Custom Weather Forecast

Transcription

1 1 of 23 Custom Weather Forecast 2018 Chicago Yacht Club s Race To Mackinac- Cruising Division Disclaimer: The user assumes all risk related to the use of this Custom Weather Forecast. The crew of the participating yacht must determine their ability and willingness to manage all weather-related challenges. Please consult the current official National Weather Service forecast, watches, and warnings before and during the race. Mark@.com Prepared: July 20, 2018

2 2 of 23 Thunderstorms Special Note: The forecast may include the potential for severe thunderstorms. The National Weather Service thresholds for a severe thunderstorm are winds exceeding 50 knots, hail greater than 1 in diameter, or the formation of a tornado. Both severe and non-severe thunderstorms can have a significant and unpredictable effect on wind speed, wind direction, and wave heights. Race participants should continuously monitor the latest National Weather Service forecasts, watches, and warnings. Mark@.com Prepared: July 20, 2018

3 3 of 23 Large-Scale Weather Pattern Figure 1: Surface Forecast Valid 7:00 pm Friday Figure 2: Surface Forecast Valid 7:00 am Saturday Figure 3: Surface Forecast Valid 7:00 am Sunday Figure 4: Surface Forecast Valid 7:00 am Monday Prepared: July 20, 2018

4 4 of 23 Friday s Forecast Mark@.com Prepared: July 20, 2018

5 5 of 23 Friday s Forecast Discussion General The slow approach and passage of a strong occluded low pressure system will dominate the weather across Lake Michigan from Friday into mid-day on Sunday. At the time of this analysis (5:00 am central) this low was centered in southwestern Wisconsin. The system's warm front extends southeast through Illinois while the cold front stretches southwest into eastern Iowa and northern Missouri. The current location of the low is very close to yesterday's forecast which suggests the forecast models may finally be getting a handle on the timing and track of this system. The low and its frontal boundaries will move slowly east on Friday before stalling near southern Lake Michigan. The low's occluded and warm front is expected to reach southern Lake Michigan by 2:00 pm on Friday while the low trails slightly to the west. The occluded/warm front will be east of Lake Michigan by 7:00 pm on Friday, but the trailing low will remain slightly west of the Lake. The low will reach southern Lake Michigan overnight on Friday where it will linger until Sunday morning. Also on Friday, a cold/stationary front associated with a low in Canada will be slowly approaching northern Lake Michigan. While this boundary may promote precipitation across northern Lake Michigan, it is not expected to reach the Lake until overnight on Saturday. The approach and passage of the low across southern Lake Michigan will produce steadily veering winds from south to northwesterly overnight. A period of diminishing winds is expected as the low passes. Precipitation/Thunderstorms Widespread showers are expected with the approach and passage of the low pressure system. The chance of precipitation ranges from 90% to 100% all day on Friday. Total precipitation from 7:00 am Friday to 7:00 am on Saturday will range from.25" to.50". Thunderstorms are also expected on Friday, with the highest risk extending across the southern half of the Lake. Organized severe thunderstorms are expected across Lake Michigan on Friday. The Convective Outlook from the SPC suggests a Slight/Enhanced risk across the southern basin and a Marginal risk across northern Lake Michigan. The NWS forecast includes the possibility of waterspouts across the southern half of the Lake. While waterspouts are possible late Friday night into early Saturday, the potential is relatively low. Cloudy skies will prevail on Friday. Surface Forecast Valid 7:00 pm Friday SPC Convective Outlook For Friday Wind Forecast Valid 7:00 pm Friday Mark@.com Prepared: July 20, 2018

6 6 of 23 Friday s Wind & Wave Forecast-Summary Northern Southeast 15 to 20 knots early afternoon. Gusts to 25 knots. Backing to the east and decreasing to 12 to 17 knots by late afternoon. Continued backing to the east northeast at 12 to 17 knots early evening. Backing to northeast at 12 to 17 knots overnight. Waves 4 to 6 feet. Southern South 20 to 25 knots early afternoon with gusts to 30 knots. Veering toward the southwest and slight decrease to 17 to 23 knots by late afternoon/early evening. Continued veering to the southwest at 17 to 23 knots early evening. Decreasing to 13 to 18 knots and veering to the west late evening. Veering northwest overnight. Waves 4 to 6 feet early building to 5 to 7 feet. Waves diminishing slightly overnight. Important Note Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Mark@.com Prepared: July 20, 2018

7 7 of 23 Friday s Forecast Wind & Wave Forecast-Detail Friday Southern Lake Michigan Northern Lake Michigan Forecast Time Wind Wind Wave Wind Wind Wave Local UTC Direction Speed (kts) Gusts Heights (feet) Direction Speed (kts) Gusts Heights (feet) 1:00 AM 6Z N/A N/A N/A N/A N/A N/A N/A N/A 4:00 AM 9Z N/A N/A N/A N/A N/A N/A N/A N/A 7:00 AM 12Z N/A N/A N/A N/A N/A N/A N/A N/A 10:00 AM 15Z N/A N/A N/A N/A N/A N/A N/A N/A 1:00 PM 18Z S 20 to SE 15 to :00 PM 21Z SSW 17 to E 12 to :00 PM 0Z SW 17 to to 5 ENE 12 to :00 PM 3Z W 13 to to 5 NE 12 to Forecast Notes The wind speed forecast is at the standard meteorological height of 10 meters / 32.8 feet. Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Waves are the significant wave height - the average of the highest 1/3 of the total wave spectrum. Individual waves may be significantly higher than the forecast range. Mark@.com Prepared: July 20, 2018

8 8 of 23 Saturday s Forecast Mark@.com Prepared: July 20, 2018

9 9 of 23 Saturday s Forecast Discussion General Early on Saturday morning, the occluded low will be centered over extreme southern Lake Michigan. The system's frontal boundaries will be well east-southeast of Lake Michigan by this time. A weak surface trough will extend westward from the low. As the low slowly drifts to the southeast on Saturday, this surface trough will move south across the Lake. Also on Saturday, a cold/stationary front northwest of Lake Superior will move slow toward northern Lake Michigan. This weak and slow-moving boundary will linger near northeastern Lake Michigan from late Saturday evening through early Sunday morning. A ridge of high pressure from Canada will build toward Lake Michigan as the low moves slowly east. As the lows moves slowly east and high pressure builds, the pressure gradient will increase across the region. In response, wind speeds will increase. Precipitation/Thunderstorms The proximity of the low will promote widespread showers and thunderstorms through Saturday. Total rainfall across Lake Michigan from 7:00 am on Saturday to 7:00 am on Sunday will range from.50" to.75" across the southern 2/3 of the Lake and.25" to.50" across the northern 1/3. The potential for precipitation will be highest in the morning and diminish throughout the day. The potential for thunderstorms on Saturday is low. Thunderstorms activity that does develop is not expected to become organized or severe. The NWS forecast includes the possibility of waterspouts across the southern half of the Lake, however the potential is relatively low. Overcast skies will prevail on Saturday. Surface Forecast Valid 7:00 am Saturday SPC Convective Outlook For Saturday Wind Forecast Valid 7:00 am Saturday Mark@.com Prepared: July 20, 2018

10 10 of 23 Saturday s Wind & Wave Forecast-Summary Northern Southern Northeast 12 to 17 knots with gusts to 20. Slight backing to north northeast and building to 15 to 20 knots by mid morning. Backing to north at 17 to 22 knots early afternoon. Slight veering to north northeast and building to 20 to 25 knots during the evening. Waves 4 to 6 feet. Northwest 13 to 18 knots overnight with gusts to 20 knots. Slight veering to north northwest at 13 to 18 knots aftern midnight. Veering to north and slight weakening to 10 to 15 by early morning. North and building to 15 to 20 knots during the afternoon. Slight veering to north at 17 to 22 knots during the evening. Waves 4 to 6 feet. Important Note Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Mark@.com Prepared: July 20, 2018

11 11 of 23 Saturday s Wind & Wave Forecast-Detail Saturday Forecast Time Southern Lake Michigan Northern Lake Michigan Wind Wind Wave Wind Wind Wave Local UTC Direction Speed (kts) Gusts Heights (feet) Direction Speed (kts) Gusts Heights (feet) 1:00 AM 6Z NW 13 to to 5 NE 12 to :00 AM 9Z NNW 13 to NE 12 to :00 AM 12Z N 10 to NE 12 to :00 AM 15Z N 12 to NNE 15 to :00 PM 18Z N 13 to N 17 to :00 PM 21Z N 15 to N 20 to :00 PM 0Z N 15 to NNE 20 to :00 PM 3Z NNE 17 to NE 20 to Forecast Notes The wind speed forecast is at the standard meteorological height of 10 meters / 32.8 feet. Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Waves are the significant wave height - the average of the highest 1/3 of the total wave spectrum. Individual waves may be significantly higher than the forecast range. Mark@.com Prepared: July 20, 2018

12 12 of 23 Sunday s Forecast Mark@.com Prepared: July 20, 2018

13 13 of 23 Sunday s Forecast Discussion General Early on Sunday morning, the troublesome low pressure system near southern Lake Michigan is expected to reach southeastern Indiana. However, a weak surface trough will extend from this low north across southern Lake Michigan. The low and its surface trough will move slowly southeast during the day on Sunday. Further north, a stationary front from a low in Canada will stretch across northwestern Lake Michigan. This front will dissipate after moving across northern Lake Michigan on Sunday morning. In addition, the next low pressure system to impact Lake Michigan will be approaching from the west. At 7:00 am on Sunday, this system will be located near eastern Montana. This system will move east on Sunday and Monday, but is not expected to reach Lake Michigan until Monday afternoon/evening. As high pressure builds over the Lake, wind speeds will diminish. Precipitation/Thunderstorms The nearby low in southeastern Indiana will cause the chances of rain to persist into Sunday. The highest probability and highest accumulation will occur over the southern portion of the Lake. Total rainfall near the Lake's southern shore will range from.10" to.25" from 7:00 am on Sunday to 7:00 am on Monday. The extreme northern basin and the Straights should remain rain free during the period. Thunderstorms are expected on Sunday. Overcast skies should gradually clear during the afternoon, particularly across the northern half of Lake Michigan. Surface Forecast Valid 7:00 am Sunday SPC Convective Outlook For Sunday Wind Forecast Valid 7:00 am Sunday Mark@.com Prepared: July 20, 2018

14 14 of 23 Sunday s Wind & Wave Forecast-Summary Northeastern Northeast 17 to 23 knots overnight. Steady weakening throughout the day. Waves 2 to 4 feet subsiding to 1 to 3 feet. Northern Northeast 20 to 25 knots overnight. Weakening to northeast at 15 to 20 knots by mid-morning. Continue weakening to 12 to 17 knots by late afternoon/early evening. Waves 3 to 5 subsiding to 2 to 4 feet. Important Note Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Mark@.com Prepared: July 20, 2018

15 15 of 23 Sunday Forecast Time Sunday s Wind & Wave Forecast-Detailed Northern Lake Michigan Northeastern Lake Michigan Wind Wind Wave Wind Wind Wave Local UTC Direction Speed (kts) Gusts Heights (feet) Direction Speed (kts) Gusts Heights (feet) 1:00 AM 6Z NE 20 to NE 17 to :00 AM 9Z NE 17 to NE 15 to :00 AM 12Z NE 15 to NE 12 to :00 AM 15Z NE 15 to NE 10 to :00 PM 18Z NE 13 to NE 7 to :00 PM 21Z NE 13 to NE 6 to :00 PM 0Z NE 12 to NE 5 to :00 PM 3Z NNE 12 to NNE 5 to Forecast Notes The wind speed forecast is at the standard meteorological height of 10 meters / 32.8 feet. Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Waves are the significant wave height - the average of the highest 1/3 of the total wave spectrum. Individual waves may be significantly higher than the forecast range. Mark@.com Prepared: July 20, 2018

16 16 of 23 Monday s Forecast Mark@.com Prepared: July 20, 2018

17 17 of 23 Monday s Forecast Discussion General Early on Monday morning, an occluded low pressure system centered in south-central Canada will approach Lake Michigan. The system's warm front is expected to pass across the northern half of Lake Michigan early on Monday morning. The system's cold front will be much further west and will sweep across Lake Michigan from late afternoon/early evening on Monday. The cold front will be well to the east of Lake Michigan by Tuesday morning. Precipitation/Thunderstorms No precipitation or thunderstorms are expected on Monday. Clear skies are expected. Surface Forecast Valid 7:00 am Monday SPC Convective Outlook For Monday Wind Forecast Valid 7:00 am Monday Mark@.com Prepared: July 20, 2018

18 18 of 23 Monday s Wind & Wave Forecast-Summary Northeastern North northeast 5 to 10 knots. Slight weakening to 3 to 8 knots during the aftenoon. Waves 1 to 3 feet. Northern North northeast at 10 to 15 knots overnight. Steady weakening to 5 to 10 knots during the afternoon. Waves 1 to 3 feet. Important Note Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Mark@.com Prepared: July 20, 2018

19 19 of 23 Monday s Wind & Wave Forecast-Detailed Monday Northern Lake Michigan Northeastern Lake Michigan Forecast Time Wind Wind Wave Wind Wind Wave Local UTC Direction Speed (kts) Gusts Heights (feet) Direction Speed (kts) Gusts Heights (feet) 1:00 AM 6Z NNE 10 to NNE 5 to :00 AM 9Z NNE 8 to NNE 5 to :00 AM 12Z NNE 7 to NNE 5 to :00 AM 15Z NNE 6 to NNE 5 to :00 PM 18Z NNE 6 to NNE 5 to :00 PM 21Z NNE 5 to NNE 3 to :00 PM 0Z NNE 5 to NNE 3 to :00 PM 3Z NNE 5 to NNE 3 to Forecast Notes The wind speed forecast is at the standard meteorological height of 10 meters / 32.8 feet. Thunderstorms usually produce much higher wind speeds and wave heights. These localized effects on wind speed and wave heights are not included in the forecast. Waves are the significant wave height - the average of the highest 1/3 of the total wave spectrum. Individual waves may be significantly higher than the forecast range. Mark@.com Prepared: July 20, 2018

20 20 of 23 Forecast Model Routing Prepared: July 20, 2018

21 21 of 23 Forecast Model Routing Overview Routing Comments Three model routing solutions are plotted on the image to the right. NAM (lime green) Estimated Duration: 2 days 13 hours Estimated Arrival: 3:48 am Estimated Distance: nm GFS (purple) Estimated Duration: 2 days 8 hours Estimated Arrival: Monday 12:21 am Estimated Distance: 336 nm GEFS (magenta) Estimated Duration: 2 days 13 hours Estimated Arrival: 4:13 am Estimated Distance: nm I think the NAM winds are too light and too quick with veering the wind to northerly. The GFS is on the right track with the trend, but the winds are too strong. The GEFS (the ensemble version of the GFS) appears to have the best handle on wind speeds and the overall trend from Friday into Saturday. Sailing the route plotted by the GEFS appears to be the preferred option. The Routing Table on the next pages provides the detail on the GEFS solution. Please Note: Waypoints on weather forecast maps and other imagery provided by are not to be used for navigational purposes. Client and crew are responsible for avoiding all navigational hazards and operating the yacht in a safe and seamanlike manner. Mark@.com Prepared: July 20, 2018

22 22 of 23 Routing Table From GEFS Forecast Model Forecast Model Routing Table Distance To Bearing To Distance To End Speed Over True Wind TRUE True Wind True Wind Time Waypoint Latitude Longitude Next Waypt Next Waypt Finish Time to Finish Ground Angle Wind Speed Direction 20 Jul 20:00 WP d 13h 13m 143 P 17 kts at Jul 23:00 WP d 10h 13m P 18 kts at Jul 02:00 WP d 07h 13m P 14 kts at Jul 05:00 WP d 04h 13m S 3 kts at Jul 08:00 WP d 01h 13m S 8 kts at Jul 11:00 WP d 22h 13m S 11 kts at Jul 14:00 WP d 19h 13m S 10 kts at Jul 17:00 WP d 16h 13m S 9 kts at Jul 20:00 WP d 13h 13m S 10 kts at Jul 23:00 WP d 10h 13m P 15 kts at Jul 02:00 WP d 07h 13m S 11 kts at Jul 05:00 WP d 04h 13m S 14 kts at Jul 08:00 WP d 01h 13m P 15 kts at Jul 11:00 WP d 22h 13m S 12 kts at Jul 14:00 WP d 19h 13m S 10 kts at Jul 17:00 WP d 16h 13m S 7 kts at Jul 20:00 WP d 13h 13m P 6 kts at Jul 23:00 WP d 10h 13m P 5 kts at Jul 02:00 WP d 07h 13m P 4 kts at Jul 05:00 WP d 04h 13m P 3 kts at Jul 08:00 WP d 01h 13m kts at Jul 09:13 WP d 00h 00m 2.42 Please Note: Waypoints on weather forecast maps and other imagery provided by are not to be used for navigational purposes. Client and crew are responsible for avoiding all navigational hazards and operating the yacht in a safe and seamanlike manner. Mark@.com Prepared: July 20, 2018

23 23 of 23 Prepared: July 20, 2018