Weather
This site is provided as a means of communications with the USPS National Marine Environment Committee (MEnvCom). We welcome your questions and comments on our courses, seminars and associated materials.
R/C
Ronald H. Kessel, SN
Stf/C Joan C. Croft, AP
Topics
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News
Launch of Wx2008
The Marine Environment Committee (MEnvCom) launched the new weather course with its completely rewritten manual at the beginning of 2009. Through the first six months 800 copies of the manual have been shipped. Wx2008 returns to a one-manual format, has four-color graphics, contains concise explanations of some of the more difficult topics in atmospheric dynamics, and includes Internet sources and content as an integral part of the curriculum.
There was a computer glitch in the processing of exam results for a significant number of exams created prior to 27 July 09 resulting in the incorrect grading of the exams. Fortunately we were able to identify those exams and manually grade them. We apologize for the inconvenience it caused. (20 Aug 09)
Wx101 and Wx102 Exams
Wx08 is now the current edition of the USPS Weather Course. Wx101/102 exams will continue to be accepted and graded until 31 December 2009. See the WX101/102 web page for support information. (03 Jan 09)
Grib Files
In its September 2008 issue, Ocean Navigator published an article on grib files, weather-related data files that can be downloaded to your boat. Quoting author Ralph Naranjo, “The term grib refers to gridded binary files, geek speak for a compressed data format favored by meteorologists as a means of digitally transmitting weather data. …Never before has there been so much valuable data within easy reach of those poking along coastlines or sailing thousands of miles from home port.” Click on http://www.oceannavigator.com/GRIB to view the entire article. (29 Oct 08)
Ocean Navigator Weather e-newsletter
Ocean Navigator's Weather e-newsletter periodically provides mariners with useful weather insights that build their understanding of marine weather. The Ocean Navigator Weather e-newsletter is written by weather consultant Ken McKinley at Locus Weather in Camden, Maine, who produces custom weather forecasts and weather routing for both recreational and commercial clients. Receiving McKinley's weather newsletters is like having your own weather expert explaining the concepts behind the forecasts. To receive it, click on www.oceannavigator.com/weather. (29 Oct 08)
Boat U.S. Hurricane Resource Center
Boat owners from Maine to Texas have reason to become edgy in the late summer
and fall: Each year, on average, two hurricanes will come ashore somewhere
along the Gulf or Atlantic coasts, destroying homes, sinking boats, and turning
people’s lives topsy turvy for weeks, or even months. This year, who
knows? Florida is struck most often, but every coastal state is a potential
target.
Experts predict that in the next 20 years there will be much more hurricane
activity than has been seen in the past 20 years. Experts also fear that
after a number of storm-free years, people in some of the vulnerable areas
will be less wary of a storm’s potential fury. But to residents of
Charleston, South Carolina, crippled by Hugo in 1989, and people in Dade
County, Florida, ravaged by Andrew in 1993, the hurricane threat won’t
soon be forgotten.
Click on http://www.boatus.com/hurricanes/brochure.asp for
more information. (16 Aug 06)
Weather 2008 Course Description
The safety and comfort of those who venture out-on-the water have always been weather dependent. In this course students will become keener observers of the weather, but weather observations only have meaning in the context of the basic principles of meteorology — the science of the atmosphere.
The course focuses on how weather systems form, behave, move, and interact with one another and reflects the availability of all sorts of weather reports and forecasts on the Internet. Wx2008 is a general weather course benefiting those sitting in their living rooms, as much as those standing behind the helm. Each student receives:
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a Weather Manual - USPS Weather - an explanatory text with full color photographs and drawings covering weather in the United States and its coastal and inland waters;
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a set of three Daily Weather Maps - learning aids with a compete explanation of map symbols designed to develop weather map reading and analysis skills; and
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NOAA’s Sky Watcher Chart - a reference to assist in identifying cloud types – helpful indicators of approaching weather.
Wx2008 is designed to be conducted over ten classroom sessions, but each instructor will determine the pace of the course.
Wx2008 Manual – Refinements and Corrections
While no significant changes in the course manual appear to be necessary or advisable, there are some technical clarifications and corrections that will be made in the next printing. Instructors should deal with them as they see fit. Given the nature of the changes there are no plans to include an errata sheet with each manual.
Chapter 1:
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Lapse Rate
Lapse rates are changes in temperature with altitude.
Page 18 Ques 20: To accurately reflect this definition, replace the question with the following: “On average, the temperature in the lower atmosphere:” Make the same change on page 216.
Chapter 2:
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ITCZ
Textbook figures illustrating global scale pressure and wind patterns (like the ones on pages 20 and 21 of the manual) typically show the ITCZ and the Doldrums as a broad band centered on the equator. While these simplified versions are quite useful for illustrative purposes, the varying widths and locations of the ITCZ and the Doldrums are actually much more complex.
Page 20 Par 11: to eliminate text inaccuracies about the width and locations of the ITCZ and the Doldrums, in the first sentence replace “roughly within 100 north and south “ with the phrase “in the general vicinity”.
Chapter 3:
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Dew Point and Persistence
When the air temperature falls below the dew point, the dew point normally is lowered.
Page 50 Par 26: The last sentence does not take into account the above relationship between air temperature and dew point. Replace this sentence with the following: “The dew point does not change during the day in the way that relative humidity does. Meteorologists say that dew point is more “persistent” than relative humidity. This “persistence” makes dew point a far more useful humidity measurement than relative humidity in describing air masses.”
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Supersaturation and Humidity
When supersaturation occurs the relative humidity can be higher than 100% and the dew point can be higher than the air temperature. The text does not deal with supersaturation and these consequences.
Page 51 Par 30: to cover supersaturation and its relationship to humidity replace the entire paragraph with the following two paragraphs:
“For water vapor to become water droplets (condensation) or ice crystals (deposition), there must be some kind of surface on which the water vapor molecules can stick. On the Earth’s surface there are all sorts of such surfaces (e.g. lakes, oceans, the ground, plant leaves). In mid-air the necessary platforms for condensation, freezing or deposition to occur are tiny nuclei. Typical condensation nuclei, for example, are sea salt, and particles of sand, dust or smoke. In the absence of these nuclei, supersaturation can occur. When the air is supersaturated, the relative humidity is higher than 100% and the dew point is higher than the air temperature.
The regular relationships among air temperature, dew point and relative humidity in the absence of supersaturation are:
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the dew point is lower than or equal to (but not higher than) the air temperature;
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the dew point spread is the difference between the air temperature and the dew point;
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the smaller the dew point spread – the higher the relative humidity; and
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when the dew point spread is zero (the dew point = the air temperature), the relative humidity is 100%.”
Page 57 Par 64: to take into account the possibility of supersaturation with the relative humidity being higher than 100%, in the 6th bullet delete the phrase “or is below”.
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Fog and Wind Speed
The wind speeds most favorable to the development of fog are 2 to 3 knots for radiation fog and 5 to 15 knots for advection fog.
Page 61 Ques 19 & 20: to clarify the ambiguous reference to speed in these questions insert “wind” before “speed”; make same changes on page 221.
Chapter 5:
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Sun Pillars
Sun Pillars are caused by ice crystal reflection. – not refraction.
Page101 Par 74: to eliminate the reference to refraction, replace the last sentence with the following: “They, however, are caused by ice crystal reflection – not refraction.”
Chapter 7:
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Tropical and Subtropical Storms
While storms in the tropics and subtropics are typically single air-mass without fronts, there are also hybrid-storms (now called “Subtropical Storms – see page 138 par 42) that have fronts. Also some “subtropical” regions experience mid-latitude weather with frontal storms during parts of the year (e.g. Florida in the Winter).
Page 131 Par 10: to eliminate the unqualified generalization that storms in the tropics and subtropics are single air-mass without fronts, eliminate the last sentence
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Intertropical Convergence Zone (ITCZ)
Accurately defining and describing the locations of the ITCZ is a fairly complicated matter. The actual front where the Northeasterly and Southeasterly trade winds converge is much narrower (up to only 300 miles) than the 200 width for the ITCZ stated in the text.
Page 132 Par 12: to eliminate inaccuracies in the description of the ITCZ, replace the 2nd and 3rd sentences with the following: “In the Atlantic Ocean, for example, the ITCZ can migrate northward as far as 15 degrees North in the Northern Hemisphere’s Summer and southward to just north of the Equator in the Northern Hemisphere’s Winter.”
Chapter 8:
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Ensemble Forecasts and Spaghetti Plots
The text should (i) explain the relationship between the Spaghetti Plot figures and Ensemble Forecasts, and (ii) make it clear that different forecasting computer runs may use not only different initial data but also different models.
Page 154 Par 26: replace the last two sentences with the following:
“Sometimes different models also are used. If the results of multiple runs (so-called “Spaghetti Plots” when graphically depicted) are quite different or disorganized the forecast is not considered reliable. If there is a uniform pattern to the results the forecast is considered more reliable. See Spaghetti Plot figures showing hypothetical plots of the Polar Jet Stream.”
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Canada Weather Radio
All the Canadian Weather channels can be received using the same radios that receive NOAA Weather Radio broadcasts.
Page 162 Par 69: Replace the 1st sentence with the following sentence: “Canada has it own “Weather Radio” that uses seven VHF channels with the same operating frequencies as NOAA, and so the same VHF receiver can be used to receive both Canadian and NOAA weather forecasts.”
Instructor’s PowerPoint Presentation
All the Wx2002 slides were included as part of the Instructor’s PowerPoint presentation to give instructors maximum flexibility in customizing their classroom presentations. Some instructors, however, would have preferred a smaller number of slides that tracked the manual contents more closely.
The present plan is to revise the Instructor’s CD with the idea of capturing the best of both worlds. Each chapter in the revised presentation will begin with a set of slides designated Wx08 that will include the figures in the course manual plus other supplemental ones. These Wx08 slides will follow the manual’s order of topics fairly closely.
The remaining Wx2002 slides from previous years that are not a part of the first set will be designated Wx02 and will follow the complete set of Wx08 slides. In this way instructors will still have the option of easily integrating the Wx02 slides into each chapter presentation as they see fit.
The idea is that Instructors can rely entirely on the slides designated Wx08 knowing that they are adequately covering the course material. From a total of about 550 slides, roughly two-thirds will be designated Wx08 slides.
The revision of the Instructor’s CD also is an opportunity to rewrite many of the slide notes for the Wx08 slides. Slide notes for the Wx02 slides, however, will not be revised.
A revised Instructor Manual will not include the Wx02 slides.
Wx2008 – Final Exam
As the Introduction in the course manual and the Instructor’s Manual states, the final closed book examination (100 multiple choice questions – 80% based on homework questions) only covers the material in the first seven chapters. There is obviously some overlap in the topics dealt with in these chapters and Chapter 8 on Forecasting. What follows are some points of clarification and some guidance for instructors and students.
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General: Every question can be answered from the contents of the first seven chapters.
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Mid-Latitude Storm: Continuing a USPS weather course tradition, every exam includes the ten questions in the Chapter 6 homework based on a frontal mid-latitude storm figure (questions 19 – 28).
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Scenarios: While there will be two of the traditional “forecasting” scenarios on the exam (e.g. “Your cruiser is 50 miles east of….”) the analysis required to answer the three questions based on each scenario does not require any of the additional information contained in Chapter 8.
Each scenario is based upon one of the following weather events or patterns: warm front; cold front; thunderstorm-squall line; advection fog; or waterspout.
A significant number of students are missing questions based on a scenario that involves a warm front pattern in the winter assuming that winter precipitation must involve a cold front. Some others are confusing an approaching warm front (indicated by a darkening sky with lowering layered – stratus type clouds) and an approaching cold front or squall line (indicated by a line or wall of dark clouds and static or lightning). -
Station Models: Unlike exams for previous weather courses, station model questions deal only with temperature, dew point, pressure, pressure tendency and wind speed and direction. There are no questions about other symbols such as precipitation, cloud type or cloud cover. These additional station model elements are covered in Chapter 8 but only in connection with the use of the Daily Weather Maps.
For all exams generated after May 26, there are no station model questions asking for the direction of the low. These require the application of Buys Ballot’s Law to a station model – a matter not specifically covered in the manual. -
Temperature Conversions: There are no exam questions that require students to convert Fahrenheit degrees to Celsius degrees or vice versa (i.e., no questions like Chapter 1 homework questions #10 and 11 will be on the exam).
Downloadable Material
See the Educational Department Help page to obtain any needed free viewers or shareware zip programs for these files. See the PowerPoint Help page for information on how to replace slides.
Weather Log
The following Weather Logs are for use in both the Cruise Planning and Weather courses.
- Weather Log in Acrobat format (PDF, 13KB)
- Weather Log in MS Excel format (XLS, 26KB)
Weather PowerPoint Slides
Slide shows of various weather phenomena for use by Weather course instructors and students. You will need Microsoft PowerPoint or its free viewer to view or print these slides. To download into a directory on your hard drive, right click on the file link and be sure to change the file name to something meaningful for you.
- Clouds ( 727KB)
- Floods (609KB)
- Hail (201KB)
- Miscellaneous (104KB)
- Thunderstorms and Tornados (1110KB)
- Weather Instruments (1475KB)
Frequently Asked Questions
There are no Frequently Asked Questions for Wx 08 at this time.
Regional Weather Guides
The MEnvCom is looking for your help with the Regional Weather Learning Guides Project. We are soliciting contributions from all Members, Squadrons and Districts to complete this ambitious and worthwhile project. Districts and individual Squadrons are encouraged to “adopt” one of the guides and contribute your local expertise to the rest of USPS. We will also, of course, accept information from any individual contributors!
Introduction to Weather for Boaters, with examples from the Upper Mississippi River Basin (1936KB, PDF)—authored by Don Hansen, St Paul Squadron, D/10
Listed below are the 15 Regional Guides we would like to complete. Following the list is a suggested outline for the guides we would like everyone to use for consistency.
1. Northeast Atlantic Coast - (New England – Long Island Sound)
2. Northeast Interior (22KB, PDF) - (Lake Ontario, St. Lawrence River, Finger Lakes & Erie Canal)
Adopted by D/6--contact Harry Winberg, Utica Squadron, with comments and updates.
3. Middle Atlantic Coast (11KB, PDF) - (Long Island South Shore, New York Harbor and Approaches, New Jersey and Delaware coasts and Bays)
Barnegat Bay from Barnegat Twp to the Metedeconk River, including Barnegat Inlet, adopted by D/4--contact Warren Timm, Barnegat Bay Squadron, with comments and updates.
4. Chesapeake Bay
5. Southeast Atlantic Coast - (including North Florida)
6. South Florida and the Northern Bahamas - (east and west Florida coasts)
7. Eastern Caribbean
8. Gulf of Mexico
9. Southern California and Baja
10. Northwest Pacific Coast - (Northern California, Oregon/Washington and British Columbia)
Adopted by D/16—please contact Vern Redecker, Bellevue Squadron, with comments and updates.
11. Great Lakes (9KB, PDF) - (lakes may be grouped or done individually as appropriate – note overlap with Northeast Interior)
Western Lake Erie adopted by D/7—please contact Doug Sewell, Berea Squadron, with comments and updates. Writeups are needed for Lakes Huron, Michigan, and Superior.
12. Mississippi River Basin Waterways (784KB, PDF)
Adopted by D/10--please contact Don Hansen, St Paul Squadron, with comments and updates.
13. Inland Western Lakes
14. Alaska
15. Hawaii – South Pacific
Please contact the MEnvCom
chair to get involved!
Regional Weather Learning Guide Suggested Outline
I. Overview of local weather.
A. What seasons provide the best and/or worst boating?
II. Where does the weather come from?
III. What systems bring good and bad weather?
IV. What conditions precede these systems?
V. These systems bring what:
A. Winds
B. Precipitation
C. Visibilities
D. Clouds
E. Seas
VI. Currents.
VII. Tides.
VIII. Where to seek shelter during a storm?
IX. Sources of weather information.
Weather Course Reference Material
Material of use to Weather course students is listed here.
- Weather symbols used on weather maps
- Suggested reference book list, May 2000 (PDF) (128KB)
- More suggested books, September 2000 (PDF) (137KB)
Questions or Comments?
If you have any questions or comments about the Weather course, please contact the National Marine Environment Committee chairman by e-mail, phone or postal service mail. Please be sure to keep your SEO and/or DEO advised of any correspondence you may have with the National committee. Addresses for the National MEnvCom chairman are listed in The ENSIGN and on the Committee Chairpersons page.
We will try to answer your questions as soon as possible, but please allow 5 working days for an answer.
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