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04/11/2012
My Forecasting Techniques; How I forecast the Weather, and the Techniques involved in making the Long Range Forecast.
When forecasting the Weather, whether it be short-range to make a forecast for tomorrow or next week, or to make long-range forecasts for a month or so ahead, I regularly check the Computer Models, which give an indication (not always 100%) as to what the weather is likely to do over a period of time, by measuring atmospheric conditions at regular intervals. The Models I look at, are the Global Forecast System (GFS), Climate Forecast System (CFS), Global Spectral Model (GSM), Japan Meteorological Agency (JMA), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and the European Centre for Medium Range Weather Forecasting (ECMWF).
My other techniques are checking the Jet Stream, which is a fast-moving rhythm of air, about 6 miles above our heads, which controls the boundary between cold air to it's northern flank, and warm air to it's southern flank. It's crucial in weather developments, hence why I always keep track of what it's doing, and making a prediction as to what I think it will do next, and how that will influence our weather. I also check Ultraviolet levels (UV), and the Polar Vortex. I check the state of the Atmosphere at all levels, to determine how the Polar Vortex may react to changes in stratospheric temperature.
I also check the Arctic Oscillation. The degree to which Arctic air penetrates into middle latitudes is related to the AO index, which is defined by surface atmospheric pressure patterns. When the AO index is positive, surface pressure is low in the polar region. This helps the middle latitude jet stream to blow strongly and consistently from west to east, thus keeping cold Arctic air locked in the polar region. When the AO index is negative, there tends to be high pressure in the polar region, weaker zonal winds, and greater movement of frigid polar air into middle latitudes.
Similar to the AO, is the North Atlantic Oscillation (NAO), which I also regularly keep track of. The North Atlantic Oscillation (NAO) is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high. Through east-west oscillation motions of the Icelandic low and the Azores high, it controls the strength and direction of westerly winds and storm tracks across the North Atlantic. It is part of the Arctic oscillation, and varies over time with no particular periodicity. I regularly check the AO and NAO, and make my own individual interpretations to determine what I think, in my opinion, is going to happen with the weather over a period of a few days, weeks or months.
Other factors I use, are the Pacific Decadal Oscillation (PDO), El Nino–Southern Oscillation (ENSO), or El Nino/La Nina–Southern Oscillation, which is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean roughly every five years. The Southern Oscillation refers to variations in the temperature of the surface of the tropical eastern Pacific Ocean (warming and cooling known as El Nino and La Nina respectively) and in air surface pressure in the tropical western Pacific. The two variations are coupled: the warm oceanic phase, El Nino, accompanies high air surface pressure in the western Pacific, while the cold phase, La Niña, accompanies low air surface pressure in the western Pacific.
I also study and undertake in-depth analysis of solar conditions, as the Sun impacts our weather more than you think. The Sun drives our Jet Stream, which in turn drives our weather, nothing at all to do with CO2, like the delusional Government have led you to believe over the past few decades or so, i.e. "Global Warming" is leading to increased storms. It's all to do with the Sun, Jet Stream and the Sun goes through 11-year cycles, when it enters periods of high and low solar activity. Geomagnetic events i.e. Coronal Mass Ejections (CME'S) impact our weather greatly, and these help me to determine what is likely to happen with our weather, and make a forecast. I also look at the current Weather Pattern and look for Trends, to gain a rough idea as to how the Weather may react further down the line. I've been studying the Weather Pattern all Summer, and throughout this Autumn.
All the information I research and gather, enables me to use my 6 years knowledge of Meteorology & Space Science, to use my own opinions and perspective to make a highly detailed forecast for the coming Winter of 2012/13 across the UK & Ireland.
Another factor I always like to look at, is the state of the Northern Hemisphere Snowfall. It’s a little early in the season yet, however studies have shown that large increases in snowfall during October/November, can lead to more High-Latitude Blocking and therefore colder weather across both Europe and the UK. Looking at the Chart to the left, you can see that snow cover and ice extent in the Arctic, have both been on the increase. The Chart from the 1st November shows much of Asia and Northern Europe, as well as Newfoundland, Alaska and Canada, are under snow cover. Parts of Eastern Europe are also getting into the swing of things, too. If this snow cover continues to increase, and spread to many other parts of Eastern Europe, then we may find an increase in Northern Blocking this winter.
Click the image for a larger resolution.
Next we’re going to take a look at something slightly more technical, but I’ll try and keep things simple. The Quasi-Biennial Oscillation or QBO for short, is the measurement of the equatorial zonal winds between Westerly and Easterly in the tropical Stratosphere, the alternating phases develop at the top of the Stratosphere and propagate downwards over a period of months. Current forecasts suggests going into this winter we’ll be in an Easterly Phase and this basically speaking can lead to a higher risk of Sudden Stratospheric Warming, which I’ve gone into, to the right.
Click the image for a larger resolution.
Above I mentioned Sudden Stratospheric Warming, this is something fairly new to Long Range Forecasting and something that is still being studied. The general idea though, is that sudden warming events high up in the Polar Stratosphere can lead to a disruption in the seasonal Polar Vortex and when this happens, we tend to see High Pressure building over the Arctic and this helps to displace the very cold air Southwards into mid-latitude regions. SSW events are hard to forecast and we wont really have an idea of what state the Polar Stratosphere is likely to be in until later in the month. However, it is thought to be a very powerful process capable of over riding all other global signals, so it’s important we keep monitoring this for possible changes.
Click the image for a larger resolution.
Another thing we like to take a look at is the ENSO pattern in the Pacific Equatorial region, El Nino is the measurement of warmer waters whilst La Nina is the opposite measuring colder waters. The current prediction for this winter is for a weak El Nino perhaps becoming neutral or even becoming a weak La Nina instead, predictions are a little all over the place at the moment but a weak or neutral ENSO is whats expected, this generally tends to allow other signals to effect our weather more than they perhaps would during a stronger ENSO year.
Click the image for a larger resolution.
Taking a look at Solar activity, the activity on the Sun at the moment is still exceptionally low from where it should be, especially as we're nearing the peak of the Solar Maximum, and the peak of Solar Cycle 24 (SC24). This puts us at the halfway point from the the Hale Cycle, which is the 22 year Cycle of the Sun. Sunspot activity on the Sun is exceptionally low, as you can see from the image of the Sunspot activity above, with only four sunspots evident.
Click image for a larger resolution.
Similar to the image I posted to the left, you can see that this ismage of the Sun, shows there is very little activity on the sun, more especially in Sunspot activity. As you can see on the chart, the number of Sunspots are well below where they should be, for this stage in the Solar Cycle. We're nearing the peak of the Solar Maximum, of SC24. Low Sunspot activity, has been linked to colder winters in the Northern Hemisphere & studies on this, are ongoing.
Click image for a larger resolution.
Below, are the latest Met Office Probability Charts for the likelihood of above-normal, near-normal, and below-normal Temperatures in the Northern Hemisphere. The Probabilities of each Temperature anomaly occuring during this Winter, the period of Dec/Jan/Feb, are as follows.
Above-normal Temperatures
0-20% Confidence
Near-normal Temperatures
0-40%
Below-normal Temperatures
60-80%
Below, are the latest Met Office Probability Charts for the likelihood of above-normal, near-normal, and below-normal Precipitation in the Northern Hemisphere. The Probabilities of each Precipitation anomaly occuring during this Winter, the period of Dec/Jan/Feb, are as follows.
Above-normal Precipitation
0-40% Confidence
Near-normal Precipitation
20-40%
Below-normal Precipitation
40-60%
The JAMSTEC Model also shows that overall, temperatures across Western Europe, including the UK and Ireland, are likely to be below-average throughout. Above-average temperatures across Russia and the Arctic, are a prime example of Northern Blocking, which drives milder air northwards, and displacing the cold down to the mid-latitudes.
Click image for a larger resolution.
Moving onto the main Forecast, I've taken into consideration all of the factors above, and many other Scientific factors, to come to a conclusion as to how I think this upcoming Winter, will pan out.
COLDER THAN AVERAGE, INTERSPERSED WITH OCCASIONAL MILDER SPELLS! MAIN EMPHASIS IS FOR COLD! SOME SIGNIFICANT SNOWFALL EVENTS ARE LIKELY AT TIMES!
DECEMBER 2012
I currently expect December to start off on a rather cool note, with temperatures below average for many. Rainfall amounts are expected to be mainly below normal, especially given the signal for blocking to the North and NW of the UK & Ireland. We could see blocking across Scandinavia, which would put us under an easterly flow. Blocking could also occur to our North or NW, putting us under a cold NE, or E flow. Low Pressure to the south, may give rise to some significant snowfalls, as fronts get thrown westwards on the northern flank of the Lows, with this synoptic most likey in the south and east. Depending on where the blocks set up, and due to conflicting signals, there is a variety of outcomes which are all equally possible during the month of December.
OUTCOME 1: High Pressure establishes across Greenland, with a trough over, or to the east of the UK. This would put the UK and Ireland under a cold NE/E airflow, potentially spreading snow showers in from the North Sea and Irish Sea, to many areas. Showers could form bands of snow across the NE and East of the UK and Ireland, with these perhaps spreading inland. Sunnier days are possible with this setup, with a biting NE/E wind, and severe frosts by night. It is possible that if this outcome establishes, we could see an emphasis for temperatures to go as low as -13C across parts of the NE and Scotland, perhaps elsewhere at times. The far west of of Ireland may remain less cold, although some colder weather likely at times.
This outcome is currently the second most likeliest outcome to occur.
OUTCOME 2: High Pressure establishes across Scandinavia, with a trough to the south, across Southern Europe. This could put the UK and Ireland under a biting Easterly flow "The Beast from the East", as it's most commonly called. This flow would bring bitter weather to all, with snow showers from the near continent, coupled with bands of snow too. Clearer days are likely, with severe frosts possible too. Temperatures will vary, but I wouldn't rule out -13C during some of the coldest nights, providing there is snowcover to enhance Nocturnal Radiational Cooling. With a trough to the south, any Low Pressure systems which run west to east through the English Channel or Northern France, could potentially bring significant snowfall events to Southern and Central Britain, as well as the East, as the fronts get pushed westwards on the northern flank of the Low.
As it currently stands, this outcome is the one most likely to occur at the moment.
OUTCOME 3: There is the equal probability of a milder westerly flow establishing, with an Azores High to the west of the Bay of Biscay, and a trough to the North of the UK. This would potentially bring a much milder spell of weather to many, with the potential for vigorous areas of Low Pressure to spread from west to east, bringing plain old zonal weather.
As it currently stands, this outcome seems like the less likeliest to occur.
In conclusion, I think it's likely that the UK and Ireland as a whole, will experience temperatures below average and at times well-below average, with precipitation around average in the South, and below-average in the North. I also believe that this December will see some fairly significant snowfalls for many, however it's too early to give precise details. Some windy or very windy periods are also likely at times.
CONFIDENCE OF SIGNIFICANT SNOWFALL EVENTS: 70-80%
CONFIDENCE OF BELOW AVERAGE TEMPERATURES: 70-90%
CHRISTMAS 2012 - WHITE CHRISTMAS FORECAST
To the right, I have my Predictions of this Christmas being a White Christmas.
Going by current trends, i.e. Northern Blocking signals, Jet Stream conditions, overall Weather Pattern, the signal for below-average Temperatures, and other signals, I've come to a decision as to the probabilities of each region of the UK & Ireland seeing a White Xmas.
A weekly White Christmas Forecast will feature on the homepage of my website, until Christmas. It will be updated weekly, to give people an indication to the likelihood of a White Christmas occurring during Christmas 2012.
UNITED KINGDOM
SCOTLAND - 70-80%
NORTHEAST ENGLAND - 60-80%
NORTHWEST ENGLAND - 60-80%
NORTHERN ENGLAND - 60-80%
WEST MIDLANDS - 50-80%
EAST MIDLANDS - 50-80%
EAST ANGLIA - 50-80%
SOUTHEAST ENGLAND - 50-80%
SOUTHERN ENGLAND - 50-80%
SOUTHWEST ENGLAND - 40-60%
WALES - 50-80%
REPUBLIC OF IRELAND
ULSTER - 60-70%
CONNAUGHT - 30-40%
LEINSTER - 60-70%
MUNSTER - 40-60%
JANUARY 2013
This is where confidence tends to slack, however I'm going to stick my neck out and give you my current thoughts on January.
At the moment, it looks like there could be Blocking to the North of the UK & across Greenland, as a Scandinavian High retrogresses westwards. A trough over southern Europe could migrate northeastwards, and set up over Eastern Europe. Cold air will drain off of the Arctic Regions and down across the UK, Ireland and Western Europe, on a biting N/NE flow. This has the potential to draw down snow showers, and bands of snow from the Northeast. Winds blowing across the Irish Sea and North Sea, have the potential to pick up moisture and dump it as heavy snow across much of Eastern/NE Ireland and Britain. Undercutting Low Pressure systems have the potential to bring significant snowfall events to Wales, Central, Southern, Eastern and SE England, alongside the Southwest. There is likely to be the odd milder period here and there, with wetter, windier weather likely. I am going for below-average temperatures on the whole, with the possibility of well-below average temperatures at times. Average or slightly-above average temperatures also cannot be ruled out. Precipitation will likely be average or below-average, especially across the north, with average or above-average values further South. It is possible that in the coldest periods, we could see temeratures plummeting to -14C, especially in the North, but not exclusively so.
In conclusion, I think Janaury will consist largely of colder than average temperatures for all, with rainfall at or below average in the North, and average or above in the south. Significant snowfall events are possible, and milder interludes are likely too.
OVERALL CONFIDENCE FOR JANUARY: 40-60%
FEBRUARY 2013
As we head into the last month of the meteorological winter, I have a gut feeling that February will be a two tale month. I think the start of February has the potential for below-average temperatures, with the threat of well-below average temperatures likely at times. Precipitation will be around average or just below for all, with perhaps the south seeing slightly above-average. Some significant snowfall events are likely, but details are too sketchy at this stage of the season. The second half of February could turn out milder, as the Greenland/Scandinavian High pulls away to the East, allowing the floodgates of the Atlantic to open, bringing us a zonal, westerly orientated flow. At the moment, confidence is low, as is all confidence at this stage.
In conclusion, I think February 2013 will get off to a cold start, perhaps very cold in a few places, with significant snowfalls possible at times. Temperatures largely below-average, with well below-average possible at times. Precipitation will be around average or just below, perhaps above in the South. Temperatures and Rainfall could pick up to average or above-average values later in the month, as the threat of milder weather increases. Confidence is slack at the moment, so there's no real signal as to what could happen, however I will keep you all updated in the short-term, with my Blog and Daily Forecasts/Alerts.
OVERALL CONFIDENCE FOR FEBRUARY: 30-40%
SUMMARY OF THE UPCOMING WINTER
All in all, I think there are good signals for Northern Blocking to become established at times during the Winter, with retrogression from Scandinavia, to Greenland. Significant snowfalls are likely at times through the Winter. Precipitation amounts overall, will be around average or below for the north, perhaps around or above normal for the south. Temperatures overall, will be below average, so this Winter is likely to be a colder than average Winter overall. Milder periods are likely at times, but the main emphasis is for colder weather. Some wet and windy spells are likely, especially during any milder periods. The Jet Stream is likely to remain to the south (JSS), warm Sea Surface Temperatures are good for blocking, as is snowcover over Northern Europe & Asia.
In conclusion, this Winter will be very interesting to say the least, and will be very different from last year. This year is looking better for cold and snow, but you also have to expect milder weather at times, although nothing on the scale of last Winter's unusually mild temperatures.
Overall Confidence - Winter 2012/13
CONFIDENCE OF A COLDER THAN AVERAGE WINTER: 60-90%
CONFIDENCE OF AN AVERAGE WINTER: 40-50%
CONFIDENCE OF A MILDER THAN AVERAGE WINTER: 0-40%
CONFIDENCE OF SIGNIFICANT SNOW EVENTS: 50-80%
CONFIDENCE OF WETTER, WINDIER WEATHER: 0-50%
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October
October is likely to feature near or below-average temperatures as a whole, although some interspersions of milder weather are also likely to develop at times especially in the southern half of the country. A number of frequent wet and very windy or exceptionally windy periods are also likely to develop for many parts of the country at times too. The cooler periods of weather will also see the development of some overnight frosts in places. These cooler periods will also be accompanied by the first falls of snow and some wintry showers in places, especially across higher ground in parts of the north as we progress throughout October.
Result = First falls of snow as predicted + a mean Central England Temperature (CET) of -1.0C
November
November is likely to feature below-average temperatures as a whole. It is likely to become progressively colder as we progress throughout the month and into the start of winter, with the development of some quite severe frosts in places. These cooler periods of weather will be accompanied by further falls of snow across higher ground, and these are also likely to develop across some lower levels of the country at times too. It is also likely to be a relatively drier month overall in terms of rainfall amounts. However, some further periods of wet and windy weather are still probable to develop at times too.
Result = Pending...
The long range winter forecast 2012/13 that was published on the 23rd June 2012 also stated:
1. A number of exceptional and unusually strong windy periods are also likely to develop at times throughout the upcoming autumn and winter period. Some of these winds could also prove to be very damaging and potentially record-breaking in places.
2. The cold and wintry conditions are also likely to arrive earlier this year i.e. in autumn.
Also stay tuned to the 4-day forecasts that are continuously updated on model suggestions at regular intervals throughout each day. Thank you for visiting Exacta Weather.
http://www.exactaweather.com/UK_Short_Range_Forecast.html
Added: 1st October 2012 16:22PM
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