Weather: Forecasts

1. Forecast Confidence
   • Best Practices for Determining Weather Confidence
2. National Weather Service Products
   • Comprehensive Displays
   • Short Term Forecast Products (1-7 Days)
   • Extended Forecast Products (1 week to Several Months)
3. Forecast Models
4. Special Wildland Fire Guidance Tools
   • Global
   • National
   • CONUS
   • Regional Tools
5. Long Range Forecast Drivers 
   • Teleconnections and Forcing Mechanisms

Forecast Confidence

The typical Confidence Horizon for an application requiring forecast information with "Very High" confidence/accuracy is about three days. What is critical is that there are frequent shifts in this relationship that both expand and contract the amount of time that "Very High" skill is available, thus changing the Confidence Horizon.

This is especially helpful when choosing the appropriate analysis tool in the Wildland Fire Decision Support System (WFDSS) (Near-term, Short-term or FS Pro), or applying the weather forecast within them. The concept is also helpful when placing explanations in the analysis or incident notes section of WFDSS.
The atmosphere is chaotic but sometimes there is rhythm in the chaos. Climate outlook scientists study coupled oceanic and atmospheric forcing mechanisms like the El Nino Southern Oscillation (ENSO) cycle and Madden Julian Oscillation (MJO). These forcing mechanisms are tied to several teleconnection or long range-long term correlated weather patterns that determine meteorological impacts across North America.
Forecast skill typically goes up (i.e., rhythm in the chaos) in the mid and long term when certain forcing mechanisms and teleconnection patterns align, thus adjusting the normal Confidence Horizon. Under these circumstances, a monthly or seasonal outlook can have medium to sometimes high confidence for certain weather patterns such as warmer and drier conditions and sometimes frequent wind events. This is a shift from Low to Very Low confidence under normal situations for longer-range forecasts.
Other teleconnection alignments can lead to mixed atmospheric forcing signals, thus leading to unusually low confidence periods (i.e., conflicting rhythm).

Best Practices for Determining Weather Confidence

Review text discussions routinely issued by the National Weather Service (NWS), Predictive Services (7 Day Significant Fire Potential), Climate Prediction Center (CPC) and Storm Prediction Center (SPC).

NWS Area Forecast Discussion – This NWS product is intended to provide a well-reasoned discussion of the meteorological thinking which went into the preparation of the gridded forecast. The forecaster will try to focus on the most particular challenges of the forecast. The text will be written in plain language or in proper contractions and confidence can often times be discerned by the verbiage used. At the end of the discussion, there will be a list of all advisories, non-convective watches, and non-convective warnings. The term non-convective refers to weather that is not caused by thunderstorms. An intermediate Area Forecast Discussion will be issued when either significant forecast updates are being made or if interesting weather is expected to occur.

PS 7 Day Significant Fire Potential: Expression of confidence will sometimes be written in the weather discussion portion of the product.

SPC - CONUS Discussions are provided twice daily for the Day 1 and 2 outlooks during the early to late morning hours. The Day 3-8 outlook and discussion is updated once per day during the afternoon.

CPC 6-10 Day, 8-14 Day, and 3-4 Week Discussions: 6-10 and 8-14 day discussions are updated Monday to Friday but not updated by a forecaster during the weekend. 3-4 week discussions are updated on Friday. Confidence is oftentimes mentioned or alluded to in these discussions.

When the weather information gets fuzzy and you are not sure where it lies on the Confidence Horizon, it is best to directly consult Predictive Service or NWS forecasters and Incident Meteorologists (IMETs). Don’t shy away from talking to all three sources so you can gain a clearer picture of the Confidence Horizon.

There are several types of questions you should consider asking.

1. Does your office have access to a high-resolution model and use it for grid editing?
2. How often do you update your discussions, is there a routine fire weather discussion during the fire season?
3. Do you have a long-range forecast expert in the office?
4. Does your office send out special email notices or produce webinar or webcasts routinely during the fire season or during significant events?
5. Inquire about the spread or consistency in recent modeling?
6. Are there any localized critical fire weather growth patterns for the area?

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National Weather Service Products

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Comprehensive Displays

NWS National GIS Map Viewer – The NWS National GIS Map Viewer is a web-based system that provides a single interface to access all things GIS related in the NWS. View the pop-up at this page for experimental products on fire.

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Short-Term Forecast Products (1-7 Days)

NWS Routine Fire Weather Forecasts – Generated twice daily during the area’s main fire season and updated when conditions warrant, these narrative forecasts include a discussion of expected weather events, general weather parameters for the forecast zone over the next 48 hours, and an outlook summary for days 3-5.

NWS Watches and Warnings – General site provides access point to different products with map emphasizing different watches and warnings. Issuance of a warning or watch implies stronger confidence levels in growth conditions between 12-96 hours ahead of an event.

NWS Spot Weather Forecasts – This interface is intended to be used solely for the relay of forecast information to the National Weather Service. Submissions sent through this online form are intended for internal agency use.

NWS Weather Prediction Center (WPC) – The WPC provides forecast products including deterministic and probabilistic quantitative precipitation forecasts and discussions, short-term and medium-range forecasts, and surface analysis.

National Digital Forecast Database (NDFD) and Wildand Fire Assessment System NDFD Point Forecasts (CONUS Only) – The NWS's NDFD graphic products are derived from a prescribed set of data contained within the NDFD. These graphics are representations of the official NWS digital forecast. Forecast information for the Canadian portion of the Great Lakes is for informational purposes only and does not constitute an official forecast. In CONUS only, WFAS provides a tool that allows NDFD forecasts to be queried for individual latitude-longitude locations.

NWS Storm Prediction Center – This Center provides convective and fire weather outlooks out to 8 days across the CONUS. They also provide special fire, convective and precipitation weather interrogation tools such as the High Resolution Ensemble Forecast (HREF) and Short Range Ensemble Forecast (SREF) viewers.

Predictive Services 7 Day Significant Fire Potential – This product highlights the likelihood that a wildland fire event will require mobilization of additional resources from outside the area in which the fire situation originates. Weather, fuels, resource availability, and probabilities of ignition are assessed each day to create the probability levels out 7 days. Forecasts of Energy Release Component, Burning Index, 10-100- and 1000-hour dead fuel moistures can also be reviewed using the main webpage.

• High Risk = Days in this category represent a probability of 20% or higher for a significant fire. 

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https://www.nifc.gov/nicc/predictive-services

Extended Forecast Products (1 Week to Several Months)

NWS Climate Prediction Center Extended Outlooks – The CPC is responsible for issuing seasonal climate outlook maps for 1-13 months in the future. In addition, the CPC issues extended range outlook maps for 6-10 and 8-14 days as well as several special outlooks, such as degree day, drought and soil moisture, and a forecast for daily ultraviolet (UV) radiation index. Many of the outlook maps have an accompanying technical discussion.

Predictive Services Seasonal Outlooks – At the beginning of each month, seasonal outlooks are posted. These outlooks serve as assessments of the current and projected fuels, weather, and fire potential out four months.

NWS Climate Prediction Center Expert Assessments – Includes Hazards Assessment, ENSO update, and others. CPC meteorologists and oceanographers review climate and weather observations and data along with model results and assess their meaning, significance, current status, and likely future climate impacts. Their findings are issued as assessments, advisories, special outlook discussions, and bulletins.

Drought Outlooks and Seasonal Climate Forecasts – These forecasts show predicted trends for areas experiencing drought depicted in the U.S. Drought Monitor, as well as indicating areas where new droughts may develop.

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Forecast Models

Meteorologists produce weather forecasts based largely on interpreting and validating weather models. Several models are available with varying update cycles, output time intervals, temporal range, and spatial resolution. Models are semi-routinely adjusted based on new research, new observing techniques, and increased computer processing power.

Deterministic and Ensemble models have different classifications such as global, regional, and convective allowing (CAMS). High-resolution models (≤ 5 km) are generally convective allowing and have 15 minute to 1 hour time-steps. They can resolve terrain induced and altered wind regimes, small scale boundary passages and banded and cellular precipitation features. Due to the differing scales, physics, and initial conditions CAMs models can produce widely differing solutions when compared to each other, thus making it tricky for forecasters to choose the right solution.

Deterministic, or operational, models use the best estimate of the current state of the weather (initial conditions) to provide a singular solution out in time. Outputs generally contain higher spatial resolution compared to ensemble outputs.

Probabilistic or ensembles are a collection of numerical model outputs that show slightly different possible outcomes. The outcomes are slightly different because each member of the ensemble has been perturbed or initialized with slightly different starting atmospheric conditions. Forecast skill can increase the first 1-2 weeks of a forecast period using these ensemble modeling systems.

The amount of spread in an ensemble model should directly be related to the uncertainty of the forecast because the actual observed weather solution should fall somewhere in between the individual members solutions. Tighter the spread, more confidence in the forecast. Wider the spread, less confidence.

There are several types of useful outputs that can result from ensemble weather modeling. For example, NAEFS provides outputs based on reviewing a 3-week period centered on the valid day using a 30 year climate record.

• Standard anomaly: How different is forecast from climatological mean?
• Percentile: Where would the forecast fall with respect to climatology? Max and Min values indicate the forecast falls out of the 30 year climate record thus a potentially significant event.
• Return interval: How often do these forecasts show up in the climatology?
• Probabilities: How many of the ensemble members are producing extreme values?

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Special Wildland Fire Guidance Tools

These tools will help identify unusual or important fire weather and danger time periods and give higher confidence to a critical fire growth or slowing pattern. Publications explaining the tools or indexes are provided in the Weather References section of this guide.

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Global

Global Wildfire Information System (GWIS) which provides 8 km ECMWF based forecasts of Fire Weather Index (FWI) out 10 days across the Globe.

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National

Hot Dry Windy (HDW): Designed to help identify days which are more likely to have adverse weather conditions. Represents the multiplication of maximum wind speed and maximum vapor pressure deficit (VPD).

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CONUS

Severe Fire Danger Index (SFDI): Five separate classifications (Low-Moderate-High-Very High and Severe) represent the normalized percentile values of combining the Energy Release Component (ERC) and Burn Index (BI). Between 2003 to 2016, 75% of all MODIS active large fire pixels and 81% of all fire radiative power occurred when the index was Very High or Severe. NWS NDFD weather forecasts feed this index thus forecasted wind speeds may not adequately represent a locally significant terrain altered wind event especially beyond three days.

Fire Potential Index (FPI): Is a linearly scaled from 0 to 100 with 0 occurring when vegetation is near or fully green and 100 hour dead fuels are too moist to burn. FPI is 100 when vegetation is fully cured and 10 hour dead fuel moisture is 2%.

Fosberg Fire Weather Index (FFWI)

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Regional Tools

Alaska Fire & Fuels (AKFF): CFFDRS Fire Weather Index (FWI) forecasts

Great Lakes Fire & Fuels (GLFF): CFFDRS FWI forecasts

Southeast US Fire Weather Intelligence Portal

Southern California Santa Anna Wildfire Threat Index

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Long Range Forecast Drivers

It’s the meteorologist’s job to understand coupled atmospheric-oceanic teleconnections but the analyst should be aware of these teleconnections because they are generally referred to in longer-range forecast discussions. The analyst will be introduced to a few important teleconnections and/or long-range outlook terms in the following table. It is important to point out that some teleconnection patterns can work together or work against each other. This is called constructive and destructive interference. Research continues in this arena and how climate change impacts traditional teleconnection impacts.

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Teleconnections and Climate Forcing Mechanisms