Jvm 1964 M.ONTHLY WEATHER REVIEW 163
THE WEATHER AND CIRCULATION OF JUNE 1954'
Illustrating the Birth and Growth of a Continental Anticyclone
JOSHUA Z. HOLLAND
Extended Forecast Section, U. S. Weather Bureau, Washington, D. C.
THE MONTH AS A WHOLE
For the third consecutive June [l, 21 heat and drought
dominated the weather over the eastern two-thirds of the
United States except for the northern tier of States, while
abnormally cool, wet weather prevailed in the Far West
(Charts I-B and III-B). On the other hand, the tem-
perature and precipitation anomalies of this June were
nearly opposite to those of the preceding month [3].
Table 1 illustrates this year-to-year persistence and
month-to-month reversal for temperature. For example,
43 of the 76 stations which reported above (A) or much
above (MA) normal temperatures in June 1952 also re-
ported above or much above in June 1954. On the other
hand, of the 21 stations which reported above or much
above normal in May 1954 only 4 again reported above
or much above in June 1954, but 13 reported below or
much below. The precipitation patterns showed similar
persistence and reversal, though not so neatly. Iowa
was a notably exceptional area where the May-June
reversal did not occur; instead, May rains were followed
by June rains to produce record floods.
TABLE 1.-Number of United States stations 1 showing repetition or reversal of abnormalcold (B or MB) or warmth (A or M A ) i n
196.4 (approzimate) Junc 196.4 as compared with June 1962, June 1963, and May
1 1 June 1964 1 June 1954 Same in Opposlta in
1-1 I
'."I Based on 100 evenly distributed stations used by the Extended Forecast Section in Vpatrsing prognostic temperature patterns.
The700-mb. circulation over North America(fig. 1)
'associated with this drought-flood combination contained
certain elements of the heat-drought pattern observed in
June 1952 and June 1953 as well as some characteristics
I Bee Charts I-XV followfng p. 172 for anslyzed climatological data for the month.
reminiscent of the Kansas flood situation of June 1951
141. The anomalous components of the flow,following
the lines of equal height departure from normal, suggest
an abnormal influx into the United States of air massea
from the North Pacific Ocean, and less than normal influx
of moist Gulf air into the Mississippi Valley. A moder-
ately strong 700-mb. anticyclone existed in the Southeast,
accompanied by positive height anomalies over the east-
ern half of the United States. A High center was also
present at sea level (Chart XI) but with negative pres-
sure anomalies in the area covered by the upper-level
anticyclone, indicative of abnormal warmth in the layer
between sea level and 700 mb.
These are familiar elements of summer drought circu-
lation in the eastern half of the United States. T. R.
Reed [5, 61 in the 1930's pointed out the importance of
superimposed upper- and lower-level anticyclones in pro-
ducing drought. A few years later a research group at
Massachusetts Institute of Technology published an
account [7]of the structure and dynamics of the conti-
nental summer anticyclone whichcould not be greatly
improved upon today. Recent occurrences of this anti-
cyclone, associated with the summer droughts of 1952
and 1953, have been related by Klein [l, 81 and Winston
[2] to the abnormal strength of the jet stream along the
Canadian border and to a welldeveloped Northeast
Pacific High.
The planetary wave pattern within which the conti-
nental anticyclone of June 1954 was set, however, con-
tained some unfamiliar combinations. The abnormady
strong anticyclonic cell which extended over the Northeast
Pacific at 700 mb. in June 1952 and June 1953 was replaced
this June by an unusually strong westerly wind stream at
middle latitudes (fig. 2), with heights below normal over
the Aleutian Islands and Gulf of Alaska, and above normal
farther south. Instead of the abnormally strong conti-
nental anticyclone over the United States being coupled,
via a well-developed westerly jet along the Canadian
border, to a deep cyclonic vortex in Canada, as in the previ-
ous two Junes, this June there was a strong positive height
anomaly centered near Labrador and dominating eastern
Canada. The common characteristic of these two
different drought patterns is the existence of abnormally
strong upper winds tangent in an anticyclonic sense to the
164 M O N T H L Y W E A T H JUNE 1964
RGWE 1.-Mean MO-mb. height contours (solid) and departure from normal (dashed) (both in tens of feet) for June 140,1954. Abnormdly strong Aleutian Low and East Padda High poured cold pscifio air into the w& while the circulation in the Atlantic and Europe was characterized by blocking, with anomalous cold troughs St low Iatitudw.
continental seat of the high-level anticyclone. In 1952
and 1953 there were strong westerlies on its north, while
in 1954 there were strong southwesterlies on its north-
.west and northerlies on its east. It is of interest that the
June droughts of 1933 and 1936 were accompanied by
strongly anomalous southerly components along the west
coast. This suggests t h a t t h e banking mechanism
postulated by Rossby [9], by means of which air is piled
up to the right of strong, presumably supergradient winds,
may be of primary importance in maintaining the conti-
nental anticyclone.
The principal features of this month’s circulation which
persisted from the preceding month were the abnormally
fast Pacific westerlies (fig. 2) and the eastern Canadian
“blocking High” (260-ft. positive height anomaly in fig. 1).
The fast westerlies had shifted eastward, however, to pour
cold Pacific air into the western United States, where the
weak May circulation had permitted abnormal conti-
nentality and therefore warmth. The negative anomaly
center in the eastern United States associated with
blocking in May had given way to a summer type conti-
nental anticyclone, bringing fair, warm weather to the
Midwest. The eastern Canadian block, together with a
deeper than normal trough off the east coast of the United
States, produced recurrent “back-door” cold front passages
along the Atlantic seaboard, similar to, but not as strong
as, those of June 1953. Thus an eastward shift of the
Pacific westerlies and the building up of a continental
upper-level anticyclone were the main circulation changes
associated with the May-June temperature reversal,
carrying on the unusual sequence of month-to-month
reversals which began last January 131.
Floods occurred on the Des Moines River in Iowa from
June 17 to 24, and on the Rio Grande and its tributaries
JUNE 1954 MONTHLY WEATHER REVIEW 165
RQWE 2.-(A) Mean 700-mb. isotachs and (B) departure from normal wind speed (both
In meters per second) for June 140,1954. Solidarrowsindicateaverage position of
the msfn 700-mb. jet stream, while dashed arrows indicate sWnd8ry axes of relative
the East PwUlo but weak in the Atlantic.
marimUm wind speed. The middle-latitude westerlyjet WBS abnormallystrong in
in southern Texas from June 27 to 30. In between these
areas record doughts occurred, with Fort Smith, Ark.,
for example, reporting only 0.38 in. of rain for the month,
equal to the previous low June reading obtained in 1914.
In a gross way these can be associated with certain features
of the mean monthly circulation. Iowa is located in the
region where the cold Pacific westerlies met the moist
southwesterly current flowing around the western end of
the continental anticyclone. There was also a zone of
maximum frequency of surface fronts running from eastern
Colorado across Iowa through the Great Lakes during the
month(fig. 3). Chart 111-B shows above normal precipi-
tation along this zone from eastern South Dakota across
the Lakes. Although somewhat off the axis of this zone of
maximum frequency of fronts, Devils Lake, N. Dak.,
reported a record high June rainfall of 8.55 in. as compared
with a previous high of 5.84 in. in 1914.
FIQURE 3.-Number Of days in June 1954 with SUrfaCe fronts Of 8Uy type (within S q U W
with sides approximately 500 miles). Frontal positions taken from Dailv WcoNur Map,
1:30 p. m., EST. Heavy rains occurred in the North Central States where fronta w m
present 85 much as 80 percent of the time.
The Rio Grande floods can be associated with the
onshore, cyclonic character of the anomalous component
of the monthly mean flow across the west Gulf Coast a t
both 700 mb. (fig. 1) and sea level (Chart XI inset).
These anomdies reflect the brief but strong cyclonic
circulation accompanying the passage of Hurricane Alice,
superimposed on a relatively normal pattern for the rest
of the month. The drought in Oklahoma, Arkansas, and
Missouri can be attributed to a peristent anticyclonic
flow regime in this area rather than to lack of moisture,
since this area was under the influence of both moist and
dry a.ir masses a t different times.
Along the eastern seaboard, despite frequent frontal
activity (fig. 3) record droughts occurred. Norfolk, Va.,
reported a total of 0.37 in. of precipitation for the month,
well below the previous low of 1.05 in. recorded in 1921,
and Savannah, Ga., reported a new record low of 0.84 in.
compared with a previous low of 0.91 in. in 1891. Near-
record low amounts were recorded over a wide arc from
Washington, D. C., to Pensacola, Fla. This is not sur-
prising when it is realized that little atmospheric moisture
was available during most of the month, the flow having
been predominantly from northerly directions with anti-
cyclonic curvature.
Despite the accumulation of the extreme anomalies
which have been mentioned so far, the weather of this
month did not have a uniform character throughout.
In fact, only in the Pacific Northwest were temperature
departures of the same sign throughout the month.
166 MONTHLY WEATHER REVIEW JUNE 1964
In the early part of the month a strong carry-over from
the cold CP regime of May was evident, while in the last
part some typical July characteristics became well devel-
oped. The warming, and with it the upper-level anti-
cyclone and its associated moist and dry tongues, grew
and spread westward during the month, from small
beginnings in the Southeast. Chicago, Ill., which reported
a high temperature of65' F. and a low of49' on the 4th,
warmed to 97O on the 11th. Winnemucca, Nev.,which
experienced a severe June frost with lows of23' on the 6th
and 3Q0 as late as the 17th, warmed to 107' on the 22d.
The retrogression was not continuous; indeed, the transi-
tion from cool to warm in the Midwest and from north-
central rains to southwestern rains was quite abrupt.
The time sequence will now be discussed in more detail.
THE FIRST WEEK: MOSTLY COLD
Figure 4A shows the average temperature departure
from noxmal over the United States for the period June
1-7,1954. Figure 5A shows the precipitation amounts
for the same week. Figure 6A shows the mean contours
of the 700-mb. surface for the 5-day period June 2-6,
1954,which covers most of the same week. These can
.... Southern Limt of Freezing Weather
ShadedAreasNormal or Above
+q o
be compared with Charts I-A and I1 and figure 1 to
reveal the departure of this week from the character of
the month as a whole. It is clear that the May regime
of strong mid-Pacifx westerly winds was still in force
during this period. Encountering the persistent blocking
pattern in Canada, the westerlies were depressed to rela-
tively low latitudes in the United States; Pacific mP air,
very cold relative to normal continental temperatures at
this time of the year, overran the western part of the
country behind a weak trough in the northern Rockiea.
Extensive frost and record-low minima caused consider-
able crop damage in the Great Basin. Farther east, this
Pacific current was met by a stream of cold air coming
southward from the Hudson Bay region to produce a
strong trough in the eastern United States. Frontal
lifting of the Pacific air produced considerable precipitation
in the North Central States. Only in the extreme South-
east was any significant northward transport of warm,
moist mT air occurring. A precursor of the continental
anticyclonic cell had appeared over Mexico, from which
warm, dry air wasflowing into southern Arizona, New
Mexico, and Texas.
Between the 5th and the 8th two impulses entered
North America from opposite sides to end the cold regime
.-..Southern Limit of Freezing Weather
7q Shaded AreasNormal or Above I -Y
\!j, ShadedAreasNormal or Above I
FIGURE 4,"Departure of average temperature (O F .) from normal for the weeks of (A) June 1-7, (B) Jupe 8-14, (C) June 15-21, and (D) June 21-28,1964. Heat replaced cold as the
continental high-level anticyclone spread westward.
JUNE 1964 MONTHLY WEATHER REVIEW 167
in the eastern and central United States. A deep Low
entered Oregon aloft and moved slowly across the northern
Rockies, accompanied by intense frontal cyclogenesis
east of the Continental Divide (note deepening from 993
to 975 mb. from the 6th to 8th on Chart X) and by a
shift of the upper-level ridge from the Southwest to the
eastern United States. At the same time a retrograde
upper-level High arched acrow Labrador from the south-
east and merged with this ridge. This ridge became the
seat of formation of the continental anticyclone; its per-
sistence was reflected in the fact that a quasi-stationary
polar front, oriented rdughtly NE-SW, was located on
its western side, in the vicinity of Iowa, almost contin-
uously from the 8th to the 21st.
THE MIDDLE PERIOD: WARMING IN THE MIDWEST
AND FLOODS IN IOWA
The temperature and precipitation patterns for the
weeksof June 8-14 and June 15-21, 1954 (figs. 4B and C,
53 and C) were relatively persistent and showed the same
general characteristics as those for the month as a whole
(Charts I-B and 11). The upper-air circulation during
this period, as represented by twice-weekly 5-day mean
700-mb. charts, also contained the essential features, with
minor variations, of the monthly mean (fig. 1). Figure 6B,
the 5-day mean chart for June 16-20, is typical of this
period, and illustrates the changes from the earlier period.
The Aleutian Low and the East Pacific High, well devel-
oped and with abnormally strong westerly winds between
them, had progressed eastward toward North America,
increasing the flow of cold air into the Pacific Northwest.
At the same time a large anticyclonic cell had developed
in the eastern United States, centered at first in the
Carolinas. The middle-latitude trough and cold air
which had been in the eastern United States passed off
the east coast and became cut off. Part of this cold air
and cyclonic vorticity appears to have entered the easterly
current south of the continental anticyclone, contributing
to early-season easterly wave activity and heavy rains in
Florida and along parts of the Gulf Coast. Moist tropical
air now began to be transported around the western end
of the anticyclone into the Central Plains, for the. most
part in a field of general anticyclonic, subsiding circula-
tion, finally to encounter the polar front and give copious
rains in the region of confluence and lifting. Both the
Pacific air from the west, curving cyclonically, and the
Gulf air from the south, curving anticyclonically, joined
FIGURE S.-Total pmipltation (Inches) for the weeks of (A) June 1-7, (B) June 8-14, (C) June 15-21, and (D) June 2248,1954. The rains shifted wwtward 8s the oontlnental anti-
cyclone expanded.
168 M O N T H L Y W E A JUNE 1954
in a strong southwesterly current across central Canada.
The sea levelcyclone tracks shifted from southeast to
northwest of Iowa during this period (Chart X) and the
northwesterly cyclonic steering of sea level anticyclones
crossing the Midwest gave way to southwesterly anti-
cyclonic steering (Chart IX) . Thus the initiation of a continental anticyclone was
favored by (1) increased west-southwesterly flow in the
Pacific Northwest due essentially to momentum flux from
upstream, (2) increased northerly flow along the east coast
associated with the cut-off Low and westward propagation
of blocking in the Atlantic, and (3) increased subtropical
easterly circulation associated with easterly wave activity
over the eastern Gulf of Mexico. This anticyclone,
because of the seasonal heating differential between conti-
nent and ocean, then acquired dynamic characteristics
(in particular, a very warm core) favoring persistence [7].
Toward the end of the third week of June, a large
migratory upper-level anticyclonic cell, breaking off from
the East Pacific High, entered the western United States,
accompanied on its north by one of the strongest bursts
of Paciiic westerlies of the month. The sea level anti-
cyclone tracks (Chart IX) show this as a retrogression of
the East Pacifk High from the 19th to the 21st and the
formation of a new High center in Wyoming on the 21st.
This shift of the jet stream to a relatively high latitude,
with marked anticyclonic vorticity on its right, ended the
confluence and heavy rains in the North Central States.
This transition will be discussed in the next section.
THE LAST PERIOD: RIO GRANDE FLOODS, "ARIZONA
RAINS," AND WIDESPREAD HEAT
In order to show more clearly the rearrangement of
moist and dry air currents which took place with the end-
ing of the confluence in the North Central United States,
charts of the mixing ratio on the 700-mb. surface for 0300
GMT, June 20, June 23, and June 26 are shown in figure 7,
These can be related to the 5-day mean flow patterns for
June 16-20, June 19-23, and June 23-27(fig. 6B, C, and
D). Although 700-mb. charts have been used in this an-
alysis, the resulting patterns and their associated weather
conform qualitatively to those described by means of isen-
tropic analysis in the 1930's by Namias and Wexler [7, lo].
The migratory upper-level anticyclone which entered
the West on June 21 passed eastward and merged with
the continental anticyclone, resulting in retrogression of
the 5-day mean High (fig. 6C) from the southern Appa-
lachians to the central Mississippi Valley. The path of
this travelling anticyclone is reflected in a strong east-
west mean ridge across the western United States, with
FIQUBE (i.-Five-day mean 7OO-mb. contours (in tens of feet) for the period (A) June 2-6, (B) June 16-20, (C) June 19-23, and (D) June 2347,1954. A blocking surge crossed the
northern United Statffl
Maritime Pmvfnees from the east to merge with the incipient continental High in the eastern United States, while a maximum of westerly winds CBme mffls the Padflc and
JURE 1964 MONTHLY W E A T H E R R E V I E W 169
flat westerly flow on the north and flat easterly flow on
the south.
Figure 7A shows the initial state of the 700-mb. mois-
ture field preceding this intrusion of anticyclonic vorticity
from the west. A moist tongue curved from eastern
Mexico to the northern Great Lakes where it branched
into two parts. A tongue of dry Pacific air curved cyclon-
ically through Arizona and Colorado, while a second dry
tongue covered the east coast and extended into the
central Mississippi Valley. This instantaneous moisture
distribution, observed a t the end of the 5-day period
represented by figure 6B, reflects closely the details of the
mean streamlines, which had been relatively stationary
during this period. To illustrate the previous histories of
someof the air parcels, trajectories have been computed
from the twice-daily 700-mb. charts. In constructing
these trajectories it has been convenient to assume that
each streamline pattern is stationary for 6 hours before
and after map time and that the particles remain on the
700-mb. surface. On these assumptions, the heavy lines
in figure 7 represent the travel, for the 5 days preceding
the time of the mixing ratio chart, of the air parcels ar-
riving a t Sioux City, Iowa, Oklahoma City, Okla., Del
Rio, Tex., and Washington, D. C. Positions of each
parcel a t 24-hour intervals are shown by heavy dots
along the trajectories. While the particular air parcels
do not, in general, remain a t 700 mb., these trajectories
can be presumed to represent, a t least qualitatively, the
antecedent travel of the main lower-tropospheric air
streams arriving a t these points. It can be seen that:
(1) The air at the 700-mb. level reaching northwestern
Iowa, where torrential rains had fallen for the preceding
three days and continued for one day following,was
apparently of Pacific oligin and had passed through the
deep mean trough in the Southwest, curving cyclonically
south of the Mexican border en route. Although not
shown here, a trajectory arriving at the same time in
central or southeastern Iowa was found to have come
anticyclonically from the Gulf of Mexico. In other words,
the histories of the two air streams arriving in Iowa on
June20 are fairly well represented by the 10,300-ft. and
10,400-ft. contours on the 5-day mean 700-mb. chart for
June 16-20. The 6 gm/kg mixing ratio line roughly
separates these two streams. Of course the actual values
cannot be explained entirely by horizontal advection since
Gulf moisture was undoubtedly being carried upward
from lower levels.
(2) Both the dry air arriving at Oklahoma City and
the moist air arriving at Del Rio at the 700-mb. level had
come from over warm tropical waters. While the tra-
jectories show no pronounced curvature, both were under
the influence of a broad anticyclonic flow field during their
6day travel. No significant rain was reported from
either station on this date or for several days before or
after.
(3) The dry cool air arriving at Washmgton, D. C., from
FIGUBE 7.-700-mb. mixing ratio (gm/kg) at 0300 GMT for (A) June 20, (B) June 23, and
6 gm/kg are stippled. Axes of relatively moist (M) and dry (D) are shown by double
(0) June 28,1954. Arm of less than 3 gmlgg are hatched and areas of more than
arrows. Trajectories for the five days preceding map time are shown as heavy m m
for airparcels arriving at Del Rio, Tcx., Oklahoma City, Okla., Sioux City, Iowa,
and Washington, D. C.; heavy dots mark 24-hour intervals along the trajectories.
supply appeared farther west when the anticyclone stagnated over the central Missls-
Moisture initially over the Great Plains w8s dlsplacad by fast wsterlim but a new
sippi Valley.
the north on June 20 could apparently be traced back
direct,ly to the southern tip of Greenland 5 days earlier.
Thus qualitatively, toward the end of this period of
relatively stable flow, the moisture axes (lines of relative
maximum and minimum mixing ratio at map time),
streamlines, and trajectories all told essentially the same
story. Three days later (fig. 7B), however, some very
striking changes had occurred, and the three sets of lines
were no longer in accord. Aswe have seen, the sub-
170 MONTHLY W E A T H E R R E V I E W JUNE 1064
tropical anticyclonic belt had bridged across the west
coast in the 5-day mean (fig. 6C) and the center of the
continental anticyclone had shifted westward cutting off
the flowofGulf air into the Midwest. The northern part
of the moist tongue, initially located far west of the
Mississippi River, had been displaced bodily to the east
coast. It was replaced by a fast stream of dry Pacific
air from high latitudes. South of the anticyclonic belt
the moist air had been displaced westward. Large mixing
ratios (over 9 gm/kg) had appeared at the 700-mb. level
in western Mexico. Isolated showers began to break out
in Texas, New Mexico, and Arizona, while the rains in
Iowa had ceased. All four trajectories show some degree
of anticyclonic curvature, although the mean streamlines
are nearly straight.
By June 26 (fig. 7C) the transition to the new state was
virtually complete. Pacific air had reached the Atlantic
Ocean in middle latitudes and entered the quasi-stationary
anticyclonic circulation over the eastern United States
(fig. SD) as a large dry tongue. The major point of entry
of moist air into the United States had shifted farther west
to Arizona, not an unusual position in late July or August,
but abnormally far west for so early in the season. One
tongue of moist air, curving somewhat cyclonically, ex-
tended northward from this source in the confluence zone
east of the East Pacific mean trough. Associated with the
moist tongue extensive shower activity occurred through-
out the Plateau States on this and several following days.
A second tongue branched to the northeast, curving anti-
cyclonically without significant precipitation through the
Central and Northern Great Plains, but producing rains
in the Lakes States where frontal lifting was active.
Heavy rains began in the Rio Grande Valley on June 25
when Hurricane Alice entered the Gulf Coast south of
Brownsville, Tex. (see Chart X). These rains progressed
up the valley and, although lasting only about a day or
two at any location, in constrast with the long regime of
heavy rains leading to the Iowa floods, they produced the
greatest floodsof record on the Rio Grande. This was
only a few days after the record flood crest had passed
DesMoines, Iowa. Neverthelesss, in the intermediate
area of Kansas, Oklahoma, Missouri, and Arkansas no
significant precipitation occurred during the entire last
half of June. I t is of interest that the mixing ratio at
700 mb. and lower levels was nearly the same a t Del
Rio and Oklahoma City on June 26. However, it is clear
from the trajectories in figure 7C that the air arriving at
Oklahoma City had travelled anticyclonically from near
the center of the continental High, while that arriving at
Del Rio had been caught in the cyclonic circulation around
the tropical storm. This differencewas,however, re-
flected in the moisture content at 500 mb., where the mix-
ing ratio was3.7 gm/kg a t Del Rio and only about 1
gm/kg at Oklahoma City. This suggests that the vertical
motion and moisture supply through a considerable layer
above the 700-mb. surface, as affected by the field of
motion along the path, played a part in producing drought
a t one place and floods at the other. On June 28 the Texas
rains were largely ended as the deep moist air over
southern Texas was replaced by a tongue of dry air which
can be seen progressing steadily westwa.rd in the three
charts of figure 7.
During the fourth week of June daily maximum temper-
atures rose to over 100’ F., first in Kansas and t.hen in
nearly all of the United States south of 40° N. New
all-time high temperatures were recorded at Casper, Wyo.,
and Macon, Ga. Extreme heat is one of the essentiaI
characteristics of the quasi-stationary high-levelconti-
nental anticyclone when well developed. As a result, the
sea level Highs were weak in this area; the 5-day mean sea
level charts showed high centers of about 1,017 mb. in the
Southeast as contrasted with over 1,025 mb. in both of the
oceanic subtropical Highs. Yet at 700 mb. the conti-
nental High was just about as strong as the oceanic
subtropical Highs, while at 200 mb. the 5-day mean High
of over 40,800 ft. over Kansas and Oklahoma for June
23-27 was the highest center in the Western Hemisphere.
The large continental High with troughs over the oceans on
both sides is a common summertime feature at 10-19 km,
This was shown both by the high-level normal charts
constructed by the Weather Bureau in 1944 [Ill and
through the study and typing of daily high-level charts by
Wulf, Hodges, and Obloy [12].
SUMMARY
During the month the birth, growth, and retrogression
of the continental anticyclone in a setting of high index
over the Pacific and low index over the Atlantic was
reflected in the temperature, moisture, and precipitation
patterns as follows:
(1) Temperature.-Unseasonablycold weather, per-
sisting from May and covering almost the entire country
in the first week but with particularly severe frosts in the
Great Basin, was replaced by unseasonable warmth,
appearing &st in the Mississippi-Ohio Valley and later
spreading over most of the rest of the country to reach
heat-wave proportions over large areas. Exceptions were
the extreme Pacific Northwest which was dominated by
cold Pacific air throughout the month, and the East which
experienced repeated prolonged invasions of cool Atlantic
air.
(2) Moisture.-The major tropical moist tongue enter-
ing the middle latitudes, a t f i s t virtually confined to the
extreme southeastern States, came northward over the
central part of the country during the middle of the month
and shifted to the western Plateau States toward the end.
Dry tongues from the Pacific, at fist covering much of the
country, retreated until they merely skirted the western
and northern borders. Dry tongues entered the East at
first directly from the North Atlantic and later from the
Pacific, returning anticyclonic~lly.
Jum 1954 M O N T H L Y W E A T H 171
(3) Precipitation.-Frontal lifting was the predominant
cause of precipitation in the first week with significant
amounts occurring throughout most of the northeastern
half of the country. Heavy rains also occurred in tropical
air over Florida. During the middle of the month the
most spectacular rains occurred in the North but drought
began to develop in the central Mississippi Valley and
parts of the Central Plains. The final third of the month
brought showers to the Southwest and Western Plateau,
with drought spreading over the Midwest.
REFERENCES
1. W. H. Klein, “The Weather and Circulation of June
1952-A Month with a Record Heat Wave,”
Monthly Weather Review, vol. 80, No. 6, June 1952,
pp. 99-104.
2. J. S. Winston, “The Weather and Circulation of June
1953-The SecondSuccessive June with Record-
Breaking Drought and Heat,” MonthlyWeather
Review, vol. 81, No. 6, June 1953, pp. 163-168.
3. W. H. Klein, “The Weather and Circulation of May
1954-A Circulation Reversal Effected by a Retro-
gressive Anticyclone During an Index Cycle,”
Monthly Weather Review, vol. 82, No. 5, May 1954,
4. L. H. Clem, “The Weather and Circulation of June
1951,” MonthlyWeatherReview, vol. 79, No. 6,
June 1951, pp. 125-128.
5. T. R. Reed, “The North American High-Level Anti-
cyclone,” Monthly Weather Review, vol. 61, No. 11,
pp. 123-130.
6. T. R. Reed, “Further Observations on the Nortb
American High-Level Anticyclone,” Monthly Weath-
er Review, vol. 65, No. 10, Oct. 1937, pp. 364-366.
7. R. A. Allen, R. Fletcher, J. Holmboe, J. Namias, and
H. C. Willett (editor), “Report on an Experiment
in Five-Day Weather Forecasting,” Papers in Physi-
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Massachusetts Institute of Technology and Woods
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Charts and Their Relation to Departures of Sum-
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Union, vol. 19, Part I, 1938, pp. 164-170.
11. U. S. Weather Bureau, NormalWeather Maps.
NorthernHemisphere Upper Levels, Washington,
D. C., 1944.
12. 0. R. Wulf, M. W. Hodges, and S. J. Obloy, “The
Meteorological Conditions in the Upper Reaches of
the Radiosonde Flights over the United States.
I. Pressures, Pressure Changes, and Types of Pres-
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VO~. 1, NO. 1, NOV. 17, 1937, pp. 15-28.
NOV. 1933, pp. 321-325. 1946.
June 1954. M. W. R. LXXXII-74
I- C
June 1954. M. W. R. LXXXII-'76
r
Chart 111. A. Departure of Precipitation from Normal (Inches), June 1954.
' LXXXII-77 June 1954. M. W. R.
B. Percentage of Normal Sky Cover Between Sunrise and Sunset, June 1954.
B. Percentage of Normal Sunshine, June 1954.
,r
I, , .
I
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I
Jqne 1954. M. W. R.
Chart VII. A. P,ercentage of Possible Sunshine, June 1954.
B. Percentage of Normal Sunshine, June 1954.
,r
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I
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I
Jqne 1954. M. W. R.
Chart VII. A. P,ercentage of Possible Sunshine, June 1954.
c
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June 1954. M. W. R. LXXXII--80
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June 1954. M. W. R. LXXXII--80
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rd a, cn
June 1954. M. W. R. LXXXII-82
LXXXII-83
LXXXII-83
LXXXII-85 June 1954. M. W. R,
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June 1954. M. W. R. LXXXII--86