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CARL O. ERICKSON

Abstract

Hurricane Dorothy, July 1966, possessed both extratropical and tropical features. A number of factors contributed to storm development, including a well-defined pre-existing disturbance, high-level advection of vorticity and kinetic energy, baroclinicity of both the extratropical and tropical-storm types, and a moderate degree of latent instability.

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Carl O. Erickson

Abstract

No abstract available.

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Carl O. Erickson

Abstract

Hemispheric composites of 700 mb height during each of four unusually warm summers in the contiguous United States show a characteristic “3-wave” pattern of anticyclonic anomalies over the eastern North Pacific, the United States and the North Atlantic. Other common features are an anticyclonic anomaly over eastern Russia and mostly above-normal heights for the entire Northern Hemisphere north of 15°N, especially over subtropical and lower middle latitudes. For tour unusually cool summers, generally inverse composite patterns are noted. Sea level pressure composites for those warm and cool summers show similar, but less well defined, anomalies.

More generally, based on 33 years of data and Monte Carlo testing procedures, there appears to be a statistically significant lagged relation between zonally averaged 700 mb height anomalies at lower latitudes of the Northern Hemisphere and subsequent mean summer temperatures in the United States. Relations from sector-averaged anomalies are mostly inferior to those from hemispheric zonal averages. Correlations of lesser significance exist between zonally averaged 700 mb height anomalies at middle and high latitudes and subsequent mean summer temperatures.

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Carl O. Erickson

Abstract

Zonally averaged composite anomalies of 700 mb height for years preceding and during four warm winters in the contiguous United States show generally positive anomalies over subtropical and middle latitudes and generally negative anomalies over high latitudes. The overall composite hemispheric height anomaly was positive for the years with warm winters. For four years with cold winters, generally inverse composite patterns are noted. In both composites, pattern reversals with respect to latitude occur during the following spring seasons. The four warm and four cold winters were those whose average temperature anomalies, nationwide, were the largest in the 33-yeu period 1948–80. The occurrence of consecutive severe winters within this relatively short record places limits on interpretation.

More generally, based on 33 years of data and Monte Carlo testing procedures, a statistical relation that is marginally significant at the 95% level appears to exist between the overall pattern of zonally averaged 700 mb height anomalies and mean winter temperatures in the United States. The relation is weaker and less coherent than that previously found with respect to mean summer temperatures. However, as with summer, the individual coefficients that are statistically significant are overwhelmingly positive in sign.

The overall correlation patterns with respect to spring and fall mean temperatures in the United States are obviously not significant. In terms of area-weighted percentages, the totals of individually significant coefficients for spring and fall are even less than to be expected from chance.

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PICTURE OF THE MONTH

A jet Stream Cirrus Shield

Carl O. Erickson

Abstract

No abstract available.

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CARL O. ERICKSON

Abstract

Several TIROS photographs of cumulonimbus clouds and thunderstorms over the Florida area are compared with synoptic surface and upper-wind data. The orientations of the cirrus anvils of well-developed clouds generally show good directional agreement with the existing vertical wind shears between the lower and upper troposphere. Limited evidence also suggests that the length and character of the anvils may sometimes be used as qualitative indicators of shear magnitude, the longer and more pronounced anvils being positively correlated with stronger vertical shear.

In agreement with earlier studies, it is found that cumulonimbus clouds often appear as relatively small or medium-sized, irregular, bright masses in TIROS pictures, hence such clouds often can be tentatively identified from their picture appearance alone. Such identification is still largely a subjective procedure. The anvils of well-developed cumulonimbi, when attached to the parent cloud, are rather distinctive and are an aid to identification.

A few TIROS pictures of the Florida area under relatively clear conditions are shown for comparative purposes. The problems arising from specular reflection and from variations in overall photo appearance resulting from changing camera angle are briefly discussed.

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CARL O. ERICKSON

Abstract

An area of disturbed weather over the Bahamas is studied in detail for the 3-day period, Aug. 9–11, 1966. The coupling of an upper level cold-core cyclone with an approaching low-level wave was largely responsible for the considerable increase in cloudiness and weather observed on August 9 and 10.

Warm anomalies in the lower stratosphere were even larger than the cold anomalies of the upper troposphere, strongly suggesting the existence of large-scale vertical motions at both levels.

Results from a diagnostic numerical model show that the Laplacian of thermal advection was the single most important forcing function contributing to tropospheric vertical motion. Agreement between observed cloudiness and calculated vertical motion was generally good.

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CARL O. ERICKSON and SIGMUND FRITZ

Abstract

The history of the Eastern Pacific tropical cyclone, Katherine, is presented for the period Scptcmhcr 8–17, 1963. It is shown that Katherine was the same storm as one which earlier had been named Jennifer.

The complementary nature of surface ship observations and satellite cloud photographs is well illustrated by this particular case. The experience suggests that both forms of data are essential to improved analyses and forecasts over data-sparse areas such as the tropical Eastern Pacific.

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Carl O. Erickson and Linwood F. Whitney Jr.

Abstract

Not available.

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CARL O. ERICKSON and LINWOOD F. WHITNEY JR.

Abstract

No Abstract Available.

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