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Christina Loren is a Certified Meteorologist with an enthusiastic passion for atmospheric science.

The Beauty of Science: Why Autumn Leaves Burst With Color

By: Christina Loren

Fall color is gradually becoming more conspicuous in California as summer swiftly comes to a close. Vivid reds, oranges, yellows, and purple hues of changing leaves will paint beautiful natural scenery from September through November, although peak color only lasts for around one to three brisk weeks.

Hours of Daylight Over Cooler Weather 

Contrary to what some may think, the reason why leaves change color in autumn is predominantly the product of available daylight hours as opposed to changing weather patterns. Picture worthy foliage is caused by changes in the process of photosynthesis which means, “putting together with light.” Chlorophyll is a chemical that makes photosynthesis happen and responsible for the green color of leaves. As days get shorter in the fall there is less available sunlight for the production of chlorophyll, which slows and eventually stops. Resultantly stunning fall colors are gradually uncovered before leaves wither and fall off of trees. Variables like temperature, wind, cloud cover, and soil conditions widely influence color intensity and duration of the foliage exhibit although they are not the main cause for the metamorphosis. 

Not All Trees Have Changing Leaves 

There are two primary types of trees: evergreens and deciduous trees. Evergreens stay true to their designation and hold on to their green color all year long. Meanwhile deciduous trees shed their leaves annually in the fall and then in the spring they grow back as days get longer. Deciduous trees are often called ‘broadleaf’ trees because instead of thin needles, they have larger and wider leaves making for a substantial surface for the photosynthesis process. 

Peak Fall Color 

Lake Tahoe: Late September through October 
Napa Valley: Mid-October through early November 
Big Sur: Late October 
Yosemite: Mid-Late October 
Big Bear Lake: Mid-October through early November

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posted by Christina Loren @ 1:14 PM, ,

Promise Falls As We Usher In The New Season

By: Christina Loren

     The Fall equinox will take place on September 23, at 1:21 a.m. PDT when the sun crosses the celestial equator from north to south. The Equinox signals that the length of day and night on September 23 will be nearly equal, about 12 hours long. Soon after the Autumnal Equinox nights will get longer than days and temperatures will dive down considerably in the Northern Hemisphere. Those who are fed up with the oppressive summer heat will be happy to hear that days will continue to get shorter, hence cooler, as we transition into Winter. There is typically increased moisture in the air in Autumn as storms begin to line up in the Pacific Ocean. California's rainy season begins in October and with a developing El Niño in the Pacific Ocean, higher than average rainfall this year looks quite promising. 
      Often referred to as 'harvest season' Fall is the time of year when many delicious fruits and vegetables have reached full maturation. These delectable items are ready to be gathered, sold, and stored before damaging frost develops in the cold winter months. Animals also take advantage of the Fall season by building up fat reserves for migration or hibernation. Overall the Fall of 2015 offers hope for ample rain, delightful produce, and cooler weather that we can all look forward to. 

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posted by Christina Loren @ 12:48 PM, ,

What is the 'Blob' in the Pacific Ocean?

By: Christina Loren

     You may have recently read snippets online or heard brief mentions on television of the warm 'blob' in the Pacific Ocean. The 'blob' refers to an unusually warm area of water in the Pacific that spans from Baja Mexico all the way up the west coast of North America, extending into the Gulf of Alaska. Ocean temperatures are running around 3- 4.5º F warmer than average in this sprawling area and the abnormality is linked to unusual weather conditions occurring on the west coast. You may recall that last winter we received a fair amount of rainfall in the Bay Area, but Tahoe saw very little snow. This occurred because most of the weather systems that moved over Northern California had ample moisture, but were too warm to produce heavy snowfall. This phenomenon can likely be attributed, at least in part, to the 'blob' in the Pacific Ocean.

      In addition to atypical weather patterns, the 'blob' is also producing difficulties for marine life since this area of warmer than average water is lacking critical nutrients. Typically this area is known for "coastal upwelling" which helps to churn up phytoplankton necessary for the food chain of marine mammals from the depths of the ocean. Normal upwelling is not taking place in this area of warmer, stagnant water and it is in turn nutrient poor. With the combination of a developing El Niño and the 'blob' it looks like the 2015-2016 rainy season could be one for the record books, particularly in Southern California.

Areas of red indicate the 'blob' of warmer than average water in the Pacific Ocean
that was identified in 2013. It extends from Alaska to Mexico and will likely persist
through 2015.

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posted by Christina Loren @ 2:05 PM, ,

Tarantula Mating Season Means Fall Is On It's Way

By: Christina Loren

     It is late August and tarantula mating season has started in the Bay Area. Male California Tarantulas are looking for love and instead of waiting for the cloak of nightfall, these nocturnal critters are coming out earlier, in the twilight of dusk. I saw this one on a a hiking trail in the South Bay hills. Tarantula mating season typically takes place late summer into early fall and after 5-8 years of maturing in solitude, males are on the prowl to reproduce with female mates. These large hairy spiders should be approached with caution although they are not looking to harm humans. They have one thing on their mind and that is reproduction. When I encountered this one it stopped in the middle of the trail and remained completely still until I moved along. Male tarantulas are searching for the females silk-lined burrows. Hopefully this guy was able to find one later in the night. What is interesting is that after male tarantulas find a mate they only live for an additional 3-6 months whereas females can live for another 25 years. Tarantulas are most commonly seen by humans in the high elevation trails, roads, and even gardens of the Bay Area.

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posted by Christina Loren @ 12:33 PM, ,

A Simple Explanation of How Hurricanes are Named

By: Christina Loren

Tropical storms and hurricanes are capable of devastating large populations and destroying wide swaths of property. Although the National Hurricane Center does the heavy lifting of forecasting and tracking tropical cyclones in the United States, they are not responsible for the names that these powerful storms receive. Instead, the World Meteorological Organization is in charge of naming tropical storms and hurricanes. Tropical depressions do not get names unless they strengthen and develop and meet certain criteria. Simply stated, a storm must have max wind speeds of 39 mph or more around a closed center of circulation in order to reach tropical storm strength and receive a name. If max winds reach 74 mph or more around a closed low, the storm is then upgraded to a hurricane.

During hurricane season it is not uncommon for multiple tropical cyclones to occur at the same time. Assigning names to these powerful systems helps to eliminate confusion and eases keeping tabs on the track and intensity of each storm. That is why the WMO creates a list of names in alphabetical order that can be repeated after a six year interval. However, when a storm is exceptionally destructive, such as Hurricane Katrina or Hurricane Andrew, the name is retired.

Hurricane Irene
August 20, 2011 - August 28, 2011

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posted by Christina Loren @ 1:28 PM, ,

What is El Niño?

By: Christina Loren

        An interesting meteorological phenomenon that dictates weather conditions for a given area is the influence of coastal winds on ocean currents. In the open ocean surface currents are directly impacted by global wind patterns. Simply stated, El Niño describes a change in trade wind patterns leading to unusually warm ocean currents in the Pacific Ocean. This alteration in surface ocean temperature has a tendency to create extreme weather changes, specifically between October through March, with peak conditions from December through February. Some of the impacts typically associated with El Niño are a lack of precipitation for parts of Indonesia and Australia and the development of strong storms packed with ample moisture that tend to aim at California and areas in the southwestern United States. Although these effects are characteristic of a strong El Niño pattern, there is no guarantee that this year's event will produce the flooding rain we saw in 1997-1998 in California. In the same way that no two storms are the same, no two El Niños are the same either. There are other atmospheric variables at play that will likely influence how this year's rain season will pan out. Nonetheless, I would be willing to bet that El Niño will at the very least provide the state of California with average rainfall for the 2015-2016 rainy season.

Read Christina Loren's answer to What are the explanations of El Nino? on Quora

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posted by Christina Loren @ 12:27 PM, ,

Wild Weather at 10,023 feet on the Haleakala Shield Volcano

By: Christina Loren

The summit of Haleakala is 10,023 feet above sea level and a stunning location to watch the sunrise. Haleakala is a shield volcano and formed over 75 percent of the island of Maui. The weather at the summit of Haleakala changes rapidly and on any given day the weather can vary dramatically from sunny and hot to rainy and cool in a matter of minutes. There is typically a 30º difference between temperatures at the summit of Haleakala vs. the temperature on the coast. Rain is common on the volcano so if you plan on visiting it is a good idea to prepare for a variety of differing weather conditions and rain gear as well as sun glasses will likely serve you well on the same trip. 

Christina Loren on Vine:

 Sunrise from the summit of Halakeala at 10, 023 feet at 5:50 a.m.

The Shadow of the mountain paints a purple haze at sunrise on top of Haleakala.

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posted by Christina Loren @ 12:50 PM, ,