Daniel Swain Offices Hours Notes 8/18/23
My rough notes from the 8/18 session.
The dude has been ripping out these sessions. Here’s the link to the 8/18 session. I don’t have notes for that one.
Here’s a link to the 8/19 session (agenda focused on Hurricane Hilary and the impacts on California), notes are below.
These are my very rough notes so treat them accordingly. Also like last time, I’m going to flag anything I may have gotten wrong with a (❓). This means I may have heard wrong, misunderstood, or was just my interpretation.
Hilary weakening, category 2 now
Potentially historic weekend for CA
Blog post went out last night
Want to recap where things are at/cover changes
Summary:
If you looked at satellite now, Hilary is cat 2 but weakening
Moving over cooler ocean waters, current location still supports hurricanes but moving to waters that do not support hurricanes
One interesting thing happening now, although storm is visible degraded, no deep convection on western side, no longer well-defined clear eye, no longer has classic look. Still a powerful storm
Storm has enhanced outflow in northwest (❓) direction, storm is going to transition, moving from tropical to mid latitude kind of storm, going through extra tropical transition process (❓)
Not too common for storms over CA to do this, some examples super storm Sandy and the Columbus Day storm of 1962 on west coast
Doubt the storm strengthens but could maintain tropical storm characteristics as it moves over CA even though ocean waters are cold
Reminder of Midwest ridge of high pressure and cutoff low to the west steering Hilary
Hilary largely behaving as predicted, expected to make landfall in SoCal or northern Baja
In terms of impact:
Potentially for widespread flash flooding
Extreme flooding areas east of mountains
Potential for flooding at a level not seen in generations
No matter the trajectory, the area near Death Valley is likely to see extreme flooding, some areas could see geologic flooding (❓) meaning it’ll reshape the land
Uncertain where the center of Hilary will go
Some models say between LA and SD but many models saying no at the border of Mexico and US
Impacts in desert regions don’t really change regardless of path
The amount of rain and wind in the LA and SD regions though depends on where Hilary makes landfall
First time tropical storm watch or warnings issued for these areas
Doesn’t look like SD and LA proper are at risk of severe flooding, certainly not like the mountains to the east
From NWS “locally catastrophic flooding”
Likely do another livestream tomorrow, perhaps at time of landfall
Storm is speeding up a little so landfall is coming sooner than anticipate
Possibility of isolated tornadoes in southeast quadrant of storm
Could be a tornado or two in the deserts of Southern California
Farther north you get the lesser the impact of the storm
Could be strong isolated thunderstorms in NorCal though, near coast less likely to see thunderstorms
From about Sacramento south to Big Sur, east of this line could see some rain, the more west and north you go the less the chance of thunderstorms or rain
This means the northwest part of California is unlikely to get rain, which could have helped with the fires
If storms did occur in northwest California, they’d likely be wet storms so hopefully unlikely lightning would start fires
When Hilary departs early next week, it could pull in wildfire smoke into NorCal, Pac NW could see eastern winds as Hilary departs which would not be great for fires
Questions
Will Hilary continue to wobble?
Basically yes until it makes landfall, then wobble is less relevant
Does national hurricane center take into account topography/have data points to forecast in these areas?
Generally yes, in “jackpot areas” rain totals could be higher than models are predicting
Forecasters at the at NHC are like, pretty good at their jobs
Impact on snowpack?
Still some left, not a lot left through in southern Sierra
Not much snow water left
Flood risks for southern slopes?
Conditional, depends on track of storm, if westerly track then risks are higher
No matter what, eastern slopes will see flooding
Will this add to Tulare Lake?
Not likely
Lucy Jones book The Big Ones is worth a read
