The eastern Pacific hurricane season began over half a month ago, back on May 15th, but it has been very quiet up until now. On average, the first named storm forms on June 10th and the second on June 25th, while the first hurricane typically forms on June 26th. Based on this year’s forecast, NOAA (National Oceanic and Atmospheric Administration) is forecasting that “an above-normal season is most likely (45% chance), followed by a 35% chance of a near-normal season and a 20% chance of a below-normal season.” By the start of next week its possible that the first two storms of the season may develop and strengthen in the eastern pacific basin.
According to the National Hurricane Center, there is currently one area of disturbed weather that has the chance for developing into a tropical cyclone within the next 5 days. In fact, it is being given a 90% chance for formation, and is being designated as Invest 91E. At this time, there is an enhancement of convection and thunderstorms associated with a trough of low pressure at around 10°N latitude. This convergence can help form a more consolidated area of low pressure, and thus a tropical cyclone. The overall environment will be conducive for the formation of the first named storm of the season by the end of the week as the disturbance tracks over warm sea surface temperatures in excess of 80°F and into an area of low wind shear.
By this weekend, Tropical Storm Aletta will likely form as it tracks to the northwest, roughly parallel to the Mexican coastline. This storm is not expected to make landfall, although the GFS and CMC models do bring the storm as a very weak cyclone into Baja California. Meanwhile, the ECMWF model keeps the storm well offshore and as a tropical cyclone into next week over the eastern Pacific, tracking west over the warm waters. Either way, this storm will not be very impactful. Elevated surf and rip currents will be the main concern along the western Mexican coast. If the storm were to track into Baja California, then there is the risk some of its moisture moves in the Southwest, therefore leading to the chance for rain and thunderstorms.
Behind Aletta we may be dealing with our next system, Bud. This potential tropical cyclone will develop similarly to Aletta along the monsoon trough, if it forms at all. All of the model guidance do develop Bud into at least a tropical storm early next week, so we’re keeping our eyes out. The GFS keeps the storm weaker and brings it into the Mexican coast as a low-end tropical storm by next weekend, while the ECMWF expects a very robust storm to form. Based on the latest ECMWF run, we could potentially be dealing with a major hurricane a couple hundred miles off from the Mexican coast during the same time period. This storm may pose a greater risk to Mexico, but at this time the forecast uncertainty is very low.