JANUARY 1939 MONTHLY WEATHER REVIEW 31
proceeding southwestward some 100 to 200 or more miles
west of the Oregon coast, lowest barometer 29.08 inches,
on the 2d. Much farther a t sea, near 43' N., 148' W. the Japanese motorship Genyo AfaTu encountered strong gales to hurricane winds, lowest barometer 28.71, on the
3d. I n connection with the midocean cyclone of this period in January, abnormally low pressures were recorded over
a considerable region south of the Aleutians. Readings close to 28 inches were had on several ships, with an
accompaniment of strong to storm gales (forces 9 to 11).
The British steamship Toorak, already nientioned as having a barometer reading of 27.76 inches on the 4th,
encountered the full strength of the wind in a north-
westerly gale of force 11 near 42' N., 176' E., on the 5th.
Stormy conditions, with wind forces of 8 to 10, continued through the 6th within the region of about 40' to 50' N.,
175' E. to 170' W., but thereafter abated. The early January cyclone east of Japan was of prac-
tically equal intensity and extent to those previously mentioned, except that the barometer did not fall to
similar depths. On the 1st and 2d the British steamship
Toorak, and on the 3d the Norwegian motorship Tai Yang, experienced northerly gales of force 11 within the locality, 41'-42' N., 153'-156' E. Outside the imme-
diate locality gales of force S to 10 occurred over a wide stretch of sea from near the coast of Japan, on to the
eastward, where the storm area merged with that prevail-
ing in middle longitudes. Widespread low pressure continued through the 10th
over the western half of the ocean, with much stormy weather. I n fact, during the first third of the month, fully three-fourths of January's gales occurred. The
7th was the day of most intense winds, with hurricane forces experienced by the Norwegian motorship Pleasant-
mlle near 38%' N., 156%' E., and by the Japanese steam- ehip Shoyo hiaru nenr 4OJL' N., 16lJi' E. Following the 10th storni energy had greatly subsided, so that, up to the 15th, only scattered gales were reported. The one intense wind of the period thus far coming to
attention was a west gale of force 12, encountered by the
American steamship President Pierce on the 13th near
32' N., 155' E. The North Pacific, during the final half of the month,
wns unusually free of gales for January, and such as were reported on estratropical waters for the 16th to 31st did
not exceed 9 in force. Those particularly to be noticed were observed as follows on the Swiftsure Bank Lightship:
Of force 8 on the 17th, lsth, and 28th, and of force 9 on
the 25th.
Gales of the Tropics.-The tropical gales reported for
the month occurred in two localities-the Gulf of Tehuan-
tepec ancl the China Sea. In the Gulf there were Te-
huantepecers of force 7 on the 6th, lSth, and 21st. On the 25th, with the crest of an anticyclone lying over the
Gulf States and the northern part of the Gulf of Mexico,
the consequent Tehuantepecer, as experienced by the American steamship Alabaman , attained an in tensity of force 11. I n the China Sea the British steamship
Lacklan encountered a northeast gale of force 10, barometer
29.95, near 15' N., 119' E., on the 8th. Fog.-Very little fog was seen on the North Pacific
this month. There were scattered occurrences in northern waters on 4 days early in January, and about midway between California and the Hawaiian Islands, fog was
observed on 5 clnys, mostly near the middle of the month. Ships reported fog on 4 days along the west coast of the
United States; on 2 days off Lower CalifornirL; and 1 day each near Cape Corrientes; in the Gulf of Tehuantepec;
and off the coast of Costa Rica.
CLIMATOLOGICAL TABLES
[Climate and Crop Weather Divlsion, J. B. KINCER In charge]
DESCRIPTION OF TABLES AND CHARTS
By J. P. KOHLER
Table 1 presents average and extreme values for 45 climatic districts, based on all available data ascertained
by regular and cooperative Weather Bureau stations. Table 2 gives the data ordinarily needed for climato-
logical studies for about lS0 Weather Bureau stations making simultaneous observations nt 7:30 a. m. and 7:30
p. m. daily, 75th meridian tinie, and for about 20 others making only one observation. The altitudes of the in-
struments above ground are also given. Beginning with January 1, 1932, all wind movements
and velocities published herein are corrected to true values by applying to the anemometer readings, correc-
tions determined by actual tests in wind tunnels and elsewhere.
Table 3 gives, for about 37 stations of the Canadian Meteorological Service, the means of pressure and tem-
perature, total precipitation, depth of snowfall, and the
respective departures from normal values, escept in the case of snowfall. The sea-level pressures have been com- puted nccording to the method described by Prof. F. H. Bigelow in the REVIEW of January 1902, 30: 13-16. Table 4 lists the severe local storms reported in the United States during the month. It is compiled from
reports furnished mostly by officials of the Weather Bureau.
In regard to discussion of charts that follow: Charts I, IV, V, and VI are based on observational data from sta-
tions listed in table 2.
Chart I. Temperature departures and wind Toses for selected slationu.-This chart presents the departures of the monthly w.em surface temperatures from the monthly
normals. The shaded portions of the chart indicate areas
of positive departures and unsliaded portions indicate
areas of negative departures. Generalized lines connect places having approximately equal departures of like
sign. Charts of monthly surface temperature departures
in the United States was first publisliecl in the MONTHLY WEATHER REVIEW for July 1909, and continued there- after, but smaller charts appear in W. B. Bidletin C for
1873 to June 1909. inclusive. An innovation has been
made in this chart, beginning January 1939. The selected wind rose data formerly published as chart VI1 has been
transferred to this chart. The wind roses are based on
hourly percentages by months for 23 selected Weather Bureau stations.
Chart 11.- Tracks of centem of ANTICYCLONES; and
Chart 111.-Tracks of ctnters qf CYCLONES. The
roman numerals show the chronological order of the cen- ters. The figures within the circles show the days of the month. the location indicated being that a t 7:30 a. m.,
75th niericlian time. Within each circle is also an entry of the last three figures of the highest barometric reading (chart 11) or the lowest reading (chart 111) the reported
a t or near the center at that tinie, in both cases as reduced
to sea level and standard gravity. The intermediate
7:30 p. ni. locations are indicated by dots. The inset niap on chart I1 shows the departure of monthly mean pressure
from normal and the inset on chart I11 shows the change
in mean pressure from the preceding month.
32 MONTHLY WEATHER REVIEW JANUARY 1939
The use of a new base map for charts I1 and I11 began
with the January 1930 issue. Chart 1V.-Percentage of clear sky between sunrise and
azmset.-The average cloudiness a t each regular Weather Bureau station is determined by numerous personal ob- servations between sunrise and sunset. The difference
between the observed cloudiness and 100 is assumed to
represent the percentage of clear sky, and the values thus obtained are the basis of this chart. The chart does not
relate to the night hours. Chart V.-Total precipitation.-The scales of shading
with appropriate lines show the distribution of the monthly precipitation according to reports from both regular and
cooperative observers. The inset on this chart shows the
departure of the monthly totals from the corresponding normals, as indicated by the reports from the regular
stations. Chart VI.-Isobars at sea level and &?otherms at suTface,
prezading winds.-The pressures have been reduced to sea level and standard gravity by the method described
by Prof. Frank H. Bigelow in the REVIEW for January
1902, 30:13-16. The pressures have also been reduced to the mean of the 24 hours by the application of a suitable
correction to the mean of 7 :30 a. m. and 7:30 p. m. readings
at stations taking two observations daily, and to the
7:30 a. m. or the 7:30 p. m. observation at stations taking but a single observation. The diurnal corrections so applied, except for stations
established since 1901, will be found in the Annual Report
of the Chief of the Weather Bureau, 1900-1901, volume 2,
table 27, pages 140-164.
The sea-level temperatures are now omitted and average
surface temperatures substituted. The isotherms cannot
be drawn in such detail as might be desired, for data from
only the regular Weather Bureau stations are used.
The prevailing wind directions are determined from hourly observations at almost all the stations. A few
stations determine their prevailing directions from the daily or twice-daily observations only.
Chart VI1.-Total snowfall.-This is based on the re- ports from regular and cooperative observers and shows
the depth in inches of the snowfall during the month. In general, the depth is shown by lines connecting places of
equal snowfall, but in special cases figures also are given.
This chart is published only when the snowfall is s a -
cientl extensive to justify its preparation. The inset on
ground at 7:30 p. m. of the Monday nearest the end of the month and is a copy of the snow chart appearing in the snow and ice bulletin for that week. Generally, the pub-
lication of the Weekly Snow and Ice Bulletin commences about the middle of December a.nd continues to near the
close of March. Charts VIII-XI1.-Aerological charts, for description
and explanations, see p. 22, of this REVIEW. Charts, XIII-XIV, etc.-North Atlantic weather maps
for particular days.
this c K art, when included, shows the depth of snow on the