BLIPMAP FORECASTS BLIPMAPs
give thermal soaring parameters
over a geographic region.
BLIPMAP = Map of Boundary Layer Information Predictions
[The Boundary Layer (BL) is the region mixed by thermal eddies]
Created by Dr. John W. (Jack) Glendening, Meteorologist
DrJack sez: May 9:
I just found that the registration software does not detect
whether your browser has cookies enabled and will blithely tell you a
cookie has been "successfully sent" even when it was not successfully
received! The person who wrote that software has been informed
and is working on a fix, but in the meantime if your browser might
have that problem you can test it by clicking on the Cookie Tester to
get a message "Cookies are enabled" or "Cookies are disabled" (if you
I have implemented
"cookieless" access for registered users, though it does not have
the full flexibility of cookie-enabled access.
May 8: Updated the
I added more information on how to deal with possible problems to the
Information webpage, although I have had remarkably
few messages describing difficulties and so far 650 registered users
have been able to successfully view forecasts.
I implemented a module to let registered viewers who have forgotten
their password or userID send that information to the email address
supplied when registering.
For those who tried to access or "Login" this AM and received an
error, that problem has now been corrected. The long story is
provided here. May 2:
"Frequently Asked Questions" page (with answers).
May 1: As of today I have implemented a
system which registers users of DrJack forecasts. The
locations of the individual forecasts have therefore
changed! The primary reason for this change is to better
assess present forecast use, particularly how many forecast users
there are and the ratio of Sailplane to HangGlider to Paraglider
use. Registration is not required but is strongly
encouraged because it will help me better
determine the future course of forecast development (if you do not
register your forecast viewings will not be counted as a use by your
pilot group). Those those who have bookmarked individual
viewer no longer works without registration. In addition,
if you have created a website with "hot links" to the individual maps
you will need to contract me. Further information is
provided when you click on a forecast link, if you are not yet
registered, and at the Registration
BLIPMAP "to-do" projects list.
Apr 21: THIS IS THE NEW WEBSITE ! If
you are reading this then you are at the new website! I have
constructed it to (hopefully) be identical to the previous one, but if
you find something that does not seem to work properly please let me
know as there are likely undiscovered bugs/deficiencies.
Apr 2: I got some
feedback on the April 1 BLIPMAPs!
Apr 2: Updated the
monthly BLIPMAP usage statistics.
Mar 30 The clouds are fixed!
I finally got things sorted out and am now running a
corrected program with BLIPMAP cloud predictions turned back on.
Bob Gibbons of Texas deserves thanks for having both the initiative to
critically evaluate the "Cumulus Cloudbase" prediction and the
knowledge to compare it to a simple surface-humidity LCL condensation
formula. As a check, the "EXPERIMENTAL" parameter in the BLIPs
will give the approximate formula prediction, which should be within
5% of the printed "Surface LCL" - after the validity of the latter has
been demonstrated I will remove the EXPERIMENTAL parameter
print. Those interested in additional details can read the
"Sfc-humidity LCL: short and long stories" posting on the DrJack Forum.
Mar 24: Contributors:
I have added an option to send you, if interested, a daily email when
the first BLIPMAP is produced for your region (this is primarily
useful on those days when the "first of the day" BLIPMAP is delayed
and you may want to "filter" it to a mailbox separate from your main
mailbox). If you wish to be added to that list please let me
Mar 22: BLIPMAP "help" page created:
A "first source for new BLIPMAP users" and summary of additional information is
BLIPMAP Help webpage.
Info on First Available Times.
Mar 21: Parameter descriptions
changed I have rewritten the parameter descriptions on
this page and created a new linked page with "parameter details",
with some diagrams, at the "MoreInfo" link of each
parameter. Having a "parameter details" page provide a good
basis for further growth since info can be added to it which would be
too cumbersome to add to the basic parameter description. If you
think anything can be improved upon or added to or leaves a question
unanswered, please let me know and I will make changes.
A Google Search specific to the drjack website has now been added (see bottom of this page)
Mar 15: HAPPY BIRTHDAY TO BLIPMAP !!!
March 16 is the first anniversary of the day on which the first nationwide
BLIPMAP forecasts became available. When did you first hear about them??
Mar 13: More timely forecasts! Additional forecasts have just
been implemented, so the BLIPMAPs you get will now have the the most
timely information possible. Last summer, when the processing
was being done on my old, slow machine, I was forced to provide only
half the possible forecasts, i.e. even though FSL provides updated
forecasts every 3 hours I was skipping every other one. Some
users have noted that the forecasts sometimes change rapidly in the AM
when conditions are uncertain. Also, some have to leave their
houses (and their internet connection) hours in advance to drive to
the gliderport. These additional forecasts will help such users,
and all users, to have more timely forecasts than were previously
possible. I should note that this is being done only after
coordinating with Bill Hall, and he has agreed to this change which
requires more processing on his machine. There is always the
chance that this will later prove to be more of a burden than
anticipated and have to be reversed - Bill is doing everyone a great
service so this processing should not become bothersome to him.
Daily "WINDIP" forecasts of upper-air winds and a simple mt. wave
forecast are once again available at the WINDIP webpage.
pilot flight experiences using BLIPMAPs.
Added a "Rainfall and Soil Moisture" note to the
model prediction notes.
I have created climatology plots from the 2002
forecasts, giving the monthly average of each parameter for
each time of day (when available). In addition, I have computed
statistics giving the average, standard deviation, minimum, and
maximum for all parameters for all regions. These plots and
statistics can be accessed via the
BLIPmap 2002 Climatology webpage.
In response to the many requests received on the first BLIPMAP User Survey,
I have created a
discussion group for thermal soaring forecasts and meteorology and
I am asking that BLIPMAP users generally use that forum if they have a
question or comment, since it likely is also of interest to someone else
in the soaring community,
rather than simply sending an email to me directly
- although the latter
is of course appropriate if there is some comment you wish to keep private.
Updated the webpage giving information on creating new
BLIP prediction locations nation-wide.
Note that there must
be a contribution to the BLIPMAP effort, of either money or time, to
create a new BLIP for your location.
Activated two new parameters intended to help forecast the presence and
cloudbase of small puffy cumulus clouds that form in the BL.
As indicated in their description, there is a theoretical difficulty
with these parameters but I have had several reports that for some sites
the method is nevertheless effective so decided to include them and
let users evaluate how well these parameters work for their site.
Jan 27: I'm glad I was able to meet many BLIPMAP
users while at the SSA Convention in Dayton and at the Wright Aviation
Museum and appreciate being presented with an SSA Exceptional
Achievement Award there. I have placed
on-line the slides
presented in my talk at the 2003 SSA Convention.
Jan 17: Summarized
results from the first BLIPMAP User Survey
are now available
Jan 1, 2003: Congratulations to the first three awardees of the newly
created "Order of the BLIPMAP Hero":Milt Hare (who flies his ASH-25
out of Williams, CA), Bill Hall (who flies with the Greater
Boston Soaring Council), and John Whitney (who flies his ASW-20 at
Blairstown, N.J.). As a testimonial to the time and effort they
have voluntarily put into helping make BLIPMAP a product useful to pilots
across the country, they have been presented with a "BLIPMAP HERO"[tm]
award suitable for displaying on any T-shirt, sweat-shirt, or
undergarment of their choice! These awards are not available for purchase in
Let's have a hearty round of applause for our "heroes"!
In response to user requests, to aid orientation with respect to the
smoothed model topography I have modified my plotting program so
placename IDs can be plotted on a BLIPMAP region. The first
such plot has been created for AZ (SouthWest region) based on data provided by
Gary Evans, so to see what one looks like you can view it
There are currently (sparse) ID plots available for the CA-NV, NorthEast, SouthEast, OK-TX, NorthCentral, SouthCentral, and SouthWest regions: to view
your region's ID plot or if you are interested in adding IDs for
your region, see the
Who Uses BLIPMAPs?
Of the 1,021 people who responded to a 3 week poll,
80% were Sailplane PIlots,
15% were HangGlider Pilots,
4% were ParaGlider Pilots,
0.6% were Weather Enthusiasts,
0.5% were Weather Workers,
and 0.4% were None of the Above.
Based on SSA and USHGA membership numbers, equally random voting
from SailPlane/HangGlider/ParaGlider pilots would have given
respective percentages of roughly
50/25/25 - the difference between those percentages and the
actual results suggests to me that those who fly longer distances are
more likely to use BLIPMAPs.
Remarkable convergence prediction!
Labor Day (today) was a remarkable day in the Sierras with many
long flights. I was particularly interested in reports of a very
long convergence line which moved eastward with time, since the
BLIPMAPs predicted the occurrence of just such a convergence!
Moreover, subsequence comparison to satellite photos confirms not only
that BLIPMAP prediction but also it's prediction of a second (unflown)
convergence line! I have created viewers to look at the hourly
development and movement of both the convergence line forecasts and
the satellite photos, with viewing instructions and a brief
Aug 18: THE FUTURE ??
I have begun experimenting with BLIPMAPs using the NWS 12km ETA model
instead of the FSL 20km RUC model. Advantages of the ETA are its
higher resolution, 12km instead of 20km, and it provides extended
forecasts out to 84 hours. Some results, for the "Current+2" and
"Current+3" days only, can be viewed here [Note: the ETA regional
areas differ from those of the RUC FSL model due to differing map
projections used - if you find a different region is needed, go to the
regional ETA webpage]. The
program is still under development and these forecasts are not
being updated daily, but these plots do illustrate what can be
done. At present, the accuracy of ETA vis-a-vis RUC is not known
and the accuracy of the longer-range forecasts is especially
unknown. Whether such products might become regular predictions
is uncertain, as each forecast requires downloading a half-gigabyte
file and there is a cost associated with that.
July 25: Added a link to an on-line version
of the July 2002 SOARING magazine
which is a good "first thing
to read" for potential BLIPMAP users.
Sep 17: For the CA-NV region, multiple times can be
CA-NV BLIPMAP Index.
Processing remains stable. Forecast
availability varies from day to day.
I only look at the webpages and maps that I use personally or that I suspect might
contain an error. If you notice a consistent problem with either, please let
If there is not yet a BLIPMAP produced for today and you want
to see what BLIPMAPs look like, try clicking on the "PreviousDay" links below
or see this
Average dry thermal updraft strength near mid-BL height.
Subtract glider descent rate to get average vario reading for
cloudless thermals. Thermal strengths will be stronger if
convective clouds are present. W* depends upon both the BL
depth and the surface heating. MoreInfo
Height of the average dry thermal tops, or Thermal Index TI=0
height. Over flat terrain maximum thermalling heights
will be lower due to the glider descent rate and other factors.
However, thermal tops will be higher over small-scale topography not
resolved by the model and some pilots have reported that in elevated
terrain the heights they can reach over local terrain features
correspond better with the TI=0 height than with Hcrit. In the
presence of clouds the thermal top will increase, but the maximum
thermalling height will then be limited by the cloud base (see the "Cloud prediction
parameters" section below). [This parameter is truncated at 22,000 for
This parameter estimates the height at which the average dry updraft
strength drops below 225 fpm and over flat terrain is expected
to give better quantitative numbers for the maximum cloudless
thermalling height than is the traditional TI=0 height given above,
although the qualitative patterns should be similar for both
(Note: the present assumptions tend to underpredict the max. thermalling
In the presence of clouds the maximum thermalling
height may instead be limited by the cloud base (see the "Cloud prediction
parameters" section below).
[This parameter is truncated at 22,000 for
This parameter estimates the variability (uncertainty) of the BL top
(TI=0) height prediction which can result from meteorological
variations. Larger values indicate greater variability and thus
better thermalling over local "hot spots" or small-scale topography
not resolved by the model. But larger values also
indicate greater sensitivity to error in the predicted surface
temperature, so actual conditions have a greater likelihood of
differing from those predicted. MoreInfo
Dry thermals may be broken up by wind shear and unworkable if B/S
ratio is 5 or less. If convective clouds are present, the actual
B/S ratio will be larger than calculated here. [This parameter
is truncated at 20 for plotting.] MoreInfo
The speed of the vector-averaged wind in the BL. This
prediction can be misleading if there is a large change in wind
direction through the BL (for a complex wind profile, any single number is not
an adequate descriptor!). MoreInfo
The direction of the vector-averaged wind in the BL. This
prediction can be misleading if there is a large change in wind
direction through the BL (for a complex wind profile, any single number is not
an adequate descriptor!). Note that there will be a abrupt
artificial gradient at the "cross-over" between 0 and 360
Maximum grid-area-averaged upward motion within the BL as created by
horizontal wind convergence. Positive convergence is associated
with local small-scale convergence lines (often called "shear lines"
by pilots) - however, the actual size of such features is much smaller
than can be resolved by the model so only stronger ones will be
forecast and their predictions are subject to much error. If
CAPE is also large, thunderstorms can be triggered. Negative
convergence (divergence) produces subsiding vertical motion, creating
low-level inversions which limit thermalling heights. This
parameter can be noisy, so users should be wary.
This evaluates the potential for small, non-extensive "puffy cloud"
formation in the BL, being the height difference between the
surface-based LCL (see below) and the BL top. Small cumulus
clouds are (simply) predicted when the parameter positive, but it is
quite possible that the threshold value is actually greater than zero
for your location so empirical evaluation is advised. I
would be interested in receiving end-of-season reports on what
threshold value worked for your site. Clouds can also occur with
negative values if the air is lifted up the indicated vertical
distance by flow up a small-scale ridge not resolved by the model's
smoothed topography. [This parameter is truncated at -10,000 for
This height estimates the cloudbase for small, non-extensive "puffy"
clouds in the BL, if such exist i.e. if the Cumulus Potential
parameter (above) is positive or greater than the threshold Cumulus
Potential empirically determined for your site. The surface
LCL (Lifting Condensation Level) is the level to which humid air must ascend before it cools enough
to reach a dew point temperature based on the surface mixing ratio and
is therefore relevant only to small clouds - unlike the below BL-based
CL which uses a BL-averaged humidity. However, this parameter has a theoretical
difficulty (see "MoreInfo" link below) and quite
possibly that the actual cloudbase will be higher than given
here - so perhaps this should be considered a minimum possible
cloudbase. I would be interested in receiving end-of-season
reports on how well this parameter worked for your site.
[This parameter is truncated at 22,000 for
This parameter provides an additional means of evaluating the
formation of clouds within the BL and might be used either in
conjunction with or instead of the other cloud prediction
parameters. Larger values indicate greater cloud probability,
but use of this parameter must be empirical since no theoretical
guidance is available - for example, pilots must determine by
actual experience the percentage that correlates with formation of
clouds above local mountains. The cloud base height is not
predicted, but is expected to be below the TI=0 height.
This evaluates the potential for extensive cloud formation
(OverDevelopment) at the BL top, being the height difference between
the BL CL (see below) and the BL top. Extensive clouds and
likely overdevelopment are predicted when the parameter is positive,
with overdevelopment being increasingly more likely with higher
positive values. Overdevelopment can also occur with negative
values if the air is lifted up the indicated vertical distance by flow
up a small-scale ridge not resolved by the model's smoothed topography.
[This parameter is truncated at
-10,000 for plotting.] MoreInfo
This height estimates the cloudbase for extensive BL clouds
(OverDevelopment), if such exist, i.e. if the OverDevelopment
Potential parameter (above) is positive. The BL CL (Condensation
Level) is based
upon the humidity averaged through the BL and is therefore relevant
only to extensive clouds (OverDevelopment) - unlike the above
surface-based LCL which uses a surface humidity. [This parameter
is truncated at 22,000 for plotting.] MoreInfo
Convective Available Potential Energy indicates the atmospheric
stability affecting deep convective cloud formation above the
BL. A higher value indicates greater potential instability,
larger updraft velocities within deep convective clouds, and greater
potential for thunderstorm development (since a trigger is needed
to release that potential). Note that
thunderstorms may develop in regions of high CAPE and then get
transported downwind to regions of lower CAPE. Also, locations
where both convergence and CAPE values are high can be subject to
explosive thunderstorm development.
Depth of the layer mixed by thermals. This parameter can be
useful in determining which flight direction allows better thermalling
conditions when average surface elevations vary greatly in differing
Link to menu of traditional meteorological forecast maps, including
cloud ceiling, precipitation, surface wind/gusts and 850/500mb winds.
However, area covered differs from BLIPMAP
region. This webpage also indicates FSL model forecast
availability in both the upper right corner and via the button
coloring, so if BLIPMAPS are not available you
can use this link to determine the likelihood of a BLIPMAP appearing
soon. (Red for all forecast plots indicates the model is
down, green for early forecast hours indicates a later forecast may be
forthcoming, and all green indicates all forecasts should be
Link to time series of traditional meteorological forecast variables,
including cloud base, precipitation, surface wind, and CAPE.
Only available for METAR locations. Users may find this page to
be more useful than the FSL RUC forcast products webpage above, to
determine the model-predicted cloud cover for example, since times are
given as actual date/hour rather than as model forecast period.
Link to webpage generating temperature, humidity, and wind profiles on
a skew-T plot. Interactive capability provides additional
functions (if your browser has java available).
BLIPMAPs predict thermal soaring conditions
resulting from surface heating of the Boundary Layer (BL), the
scientific term for the turbulent atmospheric region mixed by
surface-based thermals (so thermal tops occur at the top of the
BL). The BLIPMAP program post-processes numerical weather model
predictions to provide parameters suited to the needs of soaring
pilots. Relative differences, both in location and in time, are
expected to be more reliable indicators of soaring differences than
are the precise numerical values.
A sequence of forecasts, all for the same
validation time, is produced during the night.
The most important link is the first link on each line, "Latest",
which gives the most recent
(shortest term) forecast.
"FirstToday" link gives the first forecast from the current
day, which can be used to determine whether the model is significantly
altering its predictions during the updating. The last link,
"PreviousDay", gives the last forecast from the previous day's
prediction sequence, useful for those who want to compare their
experiences from yesterday's flight to the BLIPMAP predictions.
The parameters are averages over 20km grid squares
forecast by NOAA's Forecast Systems Laboratory RUC model.
BLIPMAPs are updated as new meteorological observations become
available. However, the 20km FSL RUC forecasts are only
semi-operational so forecast files are not always available.
Additional information is available at the
Info on First Available Times webpage
The parameter values are represented by color hues
which increase in "warmness" as the value increases in
magnitude. When many gradations are required, two cycles are
made through the color wheel with "light" and "intense" tints
respectively representing ranges of lower and higher magnitude. A
screen magnifying tool, such as the freeware Super
Magnify for Windows machines or Xzoom for
X11/Linux/Unix machines, helps when discrimination between adjacent
contours is difficult.
State outlines are depicted on each BLIPMAP in
white. The RUC topography is plotted as black contours, at 500
ft intervals with thicker lines at 2000 ft intervals, to assist in
location identification but also to emphasize the smoothed nature of
the model topography. The BLIPMAP does not predict thermal lift
created by small-scale terrain features which are not resolved by the
model topography, which often give localized updrafts significantly
stronger than those over the surrounding smoother terrain.
BLIPMAPs can also be
creates a BLIPMAP image sequence. The viewer is most useful for
quickly cycling between or through BLIPMAPs since the images exactly
overlie - but some might just consider it simpler to use than this
As with all weather products, users should check
the date on each map for currency. Small anomalous diamonds,
the size of an individual model gridpoint, may appear in the plots,
particularly for more sensitive parameters such as convergence or cloud
parameters; these result from numerical noise and should be
The BLIPMAP is still in development and there will
likely be problems, changes, and tweaks. Opinions on
factors affecting its usability are solicited.
Heros: We all thank FSL's Stan Benjamin for providing
access to the 20km FSL RUC results.
A special BLIPMAP hero is Bill
Hall of the Greater Boston Soaring Council who is presently hosting
the BLIPMAP processing on his machine.
I also want to personally thank those whose support is listed on the