Having problems with the website?
How to read the NHC Forecasts and Advisories -
TAFB Marine Products
Experiencing problems getting the latest information
from the NHC/TPC website? We've put together these notes to help
solve a few of the more common problems you may encounter.
Here's a list of the most common problems
- The advisories don't agree with the times and
numbers given on the homepage.
- The full-size maps don't match their thumbnails
in the tropical cyclone Graphics sections.
- The homepage seems to be stuck and won't update.
So what's going on here?
Here's a brief summary. Your web browser saves (caches) a
copy of every page you display so that when you return to the page (without
explicitly reloading) the browser can load its copy of the page and save
having to pull another copy of the page across the Internet. This means
faster browsing and less time waiting for a page to load. However, sometimes
browsers hang onto their local copies longer than they should, and you can
end up viewing an out-of-date page.
With slow-changing websites this is usually not a problem,
but as is the case of the NHC/TPC website the homepage can change frequently
during the course of a single day, depending on the level of storm
One important note: Don't bookmark any of
the individual tropical cyclone advisories or graphics pages! Only
bookmark the NHC/TPC homepage and reload it for the latest information. If
you bookmark one of our new dynamic URLs then you may end up viewing an
out-of-date page if your browser cache gets stuck.
If reloading or refreshing doesn't update the homepage and
you think it should, then see the following section "The Stuck Browser Cache
Fix" for ways to fix that problem. Note that the NHC/TPC homepage updates
only when there is a tropical cyclone in the Atlantic or Eastern Pacific.
The regular schedule of updates
when a tropical cyclone is active can be found in our
Hurricane Awareness section.
- Go to the outdated page or graphic image and click on the button in your browser's
toolbar labeled "Refresh" (Internet Explorer) or "Reload" (Netscape).
For Netscape users do a Shift-Reload (hold down the Shift button when
you click on Reload) to do a Power-Reload.
- If that doesn't get the latest information, then you need to manually
clear your browser's "cache" or local stash of web pages and graphics.
- Mozilla Firefox users (For Windows)
Tools-->Options-->Privacy Tab-->Cache Tab-->Clear Cache Now
- Mozilla Firefox users (For Linux)
Edit-->Preferences-->Privacy Tab-->Cache Tab-->Clear Cache Now
- Internet Explorer users
Tools-->Internet Options-->Temporary Internet Files-->Delete Files
- Now restart your browser.
- If that still doesn't work, then you may be behind a
firewall or your ISP or system administrators are using a proxy or
caching server. These servers often save (cache) local copies of
frequently requested web pages and graphics to reduce traffic loads.
Not infrequently these servers can retain their copies long after
we've changed them on our servers. In that case you need to contact
your system administrators or your ISP Tech Support for assistance.
- If you've tried all of the above, you aren't behind a
firewall, you've tried installing the latest web browsers,
and you are still seeing old advisories and images, then
contact us and we'll see
what we can do to help.
The Long-winded and Rather Boring Technical Explanation
The first thing you need to know is that when we update
the NHC/TPC homepage we read the new times and numbers directly from
the new advisories, which are sent to the servers at the same time as
the updated home page. Barring major network catastrophes and server
meltdowns (hey, we're not perfect) the servers are kept in careful and
complete synchronization at all times.
The same is true for the graphics. The small versions
displayed on the storm graphics pages ("thumbnails") are created by
literally shrinking a copy of the originals on our central server, and
then both the thumbnails and the full-size versions are sent
immediately to the servers.
So then why are you seeing the wrong stuff?
Browsers automatically save copies of virtually
everything you view on the web (html pages, pictures, sound files,
animations, and so on) in hopes that the next time you visit a web
site it will be able to use the locally saved versions instead of
downloading new copies across the Internet.
Generally, browsers will check for updated versions of
everything, but things don't always work as planned and you may end up
with stale copies in your browser cache of long-vanished pages and
images that your browser insists are current. Don't always believe
what your computer says... insist that it double check its work!
Some users set their browser preferences to check every
single time they visit a web site, effectively eliminating this
problem, but that slows down your session with the extra chatter
necessary between your browser and the Internet, reducing the speed
savings of the (normally well-behaved) cache files. Most folks just
set their browser cache check to "Automatic" or "First Time Each
Session" (depending on browser type and version). Savvy users reload
everything anyway having learned to never trust their computers.
Top-notch users periodically flush out their browser caches as a
general maintenance and preventative procedure.
Then there is the misbehaving firewall/proxy server
problem, which is outside of both our hands and yours, generally
requiring the intervention of your ISP's technicians or your system
administrators to correct the problem.