1999 South Pole Weather Highlights

January
The first month of 1999 featured a spectacular halo display on the 11th
produced by ice crystals falling from a sunny sky.   Described as a *World
Record* display by halo researchers working at the station, the event featured
no fewer than 27 haloforms and subforms.   After this display, the most
significant weather event was a storm that settled over the station on the 21st
and 22nd. The 21st recorded a maximum temperature of
-19.2(C)/-2.6(F), which was not only a record high for the day and the maximum
for the month, but also the warmest temperature recorded during the 1998/1999
summer season.   The maximum gust of 32 kts/37 mph on the 21st was also a
record for the day and the peak wind speed for the month.  The 22nd also
recorded a record high temperature and both days experienced visibility of less
than 1/4 mile, the only two such days in January.  The warm temperatures during
the storm contributed to an average temperature for the month of
-26.5(C)/-15.7(F), which was 1.6(C)/2.9(F) above normal.  The minimum
temperature of -35.0(C)/-31.0(F) occurred on the 31st as clear skies and
dropping temperatures prevailed during the final week of January.  Winds for 
the month were normal at 8.2 kts/9.5 mph from Grid North and station pressure
was 1.9mb above average at 691.9mb.

February
February brought the expected return of colder temperatures but not before
another storm once again delivered high temperatures and strong winds on the
3rd and 4th.  The 3rd set daily records for highest average wind speed as well
as peak wind gust, which was also the maximum wind speed for the month at 29
kts/33 mph.  On the 4th, the maximum temperature of -22.9(C)/-9.2(F) was not
only a record for the day but also the high temperature for the month.  The
minimum temperature of -49.9(C)/-57.8(F) occurred again on the final day of the
month.  Visibility was reduced to 1/4 a mile or less on only one day, the 3rd.
On the 15th the last of the station*s summer personnel left and the official
last flight of the season departed on the 17th as temperatures became too low
for planes to land and depart safely.  The average temperature for the month of
-41.5(C)/-42.7(F) was slightly below normal while partly cloudy and cloudy
skies prevailed.  Barometric pressure for the month was slightly higher than
normal at 686.4mb and winds slightly lower at 8.6 kts/9.9 mph.

March
March was notable for some unseasonably cold days, although the average
temperature of
-54.5(C)/-66.1(F) was only 0.6(C)/1.1(F) below normal.  Record lows were set on
the 18th, 19th and 21st, with the 18th reaching -70.0(C)/-94.0(F).  This marked
the earliest in the season that South Pole Station has ever recorded a
temperature so low and was also the minimum temperature for the month.  The
maximum temperature recorded was -39.6(C)/-39.3(F), occurring on the
5th before the extreme cold set in.  Though partly cloudy and cloudy skies
prevailed during the month, no significant storms took place.  Visibility never
fell below 1/4 of a mile and the peak wind gust for the month was 26kts/30 mph
on the 29th.  The average wind speed for the month was 8.9 kts/10.3
mph, slightly lower than average, while the barometric pressure was near normal
at 682.3mb.  The sun officially set for the season at 1000 local time (1700Z)
on the 21st.

April
The first full month without the sun brought a mix of weather to the South
Pole.  Record low temperatures were recorded on both the 10th and 11th, while
the low for the month occurred on the 23rd at -72.5(C)/-98.5(F).  The average
temperature for the month was
-61.3(C)/-78.3(F), a full 4.0(C)/7.2(F) colder than average.  There were also
several stormy days during the month, with 4 days overall experiencing
visibility of 1/4 mile or less.  Three of these days occurred during a storm
between the 13th and the 15th.  On the 14th the average wind speed for the day
broke the previous record, while the peak gust of 27 kts/31 mph tied the record
for the day and stood as the peak wind speed for the month.  The 14th also
registered the warmest temperature of the month at -51.0(C)/-59.8(F).  On the
15th the peak wind gust of 26 kts/30 mph broke the daily record.  Station
pressure for the month was very low at 672.8mb, which was 7.9mb below average
for April.  Winds for the month were very near average at 11.0 kts/12.7 mph.

May
May was the first month since January that was warmer than normal.  The average
temperature of -57.6(C)/-71.7(F) was 0.5(C)/0.9(F) above the average for the
month.  In the evening of May 5 local time (early morning May 6 Zulu time), the
temperature at the South Pole dropped below -73.4(C)/-100.1(F) for the first
time in 1999.  Record low temperatures were set on the 5th, 6th and 18th with
the 6th reaching -74.2(C)/-101.6(F), also the low temperature for the month.
Two storms late in May reduced visibility to 1/4 mile or less for a total of 3
days, the 23rd, 24th and the 30th.  The peak wind speed for the month occurred
on the 23rd at 29 kts/33 mph.  The stormy weather on the 30th brought high
winds and a record high temperature for the date of -36.1(C)/-33.0(F), which
was also the maximum for the month.  For the second straight month station
pressure was quite low, averaging 676.1mb, 4.2mb below normal.  Winds for the
month were near average at 11.5 kts/13.3 mph.

June
The weather during solstice month was relatively unremarkable since no records
were broken and there were few extremes.  The average temperature of
-58.5(C)/-73.3(F) was slightly below average.  The peak wind speed was only 25
kts/29 mph, recorded on both the 8th and the 9th, which were the only two days
experiencing visibility of 1/4 mile or less.  Winds overall averaged slightly
below normal at 10.6 kts/12.2 mph.  The maximum temperature was
-42.4(C)/-44.3(F), recorded on the 3rd, and the minimum of
-72.6(F)/-98.7(F) occurred on the 30th.  On June 17th the station recorded a
barometric pressure of 712.7mb, the highest reading since the all-time record
high pressure of 719.0mb was set on August 25, 1996.  Barometric pressure for
the month averaged 689.6mb, 8.5mb above average.  The winter solstice took
place on the 21st, marking the midway point of the 6 months without sun at the
South Pole.

July
July on the whole was colder than average but once again no records were tied
or broken.  The average monthly temperature of -62.8(C)/-81.0(F) was
3.2(C)/5.8(F) colder than normal. Extreme cold settled in on the South Pole as
both the 27th and 28th registered temperatures below -73.4(C)/-100.1(F).  The
minimum temperature of the month took place on the 28th, -74.8(C)/-102.6(F),
which turned out to be the lowest temperature recorded during the winter. The
maximum temperature for the month of
-45.1(C)/-49.2(F) occurred only two days later, a significant temperature
increase in just over 48 hours.  The first mid-winter airdrop to take place at
the South Pole in several years occurred at 10:30pm on the 10th (0530 on the
11th Zulu time) under clear skies with a temperature of approximately
-66.5(C)/-87.7(F).  There were a total of four days with visibility of 1/4 mile
or less, including the 23rd, which registered the peak wind speed for the month
o!
 f 27 kts/31 mph.  Barometric pressure and average wind speed for the month
were very near the monthly averages at 676.6mb and 10.3 kts/11.9 mph
respectively.

August
August began with a prolonged storm that reduced visibility to 1/4 mile or less
for five days out of the first week, the only such days during the month.
However, a break in the storm on the 6th allowed station personnel to sight the
first light of the season on the horizon. Considering that it is historically
the coldest month of the year at South Pole, August was relatively warm.  The
monthly average temperature of -57.3(C)/-71.1(F) was 2.5(C)/4.5(F) warmer than
average.  The minimum temperature of -71.2(C)/-96.2(F) was recorded on the 22nd
and the maximum of -38.2(C)/-36.8(F) occurred on the 5th. There were only 2
days of clear skies during the month as partly cloudy and cloudy skies
prevailed.  Winds were about average at 11.7 kts/13.5 mph with a peak gust of
34 kts/39 mph on the 7th, which was also the only record set during the month.
Barometric pressure was also near average at 675.7mb.

September
Despite the increasing light and the eventual sunrise, September was the second
coldest month of the year behind July.  The average monthly temperature of
-62.3(C)/-80.1(F) was 2.9(C)/5.2(F) below normal.  The minimum temperature for
the month of                   -72.6(C)/-98.7(F) was reached twice, on the 8th
and the 21st.  The maximum temperature of  -44.1(C)/-47.4(F) occurred on the
25th during a storm that also registered the peak wind gust for the month of 27
kts/31 mph.  The storm also brought 4 days of freezing fog and high winds,
causing three out of the four days during the month with visibility of 1/4 mile
or less.  The sun officially rose for the season at 1pm local time (2000Z) on
the 22nd, though it appeared visible for two days prior to that due to
atmospheric refraction.  No records were tied or broken during the month.
Barometric pressure was 5.3mb above average at 680.6mb while wind for the month
was 2.0 kts/2.3 mph below normal at
10.0 kts/11.5 mph.

October
The month of October started out with fairly light winds and cold temperatures.
The minimum temperature for the month of *69.3(C)/-92.7(F) occurred on the 2nd.
A storm lasting two days began on the 6th, warming the temperature up to
*38.8(C)/-37.8(F) and reducing visibility to 1/4 mile.  The middle part of the
month was also fairly stormy, with visibility of 1/4 mile or less in blowing
snow reported on the 16th and 19th.  The peak wind for the month of 29 kts/33
mph occurred on the 19th.  However, light winds later in the month caused the
monthly average wind speed to turn out a bit below average at 10.1 kts/11.6
mph.  The monthly average temperature of *51.7(C)/-61.1(F) was just
0.4(C)/0.8(F) colder than normal.  The only record broken during the month was
a record high temperature of *33.0(C)/-27.4(F), which occurred during the storm
on the 19th.  On the 25th, winds dropped off during the day, allowing the
visibility to improve enough for the first aircraft flight of the!
  summer season to land.  The month then ended with colder than normal
conditions as the temperature dropped below *50.0(C)/-58.0(F) on the 30th.
This caused the suspension of flights to South Pole for a few of days until it
warmed above *50(C) again.

November
November started with two clear and cold days featuring temperatures down to
-51.9(C)/-61.4(F), but then cloudy skies with blowing snow and warmer
temperatures were prevalent for much of the next 10 days.  Record high
temperatures were set on the 4th and 5th, with readings of -32.6(C)/-26.7(F)
and -32.0(C)/-25.6(F), respectively.  The peak wind for the month of 22 kts/25
mph occurred on both the 3rd and the 7th.  After the 12th, sunny skies with
colder than normal temperatures were dominant for the remainder of the month.
Record low temperatures were set on the 17th and 30th.  The average temperature
for the month of -40.0(C)/(F) came out to be 1.7(C)/3.1(F) colder than normal.
The average monthly wind speed of 7.6 kts/8.7 mph was considerably below the
climatological average of 9.8 kts/11.3 mph.  Station pressure was near normal
at 681.0mb.

December
Record cold was the theme for December 1999.  The average monthly temperature
of  *32.2(C)/-26.0(F) made it the coldest December on record at the South Pole.
The cold spell lasted through the entire month, with an extraordinary 13 daily
record lows broken. On December 1st, the minimum temperature of
*42.0(C)/-43.6(F) set a new record for the coldest temperature ever observed in
December at the South Pole.  Previously, all the record lows for December had
been warmer than *40.0(C)/(F).  A stable weather pattern with clear to partly
cloudy skies through most of the month allowed the cold to persist.  The
warmest temperature for the month of *24.6(C)/-12.3(F) occurred on the 22nd,
one of the few days that had a period of thick cloud cover.  In addition to all
the temperature records, December also had a record low monthly pressure of
680.1mb, which was 8.3mb below the climatological average.  The average wind
speed was a bit below normal at 7.3 kts/8.4 mph.  A peak wind speed !
 of 22kts/25 mph occurred on both the 4th and 5th of December.



 Month        Temperature (C)                          Wind (Kts)
                                         Dep.
                                         From          Avg                 Peak
                 Max      Min      Avg   Normal        Spd      Dir     Spd
Date
January -19.2   -35.0   -26.5   +1.6            8.2     360     32       21st
February        -22.9   -49.9   -41.5   -0.7            8.6     020     29
3rd
March   -39.6   -70.0   -54.5   -0.6            8.9     350     26      29th
April   -51.0   -72.5   -61.3   -4.0            11.0    010     27      14th
May     -36.1   -74.2   -57.6   +0.5            11.5    030     29      23rd
June    -42.4   -72.6   -58.5   -0.2            10.6    030     25       9th
July    -45.1   -74.8   -62.8   -3.2            10.3    360     27      23rd
August  -38.2   -71.2   -57.3   +2.5            11.7    030     34       7th
September       -44.1   -72.6   -62.3   -2.9            10.0    020     27
25th
October -33.0   -69.3   -51.7   -0.4            10.1    040     29      19th
November        -32.0   -51.9   -40.0   -1.7            7.6     030     22
7th
December        -24.6   -42.0   -32.2   -4.4            7.3     290     22
5th


1999 Climatological Summary

Temperatures:
Avg Temp....................... *50.5 (C) / -58.9 (F)
Departure from normal... *1.1 (C) / -2.0 (F)
Max Temp...................... -19.2 (C) / -2.6 (F) on January 21st
Min Temp....................... -74.8 (C) / -102.6 (F) on July 28th

Sky Cover:
Avg Sky Cover ...............  4/8ths
Days clear... 100       Days partly cloudy... 163       Days cloudy... 102

Wind:
Avg wind speed.................. 9.7 kts / 11.2 mph
Departure from normal....... *1.0 kts / -1.1 mph
Max gust............................. 34 kts / 39 mph on August 7th
Max gust direction.............. From Grid Northeast
Vectored wind direction...... 050 degrees
Vectored wind speed........... 7.4 kts
Prevailing direction............. Grid East

Station Pressure (millibars):
Avg pressure........................ 680.4 mbs
Departure from Normal....... -0.9 mbs
Highest pressure................... 712.7 mbs on June 17th
Lowest pressure.................... 657.8 mbs on August 15th

Physio-altitude in feet and meters:
Average physio-alt = 10613 ft / 3235 m
Highest physio-alt =  11477 ft / 3498 m on August 15th
Lowest physio-alt  =  9418 ft / 2871 m on June 17th

Visibility:
28 days with visibility of 1/4 mile or less.


Prepared by: Dar Gibson and John Gallagher