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On Weather & Climate Through the Eyes of Mark Vogan
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Desert Southwest Heatwave 2010
HOW DOES THE CURRENT HEATWAVE COMPARE WITH RECENT YEARS? HAS THE MOIST SOUTHERLY FLOW DENTED THE HEAT?
I have studied Southwest heatwaves for the best part of 10 years now and have written many articles on the dynamics of the American Southwest summertime heat pattern.
One must remember when looking at heat in the Southwest, there are many factors/aspects to be considered.
(1) Where the high pressure center positions itself over the region
(2) How strong the high pressure becomes overhead
(3) How large the area of "highest or strongest heights" within a high pressure cell stertches can mean small or large area coverage of record or extreme heat compared to location "averages". For example I've seen Phoenix top 115, whilst Las Vegas is only 106, or Las Vegas is 116 and Phoenix is only 108, this is caused by a sharper drop off in pressure heights within the high pressure cell itself and is often centered closer overhead to the region or city that's hottest. We can also find times, when temps reach extreme levels across most of the West, a great example of this was 2006 when Salt Lake topped 105, Las Vegas 116 (1 degree shy of all-time record), Phoenix 118, Death Valley 129 and even Downtown LA as warm as 101, this was an example in July 2006 when a huge high was over 690decameters (extremely powerful high) covered most of the Western US, in fact highs topped 97 up in Seattle the same day Palm Springs climbed to a record for July of 121 and Phoenix reached 118, the hottest in a decade. The area of maximum heights aloft can be very small or very large depending on surrounding weather system influence. Sometimes a trough or low pressure over the Gulf of Alaska can weaken the Four Corners High or it can actually pump it up. Often the deserts could be in the 115 range as close to the coast as Palm Springs, CA whilst a mere 200 miles to the west, Downtown LA may be only 80 or even cooler and the coast in the 60s, this is often when the Four Corners High is further east and the Pacific High has more influence near the coast, bringing morning fog/cloud and a stiff onshore breeze during the daytime, keeping temps down.
(4) Complex topographic varitation in both mountain alignment and their marine blocking as well as elevation variation can greatly alter surface temperatures within just miles.
Another major factor is when the Four Corners High is further east, say over eastern Arizona or New Mexico. That is exactly what we're seeing now and therefore, despite pressures being strong over the entire Southwest, all the way to the Pacific Ocean, moisture is being allowed to flow up from Tropical Mexico and is aiding in two things... High dew points in the 50s and 60s (for this regions standards), making the air feel exceptionally uncomafortable to a people more use to "dry heat", it's also allowing the development of mountain thunderstorms, some of which are fairly powerful and are migrating from the mountains into surrounding valleys and basins, not only supressing daytime heating or even cooling the air but are creating localised windstorms as these thunderstorms are releasing downdrafts, creating damaging windstorms. A great example of this was a few days ago in Palmdale, Calif, which endured power loss in stifling, sticky heat! Lightening from these storms are also creating an enhancement in the fire risk.
I believe the increase in moisture levels in the lower atmosphere from the Rockies to Ocean is what is reducing highs at Las Vegas and Pheonix to the low 110s but keeping nights hotter for the same reason and even in Death Valley which hasn't climbed above 125! It looks as though, we're going to also find that Death Valley has yet again remained above 100 degrees for the low!
Southwest Heatwave in the Media
It's hot, humid and smoky
Los Angeles Times
Dangerous heat scorching Las Vegas
Las Vegas Sun
Surviving the Valley in the summer is a matter of degrees
AZ Central (Phoenix)
It’s official: Triple digits bake the state
Salt Lake Tribune
Brief storm cools down Reno
Reno Gazette Journal
your america today forecast
by mark vogan
southwest
It appears some spots will see their hottest of this current heatwave and others may shave a few degrees off yesterday. I do believe some areas, like yesterday, particularly over the mtns, will see thunderstorms blow-up and these may either build across valleys and basins or will release cooling downdrafts, dropping low-elevation temps. I do expect highs along the immediate beaches of Calif to see the cooling, with a range in highs of, 60s on the central coast to upper 70s down by the Southland beaches, lower than the mid-80s the past few days, Downtown Los Angeles may still touch near 95 like yesterday. To the east of the coastal ranges and it's another brutal hot day with Palm Springs topping out near 117. To the north and higher in elevation, Barstow in the west high Mojave should get near 113, unless mountain storms blow in nearby mtns. To the south east and over the lower elevation Mojave, it could get close to 120 at Baker whilst Death Valley warms close to 125 like it did the past two days past. Las Vegas and Phoenix both should warm to 113 after a morning which only "cooled" to around 90, courtesy of the urban heat island! Lows tonight range from a refreshing 60 at the coast, 65 in DWN LA, 70 east of the mountains, near 80 for the desert and 90 for Vegas and Phoenix. Death Valley 95.
Today's Weather across America
From AccuWeather
Thunderstorms To Ride Rim of Heat Through Midweek
AccuWeather
Heat Wave to Bake the South, Plains
AccuWeather
Lightning Injures 3 on Friday; Tips to Avoid Same Fate
AccuWeather
Tornado Threat From Dakotas to Wisconsin
AccuWeather
Weather Talk
By Mark Vogan
IMAGE COURTESY OF WIKIPEDIA
UPDATED!
101 degrees in central South Dakota, 110s in Desert Southwest
Though it's hot across much of the US, has it been all that bad across the Southwest?
When looking purely at the numbers, the nighttime lows are impressing me more than the daytime highs at such locales as Las Vegas and Phoenix to be perfectly honest. Highs topping out at around 111-113 is pretty "average" heat when looking at true heatwaves in this region. In recent years, one could argue that times are heating up across the Desert Southwest with Vegas experiencing the greatest rise in temperature, perhaps a direct result of the rapid growth of this city? Nights are evidently getting warmer, it's holding above 100 for longer into the night and becoming harder for the temperature to drop. The past few nights have seen lows fall to only 90 or 91 degrees, that number for a low appears to becoming more common than say 10 years ago.
During one of the worst ever heatwaves the city has experieced was in 2005, I remember following it day in and day out. That July saw Vegas top 110 NINE days in a row, a remarkable four straight days at or 115 or higher, three days at 116 or higher and indeed the pinacle of this epic heatwave was a day which tied the all-time record at McCarran International Airport of 117 degrees. We also saw sweltering nights.. 5 mornings's in a row above 90 for a LOW. On the morning of the 17th, the city saw a new record for the warmest night on record, the low fell to only 93 degrees. However what was more facinating was the fact that two nights later, that "new record" would fall when on the morning of the 19th, the "low" only dropped and stopped at 95 degrees, a new all-time record for the warmest night ever in the city. That sweltering low that morning, set the base for what would be a tie of the all-time record high at Las Vegas that same afternoon.
In 2007, Vegas got mighty close to once again reaching their all-time maximum. only the thermometer stopped at 116 degrees.
As for the current heatwave of 2010, the warmest high so far is 113. That isn't that bad... sure, it would feel darn hot to walk out in, but in terms of Las Vegas standards, 112 degrees is "average" when it comes to year by year heat when the Four Corners ridge builds over Southern Nevada. Afterall it's pure desert here, it's a large valley that's locked in by mountains and therefore no marine air can enter the valley. The lack of moisture in the air and the sheltered location, well away from oceanic modification in temperature, means to me, anyway, it should not be that difficult to raise the temperature to 110 in Vegas when the high is firmly in place overhead. Sure, it's tougher to get 115 or above, due to the fact you have to have more factors come together perfectly... core of high directly overhead etc etc.
I think with this current "heatwave", though it's hot for sure, a lot of the reason why we aren't seeing those 114s or 115s is because of the POSITION OF THE HIGH, though strong over the Las Vegas Valley, a further east core and the clockwise flow pulling moisture north from Mexico is bringing dew points up to near monsoonal threshold, increasing moisture levels in the lower atmosphere and therefore, what would have been 114 or higher at the surface in both Vegas and Phoenix is lower because, some of the sun's energy is being used for evaporation, rather than heating the surface. This could also be aiding in holding nights unusually warm for mere 111-112 degree days... A drier lower atmosphere would not only raise surface temperatures than what we have seen so far but would be needed in holding nighttime lows above 90, but the "wetter air" is making for more uncomfortable conditions for people more use to dry heat, it's also holding daytime highs down but nighttime lows up. The moist air may also be responsible for what appears to have been a 101-degree LOW yesterday morning at Furnace Creek, Death Valley.
Vagaries of the Weather
India & Sub-Continental Asia Weather
By Rajesh Kapadia
Saturday, July 17, 2010
Mumbai rains and water position as on 15th. July:
Rainfall at Colaba: 1411 mms (+452)
Rainfall at S'Cruz: 1318 mms (+351)
Rainfall at the
Lakes:Vihar150mms,Tulsi:1100mms, Bhatsa: 865 mms, Tansa: 66mms,Vaitarna: 562 mms, Upper Vaitarna: 504 mms.
Lakes Storage Full Capacity: 13.0 mllitres :
Lakes Storage as on 15th.July 2010: 2.42 mllitres
Lakes Storage as on 15th.July2009: 1.85 mllitres
Lakes Storage as on 15th.July2008 : 3.88 mllitres
Lakes Storage as on 15th.July2007: 6.23 mllitres
Lakes Storage as on 15th.July2006: 8.04 mllitres
Lakes Storage as on 15th.July2005: 8.67 mllitres
Average of last 5 years Storage as on 15th. July: 6.71 mllitres.
Normal Requirement of City /Month: 1.02 mllitres
Supply today/ Month: 0.87 mllitres
So Today, we have a stock of 3 Months supply !
READ OUR PARTNER'S BLOG IN FULL HERE!
What's Reaching Today's Blogs?
Another Bad Day for Tornadoes across Minnesota into Iowa
Henry Margusity, AccuWeather
Today's US Extremes
Courtesy of AccuWeather
High: 123 degrees at Death Valley, CA
Low: 34 degrees at West Yellowstone, MT
Today's UK Extremes
Courtesy of the Met Office
High: 72 degrees at Andrewsfield
Low: 46 degrees at Albemarle
Today's Extremes here at my house
High: 61 degrees
Low: 53 degrees
Thanks for reading.
-Mark
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