DR-KNOW / IQ-2k Information Services
_ WEATHER _
By: Todd Wheatley
(c) IQ-2k 00-00-18
"If you don't like the weather in Texas ... wait 5
minutes."
Who knows how or when the longstanding joke
originated, though it's a good bet the weather mimicked
that of the past year. The majority will remember 2005
due to the vast destruction and loss of life caused by
the record hurricane season. But the basis of the joke
resides not in the ferocity of weather, but in the speed
in which it changes. North Texas barley saw a quarter
inch of rain TOTAL from the hurricanes of 2005. What we
did see however was a record high temperature on
December 3rd and a record low temperature on December
5th. Equally impressive were the pop-up thunderstorms of
mid-July and early August. Typically cloudless mornings
changed to scattered cumulus by 11am. Within 2 hours the
storms went from 0 to 50,000 feet with dangerous wind,
lightning and some hail. Had these storms occurred
before radar and instant communications, they could have
easily become the stuff of legend and the source of
jest.
Today people tend to take the weather for
granted. It happens, or not with boring regularity; and
with general disregard for forecaster predictions.
Aviators, on the other hand, can not afford to be as
cavalier with the weather. Curriculum non grata, the
study of weather is mandatory for licensed pilots.
Unfortunately even the best study guides tend to be a
cursory examination of the basics. Consider, for
example, the counter-intuitive MCC storm system which
intensifies not during the day, but at night! Where too
do the FAA study guides mention dry lines, El Ninos or
the thunderstorms which develop at the junction of
frontal boundaries and the jet stream. Furthermore we
have Nor'easters, Alberta Clippers, Santa Anna winds and
Lake-effect snow, again no mention. Most likely the
knowledge test study guides do not mention weather
systems that remain a local phenomena -- but why not?!
It's all connected. Perhaps you are aware of the times
"when a butterfly flaps its wings in China causing it to
rain in Peru," (see the butterfly effect).
Not aware of the butterfly effect? No matter,
because this article is not an esoteric guide to
atmospheric physics. Nor is it a study guide for an FAA
airman exam. This article looks solely at the weather in
the Dallas-Fort Worth Metroplex. Similar weather
patterns may be seen from Florida to the Rockies and as
far north as Nebraska. Texas, and specifically the DFW
metro area, are within the so-called Tornado Alley where
the majority of severe thunderstorms, and consequently
tornados, occur within the United States. Copious
amounts of moisture streaming off the Gulf of Mexico is
a major player in severe weather events within tornado
alley. Gulf moisture moves south-to-north off a frontal
system or the tropical jet stream, eventually meeting up
with drier, cooler air. As a result, weather happens!
Typically during the early spring and fall the
drier, cooler air from the north lacks the wherewithal
to reach the DFW Metroplex leaving storm fronts to stall
and die in Oklahoma. Other cold fronts may develop a dry
line and severe storm potential. The dynamics of these
storms are complex and outside the scope of this text,
but again as weather happens outside the metroplex some
other player must be introduced to enhance or collapse
the conditions necessary for that weather to reach the
metroplex or die outside. Quite typically that player is
the jet stream. Though not itself a single entity the
jet stream has both polar and tropical branches each
with their own characteristics.
All of the prolonged weather events in the
metroplex arise from the jet stream. There are flooding
rains that can last for more than a week or the days
long overcast common in the Texas winter. Both courtesy
of the jet stream. A winter dip in the polar jet, for
example, brings the classic "blue northern" to the
metroplex. Temperatures drop dramatically. Not quite in
5 minutes, but maybe as fast as 3 to 5 hours. Further-
more all you have to do is introduce a little moisture,
and wha-la... sleet. Such was the case in 1984. Inches
thick ice and nearly three weeks of sub-freezing
temperatures. Overall, an arctic blast for the record
books, and again, thanks to the jet stream. Yet despite
its importance to the overall weather picture, mass
media fails to include this feature in every forecast.
Still, it seems as though a new player is gaining
importance to the overall weather in North Texas. The
metropolitan "heat dome" effect. Year after year
increasing amounts of heat absorbing concrete replace
arable farm land in the outer suburbs. Temperatures
within the metroplex generally run seven to ten degrees
Fahrenheit higher than the surrounding communities.
This is by no means a phenomena endemic to Dallas-
Ft.Worth, many cities in the United States are
experiencing similar effects. It's amazing to watch a
weak storm front approach on radar. Like Moses parting
the Red Sea the front will split an dissipate as it
reaches the heat dome sometimes reforming downwind to
the east. The pronounced heat dome may have contributed
to the awesome pop-up thunderstorms mentioned earlier.
If so, pilots beware!
Last on the DFW playlist is the much publicized
El Nino and the lesser-known counterpart La Nina. The
last major El Nino of the late 90s may have had
something to do with the long hot North Texas drought,
but for the most part it was El no-show for DFW. That
spring a storm would develop on the west coast, dump
tons of rain (before reaching Texas) and die; or pass to
the north. This pattern repeated every 5 to 7 days for
two months making for a cool, cloudy, but rainless
spring. And the summer was hot! Really hot! Near record
temps over 100 degrees, though short of the mark set in
1980... 50 odd days (straight) of temperatures over 100
degrees. HOT!!! While forecasters provide only general
predictions during El Nino years the increasing
regularity and intensity of El Ninos leave all
predictions suspect.
Yes, times-r-a-chang'n. Global warming is a
reality. Combine that with an increasing metropolitan
heat dome and who knows what will happen. Drought?
Monsoon? Ice age? Weather patterns will certainly
change, however. Typically, DFW has a rainy spring, a
very warm summer, and an overcast winter. The weather
here is heavenly when spring and fall spill into summer
and winter. "Foreigners" may long for a four season
year, but an eternal spring seems far more appealing.
Nevertheless, there will be hot summers and cold winters
in the near future and weather-forecasters will still be
correct with some of the long-term predictions, but, if
you think you can predict the weather in Texas ... wait
5 minutes.
I have worked outside in and amongst the Texas
weather for over 15 years and as a licensed pilot I have
taken notice of the day-to-day weather. Still, I found
it surprising (once I began recording) that I took much
of the weather for granted. Most notably the speed at
which "weather" changes. Spring and fall morning
overcast, for example: 6:30 to 7 am, clear sunny skies;
45 minutes later, overcast. Very typical, but counter-
intuitive. Overcast should "burn-off", nevertheless, it
does not form until the sun comes out. In the summer,
typically cloudless mornings persist until the ground
heats sufficiently for vapor to rise and condense.
Without much effort you can forget and assume that it
has been cloudy from morning to noon. Weather happens.
Weather happens and though patterns emerge it is
sometime difficult to put it all into categories.
However I have done my best to do so. The tables below
represent weather that both VFR and IFR pilots can use
for flight planning purposes. Glider pilots should find
the cumulus information at the bottom of the 04 & 05
useful. Significant records have also been included to
round out the weather synopsis. Once you get the hang of
the notation the charts will be easy to decipher,
however even with a quick glance you should be able to
tell where weather events are occuring.
EX. Jul 2005 TSTORMS (thunderstorms)
[[ s5u2 ]] 1 severe , 5 pop-up , and 2 garden variety
thunderstorms
EX. Apr 2005 LOW-VFR
[[ 2+ae ]] 2 all-day , 1 am only , 1 very early am
EX. Apr 2004 LOW-VFR
[[ +-6a ]] 1 all-day , 1 am-into-afernoon , 6 am only
n.o. > no-observation . > zero / no occurance
+ -- ALL DAY u -- pop-up
LEGEND p -- PM only * -- embedded Tstorm
------ a -- AM only s -- Severe or snow
- -- into afternoon i -- Ice
e -- v.early morning g -- gust front
T -- tornado
RECORD HURRICANE season Katrina 8-23-06 thru 8-30-06
2 0 0 5
-------------- JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
BRIEF RAIN | . | p | 2 | 1 | 1 | . | . | . | 2 | 1 | . | .
RAIN |3e | 1 |*p3 | . | *1 | 1 | 4 | 5 | . | 2 | 1 | .
ALL DAY RAIN |*1 | 1 | 1 | . | 2 | . | . | . | . | . | . | .
TSTORM | 1 | 2 | p |Tp2 | 2 | e1 |s5u2|5u1 | 2s | 1 | . | .
MIST only | 3 | 1 | . | . | 2 | . | . | . | . | . | . | .
FOG | . | 1 | . | . | . | . | . | . | . | . | . | .
SNOW // ICE | . | . | . | . | . | . | . | . | . | . | . | .
TOTAL --------|---|----|----|----|----|----|----|----|----|----|----|----
Precip Inches |
---------------|---|----|----|----|----|----|----|----|----|----|----|----
IFR (no-precip)|-a1| -a | 2a | . | a | + | a | a | . | . | 3a | .
LOW VFR |2a | +1 | +a |2+ae|-5a | 2a | . | . | a | . | 1 | .
--------------------------------------------------------------------------
WIND | 1 | 1 | 2 | 5 | . | . | . | . | . | 1 | 6 | .
--------------------------------------------------------------------------
CLOUDLESS |2a2|2+a |6+2a|5+a | 1a | 4a | 6a |13a |+11a|6+6a|10+2a| .
--------------------------------------------------------------------------
(27) quick observations (no detail) (12) newscast only (no observ)
Jul. (2) fronts stall at the red river
(45) 1st CU %max SIGNIFICANT RECORDS
3-10-05 2pm 40% 5pm Feb.15 -record high- 82
4-28-05 3pm 20% 6pm Nov. 5 -record high- 90
6- 2-05 3:30pm 20% 5pm Dec. 3 -record high- 88
6-23-05 11am 45% 1:30pm Dec. 5 -record low- 32
9- 1-05 11:45am 30% 2:30pm
9 -7-05 NO CUs !! 1st Cirrus 10-2-05
------------------------------------------------------------------------------
2 0 0 4
-------------- JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
BRIEF RAIN | 2 | . | 3 | a | 1 | 1 | 2 | 2 | 2 | 3 | 4 | .
RAIN | 2 |e*2 | . |e*3 | *1 |2*3 | 1 | e2 | 1 | *3 | p7 | 1
ALL DAY RAIN | 2 | *2 | 1 | . | . | *1 | . | * | . | 3 | * | *
TSTORM | . | p | 1 | 2p | 4 |T2s5| 1 | . | s1 |s2p | . | .
MIST only | 1 | +p | +a | . | . | . | . | . | . | . | 3 | .
FOG | 3 | . | a | . | . | . | . | . | . | . | 3 | .
SNOW // ICE | . | s | . | . | . | . | . | . | . | . | . | 1
---------------|---|----|----|----|----|----|----|----|----|----|----|----
Precip inches |3.7|6.63|1.85|4.45|3.36| 13 |3.53|4.04|0.73|3.71|8.61|
TOTAL --|---|----|----|----|----|----|----|----|----|----|----|----
IFR (no-precip)|1a | 2+a| . | 2a1| 9a | 3a | 2a | | 1a |-2a2| -a | .
LOW VFR | . | . | . |+-6a|2+6a| +a | -a |2a1 | . | 2a1| -1 | a
--------------------------------------------------------------------------
WIND | . | 1 | . | 1 | 2 | g2 | . | . | 1 | 2 | 2 | .
--------------------------------------------------------------------------
CLOUDLESS | 1 | . | . | . | 1 | . | . | . | 3 | 2 | 3 | 9
--------------------------------------------------------------------------
no observ. 7/31..8/7 ; 9/9..9/12 ** NON-STD. north winds jul. & aug.
(16) 1st CU %max SIGNIFICANT RECORDS
7-22-04 10:40am 45% 5pm VD #1 1928 11.5" RAIN in JUNE
8-26-04 2pm 30% 5pm #2 2004 10.5" RAIN in JUNE
9- 1-04 10:45am 50% 4pm
9-20-04 4pm 15% 5pm
------------------------------------------------------------------------------
2 0 0 3
-------------- JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
BRIEF RAIN | . | 2 | 1 | . | 1 | . | 1 | . | 1 | . | 1 | 1
RAIN | . | . | 1 | e | 3 | 4 | 1 | 1 | 4 |pe1 | 2 |2p1
ALL DAY RAIN | . | 3 | . | . | 1 | . | . | *2 | 2 | 1 | . | 1
TSTORM | . | . | e |se1 |spe |2p4 |s2u3|2s3 | . | . | s | .
MIST only | . | 1 | . | . | . | . | . | . | . | . | . | .
FOG | . | . | 1 | . | . | . | . | . | . | 1 | 1 | .
SNOW // ICE | s | i | . | . | . | . | . | . | . | . | . | .
---------------|---|----|----|----|----|----|----|----|----|----|----|----
Precip Inches |0.8|3.43|1.00|0.90|4.10|5.22|1.04|2.49|4.94|0.61|3.81|1.18
29.53" TOTAL --|---|----|----|----|----|----|----|----|----|----|----|----
IFR (no-precip)|2a | 3a | 2a | . | . | 2a | 5a | . | . | . | - | a
LOW VFR |2a |4+3-|+4- |2+2a| . |-4a | a | a | 2a | 2a |+4a |-3a
--------------------------------------------------------------------------
WIND | 2 | 1 | 4 | 4 | . | g | . | . | 1 | 1 | 3 | 3
--------------------------------------------------------------------------
CLOUDLESS |n.o|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.| . | . |14+ | . | .
--------------------------------------------------------------------------
COMMON SIGNIFICANT RECORDS
** aug.(2) fronts stall at the red river early May Record No. of
(0) 1st CU observations (KANSAS) tornados.
7-17-03 Hurricane Claudett -due-WEST track ! Mar.2003 El Nino noted
------------------------------------------------------------------------------
2 0 0 2
-------------- JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
BRIEF RAIN | . | 2 | 1 | . | . | 1 | 2 | . | . | 2 | 1 | .
RAIN |e3 | 2 | 3 | *1 | . | * | . | . | . | p3 | . | 2
ALL DAY RAIN | . | . | . | * | . | 1 | 3 | * | 1 | * | . | +*
TSTORM | 2 | . | 2s | 1 |5p3 | e7 | p2 | 3 | 1 | . | . | 1
MIST only | . | . | 2+ | . | . | . | . | . | . | . | -e | -
FOG | . | . | . | . | 1 | . | . | . | . | 2 | . | 1
SNOW // ICE | . | s | s | . | . | . | . | . | . | . | . | .
---------------|---|----|----|----|----|----|----|----|----|----|----|----
Precip Inches |4.8|1.36|7.09|6.15|4.32|2.57|3.65|4.65|1.09|6.97|0.40|4.27
47.28" TOTAL --|---|----|----|----|----|----|----|----|----|----|----|----
IFR (no-precip)|2a | . | 2a | . | . | 3a | a | . | . | 2- | - | 2-
LOW VFR | . | . |2-2a| 4a |-4a | a | . | . | . |2+3-| + | 2-
--------------------------------------------------------------------------
WIND | 1 | 2 | 5 | 1 | 2 | . | . | . | . | . | . | 3
--------------------------------------------------------------------------
CLOUDLESS |n.o|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.
--------------------------------------------------------------------------
OBSERVATIONS OF I.F.R. WEATHER ONLY
** NON-STD jun.20-21 E-to-W surface low ** Oct. listed
jul.2 E-to-W upper-level low ** with El Nino
jet stream
------------------------------------------------------------------------------
2 0 0 1
-------------- JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
BRIEF RAIN |n.o| 2 | 1 | . | . | . | . | . | . | . | . | .
RAIN |n.o| 4 | 5 | 2 | 2 | e1 | . | 2 | ? | ? | 4 | 4
ALL DAY RAIN |n.o| 1 | . | . | . | . | . | . | . | . | . | .
TSTORM |n.o| 1 | p | . | . | p3 | e | . | . | . | . | .
MIST only |n.o| . | . | . | . | . | . | . | . | . | . | 1
FOG |n.o| 2 | . | 1 | . | . | . | . | . | . | . | .
SNOW // ICE |n.o| 1 | . | . | . | . | . | . | . | . | 3s | .
TOTAL --------|---|----|----|----|----|----|----|----|----|----|----|----
Precip Inches |2.5|5.32|5.08|1.07|4.74|0.97|4.29|5.25|4.20|2.54|1.68|2.81
40.49" TOTAL -|---|----|----|----|----|----|----|----|----|----|----|----
IFR (no-precip)|n.o| -a | a | . | . | . | . | . | . | . | 2a | -
LOW VFR |n.o|-2a | . | 2- | . | 2a | . | . | . | . | . | .
--------------------------------------------------------------------------
WIND |n.o| 1 | 1 | 2 | . | a | . | . | . | . | . | .
--------------------------------------------------------------------------
CLOUDLESS |n.o|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.|n.o.
--------------------------------------------------------------------------
OBSERVATIONS OF I.F.R. WEATHER ONLY
30-year Precipitation Normals (1971-2000)
--------------- JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
---------------|---|----|----|----|----|----|----|----|----|----|----|----
Precip Inches |2.1|2.60|3.18|3.38|5.34|3.70|2.48|2.13|3.18|4.55|2.59|2.71
37.96" TOTAL --|---|----|----|----|----|----|----|----|----|----|----|----
1991 60.04" Total Precipitation
1990 50.35" Total Precipitation
1980 26.72" Total Precipitation
------------------------------------------------------------------------------
6-28-05 >> cloudless 7 am 98-76 degrees
1st CU 12:30 am 0 wind
20 % 2 pm
35 % max 4 pm poor vert. development
6-29-05 >> cloudless 7 am 98-78 degrees
1st CU 11:30 am 12 kt s.wind
15 % 12:30 pm
40 % max 4 pm some vert. development
6-30-05 >> cloudless 7 am 100-80 degrees
1st CU 11 am 8 kt s.wind
20 % 12:30 pm
35 % max 4 pm good vert. development
1-9-05 >> 900 o.c. 8-10:30 am 20 kt WIND
1900 scatt 11 am
1-10-05 >> 500 o.c. 6-9 am lt.wind (am)
900 o.c. 10 am break-up / rebuild
1200 o.c. / 2-layer noon
1500 scatt / mid-o.c. 2 pm 68-50 degrees
mid-o.c. 4 pm 25 kt s.WIND!
1-5-04 cloudless 7 am
1200 widely scatt 8 am (no wind notation)
1200 scatt w/ banks 8:30 am (no temp notation)
1200 o.c. 9:00 am
o.c. w/ lg. holes 9:30 am
1200 scatt w/ banks noon
cloudless 2:30 pm
5-21-03 islated low clouds 6:30 am
500 scatt w/ banks 7:30 am (no wind notation)
700 broken 8 am (no temp notation)
800 broken lg.holes 9:30 am
1300 scatt 10 am
dissipatted noon
7-8-03 cloudless 7 am
800 broken sm.holes 7:45 am (no wind notation)
900 broken lg.holes 8:45 am (no temp notation)
1000 scatt w/ banks 9:45 am
* 1400 scatt w/ banks 2:30 pm 35 Min. RAIN *