National Weather Service United States Department of Commerce

Arctic Cold Front Impacting the Great Lakes into the Northeast

A powerful Arctic cold front will sweep across the Great Lakes today and into the Northeast early Thursday. Expect brief, intense bursts of heavy snowfall and gusty winds. Widespread strong winds will spread from the Northern Plains to the Great Lakes today and reach the Central Appalachians, Mid-Atlantic, and Northeast by Thursday, where some blizzard conditions are expected in the Appalachians. Read More >

Telecommunication Operations Center

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Table D3

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Table D3

Level designator ii

(when T1 = H, X, Y, or Z)
(U.S. National Practice definitions included)

Instructions for the proper application of level (elevations above the earth's surface) designator.

1. The designator specified in this table should be used to the greatest extent possible to indicate the level of the data contained within the text of the bulletin.

2. When data at more than one level are contained in the text, the designator for only one of the levels should be used.

3. When the table does not contain a suitable designator for the level, a designator which is not assigned in the table should be used.

The U.S. Practice uses 25 mb increments 1000-100 mb and are included below.

ii Designator
Level
00
Entire Atmosphere (e.g. precipitable water)
99
1000 hPa
98
Air properties for the earth's surface
97
Level of the tropopause
96
Level of maximum wind
95
950 hPa
94
Level of 0oC isotherm
93
975 hPa
92
925 hPa
91
875 hPa
90
900 hPa
89
Any parameter reduced/sea level (MSLP)
88
Ground/water properties for the earth's surface
(i.e. snow cover, wave & swell)
87
1000-500 hPa thickness
86
Boundary Layer
74
Cloud top level
85-01
Hundreds and tens digits of the hectopascal level
(e.g. 70 = 700 hPa; 03 = 030 hPa)
      To include:
      81 = 810 hPa = 6000ft FL
      82 = 825 hPa
      84 = 875 hPa
      77 = 775 hPa
      73 = 730 hPa = 9000ft FL
      72 = 725 hPa
      67 = 675 hPa
      65 = 650 hPa = 12000ft FL
      62 = 625 hPa
      50 = 510 hPa = 18000ft FL
            (U.S. National Practice uses 500 mb level)
      11 = First 30 mb average thickness (from surface)
      12 = Second 30 mb average thickness
      13 = Third 30 mb average thickness
      14 = Forth 30 mb average thickness
      45 = Fifth 30 mb average thickness
      16 = Sixth 30 mb average thickness
Note: The 810, 730, and 650 hPa levels are not being used as pressure levels, they are being used as geometric heights.