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Answers: heating, cooling degree days

By Jack Williams ©2015

Q: Several years ago, you wrote a short article for USA TODAY about heating degree days. I have depended on that article, and its links, to monitor the heating and cooling degree days in my area.  Now, I cannot access this article any longer through a USA TODAY search and I'd really like to have access to it.  I would... »

Answers: Hurricane rainbands

By Jack Williams ©2015

Q: Cross-cut figures of hurricanes show a structure like a jelly roll turned on end and sliced through the middle.  Are these rings all connected in a continuous spiral or are they multiple rings? (I suspect they are continuous.) Also, how do they develop in the evolution of a hurricane? That is, why isn't the hurricane just a big homogeneous storm?... »

Answers: Finding wind data

By Jack Williams ©2015

Q: What is your favorite source for near real time surface wind visualizations in the mid Atlantic region. I need the information for balloon flight planning in the field. Curt, Falls Church, Va. A:  I’ve yet to find any really good visualizations for surface winds because none show the winds in any real detail. That said,  best that I've found are NWS... »

Answers: Supercooled water

By Jack Williams ©2015

Q: How can water that is below 32 degrees F (zero degrees C) remain in liquid form and not freeze? That is, become "supercooled"? Matt, LaGrange, Ga. A: The best way to begin understanding how supercooled liquid water forms is to forgot what you've been told about water "freezing at 32 degrees F." This is really the temperature at which ice... »

Answers: Arizona tornadoes

By Jack Williams ©2015

Q: Do tornadoes occur in south-west Arizona, including in the Yuma area? Chris,  Yuma, Ariz. A: A few tornadoes have occurred in Yuma County in the past, which means that they can  occur in the future. Nevertheless, the record shows they are rare and usually weak. If  you go to the National Climatic Data Center's (NCDC) Storm Events Web page, select "Arizona"... »

Answers: AMS Weather Book Supplementary Texts

By Jack Williams ©2015

Q: Are The AMS Weather Book Supplementary Texts available as a whole, in one digital file, such as a PDF file (or perhaps even in hard copy)?  I would like to print and to keep those supplementary texts with my copy of The AMS Weather Book.  If so, please provide the 'Net location from which I may download.  Thank you. Dan,... »

Pilot answers: Upper air data and forecasts

By Jack Williams ©2015

Q: I use RUC soundings for flight planning, but I am befuddled by the following: When I enter a station, load the Op40 soundings, and hover with my mouse over the loaded graph I see  bold numbers on the far-left near the Pressure (mb) line, and light numbers appear directly underneath my cursor with a dynamic pink line drawn from... »

When seasons begin — revistited

By Jack Williams ©2015

Q: Hello Jack. I was wondering if anyone ever turned in an answer on your "official seasons" proposal from last summer. I am doing my senior research project on the seasons, and would like to know what you found out. Thank you for your time. Justin, Redwood Falls, MN [caption id="attachment_1938" align="alignleft" width="300" caption="Where it's light and dark on earth at 11:30... »

Answers: Weather balloons and airplanes

By Jack Williams ©2015
NWS weather balloon

Q: Hi, I enjoyed "Rise Up" in the March 2010 AOPA Flight Training magazine.   I wonder about  the danger of those weather balloons and noted your  comments about there being "no danger" as it's floating down under parachute. But really, hasn't there ever been an incident or accident associated with one of these balloons where one of them (either... »

Answers: Wind direction

By Jack Williams ©2015
National Weather Service surface chart showing isobars and wind directions. NWS chart

Q: In your article in the January 2010 issue of AOPA Flight Training, you say: "If the lines on a weather map showing air pressures of 500 millibars and 496 millibars were straight and parallel, the PGF and Coriolis forces would soon balance and the wind would flow parallel to the lines of equal atmospheric force." I thought that air... »