Extroardinary Rain and Wind in Hawaii: Did El Nino Help?

Although in the tropics, Hawaii rarely gets hit by hurricanes.  

But yesterday, the unusual happened:  hurricane Lala approached, producing stunning precipitation and winds.

The visible satellite imagery yesterday afternoon and evening shows a well-defined eye (indicated by red arrows), with the storm passing westward just south of the Big Island

This morning, we only have an infrared image (since there is no solar radiation!)  This image (indicating cloud temperature) shows the low center to the south of Oahu (red arrow) and a blow-up of convection (thunderstorms) to the northeast of the low center (blue arrow).

Precipitation totals so far have been stunning.  

During this event, some parts of the northeast slopes of Hawaii received over 32 inches.  In contrast, the "Kona" side only got an inch or two.   

All the result of strong, moist northeast winds forced by the storm.  Moist air that was forced to rise by huge volcanoes on the island.

Impressive precipitation contrast on Maui as well, with some locations receiving over 30 inches.

Then there were winds, driven by the huge pressure gradients (change of pressure over distance) associated with the hurricane.

Consider the maximum gusts yesterday over Hawai.   Some locations on the NW side of the island gusted to over 80 mph! Strong winds near the ridge crest as well

Similar gusts were found over the NE side of Maui downstream of the West Maui Mountains.  

I should note that the strong downslope winds on the West Maui Mountains resulted in the destruction of Lahaina from wildfire a few years ago.

Hurricanes are relatively rare in Hawaii, because the water temperatures are generally too cool (you read that right).  During the past 50 years, only one hurricane (Iniki, 1992) has made landfall on a Hawaiian island.

Hurricanes need warm water, generally at least 26.5 C (around 80F), and generally Hawaiian waters are cooler than that.

However, this year there is a strong El Nino, with much warmer water than normal in the tropical Pacific  (see sea surface anomaly map (differences from normal) below)

A close-in view of the sea surface temperatures shows the details.  Need to be in the greeds, yellows, or orange colors.   Just made it!  

Finally, I should note that hundreds of thousands are without power on the islands right now, with the Big Island substantially in the dark.

Not a good time for a Hawaii vacation!

Was Low Snowpack a Significant Contributor to Recent Northwest Wildfires? The Answer is Clearly No

This summer, wildfire activity east of the Cascades has been above normal.

Several media outlets and activist websites are claiming that this year's low snowpack is a major cause of the wildfires (see example below).

Poor mountain snowpack and early melt-offs have translated to low reserves, 

drying out grasses, trees, and shrubs that easily ignite and spread wildfires.

The facts are clear: such claims are wrong.  The below-normal snowpack has had little impact in promoting recent wildfire activity.

To demonstrate this, let's consider the most impactful fire this summer, the Little Giant Fire near Lake Chelan, which was initiated by lightning on July 16 (see map below).  The location of ignition (shown with a fire symbol) was at approximately 5000 ft.

We can get a good idea of snow evolution at the fire from the nearby Trinity Snotel site (see below).

The snowpack (snow water equivalent) at this location this year (black line) was generally below-normal (green line), but NOT a record low (lower red line).  

If you look closely, the snowpack at this location melted out on May 2, when on average it melts out on May 11th.   So, the snow was lost about 9 days early.   

But that does not matter for this fire, since the fire occurred OVER TWO MONTHS (July 16).  There is a large body of literature showing that only days to weeks are needed for surface fuels to become dry enough to burn after the snow has melted. 

Furthermore, most of the water from snowmelt goes into streams and rivers and is lost to the region.

Thus, by mid-July there was plenty of time for the ground and vegetation to dry out, even in a normal year with full snowpack.

Want more proof for different fires?   

Two other big fires were found to the east near the Columbia River:  the Kailser Canyon and Molrite fires (see below), which started in mid-July

There is a nearby Snotel site at Gold Mountain (4500 ft, see map)

Below are the snowpack observations at this location (again, the black line is this year, green line indicates normal).  

Way below normal snowpack!  The snow melted out around April 8 rather than the normal of April 18.  

Not important for a fire that would start THREE MONTHS LATER.

Still not convinced?  Let's consider the largest fire, the Sinlahekin blaze near the Colville reservation in north-central Washington (see map).

There are two Snotel sites near the fire, and I will pick one of them (Salmon Meadow, 4460 ft, with the horizontal line in the map below).

This site had an abysmal snowpack, melting out on April 5, when normal is May 2.    But normal melt-out was well over two months before the fire and thus the early melt-out was not relevant.

In summary, the regional snowpack melted out a week to a month early this year near the big regional fires. 

 But that is immaterial for wildfire because the mid-July fire initiation was over two months in the future.

Even with normal...or ABOVE NORMAL... snowpack, the melt out would have occurred two months before the fire, allowing more than enough time for the soils and fuels to dry out.

In short, the low snowpack made little positive contribution to the large fires that were initiated by lightning in July. 

Finally,  to provide independent evidence of this lack of connection between Washington State snowpack and fires,  the plot below presents the regional snowpack on April 1 (blue line) and the subsequent fires over the region (red line).

There is little correlation between them.

Why are some folks exaggerating the role of low snowpack on regional wildfires?  

Perhaps because they are trying to find a way to blame the burns on climate change, rather than invasive grasses, poor forest management, human land disturbance, and human ignitions.