Safety At Sea Seminar April 12, Basic Marine Weather Forecasting

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1 1 of 79 Safety At Sea Seminar April 12, 2014 Basic Marine Weather Forecasting Mark A. Thornton LakeErieWX: Marine Weather Education and Forecasting Resources

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3 3 of 79 A Weather Web Page For The Race To Mackinac

4 4 of 79 Creating A Weather Forecast: An Example August 21-22, 2013

5 5 of 79 The Big Picture Weather Makers Low Pressure Systems

6 6 of 79 The Basic Low Pressure System Model

7 7 of 79 Weather Prediction Center

8 8 of 79 Surface Forecasts Out To 7 Days

9 9 of 79 Forecasting Precipitation

10 10 of 79 Total Precipitation By 24-Hour Period

11 11 of 79 Assessing The Potential For Thunderstorms

12 12 of 79 The Nation s Severe Weather Experts

13 13 of 79 Severe Thunderstorms- According To The NWS All types of thunderstorms may be classified as severe. NWS Severe thunderstorm thresholds: Hail >= 1 Surface wind gust >= 50 kts The storm produces at least one tornado The potential for severe status increases as the duration of the storm increases.

14 14 of 79 Convective Outlooks-Highlighting The Potential For Severe Weather Day 1 -August 21, 2013

15 15 of 79 Convective Outlooks-Highlighting The Potential For Severe Weather DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1258 AM CDT WED AUG VALID Z Z THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MS VALLEY AND UPPER GREAT LAKES......UPPER MS VALLEY/UPPER GREAT LAKES... AN UPPER-LEVEL TROUGH WILL MOVE EWD INTO THE UPPER MS VALLEY TODAY. AT THE SFC...A WELL- DEFINED COLD FRONT WILL ADVANCE SEWD INTO SERN MN...NCNTRL WI AND UPPER MI BY MID AFTERNOON. THE MODELS SUGGEST. THUNDERSTORMS WILL INITIATE ALONG THE BOUNDARY AROUND PEAK HEATING WITH THE CONVECTION MOVING SEWD ACROSS THE UPPER MS VALLEY AND UPPER MI DURING THE LATE AFTERNOON. SEVERAL STORM CLUSTERS COULD PERSIST INTO THE EARLY EVENING.

16 16 of 79 Categorizing The Risk For Severe Weather Three Risk Categories Slight: well-organized storms are expected, but in small numbers and/or low coverage. Approximately 5-25 reports of large hail, 5-25 damaging wind reports and/or 1 to 5 tornadoes. Moderate: a greater concentration of severe thunderstorms and greater magnitude of severe weather. High: a major severe weather outbreak is expected with the potential for very damaging wind gusts and/or 20 or more tornadoes.

17 17 of 79 Thunderstorm 4-Hour Intervals 7 am to 11 am 11 am to 3 pm 3 pm to 7 pm 7 pm to 11 pm

18 18 of 79 Local NWS Office Hazardous Weather Outlook HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREEN BAY WI 424 AM CDT WED AUG THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST WISCONSIN. DAY ONE...TODAY AND TONIGHT SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND EVENING AS A COLD FRONT MOVES ACROSS THE AREA. DAMAGING WINDS AND LARGE HAIL ARE EXPECTED TO BE THE GREATEST THREATS. IN ADDITION TO THE THREAT OF SEVERE THUNDERSTORMS...HEAT INDICES WILL CLIMB INTO THE 90S OVER MOST OF CENTRAL AND NORTHEAST WISCONSIN THIS AFTERNOON...WITH A FEW PLACES APPROACHING 100.

19 19 of 79 Preparing Your Wind & Wave Forecast

20 20 of 79 NWS Great Lakes Website

21 21 of 79 NWS Great Lakes Website Lake Michigan

22 22 of 79 Wind Speed / Direction In 3-Hour Increments

23 23 of 79 Wind Gusts In 3-Hour Increments

24 24 of 79 Wave Heights In 3-Hour Increments

25 25 of 79 NWS Chicago Offshore Marine Forecast OPEN LAKE FORECAST FOR LAKE MICHIGAN NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 830 AM CDT WED AUG FOR WATERS BEYOND FIVE NAUTICAL MILES OF SHORE ON LAKE MICHIGAN.SYNOPSIS...LOW PRESSURE OF 29.1 INCHES LIES OVER NORTHERN HUDSON BAY THIS MORNING WITH A COLD FRONT TRAILING SOUTHWEST ACROSS MINNESOTA AND SOUTH DAKOTA. THIS FRONT WILL MOVE ACROSS LAKE MICHIGAN LATE TONIGHT. MEANWHILE...HIGH PRESSURE OF 30.1 INCHES WILL BUILD ACROSS THE NORTHERN PLAINS TONIGHT...THEN MOVE EAST ACROSS LAKE MICHIGAN FRIDAY..REST OF TODAY...SOUTH WINDS 15 TO 20 KT INCREASING TO 20 TO 25 KT THIS MORNING. WAVES 3 TO 5 FT OCCASIONALLY TO 7 FT BUILDING TO 5 TO 7 FT OCCASIONALLY TO 9 FT..TONIGHT...SOUTHWEST WINDS 20 TO 25 KT DIMINISHING TO 10 TO 15 KT DURING THE EVENING...THEN VEERING TO NORTHWEST OVERNIGHT. SHOWERS AND THUNDERSTORMS LIKELY... MAINLY IN THE EVENING. WAVES 5 TO 7 FT OCCASIONALLY TO 9 FT SUBSIDING TO 3 TO 5 FT OCCASIONALLY TO 7 FT DURING THE EVENING...THEN TO 1 TO 3 FT DURING THE OVERNIGHT..THURSDAY...NORTH WINDS 15 TO 20 KT. WAVES 1 TO 3 FT BUILDING TO 3 TO 5 FT OCCASIONALLY TO 8 FT.

26 26 of 79 NWS Marine Forecast Zones

27 27 of 79 NWS Marine Forecast Zones - A Closer Look

28 28 of 79 NWS Green Bay Nearshore Marine Forecast LMZ LAKE MICHIGAN FROM WASHINGTON ISLAND TO STURGEON BAY- NWS GREEN BAY, WI 429 AM CDT WED AUG SMALL CRAFT ADVISORY IN EFFECT THROUGH LATE TONIGHT....TODAY...SW WIND 10 TO 15 KTS...INCREASING TO 15 TO 25 KTS IN THE LATE MORNING AND AFTERNOON. WAVES 3 TO 5 FT...BUILDING TO 4 TO 7 FT IN THE AFTERNOON. ISOLATED SHOWERS AND POSSIBLE THUNDERSTORMS THIS MORNING...THEN A CHANCE FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON..TONIGHT...SW WIND 10 TO 20 KTS VEERING NW AT 5 TO 10 KTS IN THE LATE EVENING AND OVERNIGHT. WAVES 3 TO 5 FT...SUBSIDING TO 2 TO 4 FT. SHOWERS AND THUNDERSTORMS LIKELY IN THE EVENING...THEN A CHANCE OF SHOWERS AND THUNDERSTORMS AFTER MIDNIGHT. WINDS AND WAVES HIGHER IN OR NEAR STORMS..THURSDAY...N WIND 10 TO 15 KTS. WAVES 1 TO 2 FT. MOSTLY SUNNY.

29 29 of 79 Staying Weather Aware On The Racecourse

30 30 of 79 Beaufort Wind Scale

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32 32 of 79 Clouds

33 33 of 79 Clouds Offer A Few Clues Regarding Atmospheric Instability/Stability Clouds in stable environments tend to be wider than they are tall due to weak upward motion. Clouds in unstable environments are typically taller than they are wide due to stronger upward motion.

34 34 of 79 Monitoring Barometric Pressure

35 35 of 79 A Digital Barometer A Valuable Resource

36 36 of 79 Monitoring Trends In Barometric Pressure It is the trend, not the absolute value, of barometric pressure that is important. Falling barometric pressure may signal the potential arrival of inclement weather. The steepness of the decline in pressure can provide clues to the strength of the approaching system an accurate barometer will monitor changing conditions. June 22, 2011

37 37 of 79 VHF Radio Marine Forecasts Marine Observations/NDBC Buoy Reports Severe Weather Watches/Warnings

38 38 of 79 Always Use The NWS Weather Channel Closest To Your Location Best Reception Watches/Warnings Closest To Your Location.

39 39 of 79 Cellular Internet / Satellite Access Marine Forecasts Marine Observations Severe Weather Watches/Warnings Doppler Weather Radar Satellite Imagery

40 40 of 79 Marine Observations From The National Data Buoy Center (NDBC) An array of shore-based and floating observation platforms. Dial-A-Buoy program (888)

41 41 of 79 A Short Primer On Doppler Weather Radar

42 42 of 79 How Radar Works Measuring Backscattered Energy Radar stations transmit pulses of energy within the microwave portion of the electromagnetic spectrum. A very small portion of this transmitted energy is backscattered by objects toward the station s antenna. The station spends 59 minutes 53 seconds of each hour measuring backscattered energy (listening). Rain, snow, hail, etc., all backscatter radar pulses, but so do planes, birds and insect swarms.

43 43 of 79 Sampling The Atmosphere One Slice At A Time Volume Coverage Pattern (VCP) is the combination of distinct scan angles used to sample the atmosphere. Base scans, a popular product available on the Internet, is.5 degrees. Scan angles of increasing value allow forecasters to sample higher regions of weather systems, particularly thunderstorms. Individual scans are stitched together to create composite imagery.

44 44 of 79 Lake Michigan KLOT: June 22, 0048Z Base Reflectivity Composite Reflectivity Base Reflectivity Composite Reflectivity

45 45 of 79 Use The NWS Radar Station Closest To Your Location

46 46 of 79 Doppler Radar Is NOT Live Scans are completed every 5 to 6 minutes Warning: The image that you are viewing may be several minutes old. A fast-moving thunderstorm or squall line may travel 5 to 6 miles between scans. 0016Z-18.1 nm 0021Z-10.8 nm 0026Z 5.0 nm 0031Z-0 nm Until 0021Z You Are Viewing 0016Z Until 0026Z You Are Viewing 0021Z Until 0031Z You Are Viewing 0026Z Image Image Image

47 47 of 79 NWS Hazardous Weather Terminology

48 48 of 79 NWS Marine Hazardous Weather Terminology Watch -- When conditions become favorable for organized severe thunderstorms and tornadoes to develop, the SPC issues a severe thunderstorm or tornado watch. Watches encourage the general public to stay alert for changing weather conditions and possible warnings. Warning -- This is issued when either a severe thunderstorm is indicated by radar or a spotter reports a thunderstorm producing hail one inch or larger in diameter and/or winds equal or exceed 58 miles an hour. Small Craft Advisory -- regional variations exist. Generally issued when the sustained wind or frequent gusts are between 22 and 33 knots and/or waves greater than 4 feet. Gale Warning issued when sustained wind speeds are expected to be from 34 to 47 knots. Storm Warning issued when sustained wind speeds are expected to be from 48 to 63 knots. Marine Weather Warning -- issued for potentially hazardous weather conditions usually of short duration (up to 2 hours) producing sustained marine thunderstorm winds or associated gusts of 34 knots or greater; and/or hail 1 inch or more in diameter; and/or waterspouts. Marine Weather Statement -- A National Weather Service product to provide mariners with details on significant or potentially hazardous conditions not otherwise covered in existing marine warnings and forecasts. Marine weather statements are also used to supplement special marine warnings.

49 49 of 79 An Overview Of The NWS Warning Process August 21-22, 2013

50 50 of 79 Watches And Warnings Are Issued By Each Local NWS Office

51 51 of 79 It Starts With The Forecast Day 1 -August 21, 2013

52 52 of 79 KGRB 2:05 pm / 1905Z

53 53 of 79 MORE WATCHES ARE POSSIBLE ACROSS THE REGION. 1 of 19 MESOSCALE DISCUSSION 1745 NWS STORM PREDICTION CENTER NORMAN OK 0205 PM CDT WED AUG AREAS AFFECTED...PORTIONS OF WI/UPPER MI AND FAR SOUTHEAST MN/NORTHEAST IA CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID Z Z PROBABILITY OF WATCH ISSUANCE...60 PERCENT SUMMARY...SEVERE TSTM POTENTIAL SHOULD STEADILY INCREASE THROUGH MID/LATE AFTERNOON...PERHAPS INITIALLY ACROSS NORTHERN WI AND THE UPPER PENINSULA OF MI AND/OR SOUTHERN MN/FAR NORTHERN IA. SEVERE WIND/HAIL ARE THE PRIMARY HAZARDS. ONE OR

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55 55 of 79 FRONT. 3 of 19 MESOSCALE DISCUSSION 1748 NWS STORM PREDICTION CENTER NORMAN OK 0610 PM CDT WED AUG AREAS AFFECTED...PARTS OF WRN/NRN AND CENTRAL WI AND UPPER MI CONCERNING...SEVERE THUNDERSTORM WATCH VALID Z Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 494 CONTINUES. SUMMARY...STRONG TO SEVERE STORMS WILL CONTINUE TO DEVELOP ACROSS NERN AND CENTRAL WI AND THE SRN EXTENT OF UPPER MI /FROM DICKINSON TO SCHOOLCRAFT COUNTIES/. DAMAGING WIND GUSTS AND HAIL TO AROUND 1 INCH IN DIAMETER REMAIN THE PRIMARY THREATS. COUNTIES IN THE WAKE OF THE ONGOING LINE OF STRONG TO SEVERE STORMS CAN CONTINUE TO BE CANCELLED BY LOCAL WFO/S WITH THE PASSAGE OF THE COLD

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60 60 of 79 MARINE WEATHER STATEMENT NATIONAL WEATHER SERVICE GREEN BAY WI 611 PM CDT WED AUG LMZ PM CDT WED AUG THUNDERSTORMS APPROACHING THE WATERS THE AREAS AFFECTED INCLUDE WATERS OF GREEN BAY AND NEARSHORE WATERS ADJACENT TO DOOR COUNTY. AT 605 PM CDT...DOPPLER RADAR INDICATED A LINE OF THUNDERSTORMS CAPABLE OF PRODUCING WINDS OVER 40 KNOTS FROM 18 NM NORTHWEST OF CEDAR RIVER TO 37 NM NORTHWEST OF SHAWANO. THE LINE OF STORMS WAS MOVING SOUTHEAST AT 35 KNOTS. PRECAUTIONARY/PREPAREDNESS ACTIONS...THIS STORM WILL LIKELY PRODUCE STRONG GUSTY WINDS OVER 40 KNOTS...AND COULD POSE A SERIOUS HAZARD FOR BOATERS. BOATERS SHOULD CONSIDER HEADING FOR SHORE BEFORE THE STORM ARRIVES. 8 of 19

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72 72 of 79 Determining Storm Motion

73 73 of 79 Which Direction Is The Storm System Moving?

74 74 of 79 Which Direction Is The Storm System Moving? Buoy Observations Direction

75 75 of 79 Proof That Thunderstorms Are Unpredictable

76 76 of 79 Rapidly Developing Storms Ahead of Main Line

77 77 of 79 Daily Summary & Forecast Verification

78 78 of 79 Managing The Weather On The Racecourse Have a clear understanding of the forecast and risk for thunderstorms before you leave the dock. Monitor your (digital) barometer. Rapidly falling barometric pressure often signals the approach of severe weather. Listen to your VHF radio for latest weather reports, observations, watches, and warnings. Keep an eye to the sky. Rapidly vertically-developing clouds suggest an unstable environment and the potential for severe thunderstorms. / Text Message alerts from NWS, AccuWeather, etc. Cellular-internet/XM Satellite Weather to monitor radar, watches and warnings. A wide variety of applications exist.

79 79 of 79 Thank You Questions?