Eastern Pacific Hurricane Watch - Reading a Surface Chart Pt 2
Updated July 19, 2010 - How time flies! Because of my busy travel schedule this summer I'm almost a couple of weeks behind on bringing you the this Hurricane Watch Report. Things have been pretty quiet in both the Atlantic and Pacific basins over the last month. The Atlantic has only had one tropical storm, Alex and one depression, both impacting roughly the same region of the Mexico/Texas border. Heavy rains have brought flooding to much of the region and the Rio Grand actually flows to the Gulf of Mexico once again. Having been at the Texas border earlier this month, I can tell you it is a muddy flowing mess there.
Baja is still a few weeks away from our tropical cyclone threat but things are beginning to move in that direction. The earliest tropical cyclone to make landfall in Baja was in the last week of July and that was just a tropical storm. The earliest hurricane to make landfall was in 
mid-August. Our usual threat period begins the last week of August and in the last several occurrences has provided us a hurricane over the Labor Day weekend.
Over the last 40 years the Eastern Pacific has usually generated 5 named systems (Tropical Storm strength or better), 3 Hurricanes and 1+ Major Hurricane (Category 3 or greater) by the third week of July. over the last 10 years the numbers drop slightly to 4 named systems, 2 hurricanes and 1 Major Hurricane. If we look at just the last 10 years, the Eastern Pacific is right on track with those numbers, we are one Major Hurricane extra so far with 2. The Atlantic basin is way behind normal.
According to NOAA this is a year with a fading El Niño event and by late fall we are suppose to be in a La Nina 
condition. The El Niño event has a significant influence on the statistics for tropical cyclones in Eastern Pacific and particularly tropical cyclone landfalls in Baja.
In El Niño years, where the water is warmer along the equatorial regions west of Ecuador fewer hurricanes form in the Eastern Pacific. it is believed that stronger upper level winds cause shear and prevent the formation of tropical cyclones. Last year was a relatively strong El Niño and the Eastern Pacific yet saw 18 named systems (2 above the norm) 7 Hurricanes and 4 Major Hurricanes. Only one, Hurricane Jimena made landfall. Patricia and Olaf came darn close, but both late season storms fizzled before reaching our peninsula.
In La Nina years (there have been few La Nina's than Niño) it is about the same stats strangely enough as El Niño years for formation of storms. However, during those years fewer storms make landfall in Baja. The only Major Hurricane (Category 3) to ever hit baja was Hurricane Kiko in 1989, a strong La Nina year.
The worst years for Baja are the fall-off years, like 2010 would appear to be. In those years at least one and as many as three tropical cyclones make landfall in Baja. The good news is normally only one is a hurricane. So, this being a fall-off year and with the season being right on track for the last 10 years we should statistically expect a hurricane landfall some this fall. Where in Baja? Well, if I could predict that I'm certain an insurance company would snatch me up in a hurry!
Looking at Eastern Pacific Tropical Cyclones in the two weeks ahead...
The Eastern Pacific has been pretty quiet for nearly a month, just a tropical depression (6E) since Cat 3 Hurricane Darby the 26-28th of June. But again, that isn't particularly unusual. looking at the wide angle Surface Chart below as of July 19, 2010 we can see a stack of three tropical waves about to enter our basin. With an existing Low in place, there is a chance one of these waves will generate a tropical cyclone in the week ahead. After this series of waves passes there is a gap of about 5-6 days before the next wave, generated over the deserts of Africa, will reach our basin.
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 progressive seasonal warming of the Eastern Pacific, but nothing particularly abnormal. Tropical cyclones need sea surface temperature water of more than 26°C. That all important thermo cline now touches the tip of the peninsula and all of the Sea of Cortez is warmer than 26°C.
The waters along the southern coast of Mexico, from which most of the storms that reach Baja are generated, is between 28° and 29°C, perfectly capable of generating a tropical cyclone. The animated graphic left shows the progressive warming of the Eastern Pacific. Although the sun has passed the solstice a month ago tomorrow, waters between the equator and the Tropic of Cancer (which crosses the tip of our peninsula just north of Cabo San Lucas) will continue to warm for about another month.
Although we have a fair amount of thunderstorm activity along the southern coast of Mexico as of the time of this article, there is evidence of moderate to strong upper level winds. Looking at an enlarged view of today's satellite image we can easily see the east to west blurring of the cloud tops in this region. Strangely enough, hurricanes are delicate creatures. Calm, hot and humid air is required to develop the cylindrical cyclonic action that makes tropical cyclones so feed themselves and become so powerful. These upper level winds are why the NHC is not currently predicting that these areas of thunderstorm activity will generate a tropical cyclone. When these shear winds cease, we will probably have our next tropical cyclone.
The Sea Surface Anomaly graphic left continues the good news for Baja. Most 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, which plays out in this seasons normal numbers
Good news for tropical cyclones and bad news for fishing off the Pacific coast of Baja Sur is a large area of water that is as much as 2°C below normal. Extending about 500 miles south and 600 miles west this cooler than normal water contains less kinetic energy than normal. If this holds through the rest of the season it could mean storms that curve back toward Baja would have less warm water from which to gather energy before making landfall.
The Sea of Cortez is also just about normal for this time of year. Folks here in Baja Sur are delighting in the continued evening winds and cool nighttime temperatures that we have enjoyed. Our evening winds usually quit about the middle of July, but with the difference between the land's daytime solar heating and the temperatures of the Sea, the winds are a welcome relief. Fisherman have complained that the water is colder than normal, and hence the fishing a bit slower. This would be true of just looking at the last 5 years, where the Sea has consistently be 2°-3° above the 20 norm.
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.
My first prediction for the year was way off, the second right on and my last I predicted a major hurricane during the period and all we got was a tropical depression. So this year I'm not off to a great start.
It looks like these high level winds will persist through the next several days, allowing the first of three tropical waves to pass without tropical cyclone formation. With the increased moisture along the southern coast of Mexico the conditions will be ripe for a storm as soon as those winds cease. With the normal temperature waters I think the third wave will most likely generate a tropical cyclone, I'm going to say a Category 1 or 2 hurricane which will move to the NNW and pass just south of the Socorro Islands. I've named both the class and course of the next storm for extra credit, as my batting average needs the help. When your behind in Black Jack you double down, sometimes this just doubles your losses.
But what do I know...
I'm off to do some sailing in the Sea over the next two weeks, so with luck and statistics we won't have any storm threats until I return. 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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