The Real Cause of the Maui Wildfire Disaster, Cliff Mass, 8/14/23. Maps and diagrams,
"Since winds approaching the West Maui mountains will be so important consider the situation at the same time for an elevation of around 2600 ft (925 hPa…
The Real Cause of the Maui Wildfire Disaster, Cliff Mass, 8/14/23. Maps and diagrams,
"Since winds approaching the West Maui mountains will be so important consider the situation at the same time for an elevation of around 2600 ft (925 hPa pressure)-- see below. You can see the high to the north, the location of Maui (white arrow), and the hurricane (red arrow).
The wind anomaly from normal of the winds at this level is shown in color. Look carefully and you will see gray color over Maui.... five standard deviations from normal....which means VERY unusual. You will also note the clear separation of the strong winds of Dora from what hit Maui.
Not not only were strong winds approaching the West Maui mountains, but another feature that can foster a very strong mountain response also occurred: an area of stable air near the crest level of the terrain.
This is illustrated by the vertical sounding at Hilo on the Big Island six hours earlier (see below). The black line on the right shows the temperature with height. When the temperature does not fall rapidly with height, the atmosphere is generally stable. When it is constant with height or warming with height (an inversion), it is very stable.
Trust me, this stable layer is important. When strong winds accompanied by a stable layer near or just above crest level hits a terrain barrier, a high-amplitude mountain wave can form.
A wave that can produce intense downslope winds. And this is exactly what happened last Tuesday over Maui. The Smoking Gun
Last week, I asked David Ovens, a highly skillful atmospheric modeler in my group at the UW, to run a forecast of the Maui event using the WRF model at very high resolution (1.3 km grid spacing). I was stunned by the simulation, which revealed the real cause of the disaster: a high-amplitude mountains wave with very strong downslope flow on the West Maui Mountains.
Below is a forecast vertical cross-section of the situation around 2100 UTC August 8th (11 AM Hawaii time). Winds are shown by color shading and arrows. The solid lines are potential temperature.
An extraordinarily high amplitude wave had formed, with air descending the western side of the Maui Mountains, accelerating as it plummeted towards Lahaina. At low elevations, the flow abruptly ascended, in a feature often termed a hydraulic jump.
There is this data point. Mass is a climate scientist at the U of Washington.
https://cliffmass.blogspot.com/2023/08/the-real-cause-of-maui-wildfire-disaster.html
The Real Cause of the Maui Wildfire Disaster, Cliff Mass, 8/14/23. Maps and diagrams,
"Since winds approaching the West Maui mountains will be so important consider the situation at the same time for an elevation of around 2600 ft (925 hPa pressure)-- see below. You can see the high to the north, the location of Maui (white arrow), and the hurricane (red arrow).
The wind anomaly from normal of the winds at this level is shown in color. Look carefully and you will see gray color over Maui.... five standard deviations from normal....which means VERY unusual. You will also note the clear separation of the strong winds of Dora from what hit Maui.
Not not only were strong winds approaching the West Maui mountains, but another feature that can foster a very strong mountain response also occurred: an area of stable air near the crest level of the terrain.
This is illustrated by the vertical sounding at Hilo on the Big Island six hours earlier (see below). The black line on the right shows the temperature with height. When the temperature does not fall rapidly with height, the atmosphere is generally stable. When it is constant with height or warming with height (an inversion), it is very stable.
Trust me, this stable layer is important. When strong winds accompanied by a stable layer near or just above crest level hits a terrain barrier, a high-amplitude mountain wave can form.
A wave that can produce intense downslope winds. And this is exactly what happened last Tuesday over Maui. The Smoking Gun
Last week, I asked David Ovens, a highly skillful atmospheric modeler in my group at the UW, to run a forecast of the Maui event using the WRF model at very high resolution (1.3 km grid spacing). I was stunned by the simulation, which revealed the real cause of the disaster: a high-amplitude mountains wave with very strong downslope flow on the West Maui Mountains.
Below is a forecast vertical cross-section of the situation around 2100 UTC August 8th (11 AM Hawaii time). Winds are shown by color shading and arrows. The solid lines are potential temperature.
An extraordinarily high amplitude wave had formed, with air descending the western side of the Maui Mountains, accelerating as it plummeted towards Lahaina. At low elevations, the flow abruptly ascended, in a feature often termed a hydraulic jump.