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Central & Eastern Pacific Thread


Windspeed
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20 hours ago, Windspeed said:

 

 A devastating wildfire the night of August 8-9 (Tue night) destroyed the city of Lahaina on the west coast of Maui and has killed at least 36 folks. This is a result of a combination of plentiful vegetation (fuel) from a wet winter, it now being dry season, current D1 moderate drought/drier than normal ground due to recent below normal rainfall, low relative humidity, and unusually strong E to NE winds blowing from off the mountains resulting from the strong pressure gradient between major hurricane Dora passing 700 miles SSW of Honolulu, and high pressure to the north.

 From the following link to the 7/14/23 Drought Information Statement":

"Maui County
Reports from central Maui indicated that pasture conditions were poor from Kihei to Kaupo. Dry vegetation conditions have also
resulted in brush fires in West Maui over the past month in the Olowalu and Kapalua areas. These fires briefly closed Honoapiilani
Highway."

and 

"The risk of fires during this year's dry season is elevated due to the abundance of fuels produced by the wet winter and spring, combined with the expectation of below average dry season rainfall."

https://www.weather.gov/hfo/DGT

Here was the NWS forecast issued Tue afternoon;

MAUI LEEWARD WEST-  
INCLUDING LAHAINA, KAANAPALI  
339 PM HST TUE AUG 8 2023  
   
..HIGH WIND WARNING IN EFFECT UNTIL 6 AM HST WEDNESDAY  
 
   
TONIGHT  
PARTLY CLOUDY. VERY WINDY. LOWS 69 TO 74. NORTHEAST  
WINDS 35 TO 45 MPH. GUSTS UP TO 65 MPH IN THE EVENING.

 

A red flag warning had been in effect:

URGENT - FIRE WEATHER MESSAGE  
NATIONAL WEATHER SERVICE HONOLULU HI  
317 AM HST TUE AUG 8 2023  
 
...RED FLAG WARNING FOR LEEWARD AREAS DUE TO STRONG WINDS AND LOW  
HUMIDITY...  
 
.VERY DRY FUELS COMBINED WITH STRONG AND GUSTY EASTERLY WINDS AND  
LOW HUMIDITIES WILL PRODUCE CRITICAL FIRE WEATHER CONDITIONS  
THROUGH TONIGHT. 
...RED FLAG WARNING REMAINS IN EFFECT UNTIL 6 AM HST WEDNESDAY  
FOR STRONG WINDS AND LOW HUMIDITY...  
 
* AFFECTED AREA...LEEWARD PORTIONS OF ALL HAWAIIAN ISLANDS.  
 
* WIND...EAST WINDS 30 TO 45 MPH WITH GUSTS TO AROUND 60 MPH.  
 
* HUMIDITY...35 TO 45 PERCENT THROUGH THE AFTERNOON HOURS.  
 
* IMPACTS...ANY FIRES THAT DEVELOP WILL LIKELY SPREAD RAPIDLY.   
OUTDOOR BURNING IS NOT RECOMMENDED.

 

NWS discussion just before fire got bad:

AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HONOLULU HI  
821 PM HST TUE AUG 8 2023  
   
SYNOPSIS  
 
A VERY STRONG HIGH PRESSURE SYSTEM REMAINS IN PLACE NORTH OF THE   
STATE AND HURRICANE DORA CONTINUES TO MOVE WESTWARD, PASSING WELL  
SOUTH OF THE ISLANDS TONIGHT. THESE TWO PRESSURE SYSTEMS WILL   
CONTINUE TO PRODUCE VERY STRONG AND DAMAGING WINDS THROUGH THE  
OVERNIGHT HOURS. THESE STRONG WINDS COUPLED WITH LOW HUMIDITY   
LEVELS ARE PRODUCING DANGEROUS FIRE WEATHER CONDITIONS THAT WILL   
LAST THROUGH WEDNESDAY AFTERNOON. EXPECT DECREASING WIND SPEED   
TRENDS ON WEDNESDAY AND THURSDAY AS BOTH SYSTEMS MOVE WESTWARD   
AWAY FROM THE STATE. A MORE TYPICAL BREEZY TRADE WIND WEATHER   
PATTERN RETURNS FROM FRIDAY THROUGH THE WEEKEND WITH MORE MODERATE   
TRADE WIND SPEEDS IN THE FORECAST.  
 

 
   

PRELIMINARY LOCAL STORM REPORT...CORRECTED  
NATIONAL WEATHER SERVICE HONOLULU HI  
1049 PM HST TUE AUG 8 2023  
   
.TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON  
   
.DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE.  
 
..REMARKS..  
 
1047 PM     WILDFIRE         LAHAINA                 20.89N 156.67W  
08/08/2023                   MAUI               HI   EMERGENCY MNGR     
 
CORRECTS PREVIOUS WILDFIRE REPORT FROM   
LAHAINA REPORT SOURCE TO SHOW EMERGENCY   
MANAGER. SOME COMMUNITIES IN LAHAINA, MAUI   
ARE UNDER EVACUATION NOTICE DUE TO NEARBY   
WILDFIRE.
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11 minutes ago, Boston Bulldog said:

Some pretty remarkable Integrated Water Vapor Transport values associated with the modeling for our future system. Regardless of SLP track, the San Gabriels should get good drink. Primary concern would be mudslides if these depictions verify

Kathleen (1976)is a very good analog. Described as a 1 in 160 year event

https://en.m.wikipedia.org/wiki/Hurricane_Kathleen

Kathleen_1976_track.png

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Looks like the forward speed slows down just enough around 30N that things fall apart on final approach. Still would be a very impactful rain/wind event. Not sure how this would compare to some of the strong winter storms that hit California regularly. I know those are generally further North but they do sometimes impact areas close to LA.

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1 hour ago, NJwx85 said:

Looks like the forward speed slows down just enough around 30N that things fall apart on final approach. Still would be a very impactful rain/wind event. Not sure how this would compare to some of the strong winter storms that hit California regularly. I know those are generally further North but they do sometimes impact areas close to LA.

To answer your question bluntly: there is no comparison between a TC and our winter storms.  The strongest winter storms put down 30 sustained with gusts in the 60’s.  Maybe 2 inches of rain.  A direct tc strike puts a little more wind and double to the rain.  The second part is what will be devastating.  The wind we can deal with

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5 minutes ago, Normandy said:

To answer your question bluntly: there is no comparison between a TC and our winter storms.  The strongest winter storms put down 30 sustained with gusts in the 60’s.  Maybe 2 inches of rain.  A direct tc strike puts a little more wind and double to the rain.  The second part is what will be devastating.  The wind we can deal with

The 12z GFS has a 10"+ swath in the rural areas (Mostly dessert) and away from the major population centers. But certainly that amount of rain and intensity on that type of terrain would cause significant issues.

It doesn't look like wind will be a major factor as the storm unravels pretty quickly on approach. 

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