Eastern Pacific Hurricane Watch - Reading a Surface Chart Pt 2
Updated June 23, 2010 - Although the Eastern Pacific is beginning to spawn tropical cyclones at a pretty good clip, the Baja tropical cyclone season is still a ways in the future. So, while we will run down the possibilities of tropical cyclone formation in the Eastern Pacific, we are also going to spread a little information about how to read a Surface Chart. This is part two of the three part series. Click here to read part one. Yes, it started out as a two part series, but with so much information in Surface Charts, we'll need part 3.
If you are just here to see what is in store for the next few weeks and a strategic look at the possibilities of tropical cyclone formation in the Eastern Pacific click here.
Reading a Surface Chart - Part 2
What is a Surface Chart? ( Click here to see the current Eastern Pacific Surface Chart) It is a map of weather conditions and forecasts for the next period. According to Answers.com a Surface Chart is as follows:
"An analyzed synoptic chart of surface weather observations; essentially, a surface chart shows the distribution of sea-level pressure (therefore, the positions of highs, lows, ridges, and troughs) and the location and nature of fronts and air masses, plus the symbols of occurring weather phenomena, analysis of pressure tendency (isobars), and indications of the movement of pressure systems and fronts. Also known as sea-level chart; sea-level-pressure chart; surface map. "
The first surface charts were created in the middle 18th century from information from reporting stations. Through much of weather forecasting history most of the tools used to predict the weather come from each of these stations. It is only in recent years that satellite imagery, radar and other high-tech tools have supplanted the station report as the most valuable tool in forecasting. Today, through the internet, the National Weather Service also takes in data from thousands of civilian weather stations, connected to home computers around the globe. There are more than 
650 civilian reporting stations in Los Angeles alone. This large number of data points are obviously not plotted on the weather charts we see here, but add to the amount of data and understanding of weather anomalies and future forecasting techniques.
Therefore, it is arguably said, that the station model is the most important weather feature on a surface chart, as almost all other features are drawn from its data. The station model is in fact, jam packed with lots of information in a tiny little space. Unfortunately, to conserve space on the map one needs to write in code. Station models are coded to express almost all weather phenomenon. From the station model ascertain weather closer to you and if you are a sailor, predict the best course to plot for the wind and seas.
Station models are also probably the most prolific of all features on the surface chart as well. Looking like so many tiny golf course flags scattered haphazardly across the map, most are airports and military installations with calibrated instrumentation. Some reporting stations are ships as the example above shows. This is most likely the US Coast Guard Cutter running interdiction off the coast of Baja. There is also a seemingly endless number of symbols applied to Station Models and we will cover the most significant. There are so many different symbols that in my research I did not find one site that defined all of them. (here are some of the best examples found... Station Model Symbols01 Surface Model Symbols02 and Station Model Symbols03)
The graphic left shows a majority of the information provided in a standard Station Model. Click in the descriptive titles to learn more about each of the weather characteristics encoded in a Station Report.
There is additional data that can be included in the Station Model, but these are the most common and most useful to those using surface charts to predict the weather in their area.
The first frame shows a semi-complete Station Report. By clicking on Layers 1 and two you can view the definitions of each of the code locations.
If you want to test your understanding of Station Reports and Surface Charts click here to see the World Detail Surface Chart for today (3mb PDF)
Looking at Eastern Pacific Tropical Cyclones in the two weeks ahead...
June 23, 2010 - The Eastern Pacific has been a busy place the last 6 days. First we had Tropical Storm Blas, a mild system that moved west from the Tehuantepec into the cooler waters of the central Pacific. Now we have Hurricane Celia which once threaten to not only be the first hurricane of 2010 in the Eastern Pacific, but the first Major Hurricane as well. Now it appears Celia has passed it's peak at Category 2 and will also ,meander off into the Central Pacific. As this article is written, Tropical Storm Darby is building, and is expected to also become a hurricane over the weekend.
When we look at the Wide Angle Surface Chart for Wednesday, June 23, we see there is no shortage of tropical waves (orange arrows) headed toward the Eastern Pacific. Three more tropical waves are likely to pass through the basin by next Wednesday. Then it appears we'll have a several day gap toward the end of next week, before the next wave, which has yet to be generated over the deserts of Africa makes it to the Eastern Pacific.
More below...
Sea Surface temperatures give us a strategic look at where storms might form. When taking a look at this weeks Eastern Pacific Sea Surface Temperatures we see the 
evidence of the passing of three tropical cyclones in the stretch between the southern coast of Mexico and the Central Pacific due west. The +30°C water has disappeared and the 28-29°C water has diminished as well. Tropical cyclones are natures engine for disseminating equatorial energy northward, away from the blistering heat of the summer sun.
The Sea of Cortez warmed a little, particularly in the NE corner, but the all-important 26°C thermo cline changed little in position. In fact, south of Cabo San Lucas, the Pacific continues to cool. Since the 26°C thermo cline remains well south of Baja the potential for landfall here of a tropical cyclone is very remote. for at least another month. The cyclonic action generated by a tropical cyclone depends on gathering energy from waters warmer than 26°C. Until that warm water reached the coastline of Baja Sur, there is little chance of a storm of cyclonic action to reach our peninsula.
The Sea Surface Anomaly graphic right continues the good news for Baja. Almost all of the Eastern Pacific basin is at or near normal sea temps for this time of year. From the perspective of the energy contained within the ocean's surface, it means we should be having a normal year.
This in fact is true. At the moment we are right on track for a normal year with an average number of named systems and hurricanes generated so for in 2010.
We do see a very small area in the NE Sea of Cortez that is slightly above normal (appears yellow) in the June 19 SST Anomaly graphic right. The good news is that big blue hole developing south of Cabo San Lucas. This region is 1°C below normal and more. This doesn't mean we won't get a tropical cyclone, but it does mean there is less energy there to create or fuel a storm headed in our direction.
But that's right now. These fluctuations take place to the tune of 3-6°C +/- over the course of the season.
Oil Spill Brings Gulf of Mexico to a boil...
Our fellow hurricane sufferers in the Atlantic may not be so lucky. When we look at the Atlantic Basin, we can see the route that the tropical waves take across the Atlantic is almost ALL above normal. (yellow arrow) Another interesting factor is the VERY warm water developing off the coast of Louisiana, (red arrow) nearly 6°F above normal for this time of year. There are certainly several mitigating factors which could be contributing to this over temperature water, none the least of which could be the oil contamination from the BP spill. Curious how the over-temp water nearly conforms to the Spill Map on CNN's website! Should this warming trend continue in this region massive coral bleaching and environmental damage could result from the warming of the waters alone.
So now for the fun part...
In every Eastern Pacific Hurricane Watch Report I take my best shot at a strategic look at the two weeks ahead.
I started off with a bad week, but last Watch Report nailed the generation of Blas and Celia down to the tropical wave that spawned them. Tropical Storm Darby arrived in the cusp, between reports, so we'll just ignore that. (hey, it is my statistics, I make the rules!)
I expect with whatever energy Darby is able to eke out of the Eastern Pacific, we'll be pretty wrung out for a while. A Tropical system may develop in the Caribbean (yellow arrow on wide-angle graphic) and absorb much of the energy from the first of three waves headed our direction. Then we will have a several day break in tropical waves.
I expect as we near the first of July we'll get another parade of tropical waves and by then the kinetic energy stored in the surface waters of the Eastern Pacific should be ready to spawn two more storms before the 4th of July. I expect the first of the two will achieve Major Hurricane Status and both will move off into the Pacific.
But what do I know...
Our Hurricane Watch Reports will be issued every two weeks until mid August, when our Tropical Cyclone threat begins to heat up. So look for this report again on July 5. Until then, fair winds....
Tomas Zyber
Our Eastern Pacific Hurricane Watch is an editorial/entertainment analysis of data from the National Hurricane Center, NASA and NOAA and is based on information provided by the same, but is an amateur endeavor. For actual storm information readers should refer to notices and warnings posted by the National Hurricane Center. or visit the Mexican Nation Metrological website for more information.
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