Commanders’ Weather Seminar,
February 27, 2016
Pequot Yacht Club
Long Island Sound sea breezes
Long Island has 3 potential sea breezes
Sea breeze circulation
Stability
• In a standard atmosphere, the temperature falls 3 degrees for every 1000
feet of elevation
• In an unstable atmosphere, temperature falls more than 3 degrees for
every 1000 feet of elevation
• In a stable atmosphere, temperature falls less than 3 degrees for every
1000 feet of elevation
• When an inversion is present, temperature actually rises as you gain
elevation – this is extremely stable
Gray, ME upper air data
74389 GYX Gray Observations at 12Z 10 Apr 2015
----------------------------------------------------------------------------PRES HGHT TEMP DWPT RELH MIXR DRCT SKNT THTA THTE THTV
hPa m C C % g/kg deg knot K K K
----------------------------------------------------------------------------1004.0 125 0.0 0.0 100 3.83 60 2 272.8 283.3 273.5
1000.0 158 0.4 0.2 99 3.90 125 3 273.6 284.2 274.2
993.0 214 1.2 1.1 99 4.19 135 6 274.9 286.4 275.6
981.8 305 1.0 0.8 99 4.16 150 12 275.6 287.1 276.2
945.2 610 0.2 0.0 99 4.07 160 18 277.8 289.1 278.5
932.0 723 -0.1 -0.3 99 4.03 167 27 278.6 289.9 279.3
925.0 783 0.6 0.6 100 4.34 170 32 279.9 292.1 280.6
910.1 914 3.6 3.6 100 5.46 180 36 284.3 299.7 285.2
910.0 915 3.6 3.6 100 5.47 180 36 284.3 299.8 285.2
876.6 1219 2.6 2.5 99 5.26 190 35 286.4 301.4 287.3
855.0 1422 2.0 1.8 99 5.12 198 38 287.7 302.5 288.6
850.0 1469 2.2 2.1 99 5.27 200 39 288.4 303.6 289.4
829.0 1672 2.6 2.6 100 5.60 211 41 290.9 307.2 291.9
821.0 1750 3.8 3.8 100 6.16 216 41 293.0 311.0 294.1
813.1 1829 3.6 3.6 100 6.12 220 42 293.6 311.5 294.7
807.0 1890 3.4 3.4 100 6.09 223 44 294.0 311.9 295.1
783.2 2134 4.6 4.6 100 6.83 235 50 297.8 318.1 299.1
779.0 2178 4.8 4.8 100 6.97 237 50 298.5 319.2 299.8
754.5 2438 3.9 3.9 100 6.74 250 50 300.3 320.5 301.5
Convergence and divergence
Convergence and
divergence
Low pressure
Air converges at the surface and
rises to form clouds
Aloft, the air diverges, which
allows the clouds to expand
High pressure
Air diverges at the surface and
causes the air to sink and clouds to
evaporate
More convergence aloft, the more
sinking and the clearer the skies
will be
Wind shear
Directional shear – wind
directions change with height
Wind speed shear – wind speeds
change with height
Directional and speed shear –
wind directions and wind speeds
change with height
Why is this important
• If the air is sinking, winds will be gusty. How will the wind gusts
change the wind direction and how strong will the gusts be?
• What type of twist will you have on your sails?
• Will there be a change in winds from near land to offshore?
Sea breeze quadrants in the northern
hemisphere
Quadrant 1 sea breeze
• NW gradient wind, 15-20 kts or less
• Divergent breeze along the shoreline, so just offshore will calm 1st
with strongest winds on the land and offshore ½ to 1+ miles
• Good sea breeze, once it develops, since the gradient wind enhances
the winds aloft/flow aloft
• Sea breeze develops as a SSW wind and veers late afternoon, as it
builds
• All cumulus clouds inland. If cumulus clouds move offshore, the sea
breeze will weaken, veer, and probably become NW
• Sea breeze ends quickly around sunset
NW Gradient wind, 0600edt
NW Gradient wind at 0900edt
NW Gradient wind at 1100edt
NW Gradient wind at 1400edt
No wind
NW Gradient wind at 1600edt
NW Gradient wind at 1800edt
Quadrant 2 sea breeze
• NE gradient wind
• Convergent breeze within ½ mile of the shoreline. Wind is NNE at the
shoreline and NE just offshore
• NE gradient wind must be 10 kts or less and skies must be sunny
• Large wind hole develops 1st 1-2 miles offshore
• Sea breeze is slow to develop from the SE
• Sea breeze will oscillate right as it increases, but it is generally a light
or very light sea breeze
• Increasing clouds or setting sun will lead to the winds quickly backing
to gradient
Quadrant 3 sea breeze
• SW gradient wind
• Left twist into the shoreline
• Gradient wind opposes the sea breeze circulation
• SW wind diminishes mid-day/early afternoon
• Sea breeze influence will cause the winds to shift left and freshen mid
afternoon
• Sea breeze typically peaks very late afternoon/early evening and
slowly oscillates right
• Need to be patient, waiting for a good, late afternoon sea breeze
SW Gradient wind at 0800edt
SW Gradient wind at 1100edt
Very little wind
SW Gradient wind at 1500edt
SW Gradient wind at 1700edt
SW Gradient wind at 1900edt
Quadrant 4 sea breeze
• SE gradient wind
• Convergent breeze inshore with a left twist
• If sunny and SE wind under 10 kts, the winds will diminish and
oscillate right early afternoon
• Sea breeze will be late to develop and will be quite light
• Increasing clouds or approaching sunset will lead to the winds
backing or moving right
• This is a very poor sea breeze day
Land breeze
• Totally different from a sea breeze
• No wind during the evening
• If skies are clear, the land cools quickly, especially away from the cities
• If the ocean is warmer than the land, the pressure becomes higher
over the land and the air starts to flow from the land to the ocean,
starting 1st at the shoreline
• Cooler the land temp relative to ocean, the stronger and larger the
land breeze will be
• Land breezes are stronger in the Fall and weaker in the Spring
2016 Newport to Bermuda Race
Ocean Prediction Center
• http://www.opc.ncep.noaa.gov/
Ocean Prediction Center
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Pros
1) The information is free
2) Easy to download
3) The weather information is frequently quite accurate
4) Provides some near real time buoy and ship data
a) buoy data is 10m wind obs every 10 minutes
b) ship data is less reliable since the obs are not consistent to a specific format and the observing equipment is
not standardized and frequently not calibrated
Cons
1) You need to have knowledge of how weather systems work and interact
2) A general area forecast and not specific to a location
3) Limited wind data
Weather models
• http://meteocentre.com/models/models.php?mod=gemglb&map=na
&run=00&lang=en
• http://justin.wiscwx.com/
• http://www.weatheronline.co.uk/cgibin/expertcharts?LANG=en&CONT=euro&MODELL=gfs&VAR=prec
Weather models
1) GFS – this the US global forecast model
a) it is free and updated 4 times per day
2) NAM – this is a high resolution US model and limited to N America and the immediate
surroundings
3) Other global forecast models
a) GEM – Canadian
b) NAVGEM – US Navy
c) UKMET – Great Britain
d) ECMWF – European
4) WRF is a global model used for mesoscale forecasts
5) Ensemble models
a) several global models run parallel programs with slightly different physical approximations, so
you end up with a range of potential weather solutions
6) Several companies cannibalize the GFS or WRF and produce hires local models
Free sources for grib files
1) UGRIB - http://www.grib.us/
2) SAILDOCS - http://www.saildocs.com/
3) SQUID - http://www.greatcircle.be/en/squid-grib-files-viewerrouting-2/
All can be accessed via a land line.
All are legal to access during the Newport to Bermuda Race
Gulf Stream
• SW to NE current, averaging 2-4 kts and on occasion 5+ kts from Florida to
Cape Hatteras
• Meanders once the GS turns east from Cape Hatteras
• Frequently a meander near the Newport to Bermuda rhumb line
• Warm eddies N of the GS flow clockwise
• Cold eddies S of the GS flow counter-clockwise
Sources for Gulf Stream information
• http://ecowatch.ncddc.noaa.gov/JAG/Navy/data/satellite_analysis/gsncofa.gif - northern Gulf Stream analysis
• http://ecowatch.ncddc.noaa.gov/JAG/Navy/data/satellite_analysis/gsscofa.gif - southern Gulf Stream analysis
• http://www7320.nrlssc.navy.mil?GLBhycom1-12/glfstr.html
• http://fermi.jhuapl.edu/avhrr/gs_n/index.html - satellite imagery for the Gulf Stream
• http://marine.Rutgers.edu/cool/sat_data/?product=sst&region=northMAB&notthumbs=0 – satellite imagery for the Gulf
Stream
Gulf Stream analysis from Dr Walstad for
2014 Newport to Bermuda Race
Optimum routing examples
• 2015 Transpac with Wild Oats, start 1900utc July 18, 2015
• 2015 Sydney to Hobart with Comanche, start 0100utc December 26
• 2014 Newport to Bermuda Race, start 1600utc June 20, 2014
EAC – offshore SE Australia
El Nino and La Nina
• El Nino occurs when water temps are warmer than normal in the
eastern equatorial Pacific
• La Nina occurs when water temps are colder than normal in the
eastern equatorial Pacific
El Nino
El Nino
• Reduced tropical activity in the North Atlantic – water temps cooler
than normal in the western North Atlantic
• Increased squall and tropical activity in the eastern North Pacific –
earlier departure to head southwest to the South Pacific
• Decreased squall and tropical activity in the western North Pacific
during the early part of the season
• Very stormy on the US West Coast during the Winter
• Warm in the northern US, east of the Rocky Mountains, but stormy
from Texas to the Carolinas
• High frequency of SW winds in Auckland
La Nina
La Nina
• Very busy tropical season in the North Atlantic, as water temps are
higher than normal
• Less tropical activity in the eastern North Pacific
• Very busy tropical season in the southern South Pacific from
Vanuatu/Fiji to the southeast
• Dry and quieter than normal tropical season from the southern
Philippines to the South China Sea
• Warmer than normal and quieter winter season across North America
Sea surface temps now
Historical El Nino/La Nina
Year
DJF
JFM
FMA
MAM
AMJ
MJJ
JJA
JAS
ASO
SON
OND
NDJ
1996
-0.9
-0.7
-0.6
-0.4
-0.2
-0.2
-0.2
-0.3
-0.3
-0.4
-0.4
-0.5
1997
-0.5
-0.4
-0.2
0.1
0.6
1
1.4
1.7
2
2.2
2.3
2.3
1998
2.1
1.8
1.4
1
0.5
-0.1
-0.7
-1
-1.2
-1.2
-1.3
-1.4
1999
-1.4
-1.2
-1
-0.9
-0.9
-1
-1
-1
-1.1
-1.2
-1.4
-1.6
2000
-1.6
-1.4
-1.1
-0.9
-0.7
-0.7
-0.6
-0.5
-0.6
-0.7
-0.8
-0.8
2001
-0.7
-0.6
-0.5
-0.3
-0.2
-0.1
0
-0.1
-0.1
-0.2
-0.3
-0.3
2011
-1.3
-1.1
-0.8
-0.6
-0.3
-0.2
-0.3
-0.5
-0.7
-0.9
-0.9
-0.8
2012
-0.7
-0.6
-0.5
-0.4
-0.3
-0.1
0.1
0.3
0.4
0.4
0.2
-0.2
2013
-0.4
-0.5
-0.3
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.2
-0.3
2014
-0.5
-0.6
-0.4
-0.2
0
0
0
0
0.2
0.4
0.6
0.6
2015
0.5
0.4
0.5
0.7
0.9
1
1.2
1.5
1.8
2.1
2.2
2.3
…
Summer of 1998 and the Newport to
Bermuda Race
• Active hurricane season, especially late in the season
• Cyclones in late Oct/early Nov and again Nov 24 to Dec 1
• Slow Newport to Bermuda Race
• 1st to finish Alexia took 4 days to finish
• Last boat to finish, Sunstone took 8 days to finish
• Llwyd Eccelstone and Kodiak were the overall winners