Quick update on Northern California Wildfires (plus weather forecast)

As of now (5:30 pm PDT), the death toll in the California Wildfires is up to 35 and is expected to go up further. 18 inĀ  Sonoma County, 9 in Mendocino County, 4 in Yuba County and 4 in Napa County. 5700 structures have been destroyed and 221,000 acres have been burned. Treating the conglomeration of fires as a single event (as all the Northern CA ones initiated Sunday Night), this is by far the most destructive fire event in state history and one of the deadliest. Simply horrifying and very sad.

Firefighters have begun to have some containment success the past 48 hrs with slower winds and at least some periods of slightly improved humidity. However, tonight-Sunday morning will feature an intensification of extreme fire danger. This is because a strong surface high pressure system will advance toward the central Intermountain West this weekend, intensifying downsloping Diablo winds from the hilly and foothill mountainous terrain of Northern California. North-northeast winds may gust as high as 45-60 mph Saturday, inducing very low humidity values, drying out fuels and potentially promoting extreme fire behavior (high forward speed, rapid growth) in existing fires as well as any new fires. Red Flag Warnings have been issued by the National Weather Service to cover this forecast potential.

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Strong high pressure moving over OR, ID and NV Saturday will promote strong Diablo winds over Northern California. (NWS forecast surface map valid 11 am PDT Saturday).

There are no thunderstorms forecast, so any new fires would be likely started by human activity. So folks in these areas need to very much be careful with anything which can potentially start fire and really…just avoid starting any outdoor fire or usingĀ  anything which sparks.

Some good news…mid-range computer model forecasts suggest a pattern shift toward precipitation and cooler weather by the end of next week. Just have to get through the next week of fire activity before some meaningful hydrologic relief to aid the firefighting efforts.

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The Global Forecast System Model forecast accumulated total precipitation valid 8 pm PDT Friday. This is one forecast scenario, but all global models point toward a wetter pattern, beginning the second half of next week into next weekend.

–Meteorologist Nick Humphrey

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Potential Impacts by Tropical Storm Nate this Weekend

Tropical Storm Nate, which developed as a depression yesterday, made landfall in Nicaragua this morning and is moving over eastern Nicaragua and Honduras this evening. Very heavy rainfall and flash flooding has already resulted in 22 deaths in Nicaragua and Costa Rica.

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Heavy showers and thunderstorms producing heavy rain over portions of Central America from Tropical Storm Nate this evening and into tonight. (image valid at 5:15 pm CDT).

Nate is progressing generally northward and will emerge over the Northwest Caribbean Sea late tonight where it will have an opportunity to reorganize. The waters over that region are running in the range of 84-86 degrees F (29-30 degrees C), more than sufficient for re-intensification. With that said, the inner core will likely be badly “gutted” by the mountainous terrain of Nicaragua and Honduras and with a second landfall possible Friday evening, time will likely be limited for more robust intensification. With that said, minimal hurricane strength is possible, with a lower chance that the storm may get stronger if it’s inner core can re-organize quickly Friday.

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National Hurricane Center forecast (issued 5 pm EDT Thursday) showing a likely landfall on the Yucatan Peninsula of Mexico Friday evening and likely US impacts on the northern Gulf Coast beginning Saturday evening.

A Hurricane Watch and Tropical Storm Warning is in effect for much of the coastal Yucatan Peninsula. Again, the major threats will be from water…heavy rain and freshwater flooding and also modest (although still hazardous) storm surge and high wave action.

Potential Impacts for Central Gulf Coast of US-

While many details are still in need of being honed in for the Central Gulf Coast…it is highly likely a tropical storm or minimal hurricane will approach the region Saturday evening with landfall early morning Sunday. The biggest threats will be from water (flooding/surge) with wind producing damage from falling trees and power outages.

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NWS Weather Prediction Center 5 day accumulative rainfall forecast (valid beginning 7 pm CDT Thursday) showing heavy rainfall along the track of Nate and its remnants expected, particularly Saturday afternoon into early next week. Very heavy rainfall possible in Greater New Orleans area which is prone to freshwater flooding.

Sea surface temperatures are slightly cooler along the northern Gulf Coast north of the Loop Current (82-84 degrees F/28-29 degrees C). Still more than warm enough for intensification if the system can remain over the current (a slightly farther west track may leave it over slightly cooler waters longer).

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Analysis of Sea Surface Temperatures and the Loop Current. Nate will track along the Loop Current much of its track over water, providing with fuel to re-intensify. (Analysis by Earth Nullschool).

Also, given the shear currently over the Central Gulf will relax over the next couple of days (as an area of upper-level high pressure over Texas shifts westward and weakens), Nate will have an opportunity to re-intensify over the Gulf after leaving the Yucatan Peninsula. Computer models have some variability in timing of an upper trough which will move over the US Central Plains during the day Saturday. This will ultimately influence the exact track of the center of Nate. However both deterministic and ensemble members of the various models depict a likely landfall of the center somewhere from Southeast Louisiana to coastal Mississippi/Alabama. Regardless, widespread heavy rain (particularly near and east of the center), moderate storm surge flooding and high wind conditions will be likely over the coastal areas of these states by Saturday afternoon, spreading inland Saturday night and Sunday. Tropical storm force winds (sustained 39 mph+) will likely arrive on the LA Coast Saturday evening.

 

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Earliest Reasonable Arrival Time for Tropical Storm-Force (issued 5 pm EDT). Folks along the Central Gulf Coast should have preparations for stormy conditions completed by Saturday afternoon.

Tropical cyclone watches will likely be issued for portions of Louisiana, Mississippi and Alabama late tonight or early tomorrow morning.

Climatology Update-

The Atlantic Hurricane Season is currently running above normal (1966-2010 norms in parenthesis): 14 named storms (9), 8 hurricanes (6) and 5 major hurricanes (2). In terms of Accumulated Cyclone Energy (a function of maximum sustained winds over time), 2017 ranks (as of this post) as the 6th most active season on record for the North Atlantic Basin. The average temperature of the North Atlantic Main Development region (open tropics west of Africa) exceeded 83 degrees F (~28 degrees C) for the 9th time since 2002 (had never done so in the record prior going back to 1981). The MDR is the 3rd warmest on record overall.

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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).

Violent Hurricane Irma direct threat to Florida Sunday

Violent Hurricane #Irma direct threat to #Florida Sunday. #FLwx

The following is an analysis of the situation related to the potential landfall of Hurricane Irma this weekend in the United States. Let’s take a look at things currently (as of 5 pm CDT Thursday)-

Hurricane Irma is a violent Category 5 hurricane with maximum sustained winds at 175 mph (150 knots). Numerical models have been struggling on the exact path of the hurricane, but the general scenario is clear; there appears to be high confidence that the hurricane will make landfall in South Florida early-Sunday morning. The National Hurricane Center has the hurricane intensity forecast as a high-end Category 4 hurricane near landfall (max winds 150-155 mph with gusts up to 180-190 mph). This is after the hurricane impacts the southern Bahamas and the north Coast of Cuba with hurricane-force winds Friday-Saturday. After landfall either near or just north or south of Miami (this has been fluctuating in forecasts), the system is expected to advance northward spreading destructive winds, heavy rain, and (along the coast) damaging surf/surge northward up the Peninsula of Florida.

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Track forecast and current wind extent for Hurricane Irma by the National Hurricane Center as of 5 pm EDT Thursday.
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Category 5 Hurricane Irma plowing its way through the Turks and Caicos Islands at this time. Maximum sustained winds up to 175 mph with gusts to 210 mph in the inner eye wall surrounding the eye.
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Close up view of eyewall of Hurricane Irma impacting the Turks and Caicos Islands this afternoon.

I will not sugar coat this. This is most one of the most serious hurricanes Florida has faced in a very long time. Certainly since Charley in 2004 (Category 4) and perhaps since Andrew in 1992 (Category 5). Enhanced locally by issues such as sea-level rise (climate change) and especially land use changes and urban population growth and land cover changes (geographic changes). In addition sea-surface temperatures (SSTs) were the 3rd highest on record globally for the month of August behind 2016 and 2015 (extraordinary considering no El-Nino in the tropical Pacific…much of the Atlantic basin is running above normal; in the long term trend, SSTs are warming because of climate change, however, shorter term climate variability, including the continued shorter multi-decadal cycle for enhanced SSTs and hurricane activity in the Atlantic contributing). The enhanced SSTs and deep warm waters (oceanic heat content) are leading to Irma having ample fuel to remain extremely powerful for a very long period of time. In fact, it became the longest tropical cyclone ever observed in the satellite era (since 1966) to have a strength of 160 knots (185 mph for 37 hrs straight). It has been a category 5 storm operationally since 8 am EDT Tuesday Sept 5th (now third longest streak on record in the Atlantic Basin as of this post, being out 2004 Hurricane Ivan). All this is from warm SSTs, low wind shear not sufficient to disrupt the circulation and low land interaction with the terrain of Hispaniola, which it managed to largely avoid last night (minus minor inflow of drier air off the mountainous terrain to south of the eye, lowering its intensity slightly).

A HURRICANE WATCH has been issued for much of the coastal areas, including the Keys and Lake Okeechobee (see NHC advisories for updates). Hurricane warnings will likely be issued by tomorrow night as the hurricane continues to approach. Evacuations have been called for portions of the Keys and for Miami-Dade County and other areas. If you are in South Florida and in an evacuation area for storm surge and haven’t evacuated, I would highly suggest you do so or call 311 for aid if you are disabled and have difficulty leaving your home. Surge in portions of South Florida from this hurricane could reach 10 ft or more. This is simply not survivable if you’re along the open ocean coast. It is twice as high as my height (I am 5′ 6″ tall). Surge is dependent upon the track and strength of the storm as well as the tidal heights…and if you stay, you basically put your life in the hands of a lifeless beast…

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NHC storm surge guidance (with intertidal layer included to neglect surge flooding in those areas). Based on current forecast track and subject to change (see NHC for updates).

In addition, I do have serious concern Irma could make landfall in South Florida stronger than forecast. The system currently has much going for it. Thus far, the hurricane has exhibited INCREDIBLE resilience. It’s been unable to be significantly impacted by outside forces (weak vertical wind shear which would hamper weaker systems) or internal fluctuations in the inner core region surrounding the eye where the strongest winds are located. This is why Irma has remain so powerful for so long. In addition, beginning basically tonight into tomorrow, it will be entering a region of increasing sea surface temperatures and oceanic heat content (increasing heat with greater depth) and at the same time, the relatively modest vertical wind shear which has attempted to disrupt (largely unsuccessfully) the “inertially stable” inner core will remain modest or even weaken. This means, unless the system moves farther west than forecast and hits Cuba (which would be a catastrophe for them) before turning north, it would will likely (in my opinion) be a Category 5 hurricane as it approaches South Florida last Saturday night-early Sunday. So at least 160 mph sustained with gusts perhaps over 175 mph within the inner eyewall. The surge would be higher than currently forecast and as a result more lethal along the coast, extending farther inland. The winds would also be more destructive at landfall and with greater extent farther inland.

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Sea Surface Temperature Analysis for Sept. 6th showing waters of 29-30 degrees C (84-86 degrees F) under Irma currently and waters of 30-31 degrees C (86-88 degrees F) in its path between Cuba and the Bahamas. (NOAA/AOML)
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Tropical Cyclone Heat Potential showing oceanic heat of 70-90 kilojoules per sq cm under Irma. It increases up to 100-120 kJ/sq cm between Cuba and the Bahamas.
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Shear Analysis showing favorable conditions for vertical wind shear for Irma as it is forecast to move between Cuba and the Bahamas Friday. (CIMSS)

With that said, regardless, of Category 4 or 5, the south-to-north track up the peninsula as a violent hurricane moving at a relative speedy clip (over 15 mph) is a worst-case scenario at it exposes many significant populations to hurricane-force high wind event. A category 4 hurricane at landfall is a catastrophic storm for all hazards as well. Obviously if you are inland and far from the potential surge areas, be ready for days of outages with the necessary supplies and gas (which is quickly running low in many areas!).

If you are in parts of Georgia and South Carolina…keep track of Irma’s track…while there was some talk of it actually making its first landfall in those states, it appears the Florida chances of first landfall are increasing. However, damaging wind gusts (as well as very heavy rain and inland flooding) associated with the landfalling hurricane may spread northward into these states Sunday night-Monday. Track the latest forecasts and be ready for deteriorating weather conditions by the end of the weekend.

I will continue to have frequent updates on things on Twitter and Facebook. I’ll see about more extensive updates on the blog in the coming few days. Hopefully all this writing is wrong and this system misses Florida completely. There has already been incredible damage in Barbuda, Anguilla, the British Virgin Islands, as well as extensive impacts in the US Virgin Islands and Puerto Rico. The Turks and Caicos Island are suffering a direct hit this afternoon/evening. A truly awful storm we can all hope comes to a conclusion soon. But unfortunately the US may be the last on the list of targets folks in the path must be prepared to action to protect life and property.

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–Meteorologist Nick Humphrey

EDIT at 7:50 pm CDT: Excuse the typo in the shear analysis graphic. That should say “Hurricane Irma”.

Catastrophic Hurricane Irma heading for Leeward Islands. Florida must get ready.

Category 5 Hurricane Irma bearing down on the Leeward Islands at 8:45 am CDT Tuesday.

If you’re in South Florida or the Florida Keys…you need to know what you’ll to once watches and warnings are issued BEFORE they are issued. I do have enough confidence in the path of Hurricane Irma to state that Florida is in a very serious situation based on forecast data and so folks need to 1) track the forecast 2) know your plan, especially if you live in coastal evacuation zones 3) have emergency supplies ready. This storm already has the potential to be devastating for many people all week as it buzzsaws its way through the northern Leeward Islands, close approach to US and British Virgin Islands, then the US territory of Puerto Rico with 3.5 million people, the Dominican Republic, then portions of the Bahamas, before a close passage of the coast of Cuba. And it could do this as a large Category 4-5 hurricane. 
Most likely time of arrival of tropical storm force winds overlay 7 am CDT probability of those winds during 5 day forecast period. Note South Florida is most likely to see winds arrive by Saturday morning and they could arrive overnight Fri-Sat, with the eye not expected near Florida until Sat night-Sun morning.

Get ready, be ready to act if/when watches/warnings are issued and keep track of the latest forecast. Also, hope the best for our friends facing Irma right now.

I’ll updates on Irma throughout the week and you can follow me on Facebook and Twitter.

EDIT AT 10:20 am CDT: Winds in Hurricane Irma increased to 180 mph, making it the most powerful hurricane (by wind) ever observed in the North Atlantic outside the Gulf of Mexico and Caribbean Sea.

–Meteorologist Nick Humphrey