Lettau 18Z pressure 1986 - 991.9 989.7 979.4 992.4 990.6 978.7 979.9 976.4 971.5 974.5 981.8 1987 992.7 988.9 985.4 987.4 983.0 985.8 991.2 975.4 989.2 977.4 978.2 985.6 1988 988.4 984.3 984.9 981.4 989.0 995.0 975.2 974.8 983.2 989.0 981.4 983.6 1989 984.7 985.2 982.9 987.7 969.1 979.7 977.3 982.7 980.4 973.5 976.5 989.3 1990 988.5 983.1 985.6 991.5 997.1 985.2 995.4 979.3 970.0 980.7 982.8 983.2 1991 982.4 989.2 980.3 983.9 987.3 988.9 990.8 - - - 983.1 995.0 1992 988.6 994.7 987.9 984.4 989.6 993.0 - - - - 977.4 983.1 1993 996.3 978.1 985.6 980.7 982.5 - - - - - 979.7 983.9 1994 985.1 982.3 978.3 984.2 985.6 997.5 986.8 972.9 987.8 976.8 985.1 981.6 1995 981.2 981.1 991.0 982.1 980.3 986.1 - - - - 977.5 977.6 1996 986.2 - - - - - - - - - - 985.2 1997 989.0 - - - - - - - - - - - 1998 - - 981.6 974.0 982.1 - - - - - - - 1999 - 987.0 983.5 980.1 976.6 999.4 979.5 981.7 981.1 964.1 - - 2000 - - 982.7 982.4 982.4 984.0 979.5 982.6 986.5 975.1 - - 2001 - - 983.1 978.1 983.4 981.3 985.5 981.5 976.2 971.3 - - 2002 - - 989.8 979.7 992.2 993.3 986.6 977.2 985.5 990.3 - - 2003 - - - - - 991.0 976.8 - - 971.2 - - 2004 - - - - - - - - - - - - 2005 - - 980.3 977.9 - 988.4 978.8 974.2 973.2 968.4 - - 2006 - - - - - - - - - - - - 2007 - - - - - - - - - - - - 2008 - - - - - - - - - - - - 2009 - - - - - - - - - - - -