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HomeMy WebLinkAbout320.004 - Wildland Belt Weather Kit Kestrel MeterEffective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 1 of 11 300 Training and Equipment Manual SECTION 320.004 WILDLAND BELT WEATHER KIT/KESTREL METER PURPOSE The purpose of this procedure is to provide information to Fresno Fire Department (FFD or Department) members on belt weather kits and Kestrel Meters. APPLICATION For taking weather observations when gathering situational awareness during incidents. OPERATIONAL POLICY These kits are to be used by personnel while assigned to wildland fires. Members should be reminded if any of the items are left on the fire line at a major incident; an ICS-213 form should be completed and turned into supply for restocking. If not available at the incident, obtain an “S” number for reimbursement. OPERATIONAL GUIDELINE During wildland incidents, weather readings should be taken every hour to recognize any trends. If fire activity is increasing and/or the weather is becoming hotter and drier, weather readings should be taken more frequently. PROCESS 1. Belt Weather Kit: a. How to Take Weather Readings: i. Inspect the cotton wick on the sling psychrometer and ensure it is in good condition and firmly in contact with the thermometer bulb. A psychrometer with a dirty, yellowed, or frayed wick does not provide an accurate reading and the wick should be replaced. Do not touch the wick with fingers because contaminants affect the accuracy. Fresno City Fire Department Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 2 of 11 ii. Check for a separated mercury column in the thermometer; if found, this can sometimes be repaired by dipping the thermometer in ice water, then hot (not boiling) water. b. Using a Psychrometer: (Figure 1) i. Find a location representative of the fuels the fire is burning in. Stand in a shady spot so radiant heat from the sun does not affect the thermometers. Use your body to shade the instrument if necessary. ii. Thoroughly saturate the wick of the sling psychrometer with distilled water. If the water beads up and does not easily soak in, the wick should be replaced. iii. Begin swinging the psychrometer at arm’s length at a steady pace (about two turns per second). Be extremely careful not to strike the psychrometer on a hard object. Keep it far enough from your body and face into the wind so you don’t draw body heat and humidity into the instrument. iv. After approximately one minute, stop and quickly check the wet bulb temperature. (Stop too long and the temperature starts to change.) Do not put fingers on the glass. Continue swinging the psychrometer for approximately one minute. Check the wet bulb temperature again to see if it has changed from the previous reading. If it has, continue swinging for another minute and check again. Repeat as necessary. The goal Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 3 of 11 is to get the lowest possible reading out of the wet bulb thermometer. Note: Ensure the wick does not become too dry. If it does, add another drop or two of distilled water and start over. v. Carefully, but quickly, read and record the final wet bulb and dry bulb temperatures. c. Tips: The following common mistakes can lead to inaccurate psychrometer readings: i. Not ventilating the psychrometer long enough to reach equilibrium. ii. Not getting the wick wet enough, or letting it dry out. iii. Holding it too close to the body or taking too long to read the thermometers. iii. Touching the bulb ends with the hands while reading. iv. Not facing into the breeze. Each of these mistakes can lead to a wet-bulb temperature reading that is too warm and subsequently, an RH (relative humidity) that is too high. d. Computing Relative Humidity (RH): There are various methods to compute the RH from the dry and wet bulb readings: Slide Rule Calculator: Not normally used on the fire line because the table is only accurate at sea level. Handheld Computer: The quick and easy way, but using tables is also a proven method (explained below). Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 4 of 11 Pocket Weather Instrument (such as Kestrel): Fast way to get the RH, as well as dry bulb temperature. RH Tables: Charts of numbers where the dry and wet bulb temperatures can be referenced, and the corresponding RH (and sometimes dew point) can be found. These tables should come with the belt weather kit. If the tables cannot be found, use the slightly less accurate tables in the Incident Response Pocket Guide. Before looking up the RH, verify the proper chart for the elevation is used. Each chart has the elevation range printed at the top. Note: Elevation ranges and dry-bulb temperature increments are broader in the Incident Response Pock Guide and thus, not as accurate. e. Find the RH using the tables: To use the tables that come with the belt weather kit, locate the row with the dry bulb reading along the left side; follow that row to the right until it matches the wet bulb reading printed above. Two numbers are found here - the dew point on top, and the RH on bottom. (To remember which is which, the terms are in alphabetical order from top to bottom.) To use the tables in the Incident Response Pocket Guide: i. Calculate the “wet bulb depression”, which is simply the wet bulb minus the dry bulb. ii. Find the row with the dry bulb reading along the left side and follow that row to the right until it matches the wet bulb depression printed above. Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 5 of 11 (Figure 2) (Figure 3) The table on the upper left is from the Incident Response Pocket Guide, for elevation range 5000 – 9200. The table on the upper right is from an RH & Dew point table found with a belt weather kit, for elevation range 6101 – 8500. If dry bulb = 86 and the wet bulb = 55, the first table gives an RH = 13% (wet bulb depression is 86 – 55 = 31). The second table gives an RH of 14% and dew point of 31. f. Completing and Recording Measurements: Once the dry bulb temperature, wet bulb temperature, and relative humidity have been measured, with the time of day, Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 6 of 11 record the measurements in the Weather Log. In addition, wind speed and direction need to be measured and the clouds observed as follows: i. To accurately determine wind direction briefly, tie a two- foot length of flagging to a bush or shrub in an unsheltered area. Make a note of the predominant wind direction. Mark “variable” or “still” if there is little or no wind to measure. ii. Measure wind speed using the anemometer. Hold the instrument out at arm’s length into the wind. Grasp it at the top; do not to block the hole located at the bottom of the back side. This hole is where the wind blows into the instrument, causing the tiny ball to rise. Read the wind speed by looking at the numbers on the left side. (Figure 4) In the event the wind speed is greater than 10 mph, the scale is to be used on the right side. To do this, place finger over the hole on the top of the instrument; the ball should quickly drop as the alternate scale is used. Do not be tempted to blow into the hole; this can introduce moist air into the instrument and cause the ball to “stick”. Make a note of the average wind speed, and the maximum gusts. This may be recorded like this: “5/10” (meaning 5 mph average, 10 mph gusts). Lastly, look around at the sky. What type of clouds can be seen? What part of the sky are the clouds in (N, E, S, and/or W)? How much of the sky is covered by the Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 7 of 11 clouds? Can any storm cells or lightning be seen? Record these observations in a concise manner. For example: “25% cumulus in SW”. (Figure 5) Above is an example of completed weather observations recorded in the Weather Log. This information is invaluable to the local Fire Behavior Analyst and Meteorologist, who may refine future predictions based on actual recorded observations. g. Broadcasting the Weather Observations: i. On the fire line, do not keep weather observations to yourself! Monitor the trends on a regular basis and disseminate the information to other personnel. As a rule, “take the weather” and broadcast a concise weather report at least every 60 minutes on the fire line. During changing weather conditions, increase measurements to every 30 minutes or more. Be sure to include trends in the report. The following is a good example of a radio report: “All units on the Big Hill Fire stand by for weather.” Wait for personnel to get pens and paper ready. “At 1200, temperature was 85 degrees, up 4 degrees over the last hour. RH is 18%, down from 21%. Winds are 5 to 10 mph from the Northwest. Anyone need a repeat?” 2. Kestrel Meter: a. Turning on and Off: i. Press the Power Button to turn on. ii. Hold the Power Button for 3 seconds to turn off. Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 8 of 11 b. Select Measurement Mode: i. Press arrows to access each Measurement screen: Wind Speed Temperature Wind Chill Relative Humidity Heat Stress Index Dew-point Temperature Barometric Pressure Altitude Wet Bulb Temperature Backlit Display Pressure Trend c. Select the unit of measurement by holding the power button and pressing the right arrow button to scroll through the available units of measurement. d. Replacing the Battery: i. Use a US Nickel or similar coin to twist open the battery compartment. ii. Replace battery with a new, clean CR2032 coin cell battery, with the positive side up. iii. Be sure to keep the black rubber O-ring in the groove on the case. e. Refer to Kestrel Owner’s Manual for Sensor Calibration. Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 9 of 11 INFORMATION (Figure 6) (Figure 7) (Figure 8 - Parts) Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 10 of 11 Pencils Writing Board Water Bottle Slide Rule Anemometer Humidity Table Notebooks Compass Psychrometer See the following links for more information on Kestrel: Kestrel 3500 FW Fire Weather Owner’s Manual Kestrel 3500 FW Fire Weather Overview Video WFSTAR: Kestrel Digital Weather Meter Tutorial (Figure 9) DEFINITIONS 1. Psychrometer: A hygrometer consisting of a wet-bulb and a dry- bulb thermometer, the difference in the two thermometer readings being used to determine atmospheric humidity. Effective Date: November 2014 Evan Sutliff, Fire Captain Current Revision Date: 9/27/2022 Section 320.004 Next Revision (1) Date: 9/27/2024 Page 11 of 11 2. Anemometer: An instrument for measuring the speed of the wind. CROSS REFERENCES No cross-references recognized.