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The real difference between Subtropical climates and Temperate climates from what I have studied/read...has much more to do with the genetic differences (prevailing air masses, wind zones, etc)...than rainfall or even temps:
In Temperate Climates like Seattle or the Pacific northwest (or 60% of the USA mainland for that matter), the theme 8 months out of the year is the prevailing westerlies, the frequent cyclones/anticyclones, and the changeable weather that are part of the climate character of locations between 40 and 55 latitude. Early mariners where well aware of these stormy latitudes when they got to observe them over the world’s oceans: They referred to them as “the roaring forties” …or the “furious fifties”. In these locations at sea - gale follows gale with brief intervening lulls. The weather is changeable and anything but steady most of the year.
In Subtropical Climates…the genetic factors are totally the opposite. In subtropical latitudes like the Mediterranean coast...much of the year the prevailing westerlies are to the north of these latitudes. Irregular, nonperiodic weather changes (while present) are much weaker in subtropical latitudes. For half the year (depending on the geographic location)…subtropical latitudes have a daily constancy not found in temperate latitudes. The French Mediterranean is at the very northern edge of the dry summer (or Mediterranean) climate, but even in this location the 5 months of the year have a stability in the weather.
The USA mainland is a much better example. Most locations in the subtropical portions of the country (from 30 to 34 latitude), like San Diego, Houston, Savannah, etc, have stability to their weather in terms of temperatures, sunshine, and diurnal regularity for 70% of the year. This is particularly true at the time of ‘high sun” (late spring, summer, early fall). During the high sun period…because subtropical latitudes border the low latitudes, where sun control prevails, they possess many of the tropics weather characterticds – chiefly among them stability. Storms, fronts, jets, changes in air masses…etc are the exception in subtropical latitudes. One day is much like another. Once the late fall rolls around (November or so), and the westerlies have pushed far southward, is there some changeability to the weather in the subtropics.
In climates like the Pacific Northwest (or any temperate climate), storms, fronts, highs, lows…etc are the normally prevailing factors that create the climate. In subtropical climates (Mediterranean or Humid subtropical) weather changes are at minimum during 70 % of the year.
Yes, I think from what I read the main reason why parts of the PNW is so dry in the summer has more to do with local topography than anything else. Seattle and Victoria are in a partial rain shadow which blocks out most of the moisture in July and August. There is some influence from the subtropical permanent high pressure zone but at 47-48 degrees north, it's so weak that it only provides stable weather for at most 1-2 months compared with say 4-5 months in more typically Mediterranean locales.
Looks like it’s a foot race between the high mountains of New Hampshire/Northern Maine…and the coastal Washington (both have about 180 hours per month). Most of the East Coast from Connecticut south to Georgia gets 220 hours…still more than anywhere on the West Coast north of around Eureka, California. I checked fall, from October through June, the coast of Washington has the least sunshine of anywhere in the USA (even the mts of northern New Engalnd). The big cities on the East Coast (NYC, Philly, Bailtmore, Washington) and the Atlantic coastal plain (Long Island south to Gerogia) get more sunshine any month of the year (and much more in winter) than anywhere in PNW. Also, look at the areas around Yuma and Palm Springs...and notice the subtropical rainy season from Savannah, GA south to Florida.
Yes, I think from what I read the main reason why parts of the PNW is so dry in the summer has more to do with local topography than anything else. Seattle and Victoria are in a partial rain shadow which blocks out most of the moisture in July and August. There is some influence from the subtropical permanent high pressure zone but at 47-48 degrees north, it's so weak that it only provides stable weather for at most 1-2 months compared with say 4-5 months in more typically Mediterranean locales.
Exactly:
When the Pacific High attains its north most position (July, August)…the weather in the PNW becomes just like the weather where the high dominates much of the year (say San Diego): Stable, semi-dry, sunny…etc. It works the same way here on the East Coast: This time of year the Middle Atlantic/Tri-State area is much more stable than in the winter months. This summer has been a classic steady Middle Atlantic/East Coast summer…hot, humid, warm nights, quick showers, and solar control is the dominate theme.
Although the Bermuda High lasts a little longer in the Middle Atlantic states than up in Portland or Seattle…nevertheless, come October, when the westerly flow moves southward, the number of storms, fronts, jets,…etc will greatly increase. Of course places like San Diego or Savannah, GA will experience these change only in a much more modified and sporadic form. It’s really only in winter/very early spring that subtropical latitudes have changeable weather (Dec to early April)
Now we know why 200 years ago, the rich folks like the Astors/Gettys in Newport, RI would have winter homes in Bermuda and Florida…they couldn’t take all the wild changing weather!
Looks like it’s a foot race between the high mountains of New Hampshire/Northern Maine…and the coastal Washington (both have about 180 hours per month). Most of the East Coast from Connecticut south to Georgia gets 220 hours…still more than anywhere on the West Coast north of around Eureka, California. I checked fall, from October through June, the coast of Washington has the least sunshine of anywhere in the USA (even the mts of northern New Engalnd). The big cities on the East Coast (NYC, Philly, Bailtmore, Washington) and the Atlantic coastal plain (Long Island south to Gerogia) get more sunshine any month of the year (and much more in winter) than anywhere in PNW. Also, look at the areas around Yuma and Palm Springs...and notice the subtropical rainy season from Savannah, GA south to Florida.
Interesting series of maps. It seems slightly different than the ones from the link I posted but yours are easier to read and are more detailed. Where I live on the East Coast (Western Massachusetts) gets no more sunshine than the PNW and maybe even slightly less than the southern portion.
I've noticed that the mountains of New Hampshire tend to be more overcast than other places in the northeast but not obviously. Coastal Maine (like Acadia National Park) always felt very cloudy, though, which the map doesn't show. Perhaps the map doesn't show enough detail to show its cloudiness or I just went there at a bad time. I think the clouds are only in the 5-10 from in coast.
Exactly:
This summer has been a classic steady Middle Atlantic/East Coast summer…hot, humid, warm nights, quick showers, and solar control is the dominate theme.
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This summer doesn't does seem normal. So far it's been one of the warmest on record for the Northeast.
Places like Long Island, NY get about twice the number of hours of sunshine as places like Seattle, London, New Zealand...etc in winter.
Here is December…the most cloudy month annually in the USA. A large area of the PNW gets less than 60 hours of sun....while only isolated spots of extreme N/W NY get 80 hours. Most of NY state gets 100 hours of sunshine in December. As you can see the Pacific Northwest stands alone in least hours of sun:
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You can leave New Zealand out of that comparison - it's patently false.
San Jose, California. Not unlike Melbourne in terms of temps year round....but they have 300 sunny dyas per year with only 366mm rainfall......surprising considering the very small distance to foggy and cold San Francisco.
San Francisco still gets 64% possible sun annually. Facts are more important than subjectivity.
This summer doesn't does seem normal. So far it's been one of the warmest on record for the Northeast.
Getting back to sunshine - for 6 cities listed in NY, NYC gets 58% annually and Syracuse is lowest at 46%. In Washington, the table says 43% for Seattle C.O. and 47% for Seattle-Tacoma airport, 55% for Spokane and 33% for Quillayute. For Oregon it only quotes Portland at 48%, but of course on the "lee side" things are much sunnier in that state I gather.
I know NYC is supposedly much colder and cloudier than it really is, most of what I read in the city vs city section is just hilarious, I don't go there (city vs city) anymore. I've had to prove time and time again that NYC isn't Minneapolis. I also read LA was very hot too lol.
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