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lukemc

Differences Between The Climate Of Ne Usa And The British Isles

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Hi,

One of the things that intrigues me is the differences between different climates in particular the difference between continental and maritime climates including how synoptics can differ in these climates. So I have decided to discuss the differences in the climate between the UK/BI and the Northeastern USA. So I do know that the NE USA has on average, colder and snowier winters than the UK, with hotter and more humid summers. I have a few questions though about the specifics of the two climates, for example overall would you say that do they get as much frontal precipitation as we do in the NE United States, and do they get any frontal rainfall in the summer (I know they do get a lot of convectional rainfall though showers and thunderstorms). Also is it true that when a mild spell does occur in the Northeastern states during the winter, it can be as mild or even milder than the UK, for example I have read that 25 degrees C has been recorded in New York in February which I would imagine would be way above the record high for the UK during February does anyone know why this would be the case. Also, for example New York City when it gets snowfall in the winter is most of its snowfall frontal or convectional (like lake effect snow). For example when NYC got the big dumping last week from the Northeaster storm, is that snowfall frontal in nature (rather than convectional) and is it similar to the battlegrounds that we sometimes get with a very cold airmass and a milder airmass doing battle? Also during some Northeaster storms I remember NYC getting rain rather than snow (with Upstate NY getting tons) is this because they can sometimes be effected by a warm sector? And is also is NYC/Long Island/New Jersey milder in winter than most of upstate New York and is this because of Atlantic influence? Also how many Ice Days do they get per winter? And I have also read that the changes in temperature from day to day can be far more dramatic than they are here, for example can it sometimes be 30C one day and 15C the next (or visa versa) when a front passes though? And also how do the summers in the NE US compare to ours, yes I know that they are on average hotter than ours (for example average daytime highs of 25C) but are they more settled than ours and are they more sunny than ours? It would be interesting to here you thoughts of experiencing the two climates an to point out any further differences you have experienced.

Luke

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A few quick "answers"....

Yes, they get frontal rainfall in summer. They are not on the western edge of a continent, therefore do not have Mediterranean climates (meaning dry summers and wet winters). Rainfall is reasonably evenly spread over the year.

Their frontal rainfall may well turn out to be more convective though (organised on the cold front).

Everywhere in the world outside the tropics gets effected by "warm sectors". These are nothing special or exotic, just the area behind a warm front and ahead of a cold front.

Their summers are sunnier. Some places in that area (eg NYC) average up to 10 hours of sunshine a day in the summer months. Most places in the UK average 6-7 hours of sunshine in high summer.

As for "settled", perhaps not in general. It would vary by the year. If you want guaranteed settled, dry summers you really have to go to Mediterranean climates (eg the Med itself, California, Western Australia, parts of south Australia, western South America. Basically anywhere that exists on the cold side of the main permanent areas of high pressure in the world (being the Azores High, the North Pacific High, the South Pacific High, the Indian Ocean High - of all these, the Pacific Highs are typically the strongest and most dominant).

Yes they can be milder in winter than the UK, and also colder. And yes they are capable of bigger day-to-day changes than the UK.

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You have to keep in mind that NYC is at about 41.5 to 42 deg N, about the latitude of central Italy, so at all times of year they are getting considerably more insolation than the UK. If a winter pattern is mild and the trajectory of the air mass is from the southwest, the source may be the Gulf coast or even the deserts of the southwest U.S. with no snow cover between there and the northeast U.S. (but only in a mild pattern). So this explains why some winter record highs are well above anywhere in the UK.

However, to balance that out, the jet stream takes a much more southerly course in winter in North America on average than it does in Europe. There is a mean (avg) upper level trough at about 80-90 W that makes the average winter temperature in Iowa (due west of NYC) about -8 C in January (with quite a range). Now the average in NYC is more like -2 C but that is about the coldest monthly mean per century in much of the UK. So in general, the climate of the northeast U.S. is a wide variety of air masses, and year to year there can be huge differences. The average high in December in NYC has been as high as 9-10 C and as low as -3 C. Some winters have had many snowstorms and snow on the ground fairly continuously, others have had almost no snow and maybe one or two minor snowfalls.

This variety of weather is even more obvious in the Great Lakes area because of the addition of lake effect snow to the mix.

Meanwhile, in summer most of the northeast U.S. is much hotter than the UK or even northern or central France. Away from the oceanfront the average daily high in July is pretty close to 29-30 C in many places. The humidity levels are much higher than what you're used to seeing, dew points of 22-25 C are quite frequent. And it can get as hot as 40 C if there's a heat wave with westerly winds.

The weather patterns might be more similar in transitional months like April and October but still there is more variation in the U.S. climate then. North American weather systems tend to be more organized and air mass changes come very quickly, sometimes in March you can start out in the 15-20 C range and end up around -5 C or lower.

One thing that's similar is that prolonged periods of northeast winds bring cool, wet weather in the northeast U.S. and these spells are more frequent and wetter than they would be in the midwest states. Last June and early July were like that, day after day of low cloud, temperatures near 15 C and rain. This was quite unusual but such months do occur maybe once a decade or so.

Intense storms or tropical remnants are a big part of the climate of the northeast, you don't see similar storms in the U.K., to get one you would have to imagine a very deep low forming near the north coast of Spain and moving northeast through France into the North Sea, with the UK on the back side of that track getting strong northeast winds and heavy precip. I've never seen a storm quite like that, I suppose it has happened once or twice, but the U.S. coast gets these storms in all seasons and especially in the spring and fall months, if they get one in the winter it is usually a blizzard. The kind of low that comes in towards the UK from the Atlantic and creates strong winds also happens in this U.S. climate, and produces about the same kind of weather, although with more risk of tornadic wind streaks.

There are sometimes much stronger tornados in the northeast U.S. than in Britain, not very often, but for example there have been two F4 or possibly F5 tornados in the past 60 years in New England, one of which killed about a hundred people in Worcester, MA in 1953, the other one happened in Oct 1979 in Hartford CT but was much less catastrophic due to better warnings and some luck as to the track (it took out part of an airport). Now these really strong tornados are nowhere near as frequent as in Ohio or states further west, but they can happen, even as far north as parts of Ontario.

Final point, the northeast US especially inland from the coast gets hit occasionally by severe ice storms which are almost unknown in the UK, events where an inch or more of ice accretes to trees and power lines and causes millions of dollars in damages, I believe the only similar event in the UK in recent history was in Jan 1940, but these storms happen somewhere in the eastern US about once or twice a winter season. They are rare near the coast because if the set-up is good, the warm front usually pushes about 5-10 miles inland so it would be very unusual for New York City to get an ice storm, but quite normal for places just north and inland a ways to get one.

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I dont think NYC gets lake effect snow? in fact i heard that NYC isnt really as snowy as some people think. is this true. i think people get mixed up with the city and state when it comes to snow and lake effect, i dont think the city can get lake effect. someone correct me if i am wrong with that one. new york city weather can be similar to ours. this week the 5 day forecast show temps twic in double digits, with a couple of days below 4c and a an ice day. so its not exactly as extrme as new york state and places like chicago, etc.

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NYC does not get lake effect snow as it is on the coast and far from the great lake region...NY state does though as the eastern part of the state borders lake ontario and erie. NYC is located in the extreme southern tip of NY state and is sheltered somewhat from colder weather to the north and east by the Appalachain mountians.

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