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Most of Cali, Southern Nevada, many parts of AZ, you could even say ST. George,Utah(could be a stretch,though) all have very mild/warm winters. While back east in the south east its already dropping close or below freezing even before the Nov1st. 5 degrees in Nashville one Jan morning, last year the coldest was 10, I believe. Vegas which is on the same latitude as Nashville coldest temp ever is about 8 or 10 degrees. Redding, California is on the same latitude as NYC. Not only do they have skyscraper palm trees you find in LA and the rest of warm southwest, the weather is nothing like NYC. In Redding their winter lows could be consider a nice day as a high in NYC. In the east the closer you are to or better below 30 degrees latitude the weather temperature wise is close to southwest & Cali. So what makes the southwest keep so warm and mild in the winter?
First, the West Coast is insulated by the Pacific Ocean as the prevailing flow is West-to-East providing a marine/Mediterranean air mass depending on the latitude; whereas in the East a West-to-East flow yields a continental air mass either hot or cold depending on the prevailing wind.
Second, the West is much drier than locations out east due to the rain shadow effect causing most of the moisture is averted in the mountains east of the Pacific. The Eastern US has an endless supply of moisture from the Gulf of Mexico. Dry air has a lower specific heat than humid; in other words, it takes less energy for change the temperature. Therefore, while it may get warm in the daytime, it could get colder at night.
Third, sometimes the East is much warmer than the west. It depends on the prevailing wind flow from the Jet. That is, sometimes the trajectory is more favorable for colder air in the East than the West. However, other times the converse is true. This year for several other facts that would warrant a new thread, the trajectory favored a cold east winter.
Arizona's northern deserts are called rain shadow deserts. Northern Arizonas mountains, up to 9,600 feet, rob the deserts of the rain. So all that passes over the deserts is clouds because all of the rain is dropped on the mountains. Same thing happens with central nevada, the Central Valley in Cali, Denver, and Albequerqe. Also, the east experiences a different variety of weather patterns, bringing most rain out of the gulf or the northwest. The southwests rains are seasonal, usually happeining in Winter and Summer, whereas, it could rain any day back east, with the right conditions. Also, the ebntire southeast coast has warm water, and due to the gulf stream, makes conditions humid and moist, creating rain showers. The california, Oregon, and Washington coasts are filled with cold water and cold currents, bringing storms from the arctic instead of the tropics, which are always moist.
Most of Cali, Southern Nevada, many parts of AZ, you could even say ST. George,Utah(could be a stretch,though) all have very mild/warm winters. While back east in the south east its already dropping close or below freezing even before the Nov1st. 5 degrees in Nashville one Jan morning, last year the coldest was 10, I believe. Vegas which is on the same latitude as Nashville coldest temp ever is about 8 or 10 degrees. Redding, California is on the same latitude as NYC. Not only do they have skyscraper palm trees you find in LA and the rest of warm southwest, the weather is nothing like NYC. In Redding their winter lows could be consider a nice day as a high in NYC. In the east the closer you are to or better below 30 degrees latitude the weather temperature wise is close to southwest & Cali. So what makes the southwest keep so warm and mild in the winter?
Let me just mention a few things…because your perceptions seem a bit in error. First of all, you have to understand that last winter (2009/2010) was the coldest winter in the East/Southeast in 25 to 70 years (give or take). It was quite extreme in terms of temperatures.
In most winters…the southeast is warmer than the southwest. In the 3 month winter season (Dec/Jan/Feb)…only isolated areas of deep southern California and far southern Az are even close to as warm as areas of the Gulf/South Atlantic states. Here is a map of mean January temperatures – the first coldest month of the winter:
As you can see, mean temperatures in the southern half of the Gulf/South Atlantic States are in the 50’s…while only a tiny area along coastal California/Palm Springs area and southern Az have mean temperatures in this range (Nowhere in Utah has mean temps in the 50’s – in fact only a tiny area in the extreme southwest has mean temperatures above 40 –lol). If you look at the swath of places between 40 and 50 F…there is a much bigger area in the middle/upper South...than in the Western States. Even Nashville, which is one of the coldest areas of the upper south (do to topography), is still warmer than most of AZ and 80% of NV. Of course, the extreme lower East Coast (Florida) crushes anywhere in the West in terms of warm winters…Miami is 12 F warmer on average than San Diego in winter.
Not only are winters warmer in the Gulf/Southeast…but if you look at average annual mean temperatures (the daily average during the whole year)…the highest mean temperatures are in the southeastern USA. Here is a map of average annual mean temps:
As you can see…only a small area in the southwest has an annual mean temperatures of 60 F or higher (really just southern CA, a small part of AZ, and the tip of southern NV)….while a huge swath of the Gulf/South Atlantic states have mean temperatures above 60 F (from eastern North Carolina southward/westward to Texas. There is a much larger region in the warmer zone 1/2 in the lower Eastern USA...than in the lower Western USA. Most of the region in zone 1 and In fact, if you can see the 65 F isotherm (running from deep South Carolina west across Texas) is warmer than anywhere in the southwest outside of the deserts around Yuma/Palm Springs. Of course, the biggest area with annual mean temps over 70 F ...is also on the East Coast - Florida .
Also, another interesting thing…notice, that places along the Northern California coast and interior northen CA (Redding)...have annual mean temps not much different from the Middle Atlantic region. It’s only the 4 cold months (Dec – March) of winter than pull down the yearly average for places like NYC or Washington DC. Washington DC for example, has daily highs warmer than San Diego or LA for half the year.
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I understand why the West coastal areas are mild, but some averages of the inland West are a bit unusual.
Phoenix's average January high of 70F (21C) seems a little high - it's 33'N quite a distance inland. A comparable station in Australia would record 16-17C even on a sunny day.
Salt Lake City - I know it's in a desert, but it's also over 1000 m and yet still manages 33-34C averages, with Denver, the 'mile high city' still averaging at least 30C (86F). Nothing all that spectacular, but a location in Australia at a similar latitude (highlands of Tas?) would be typically 10-12C cooler. Of course totally different climates, and the US is much more continental.
The maritime influence of the Pacific seems to penetrate pretty far inland: to Missoula/the Bitteroot Ranges in Montana, and even beyond the Sierras to an extent (although they are the highest peaks in the lower 48).
Phoenix's average January high of 70F (21C) seems a little high - it's 33'N quite a distance inland. A comparable station in Australia would record 16-17C even on a sunny day. .
Gulf of California/Sonoran Desert in nearby Mexico perhaps?
I understand why the West coastal areas are mild, but some averages of the inland West are a bit unusual.
Phoenix's average January high of 70F (21C) seems a little high - it's 33'N quite a distance inland. A comparable station in Australia would record 16-17C even on a sunny day.
Salt Lake City - I know it's in a desert, but it's also over 1000 m and yet still manages 33-34C averages, with Denver, the 'mile high city' still averaging at least 30C (86F). Nothing all that spectacular, but a location in Australia at a similar latitude (highlands of Tas?) would be typically 10-12C cooler. Of course totally different climates, and the US is much more continental.
The maritime influence of the Pacific seems to penetrate pretty far inland: to Missoula/the Bitteroot Ranges in Montana, and even beyond the Sierras to an extent (although they are the highest peaks in the lower 48).
As you well know, there are many sources of data, and several don’t always say the same thing. Here is a map of average January Highs in the USA:
From what I can tell, there is no official NWS station in the USA outside of Florida… that has daily highs in the 70’s F (21 – 26 C) in January.
Daily highs in the 60’s (16 – 20.5 C) in January…in the Southwest USA occur mostly in the southern/coastal California (San Diego, Los Angeles, Palm Springs…etc) and southern AZ (Tucson, Yuma, Phoenix)…and in the Southeast USA occur along the coastal plain of the Gulf/South Atlantic region from coastal South Carolina southward/westward Texas (Charleston, New Orleans, Houston, Corpus Christi…etc). Only parts of the intermountin West, the upper Midwest, and far Northeast (upper New England) have daily highs below 0 C (32 F) in winter on average
In the above locations, latitude is the reason why most of these regions are the warmest in winter. On the East Coast/Gulf coast – the warm ocean waters also help to boost winter-time daily highs. On the lower West coast, even though the Pacific is cool (about 16 C ) in winter, it is far from cold. Also, lower West coast locations are located on the stable eastern sides of the the subtropical high...so truly cold air (below 0 C) is very, very, rare.
In summer (June – Aug) places like Denver and Salt Lake City, Utah has daily highs of 86 to 92 F (30 - 32 C). As you say, this is because the temps in the central/northern USA are more continental compared to Australia at the same latitude. However, at least 25% of the USA has daily highs close to 90 F (32 C) in July/Aug.
When you look at the USA as a whole...really its only the locations south of 34 latitude that don't have a continental rhythm to their seasonal temps...and even here the USA landmass is so big that they still have a bit of wider swing than normal for their latitude.
From what I can tell, there is no official NWS station in the USA outside of Florida… that has daily highs in the 70’s F (21 – 26 C) in January.
Are you talking about the mean high for January? McAllen, Texas averages a high of 69 F in January, but there are days within the month of January that average a high of 70 F. Same goes for Brownsville.
But generally you are right. Central and South Florida, and extreme South Texas are probably the only locations of the country that have average January highs around 70 F +.
Are you talking about the mean high for January? McAllen, Texas averages a high of 69 F in January, but there are days within the month of January that average a high of 70 F. Same goes for Brownsville.
But generally you are right. Central and South Florida, and extreme South Texas are probably the only locations of the country that have average January highs around 70 F +.
Yes, your right. I always forget deep south Texas on the Gulf Coast...there is a small area that has ave winter highs in the 70's (how did I not notice it was on the map above right in front of me ). In fact, someone said that deep south Texas on the Gulf is the only area outside of Florida than can grow coconut plams in the USA.
Let me just mention a few things…because your perceptions seem a bit in error. First of all, you have to understand that last winter (2009/2010) was the coldest winter in the East/Southeast in 25 to 70 years (give or take). It was quite extreme in terms of temperatures.
In most winters…the southeast is warmer than the southwest. In the 3 month winter season (Dec/Jan/Feb)…only isolated areas of deep southern California and far southern Az are even close to as warm as areas of the Gulf/South Atlantic states. Here is a map of mean January temperatures – the first coldest month of the winter:
As you can see, mean temperatures in the southern half of the Gulf/South Atlantic States are in the 50’s…while only a tiny area along coastal California/Palm Springs area and southern Az have mean temperatures in this range (Nowhere in Utah has mean temps in the 50’s – in fact only a tiny area in the extreme southwest has mean temperatures above 40 –lol). If you look at the swath of places between 40 and 50 F…there is a much bigger area in the middle/upper South...than in the Western States. Even Nashville, which is one of the coldest areas of the upper south (do to topography), is still warmer than most of AZ and 80% of NV. Of course, the extreme lower East Coast (Florida) crushes anywhere in the West in terms of warm winters…Miami is 12 F warmer on average than San Diego in winter.
Not only are winters warmer in the Gulf/Southeast…but if you look at average annual mean temperatures (the daily average during the whole year)…the highest mean temperatures are in the southeastern USA. Here is a map of average annual mean temps:
As you can see…only a small area in the southwest has an annual mean temperatures of 60 F or higher (really just southern CA, a small part of AZ, and the tip of southern NV)….while a huge swath of the Gulf/South Atlantic states have mean temperatures above 60 F (from eastern North Carolina southward/westward to Texas. There is a much larger region in the warmer zone 1/2 in the lower Eastern USA...than in the lower Western USA. Most of the region in zone 1 and In fact, if you can see the 65 F isotherm (running from deep South Carolina west across Texas) is warmer than anywhere in the southwest outside of the deserts around Yuma/Palm Springs. Of course, the biggest area with annual mean temps over 70 F ...is also on the East Coast - Florida .
Also, another interesting thing…notice, that places along the Northern California coast and interior northen CA (Redding)...have annual mean temps not much different from the Middle Atlantic region. It’s only the 4 cold months (Dec – March) of winter than pull down the yearly average for places like NYC or Washington DC. Washington DC for example, has daily highs warmer than San Diego or LA for half the year.
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You got hat right, 2010 winter was record breaking in the southeast. But this is an old topic before that winter. You are also right when you say in general the southeast is warmer than the southwest as a whole. But compare ATL, Charlotte, and Nashville weather to Vegas, Phoenix, and Sacramento. Definetly warmer in those cities any season of the year. Now if you compare lets say Utah,Nevada, Colorado, New Mexico and even some Arizona cities than yeah ofcourse its warmer in the southeast. You can say Socal, Phoenix, Tuscon, and Vegas(is the chilliest) has the warmest winters at similar latitudes in the world. I mean, look at LA. In any given January it can get close to 90 there.
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). In fact, someone said that deep south Texas on the Gulf is the only area outside of Florida than can grow coconut plams in the USA.
