Fire Conditions expected rest of this week and weekend for California

The fire conditions Wed Night into this morning were not as severe as expected thanks to weaker winds. This allowed firefighters to make some ground against fires through the night, however high fire danger remains and will continue for days into the future, with no rain in sight.

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Strengthening pressure gradients along the mountainous terrain of interior California and the warm, very dry air mass will promote high far danger with windy conditions near the mountains and adjacent valleys Fri Night-Sunday. (See tightly packed isobars…lines of equal pressure…on the map in CA just west of Nevada as high pressure shifts SE-ward over the Intermountain West).
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Very low dew points during the day Sat could mean relative humidity values as low as 10-20% across interior California, along with gusty winds for high fire danger.

Air quality remains terrible in the Bay Area. Folks in that region should do what they can to avoid being outside if at all possible.

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Unhealthy air quality exists across the entire Bay Area. Expect harmful air quality to be problematic into the weekend.

I’ll add any additional updates related to fires on this post today. Stay safe in these areas!

–Meteorologist Nick Humphrey

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Update on Wildfire Situation in Northern California.

The Northern California wildfires continue to rage and risk both lives and property. At least fifteen fires are currently burning across Northern California with little to no containment. The most significant fires include the Atlas Fire, Tubbs Fire, the Cascade Fire, Nuns Fire, and the Redwood Complex Fire. As of 8 pm PDT, there have been 17 deaths reported (11 in Sonoma, 2 in Napa, 3 in Mendocino and 1 in Yuba Counties). 180 people have been reported missing in Sonoma County with 57 out of originally 240 reported missing found since yesterday. More than 2,000 structures have been destroyed. 115,000+ acres have been burned with many fires at 0% containment.

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A SUV burns in the driveway of an already burned down home threatening another home in neighborhood off Fountaingrove Parkway near the Hilltop in Santa Rosa on October 9, 2017 in Santa Rosa, California. (Photo: Brian Van Der Brug/LA Times Via Getty Images).

Today, the atmospheric conditions were initially better for fighting fires this morning with higher humidity values and low winds. Winds have remained lighter today compared to previous days, but humidity has once again dropped this afternoon below 30% or even 20% in many areas in the hilly elevated terrain down into Napa Valley, allowing fires to continue to steadily spread.

Humidity
Low humidity values north of the Bay Area allowing fires to more easily attack vegetation and structures. (earth.nullschool.net).
Particulates
Very high surface particulates causing very poor to hazardous air quality over much of Northern California (particulate matter on map <2.5 micrometers). (earth.nullschool.net).

I wish there was more good news to give to the folks in NorCal, but unfortunately, NO rain is forecast for the region for the next seven days. In addition, the National Weather Service issued a RED FLAG WARNING for Wed Night-Thurs Afternoon as high easterly winds blowing out of the hilly terrain will produce very low humidity, allowing for potentially explosive wildfire growth.

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Global Forecast System model forecast valid 1 am PDT Thursday morning showing high pressure building over the elevated terrain of Nevada and northeast California. Strong easterly downsloping winds will develop, intensifying wildfire potential.
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Global Forecast System model forecast valid 1 am PDT Thursday morning showing wind gusts of 25-45 mph across north-central California.
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Global Forecast System model forecast valid 1 am PDT Thursday morning showing humidity values falling below 25%, keeping fuels dry for fires to spread.

If you know anyone in or near the effected region (or in the RED FLAG WARNING areas), tell them to make sure they clear vegetation near their homes/businesses and have an emergency plan in case evacuations are issued for their area. Unfortunately, this wildfire disaster is ongoing and requires those who are in or near rural country to be ready to escape at a moment’s notice.

Live Updates by the San Francisco Chronicle: HERE

—Meteorologist Nick Humphrey

Start of October Drought and Climate Update

Nearly 14% of the Continental US is in at least moderate drought conditions right now. The most highly afflicted areas are over the northern tier states west of the Mississippi River…the Dakotas, Montana, Idaho, Washington and Oregon.

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There are scattered areas of drought and abnormally dry conditions across other parts of the country. However, an isolated area of severe to extreme drought has been hitting south-central Iowa for much of the summer and there are also areas of moderate drought developing over the the Desert Southwest and eastern Maine.

The level of dryness, particularly over Western North America has promoted a significant fire season, which continues at this time. British Columbia is having its worst fire season on record and the Western US is having an unexpectedly destructive fire season. This even after much of the region had a wet winter, showing that a significant period of dryness following well-grown fuels from a wet season can still lead to a major fire season. As of October 4, 2017, nearly recordĀ 8.5 million acres have been burned in the United States in 2017.* While below the 2015 record of 10.12 acres, it should be noted that anthropogenic climate change is increasing the risk of fire seasons in the US over 3 million acres and there has been a significant increase in fire seasons of 3 million acres or more since the turn of the century. 2017 may rank in the Top 3 for fire seasons (along with 2015 and 2012). Temperatures across the West were well-above normal or record levels over the summer. Various records for heat (as well as persistence of warmth and dryness) were broken in places such as Western WA/OR, central and southern CA as well as the portions of the Interior West.

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Drought Outlook for October 2017. Drought is expected to dissipate in Western WA from the incoming wet season, and improve somewhat in northeast MT. However, much of the drought in the US will persist and in fact additional areas may develop over the central Midwest and Mid-Atlantic states.
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The Probabilistic Precipitation Outlook valid Oct 10-16, 2017. This suggest by mid-month, the atmospheric pattern will be favorable for drier than normal conditions over the center of the nation with near normal or wetter than normal conditions over the coastal regions. The Climate Prediction Center also shows above normal temperatures likely over the Southwest US and Eastern third of the country. Dryness will maintain or promote further development of drought conditions in portions of the nation’s interior.

As of today, the NWS Climate Prediction Center indicates a 55-60% chance that a La Nina climate pattern will develop late in the Northern Hemisphere Fall and into the Northern Hemisphere winter. This is characterized by an intensified Walker Circulation (the east-west tropical Pacific wind circulation) and intensified cold water upwelling along and offshore the coast of South America.

Weather patterns common during La Nina events include abnormally wet, cool conditions in the western Pacific Northwest and TN/OH valleys, but abnormally dry and warm conditions across the southern tier of the United States. This is partially incorporated into the monthly and seasonal drought and temperature/precipitation outlooks.

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For those curious, the climate models are showing the US having a more than likely above normal winter throughout (including AK) with the La Nina-like distribution of precipitation (likely above normal Northwest, below normal Southeast). More on winter as we get closer.

*-I incorrectly stated that total acres burned in the US was around 3 million acres. (10/4/17)

Global Climate Change and its Potential Connection to Hurricane Activity (cited research)

Because of recent North Atlantic Hurricane Season activity…many people have questioned whether hurricanes are becoming stronger and more numerous because of climate change. In the social media universe, I’ve seen many opinionated debates within the general public, as well as meteorologists and perhaps a few sprinkling of climatologist opinions here and there. Not to mention, interesting statements from non-climate scientists. What I have not seen much, however, is any discussion of peer-reviewed research on the topic. There’s so much knowledge being gathered every year by scientists trying to answer important questions about our past, present and future. How climate change will impact regional weather and climates is one of the most important questions because of potential impacts to people, agriculture and natural resources.

I decided to do a (very brief) search of literature on science’s current understanding of climate change as it relates to tropical cyclones. I looked into both the potential connection of global warming to these events in the current climate (attribution), as well as projections for these events based on the “business-as-usual” scenario for carbon dioxide emissions, which is a high emissions scenario and steady increase in CO2 concentration. Research cited are just a sampling of what’s out there and what I looked over. Here are some themes I found interesting (takeaway statements at the end):

Climate models* appear to show a signal toward more intense (Category 4-5 Saffir-Simpson) tropical cyclones overall in the world by the latter half of the 21st century. However, there is also a potential for a downward trend in cyclone numbers in many basins (see #1-4).

The decrease in overall cyclone numbers by the second half of the century is thought to be a product of increasing vertical wind shear over tropical oceans limiting weaker storms. However, many researchers expect there to be a significant upward trend in more intense storms (Category 4-5) as the oceans continue to warm and tropical cyclone formation and track density moves poleward. So formerly less favorable sub-regions of basins may see an overall increase in cyclone activity (with more storms which will be stronger than before in those regions) and in the increasingly less hospitable regions (over the long term), storms which do form when conditions are favorable on short time scales may see cyclones which are also more intense than in years past.

As for historical conditions leading to the present…there does not appear to be a conclusive signature by global warming on tropical cyclone intensity outside of natural variability on a global scale (3-4). However, some regional signals related to frequency changes are being actively studied. 

There is some suggestion (4) based on modeling past climate change to the present time that warming (which would enhance the potential intensity for hurricanes) has been muted by the industrial production of aerosols (particulates like sulfates and nitrates), which actually reflect sunlight from reaching Earth’s surface. However, as warming continues into mid-century, its effect of trapping heat will begin to significantly exceed aerosol cooling effects leading to the more pronounced impacts on cyclone intensity stated earlier (unless CO2 emissions are significantly reduced soon). So while global warming is happening in the background, hurricane potential intensity as we currently witness it is likely still being dominated by natural cycles. (For more on climate change research into tropical cyclones, you can also see this webinar done by climate change researcher Dr. Kerry Emanuel for Climate Central).

With that said, some researchers see signs of a global warming signature associated with recent increased tropical cyclone *frequency* in sub-regions of basins. These include the far eastern portion of the North Atlantic Basin (4), close to the East Asian Coast (5), and a portion of the North-Central Pacific Basin (6). Research is still ongoing on global warming’s past and future influence on activity in individual tropical cyclone basins.

Meanwhile, there is evidence of other impacts related to tropical cyclones (and other significant weather phenomena) and climate change. These include higher rainfall rates (7) and higher storm surge related to sea-level rise from the melting polar ice sheets and thermal expansion of the oceans (8). In addition, there is some scientific evidence that tropical cyclones in recent decades have begun to intensify more rapidly because of increased ocean warming (9). And while not completely clear yet whether it is fully tied to climate change, it is known that the observed North Atlantic Power Dissipation Index (PDI) has increased significantly since the mid-1970s (10; positively correlated to sea surface temperatures) and globally, the strongest tropical cyclones in respective basins have grown stronger since 1981 (Elsner et al, 2008…not included here). Note that scientific critics point out the use of observational data with differences in quality – satellite intensity estimates and reconnaissance flights (or lack of them) – over recent decades could put some uncertainty in these results.

My thoughts? Although inconclusive, possible intensity signals may be a hint of the projected effects of climate change as PDI and high-end cyclone intensity are highly correlated to sea surface temperatures. SSTs are increasing from global warming and this would connect with what climate models suggest of future tropical cyclone activity, if these historical trends are, in fact partially related to climate change.

The Takeaways:

  1. Tropical cyclone intensity at the highest end of the scale appears likely to increase through the 21st century because of climate change, especially if human civilization does not significantly reduce greenhouse gas emissions soon.
  2. While a current climate change signal to intensity is difficult to detect and still a matter of debate, storms in recent decades appear to be intensifying faster, are capable of producing more extreme precipitation events and higher storm surges because of rising sea levels caused by ice sheet melting and thermal ocean expansion. There also appears to be some detectable changes in frequency of storms within individual basins which may locally enhance risk.
  3. Regardless of the exact changes in frequency and intensity of tropical cyclones, the risks to individuals and society because of climate change will increase into the coming decades. It will be important for people and governments to make decisions (beyond greenhouse gas emissions) related to property, coastal land use and emergency management policy to mitigate increasing tropical cyclone hazards, particularly from water (storm surge/inland flooding).

Note: It is of EXTREME importance that those with a desire to communicate climate change issues try to inform our fellow citizens to the best of our ability. Climate change is one of the important issues facing our world (the impact on the global food supply and human health may be actually of greatest importance, but rarely discussed as those aren’t “sexy” topics…). People have their thoughts on the issue based on experiences, politics, religious/spiritual beliefs, etc. However, at the end of the day, we must inform and connect what we know to people’s concerns and allow people to decide as they may. Without censorship (“We can’t discuss climate change right now!”) or nonsensical exaggerations (“So many hurricanes, it’s a new era of superstorms!”). Stay informed (give informed opinions) and tell people why they should care as it relates to their lives. Like everything else we should communicate to the concerns of people. Considering most Americans are now, in fact, concerned about climate change, there’s really NO excuse not to discuss the issue in a serious, informed manner if we have the interest to discuss it at all. 


Additional Note: *-Climate models are not weather forecast models. They do not forecast the atmosphere using initial conditions, but take a climate state (for example, our current climate) and adjust “forcings” on the climate system (carbon dioxide emissions for example). The effect of these changes to “boundary conditions” over time are interpreted for land, sea, the cryosphere and (for Earth System models), the biosphere. Global climate is based on thermodynamic and hydrologic balances which will look for equilibrium when changes to a part of the system are applied. (For more on climate models you can see this webinar by Research Meteorologist Keith Dixon of NOAA’s Geophysical Fluid Dynamics Laboratory for Climate Central).

References (links are PDFs):

#1 – Bell et al. (2013)

#2 – Murakami et al. (2011)

#3 – Wang and Wu. (2013)

#4 –  Sobel et al. (2016)

#5 – Cheng-lin et al. (2016)

#6 – Murakami et al. (2015)

#7 – Knutson et al. (2013)

#8 – Jevrejeva et al. (2016)

#9 – Kishtawal et al. (2012)

#10 – Emanual (2005)

—Meteorologist Nick Humphrey

Update on Hurricane Maria (2:30 pm EDT). High winds and flooding rains impacting Puerto Rico.

Hurricane Maria is beginning to emerge from the island of Puerto Rico after the center made landfall 8 1/2 hrs ago as a Category 4 storm with max winds of 155 mph (Cat 5 is 156+ so catastrophic wind speeds occurred). 

The hurricane is now a Category 3 storm with 115 mph sustained winds and gusts over 130 mph near the center. Damaging winds and torrential flooding rains will continue for the rest of the afternoon as the system continues to push out into open ocean water.


Most computer models indicate the system should remain offshore the United States as it moves north in a weakness in the upper level higher pressure field caused by the presence of Tropical Storm Jose offshore the Mid-Atlantic and southern New England.

 
The crucial timing to be rid of Maria forever will be the approach of a significant upper level trough of low pressure from the Midwest midweek next week to “kick” the dying hurricane out to sea. Most models show this connection keeping the system offshore being, however there is higher variability in the track after Monday which could bring the system closer to shore than expected. Currently, I feel direct impacts…the tropical storm force wind field and significant rain bands…will likely (66%+ probability) stay offshore. But potential variability makes the situation worth watching closely. 

Regardless, high surf and rip currents (currents which pull water offshore and make swimming dangerous) are likely by early next week. The system will also be weaker offshore the East Coast thanks to less intense sea surface temperatures and increasing vertical wind shear from mid-latitude winds.

In the meantime, direct impacts from a Cat 3-4 storm are likely for north coast of the Dominican Republic, the Turks and Caicos Islands and the southern Bahamas. Hurricane warnings are in effect for all these areas. 

–Meteorologist Nick Humphrey

Update on Hurricane Maria (9:25 am EDT). Catastrophic flash flood/violent wind event ongoing.

Maria made landfall as a powerful Category 4 storm near Yabucoa, PR with maximum sustained winds of 155 mph and minimum central pressure of 917 millibars (at 6:35 am EDT). The hurricane continues to move across the island delivering destructive hurricane force winds and torrential amounts of rain leading to massive flash flooding (including 5-7 inch/hr rainfall rates).

The storm currently has max winds of 145 mph. 

River gauges across PR are rising incredibly fast from the high rainfall rates:


Radar near time of landfall (currently offline):

Update on Hurricane Maria (6:30 am EDT)

#Maria is making landfall in eastern Puerto Rico as a Category 4 Hurricane with maximum sustained winds of 155 mph. Gusts of 160+ are likely in progress over northeast coast of PR. Catastrophic weather conditions will continue to spread across the island over the next couple of hours. 

Terrible situation for the 3.5 million people hunkering down this morning. 

PR Radar failed just before 6 am EDT. More inbound winds of 155 mph or higher as eyewall moved over radar site (which is in elevated terrain and winds likely much stronger).