New England Snowstorm Summary...

Well, parts of New England had quite a nice snowstorm.  Where my parents live in northern Rhode Island, they received a heavy, wet 6 inches of snow.  This is the type of snow that plasters everything and weighs down branches and power lines.  In fact, my parents lost power today from the wet snow.  The storm started in the wee hours of the morning and was more or less finished by 1 or 2 PM today.  I am trying to find some snowfall totals from the storm, so stay posted.

Snowstorm for New England on Monday?

Take a look at the latest run of the North American Model. This is the 18Z run, which is much snowier for Rhode Island and southern New England than the earlier runs. As it stands now, portions of the region are predicted to receive 1.00" in liquid equivalent precipitation. Depending on the liquid content of the snow, this amount of precipitation would produce anywhere from 10 to 20 inches!!!!! The GFS model is not as impressive with precipitation amounts, but it does produce a 4 to 8 inch snow event.

The North American Model has the storm beginning in the wee hours of the morning on Monday, January 14th and wrapping up later in the evening. We will need to monitor future model runs as we get closer to the event, but if this scenario plays out, then we have a nice little snowstorm on our hands.

How does a strong jet influence storm strength?

First off, what is a jet stream? A jet stream is a fast flowing river of air in the upper atmosphere that steers our storms. Within the jet stream, there are pockets of air that are moving fast. The faster moving pockets are called jet streaks. We usually look at the 250 mb level to detect where the jet stream and its associated jet streaks are located.

Next, how does the jet streak influence storm strength? When a strong jet streak is positioning itself correctly over a surface low pressure, upward vertical motion is enhanced. The enhanced motion can lead to explosive storminess. Many times, a relatively innocuous storms explodes into a monster that means business when the strong jet streak comes to town.

What does pressure have to do with storm strength?

I recently was asked why a 960 mb storm means that the storm is strong. Before fully answering the question, we need to understand the definition of air pressure. Air pressure is the weight per unit area of the air in the column above our head. Therefore, as we go up in elevation, less air is above our heads, and hence, we see a corresponding decrease in air pressure. At the surface, low pressure indicates inclement weather whereas high pressure is more commonly associated with fair weather.

Next, we need to understand why a low pressure would be a favorable location for inclement weather. In order to understand this, we need to know something about the pressure gradient force. The pressure gradient force is the force that acts from high to low pressure. In other words, air flows from regions of high surface pressure to regions of low surface pressure. Many of us have seen the pressure gradient force in action when we fly. When you open your water bottle to take a sip when flying, you fill the bottle with lower air pressure. Once the plane lands, we are at ground level where pressure is higher than it was in the cabin when the plane was aloft. We notice that the bottle appears to be crunched together. This crunch occured because the pressure inside the bottle is lower than the pressure outside the bottle, and effectively squeezes int he bottle. The same thing happens in the atmosphere. As air flow in from all sides of the low pressure region, it converges. Because air cannot enter the ground, it is forced to rise. This rising motion leads to stormy weather.

So when we ask what pressure has to do with storm strength, the simple answer is that a lower surface pressure causes stronger convergence, which means we have more vigorous upward motion. The more vigorous upward motion creates stormier weather. Of course, this is a simple explanation to a more intricate phenomenon.

California Radar at 6:30 PM Pacific Time...

Check out this radar. The heaviest rain is just starting to affect the area, as I predicted in earlier posts. If you are located on the south or southwestward side of a mountain, expect even heavier rains in your location due to orographic lifting. In this radar image, you can almost see where the mountains are located by tracing the yellow radar echoes from Santa Barbara to north of Burbank. The rain is heavier in these locations because of the air being forced to rise over the mountains. From this point on, the rain intensity in Los Angeles is going to be picking up. Furthermore, expect winds to increase in speed. I am expecting 25 mph winds, with the occasional gust to 40 or 50 mph. My current forecast looks right on track.

Current Radar Imagery...

Take a look at the current radar imagery. This image is valid as of 11:45 AM Pacific Time. The central and northern coast is getting battered by heavy rain and high winds, and this is only heading south. The culprit? A 960 mb storm off the Pacific Northwest, associated with a strong jet slamming into the West Coast. This precip is working down the coast, and just beginning to reach the Los Angeles area. Expect on and off showers this afternoon with pick up in intensity tonight. All that green and yellow is heading towards Los Angeles, so start building your Arc!

Update on January 4-5th California Storm...

I just finished taking a look at the latest model data. I am going to break it down using two of my favorite models--the GFS and the NAM.

Here is what the GFS predicts:

• Between now and Sunday night, the model is projecting about 3.5 inches of rain to fall in Los Angeles coastal plain.
• Rain begins today, and picks up in intensity through the evening. In a 12 hour time frame, from 4 pm to 4 am, we can expect to see upwards of 2 inches of rain!
• Most intense winds occur late tonight, with winds sustained between 25 and 30 mph. We can expect gusts up to 45 mph.
• Next heavy dose of rain for the area focuses between 10am and 4 pm on Sunday, with about 0.75 inches of rain falling during the time period. This episode of precipitation brings the chance for gusty winds--comparable to what we can expect tonight and perhaps a bit stronger.
  
• On and off rain between the two heavier periods, but most of the 3.5 inches should fall between 4 pm and 4 am tonight and then again on Sunday.

Here is the NAM prediction.

• Very similar to the GFS, but not as wet for Los Angeles proper. Although it is slightly drier, the model is still projecting about 1.25 inches of rain during the 4 pm tonight to 4 am tomorrow morning time frame.
  
• Comparable with wind to GFS for tonight's event.
• Also drier and later with Sunday's system. NAM predicts next bout of precip to fall from 4 pm to 10 pm on Sunday evening. According to NAM, we can expect 0.25 to 0.75 inches of rain from this system.
• Furthermore, the NAM is not as windy as the GFS in regards to Sunday's system.

What is my thinking? I think we are going to get a lot of rain tonight, which can be made worse by gusty winds. I am expecting more rain to fall during Sunday afternoon/evening time frame, but I will need to monitor the winds with that event. My suggestion? Go out now, rent some movies, puts on your pajamas, and enjoy the night in your house.

Humidity

I just got off the phone with my friend Tressana, and told her to check out the latest observations in Rhode Island. She is sitting in her warm apartment looking out the window at 55 degree weather while I sit here freezing. I think God is answering menopausal women's prayers, because there is no way anyone could sweat in this cold. Anyways, Tressana noticed that the relative humidity is high in Rhode Island. She asked me how that could be true if the temperatures are so cold.

The answer is that relative humidity is a relative number. In other words, the higher the temperature, the more moisture that air can hold before the airmass is saturated. The opposite also holds true, in which lower temperatures are able to hold much less moisture. As a result, we could have a lot of moisture in the air, but a very high temperature would mean the air could hold a lot more moisture. Hence, the air is dry relative to the amount of water the air could actually hold. In this case, we would see a LOW relative humidity. In the case where the temperature is very cold (as in Rhode Island tonight), the air can only hold very little moisture. As it turns out, there is some moisture in the air, but only a small amount. The truth is that this cold atmosphere couldn't hold much more. In this case, we have a HIGH relative humidity because the air is already holding almost as much moisture as it possibly can.

Yep! It is 1 degree out!

That's right folks. I am writing to you huddled under a blanket sitting in my oven to catch any warmth I can find. It is only 1 degree F out at 2:40 AM!!! This is quite a cold blast, but I expect a moderating trend to occur over the next few days. Rhode Island's temperatures will start out frigid tomorrow morning, but will recover to the upper 20's and lower 30's. By the time the weekend rolls around, expect high temperatures to be in the 40's. During ealry next week, I am expecting parts of the area to reach highs near and around 50. But all I have to say now is that 50 is 49 degrees away!

BIG STORM IN CALIFORNIA!!!!

Seriously folks, this storm looks big. Was checking out the latest model data, and I expect that we will see a lot of rain and wind from the upcoming series of storms. We have 3 different systems affecting the area, and the second in line will be the most potent. Because I live in Los Angeles, I am going to focus on that area.

Here's what I expect:

The first pulse of energy slides through tonight, bringing with it the chance for some rain.

Tomorrow, the second and strongest system begins to slide down from the central California coast. I am expecting winds to increase through the day to a sustained 20 to 30 mph. If we look at winds at the 850 mb level, which is about 1500 ft (roughly) off the ground, we see sustained winds between 40 and 50 mph. With lots of vertical motions in this storm, I wouldn't be surprised to see some of this higher momentum air brought to the surface periodically. As a result, don't be surprised to see gusts in the Los Angeles area up to 40 or 50 mph. When we head to canyons, passes and mountains, all bets are off. With a strong southerly flow, we can expect lots of orographic enhancement in terms of precipitation. What this means is that as air flows towards the mountain and is forced to rise, the air will wring out even more precipitation. This is sort of like squeezing a wet sponge of all the remaining water. In coasts and valleys of the Los Angeles area, expect anywhere from 2 to 5 inches of rain. When we look at regions experiencing orographic enhancement, I wouldn't be surprised if we saw up to 10 inch rainfall amounts!!!!! And lest we forget the wind! This will be a storm to remember.

The last pulse, which is the middle sister in terms of strength, will bring with it another chance of rain. This system will be much colder, so we could see snow levels dipping to about 4000 ft. Expect rainfall amounts to measure from .5 to 1.5 inches.

Anyways, I based this forecast on a cursory look at all model data. I am a little crunched on time, but this is my best guess at the moment. Oh, and wish me luck! I am flying back to Los Angeles from Boston, and I expect to land just when the height of Friday's storm begins to pick up! Ughhh!!!! Let's just hope the pilots know what they are doing!

FREEZING OUT!!!!

My blood must really be thinning out because I feel like I have icicles forming on my nose and fingers. Just checked the thermometer and found the temperature has dropped all the way to 12 degree Fahrenheit!!!! And it is only 9:55 PM ET. That means that the night is only going to get colder. Just so you know, the coldest part of the night occurs just before sunrise. The reason for this is the ground is emitting infrared radiation all night long without receiving any input from the sun. So basically, the ground is losing energy to space, which means that it continues to cool. Once the sun starts to shine above the horizon, then the cooling stops and things begin to warm up. Unfortunately, tomorrow's sun is going to be useless! The forecast is for high temperatures to hover around 15 degrees F. This is why California can be so nice in winter....we don't need to put up with this crap! I love the snow--hate the cold!

Welcome!

Welcome to a blog devoted to my love for all things weather related. I have been visiting my family in Rhode Island for the past couple of weeks, and storm after storm has been hitting the area. Because I live in southern California, I forgot how excited I get when I know a new storm is heading in my direction. My focus on this blog will be to discuss upcoming, present and past storm events and anything that is related to severe weather phenomena. If you ever have a weather related question, please feel free to ask. I may not always know the answers, but I am sure I can try to at least find one.