Baja Weather

Hurricane Norbert has struck
Mexico’s Baja California Sur peninsula with heavy rains and 103mph (165km/h) winds. The storm made landfall near the city of La Paz, blowing down roofs and uprooting trees. Thousands of residents have fled to shelters. Forecasters say Norbert will cross the Gulf of California, before making a second landfall on Mexico’s north-western mainland. It is expected to hit the agricultural states of Sonora and Sinaloa later. Nearly 3,000 people were evacuated to temporary shelters on Mexico’s Pacific coast as the storm came ashore, bringing with it 13ft (4m) waves.

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At 800 am PDT the center of Hurricane Norbert was located near latitude 20.6 north…longitude 113.4 west or about 275 miles…445 km…southwest of the southern tip of Baja California. Norbert is moving toward the north near 10 mph…17 km/hr. A turn toward the north-northeast with an increase in forward speed is expected tonight. A faster motion towards the northeast is expected on Saturday. On this track…the center of Norbert will be nearing the southern Baja California peninsula Saturday morning.

Maximum sustained winds have increased to near 100 mph…160km/hr…with higher gusts. Norbert is now a category two hurricane on the Saffir-Simpson scale. Some weakening is forecast during the next 24 hours before Norbert reaches the Baja California coast. An Air Force Reserve hurricane hunter aircraft is scheduled to investigate Norbert around midday.

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Hurricane Norbert has weakened since yesterday’s impressive Category 4 showing, but still remains a dangerous major hurricane over the Eastern Pacific Ocean. Infrared satellite loops show a well-formed eye with a large area of heavy thunderstorms, but the cloud tops have warmed today, indicating that they are not as vigorous and do not extend as high into the atmosphere. There is excellent upper-level outflow in all quadrants, and wind shear remains low, near 5 knots. The satellite appearance has not changed significantly in the past eight hours. Norbert may go through an eyewall replacement cycle today, where the main inner eyewall collapses, and a new outer eyewall forms. This process could cause a temporary weakening of the storm. The first Hurricane Hunter mission into Norbert is scheduled for this afternoon.

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Norbert is moving ahead in roughly the expected path - it looks to the writer like the point of turning on to the Baja and cross it in direction mainland is a little bit more to the north as yesterday thus La Paz is no more in the direct predicted path. But as we all know, ones don’t need to be a seasoned Baja Nomad to know that Baja hurricanes do what they want…. well, I guess they do that everywhere, not only on the Baja Peninsula.

Further south we have 2 more systems, Tropical Storm Odile and Invest 92. Both are to far away and to “new” to get any predictions. We will keep an eye on them and report of course any changes that should be if interest for the Baja Sur

Hurricane Norbert
Norbert has strengthened into the seventh hurricane of the Eastern Pacific season as of 2 a.m. PDT Tuesday. Norbert’s top winds were estimated to be near 75 mph and was located about 585 miles south-southeast of Cabo San Lucas, Mexico, and is moving to the west-northwest near 8 miles per hour, and this general motion is expected to continue over the next couple of days. Norbert could move toward Baja California later in the week or over the weekend, so interests there should monitor the progress of the system. Check out Norbert’s projected path.

It is often difficult to tell from looking at forecast model data whether a low that is expected to develop near the coast will be tropical, subtropical, or extratropical. The difference is important, since tropical systems have the potential to quickly grow into hurricanes, while extratropical or subtropical storms do not. So, here’s a quick meteorology lesson on the normal progression one sees from extratropical cyclone, to subtropical cyclone, to tropical cyclone.

1) An extratropical cyclone forms. Extratropical cyclones have cold air at their core, and derive their energy from the release of potential energy when cold and warm air masses interact. These storms always have one or more fronts connected to them, and can occur over land or ocean. An extratropical cyclone can have winds as weak as a tropical depression, or as strong as a hurricane. Examples of extratropical cyclones include blizzards, Nor’easters, and the ordinary low pressure systems that give the continents at mid-latitudes much of their precipitation.

2) If the waters under the extratropical cyclone are at least 21C (70F), thunderstorm activity will gradually build inside the storm and moisten and warm the lower levels. Over time, the core of the storm may gradually go from cold to warm, and the storm will start getting some of its energy from “latent heat”, which is the energy released when water vapor that has evaporated from warm ocean waters condenses into liquid water. Latent heat is what powers tropical cyclones. At this point, the storm is called subtropical. If the winds are already more than 39 mph (as happened in the case 2007’s Subtropical Storm Andrea), it is called a subtropical storm. If the winds are less than 39 mph, then it is called a subtropical depression. So, you don’t need to start with a subtropical depression in order to get a subtropical storm.

A subtropical storm typically has a large, cloud free center of circulation, with very heavy thunderstorm activity in a band removed at least 100 miles from the center. The difference between a subtropical storm and a tropical storm is not that important as far as the winds they can generate, but tropical storms generate more rain. There is no such thing as a subtropical hurricane. If a subtropical storm intensifies enough to have hurricane force winds, than it must have become fully tropical. The definition of a subtropical storm, according to the National Hurricane Center: A non-frontal low pressure system that has characteristics of both tropical and extratropical cyclones.

The most common type is an upper-level cold low with circulation extending to the surface layer and maximum sustained winds generally occurring at a radius of about 100 miles or more from the center. In comparison to tropical cyclones, such systems have a relatively broad zone of maximum winds that is located farther from the center, and typically have a less symmetric wind field and distribution of convection.

A second type of subtropical cyclone is a mesoscale low originating in or near a frontolyzing zone of horizontal wind shear, with radius of maximum sustained winds generally less than 30 miles. The entire circulation may initially have a diameter of less than 100 miles. These generally short-lived systems may be either cold core or warm core.

Credits: Dr. Jeff Masters