKS

National Hurricane Center

BBC Weather - North America Forecast

BBC Weather - Weather News

BBC News - Workers at BP spill site get ready for evacuation

Met Office - Tropical Cyclones

Beautiful Sunrise

2010-07-21T20:44:00.000+01:00

Hi everyone!

I captured this beautiful sunrise on the way to work the other day and thought I'd share it with you.

I love the tinge of pink and orange in the distance.

A full blog post due very soon!

So Why So Dry?

2010-07-06T21:20:00.002+01:00

Whilst many of us have been enjoying the very warm and sunny weather bathing the United Kingdom over the past few weeks, the lack of rainfall is starting to become a bit of a concern.

Figures released by the Met Office show that the UK has had its driest first six months of the year since 1929 - 81 years ago!

From January to June this year an average rainfall of 356.8mm fell across the UK.

Whilst this is some way short of beating the 275.7mm that fell from January to June in 1929, it is still well below normal.

Looking at regional differences in rainfall across the UK, it is northwest England that stands out with some startling figures. Normally from January to June an average of 530mm of rain would fall across northwest England. This year little more than half that amount has fallen, with 299mm.

The impact of the lack of rainfall in northwest England has been evident from reservoir levels.

Normally at this time of year reservoirs would be around 80% full. This year at Haweswater and Thirlmere the reservoir is just 61.4% full.

These drier than average conditions have put pressure on water resources, with some areas placed on drought alert.

Well those are the facts, but you're probably thinking why has this year been so dry?

The most common weather pattern in the UK is for low pressure to move in from the Atlantic Ocean, bringing cloud, wind and rain.

This year, however, has been different. The number of rain bearing low pressure systems has been lower compared to previous years.

Instead, there have been long periods of settled weather, with high pressure over or close to the UK. This acts as a block to low pressure systems which are diverted northwards or southwards around the periphery of the high pressure, leaving the UK mainly dry.

There has been a slight change in the weather pattern during the past week or so. The jet stream - a fast moving ribbon of winds high up in the atmosphere that drive the weather - has moved a little further southwards.

Figure 1 - Image courtesy of Wetterzentrale - Shows the forecast jet stream indicated by the

yellow/orange/red areas just west of Ireland. Low pressure forms on the front left side of the jet stream.

Figure 2 - Image courtesy of Wetterzentrale - Shows forecast pressure, where the white

lines are isobars. Compare with figure 1 and notice how the low pressure (line labelled 995)

has formed on the front left side of the jet stream that is located just west of Ireland.

This has allowed rain bearing low pressure systems to develop (figures 1 & 2) and reach northern and western parts of the UK, bringing much needed and welcome rain.

Unfortunately towards the southeast of the UK, high pressure remains which means very little rain is reaching these areas, with the relatively dry weather continuing.

No doubt all eyes will be on the forecast to see what the next few weeks will bring!

USEFUL LINKS

Met Office - Driest start for more than 80 years

Met Office - Drought

Wetterzentrale - Weather Charts (in German)

BBC Weather

Environment Agency

Wikipedia - Jet stream

Alex to Become First Atlantic Hurricane of Season

2010-06-29T12:25:00.001+01:00

In a previous post I mentioned that the major forecasting centres of the world were predicting an active Atlantic hurricane season this year.

So far, there have been a few potential areas of development, but none have had the favourable conditions to get to hurricane status.

Well that is about to change as Tropical Storm ALEX looks set to become the first Atlantic hurricane of the season.

ALEX will gain strength as it draws energy from the warm waters of the Gulf of Mexico.

The National Hurricane Center in Miami is forecasting ALEX to become a hurricane during Tuesday as it drifts northwestwards across the Gulf of Mexico.

The latest forecast track (figure 1) takes the storm towards the northeast of Mexico, very close to the border with Texas, where it's expected to hit the coastline during Thursday.

Figure 1 - Image courtesy of NOAA - Shows the forecast

track and strength of ALEX for next 5 days.

When it hits the coast winds are forecast to be averaging 95mph (152 km/h) with gusts up to 120mph (193 km/h).

This would make it a strong category 1 storm, bordering on category 2. As a result, a hurricane warning is in effect for the coast from Southern Texas into Northern Mexico.

Figure 2 - Image courtesy of NOAA - Shows an infrared satellite

picture of ALEX just northwest of the Yucatan Peninsula.

As well as strong winds, heavy rain is expected. Over the next few days 5 to 10 inches (125 to 250mm) of rain could fall. Such large amounts of rain would cause life-threatening flash floods and mudslides, particularly in mountainous terrain.

The strength of the wind will also create a storm surge, raising water levels by 3 to 5 feet (0.9 to 1.5 metres), enhancing the flooding risk to coastal locations.

ALEX could influence the weather further afield as well. The storm will feed a supply of hot and humid air towards the Gulf states of the USA for the rest of the week. This will provide the ingredients for intense and slow moving thundery downpours, bringing a risk of flash flooding to some places.

Whilst the future path of ALEX will be of great interest during the next few days, it's worth highlighting that this storm has a history stemming back to when it was just a tropical wave (an area of showers and thunderstorms) in the Caribbean Sea (figures 2, 2a &2b).

Figure 2 - Source: Wikipedia - Shows historical track

of ALEX from when it was a tropical wave.

Figure 2a - Source: Wikipedia - Key for storm strength.

Figure 2a - Source: Wikipedia - Key for storm type.

As it moved westwards through the Caribbean Sea, it brought flash flooding to the Dominican Republic as rivers burst their banks. Hundreds of houses were flooded and an evacuation of 3,000 people occurred. Neighbouring Haiti also reported some minor flooding.

On becoming a tropical storm, ALEX brought torrential downpours to the Yucatan Peninsula, southern Mexico and northern Guatemala.

This shows how much of an impact such storms can have when they are still in their infancy.

Don't forget, frequent forecast updates are available from the National Hurricane Center.

USEFUL LINKS

National Hurricane Center

BBC Weather - Central America

BBC Weather - North America

Met Office - Tropical Cyclone Facts

Wikipedia - Tropical Storm ALEX (2010)

Wimbledon Weather

2010-06-21T15:30:00.001+01:00

Well it's that time of year when SW19 becomes the focal point for the Wimbledon Tennis Championships.

Whilst there are some things you can guarantee every year - strawberries & cream, champagne and jugs of Pimm's. There are some things you can't guarantee - the British weather!

 Whilst the threat of rain is perhaps not as menacing as it used to be now that they've added a roof to centre court, it can still cause delays to play on the outdoor courts.

So, the big question is - what does the weather have in store for Wimbledon this year?

Well in a nutshell, for the first week of the tournament it looks like there'll be some great tennis weather.

An area of high pressure will sit across the UK meaning that it will be settled with light winds, lots of sunshine and high temperatures. There could be an isolated shower towards the end of the week, but all in all it looks like staying dry!

Whilst the prospect of fine weather is likely to be music to everyone's ears, there are some important things to remember when being outdoors when it's sunny and very warm at this time of year!

The summer solstice occurred today, which means that the sun is at its highest point in the sky overhead.

With the sun very strong during the summer months, it is worth thinking about protecting from UV rays with sunscreen.

A hat, or if you've got the space, a parasol can offer shade from the sun during the hottest part of the day.

Given the peak of the grass pollen, those with hayfever are likely to feel the effects of the very high pollen levels expected across much of England and Wales this week.

Also, with little or no wind expected, the heat will be even more noticeable, so no doubt bottles of water will be in demand to quench the thirst of those playing and spectating!

As ever, keep an eye on the forecast during the next couple of days to stay updated.

USEFUL LINKS

BBC Weather - Wimbledon Forecast

Met Office - Wimbledon Forecast

UK Pollen Forecast

Wimbledon Championships

All Eyes on the Eastern Pacific

2010-06-16T17:21:00.000+01:00

This post is a follow on from one that I made on the 14th June titled 'Potential Trouble Brewing in the Tropics'. It talked about the potential for tropical cyclone formation to occur in the Atlantic Ocean as well as the Eastern Pacific Ocean.

Two days on and things have changed a little. The potential storm that was in the Atlantic Ocean has now faded, with little prospect of becoming a major system.

In the Eastern Pacific, however, things remain very interesting. There are still two areas of notable showers and thunderstorms present - one of which has a high chance (60%) of becoming a tropical cyclone in the next 48 hours.

The red circled areas in figures 1 & 2 show where there is a high chance of a tropical cyclone forming, near the Gulf of Tehuantepec, Mexico. Environmental conditions favour further development, and even if a tropical cyclone doesn't form, heavy rain is expected for the Mexican coast.

Figure 1 - Image courtesy of NOAA - Note red and orange circled

areas highlighting areas of potential tropical cyclone development.

Figure 2 - Image courtesy of NOAA - Note red and orange

circled areas highlighting showers and thunderstorms.

The orange circled areas in figures 1 & 2 show where the second potential storm is located. However, at present there is a medium chance (50%) of this becoming a tropical cyclone in the next 48 hours.

No doubt forecasters at the National Hurricane Center in Miami will be keeping a close eye on all of these potential storms, with frequent updates available on their website.

USEFUL LINKS

National Hurricane Center

BBC Weather - Central America

Met Office - Tropical Cyclone Facts

Slow Moving Low = Heavy Rain for Southern Europe

2010-06-15T14:28:00.011+01:00

Quite often when low pressure is mentioned in the weather forecast, everyone thinks that cloud, wind and rain is on the way - which is often the case.

Normally low pressure systems move fairly quickly, driven along by the winds in the upper part of the atmosphere. This means that in most cases, after 3-6 hours of notable rain, it becomes dry again and eventually the skies brighten.

Sometimes, however, an area of low pressure can become slow moving and get stuck in the same place for a longer period of time. When this happens, rain can fall over the same area for a few days (in the worst case scenario), resulting in flooding.

During the next 48 hours an area of low pressure will become slow moving over some southern parts of Europe. This system has some very warm and potentially energetic air mixed in with it, meaning that as well as heavy rain there could be some thunderstorms mixed in.

Thunderstorms have the ability to produce intense rain in short spaces of time and it is this kind of intense rainfall that can cause flash floods.

Coloured Infrared Satellite Picture of Europe.

The coloured infrared satellite picture (figure 1) was taken at 0600GMT on Tuesday 15th June. Infrared satellite pictures work by interpreting the temperature of the cloud tops in the atmosphere.

As it generally becomes colder the higher up in the atmosphere you go, in most cases clouds of a lower temperature are higher up in the atmosphere, which is a sign that they are more developed.

The scale at the bottom right hand side of the image is in degrees celsius (C) and shows that white = 0C, blue = minus 17C and green = minus 51C.

The low pressure system on the satellite picture is clearly marked by the blue and green colours extending from Corsica into France and the Alps. Here the clouds are more developed and have lower temperatures and greater potential to deliver heavy rain and thunderstorms.

Some of the weather forecasting models are suggesting that locally as much as 50mm of rain could fall in as little as 6 hours, with a lot more falling during the next two days. The Alps and southeastern parts of France look most at risk at the present time.

Figure 2 - Meteoalarm weather watches (yellow) and

warnings (orange) for Europe on Tuesday 15th June.

Figure 3 - Meteoalarm weather watches (yellow) and

warnings (orange) for Europe on Wednesday 16th June.

Meteoalarm, which is a joint initiative between the national meteorological services of Europe, shows that numerous weather watches and warnings for heavy rain and thunderstorms have been issued across much of southern Europe during the next 48 hours (figures 2 & 3).

Although the most intense rain looks likely during the next 48 hours, the risk of showers remains into the weekend.

USEFUL LINKS

Meteoalarm

BBC Weather - Europe

Met Office - Europe Weather

Potential Trouble Brewing in the Tropics

2010-06-14T20:54:00.008+01:00

The Atlantic hurricane season officially started on the 1st June, with both NOAA and the Met Office suggesting that this year is likely to be an active season, meaning more storms than normal.

So far all has been quiet across the open waters of the Atlantic Ocean, but that could change during the next 48 hours.

A cluster of showers and thunderstorms (Figure 1) associated with an area of low pressure was present about 1375 miles east of the Windwards Islands on Monday.

Whilst the showers and thunderstorms have become a little less organised during the last 24 hours, there is still a medium chance (40%) of this system becoming a tropical cyclone in the next 48 hours.

Figure 1 - Image courtesy of NOAA - Note orange

circled area highlighting showers and thunderstorms.

Meanwhile, in the Eastern Pacific Ocean, two areas of showers and thunderstorms are showing up clearly on recent satellite imagery (Figure 2).

Figure 2 - Image courtesy of NOAA - Note orange and

yellow circled areas highlighting showers and thunderstorms.

The yellow circled area is showers and thunderstorms, but this shows little signs of further development, with just a low chance (20%) of becoming a tropical cyclone during the next 48 hours.

The orange circled area shows better organised and more extensive showers and thunderstorms located about 350 miles west-southwest of Acapulco, Mexico. With this being more developed, there is a medium chance (40%) of a tropical cyclone forming during the next 48 hours.

Even if these two areas of showers and thunderstorms don't develop into tropical cyclones, they are still likely to take pulses of very heavy rain towards central America.

At the moment, it looks like southern Mexico, Guatemala and El Salvador could see more torrential downpours - places which are still getting over the effects of Tropical Storm AGATHA.

USEFUL LINKS

National Hurricane Center

BBC Weather - Central America

Met Office - Tropical Cyclone Facts