Bud in the Eastern Pacific becomes a major hurricane well-offshore Pacific Mexico; threat to Baja late-week.

Hurricane Bud has continued its robust intensification, as expected, now a Category 3 hurricane (at 8 am PDT) based on satellite intensity estimates with maximum sustained winds of 120 mph and gusts to 150 mph.


The hurricane continues to show strong blow ups of thunderstorms with very cold cloud tops in its inner core region known as the “central dense overcast” or CDO Region indicating that it is continuing or organize and additional strengthening may occur during the day today into this evening.


As mentioned last night, given the thermodynamic environment (abnormally warm waters below unstable air above for air to rise), low wind shear (winds not increasing in speed with height so the low pressure system remains “vertically stacked”) and favorable poleward outflow (air from the surface low being sent up upper atmosphere and blown off generally northward and away, allowing surface low to intensify further), there’s little to stop Bud from strengthening further, except for the system itself. Unpredictable structural changes in its eyewall could inhibit further strengthening, but for now that doesn’t appear to be imminent. However, by tomorrow, the steering currents are forecast to slow down somewhat and its own powerful inner core may act as a “negative feedback” and cool the waters under it as a result of upwelling of colder water from greater depths not as well heated by sunlight. This will likely result in a gradual weakening. After this, it will also begin to traverse somewhat lower temperature waters already on the surface itself, limiting any opportunity for re-intensification as it approaches the Baja California Peninsula late-week. So an overall weakening trend should begin after Tuesday.144123_5day_cone_no_line_and_wind

It appears the hurricane’s tropical storm-force wind field will largely stay offshore the Pacific coast of mainland Mexico, although gusts of 40+ mph are certainly possible in gusts as the rain bands hug the coast line near Manzanillo and points with a couple hundred miles north and south over the next 48 hrs. The system should pull away from land the tropical storm watch area after Tuesday and the threat of locally heavy rain and gusty winds will diminish (rip currents and heavy surf will continue) and the threats will shift and increase for the Baja CA Peninsula. There has been a trend in some numerical models to track the to system more toward the southern tip of Baja or slightly towards the Gulf of California. Any track farther away from the open Pacific waters would mean more of its circulation over warmer waters (compared to the more open Pacific) for more thunderstorm activity to keep the system stronger in terms of winds, wave action and heavy rain. So far, given the decrease in ocean heat content and increasing wind shear, this still looks far more like a tropical storm event than a hurricane event for Baja and the possibly the southern Gulf waters. But this would still mean areas of heavy rain, flash flooding and landslides over mountainous terrain and wave hazards along coastal areas. In addition, if Bud moves more toward the Gulf, this may induce a stronger moisture surge up into the Southwest US, enhancing the monsoon flow pattern change and increasing thunderstorm activity.

9-km ECMWF USA Cities undefined undefined 168

One model depiction of the total precipitation over the Southwest US between Sunday evening (6/10) and next Sunday evening (6/17) local time. Much can change and will depend on the track of Bud, but if the system approaches the southern tip of Baja or moves into the Gulf of California a strong low-level moisture surge would result, bringing an unstable air mass for abundant thunderstorms to much of the Four Corners States over the weekend. Virtually all the US rain on this map and much of northern Mexico is forecast to fall beginning Friday night from the south.

While *again*, amounts will change depending on the track of Bud, some monsoon-related switch in air flow pattern is expected and if the moisture is as abundant as possible with a very abnormally warm Gulf + remnant moisture from Bud, folks living in the Four Corners region should watch forecasts specifics related to possible thunderstorms and locally heavy rainfall this weekend. Given the extreme to exceptional drought conditions in this region, the soils are likely very dry and hard and heavy rain which falls will not be absorbed as quickly as it would be otherwise (rainfall will help, but too much too soon is bad for rapid runoff). So details can only be found in future forecasts, but it’s something to keep in mind at the moment.


Follow updates as I get them on my Twitter and Facebook!

–Meteorologist Nick Humphrey

PS: I was just asked a question about the Eastern Pacific Hurricane Climatology compared to how things are going thus far in 2018. Numbers of systems thus far are listed with days, late or normal listed in parentheses). The normal values are based on 1971-2009 baseline. Still very early in the season and early season activity doesn’t necessarily provide clues to future activity.

Tropical Storms: 2 (2nd storm formed 16 days earlier than normal).

Hurricanes: 2 (2nd hurricane formed 34 days earlier than normal).

Major Hurricanes: 2 (2nd major hurricane formed 69 days earlier than normal).

For the North Atlantic, which is quiet at the moment (based on 1966-2009 baseline):

Tropical Storms: 1 (1st storm formed 45 days earlier than normal).

Hurricanes: 0 (normal until August 10th)

Major Hurricanes: 0 (normal until September 4th)



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