Wednesday August 15 2018

  • Four week Sea Surface Temperature graphic showing +26°C water creeping up the Pacific coast of Baja California Sur
  • Wide Angle Surface Chart showing Tropical Waves moving west toward the Eastern Pacific
  • Precipitation Anomalies from August 1 to Sept 30
  • Mid Level Wind Anomalies forecast for August 1 to September 30
  • Madden Julian Oscillation Eastward Evolution August 14 to August 30
  • Upper Level Winds Anomalies in the Eastern Pacific
  • Outbound Longwave Radiation Anomalies
  • Mid-Level Wind Anomalies

August 14- 20, 2018 The week ahead will begin quietly but the Eastern Pacific is likely to get more active with tropical cyclone activity as we move into late August.  A well-defined low pressure system is located about 1050 miles southwest of the southern tip of the Baja California peninsula. Associated thunderstorm activity continues to gradually increase in organization, and a tropical depression is likely to form tonight or Wednesday while the disturbance moves westward at 10 to 15 mph.

There are four tropical waves moving west from the deserts of Africa and one to the southwest of Cabo San Lucas, which is stimulating the more promising of the areas of development, this one 1000 miles to the southwest. The first of the string of four waves will enter the Eastern Pacific basin late this week. An additional wave will enter the basin 48-72hrs later, for the next three waves through the last week of the month.

The study of the Madden Julian Oscillation yields several indicators for the last part of August. These include OLR (Outbound Longwave Radiation), wind anomalies, and precipitation anomalies. In brief, the Eastern Pacific basin is going to be abnormal in all of these factors through the end of the month.

The good news in all of this is the current MJO cycle is not a particularly strong one, and is not expected to be the largest contributing factor to tropical development. The bad news is, as weak as the wave is, it will be coming to our region of the Eastern Pacific over the next two weeks.

Looking at the OLR anomalies from the period July 10 to August 8, the area of decreased OLR (increased convection) crept across the Pacific westward. Fortunately, the intensity of the wave decreased and dispersed in its westward migration. The wave also propagated at a less than predicted rate over the last three weeks.

 The mid and upper level winds analysis and forecast indicates a slow breakdown of the easterlies than have shielded the peninsula. Forecasts indicate an increase in westerly anomalies from 15N to the area of the Socorro Islands and a southeasterly anomaly along the Pacific shores of the peninsula. Should these forecasts hold into the last two weeks of the month the effects would be to steer systems that develop along the southern coast of Mexico closer to the mainland coast, then northwest along the Pacific coast of Baja California Sur.

The current status of the El Nino Southern Oscillation (ENSO) is a neutral state. This is statistically bad for Baja California Sur, as there has been on an average a landfall of at least one tropical cyclone on the peninsula in every neutral year.

Finally, in looking at the Sea Surface Temperature Analysis and Anomalies and their effect on tropical cyclone formation. Much of the Eastern Pacific basin is warmer than normal, most about 1°C, with an area southwest of Cabo, where the current storm is forming, about 2°C warmer than normal. The waters along the Pacific coast of Baja California are the most abnormal, as much as 3°C warmer than normal. The waters along the Pacific coast of Baja California Sur are as much as 1.5°C cooler than normal. The all important 26°C thermocline now reaches as far north along the Pacific coast as Todos Santos. Tropical cyclones require water of 26°C or warmer to sustain and build. This means the tip of the peninsula is now exposed to the development and landfall of a tropical cyclone.

In summation: The indicators point to an active period in the Eastern Pacific over the next 15 days. Systems are likely to develop progressively closer to the southern coast of Mexico through the period. Westerly mid level wind anomalies are expected to build south of the peninsula and southeasterly mid level winds will build from south of Cabo San Lucas along the Pacific coast of the peninsula. A series of four tropical waves will enter the Eastern Pacific basin over the next 16 days in 3-4 days succession.

The southern portions of the Baja peninsula will become increasingly exposed to an increasing number of potential systems. Again to state, that the 15th of August is the statistical beginning of the Baja Tropical Cyclone Season... and here we go.

There are no active systems in the Eastern Pacific; it might be a good time to apply for homeowners insurance if you have property in the southern peninsula.

So my Ouija board prediction for the week ahead is some relative quiet for the Eastern Pacific, while the weekend will see the birth of our next area of interest developing several hundred miles off the southern coast of mainland Mexico. Like the current developing system the next one or two will also follow a westward path. Next week look for multiple developing systems by week's end. The last week of August may bring the next real threat to the peninsula.

So far this year I'm batting 1000.

But what do I know?

The information on this page will be updated next Monday or in the event of a tropical cyclone formation. 

Enjoy your day... 



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