Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: N. E. LaSeur x
  • Refine by Access: All Content x
Clear All Modify Search
N. E. Laseur

Abstract

No Abstract Available

Full access
Sterling C. Gilbert
and
N. E. LaSeur

Abstract

A detailed investigation of the hourly rainfall patterns accompanying a dissipating hurricane over the southeastern United States demonstrates the pronounced asymmetry in the decay of release of latent heat, the primary energy source of the storm. This appears to be associated with the incorporation into the storm circulation of dry air in the layer from 800 to 400 millibars. This air is first drawn in from the outer portions of the left-front quadrant, then sweeps rapidly around thestorm into the right-rearand right-front quadrants.

Full access
J. Levine
,
M. Garstang
, and
N. E. LaSeur

Abstract

A 3-hr flight of a constant-volume balloon which is entrained into a cumulus congestus cloud and lifted to an altitude of nearly 3 km provides an opportunity to determine the trajectory and vertical velocity of the balloon and, in turn, relate these to the circulation of the cloud. Simultaneous supplementary observations by radar, cameras, satellite, and other ground based instruments provide the meteorological context for the event. Computations show that the vertical velocities of the cloud may approach 10 m sec−1, and sustained upward velocities of 3–5 m sec−1 are maintained for considerable periods of time and height. Comparison with a “jet” model shows remarkable agreement, while the “bubble” model would require unreasonably large values of the radius to generate the observed vertical velocities.

Full access
J. C. Hess
,
J. B. Elsner
, and
N. E. LaSeur

Abstract

This paper demonstrates that improved forecasts of the annual number of hurricanes in the Atlantic tropical basin are possible by separating tropical-only hurricanes from hurricanes influenced by extratropical factors. It is revealed that variables previously shown to have a predictive relationship with the annual number of Atlantic hurricanes have a significantly stronger predictive association with the number of hurricanes formed solely from tropical mechanisms. This stronger relationship exists for extended-range (6-month lead) as well as for short-range (0-month lead) forecast models. Any future study of seasonal hurricane activity over this region should consider tropical-only hurricanes as separate from hurricanes influenced by baroclinic disturbances. The annual number of hurricanes that form or intensify as a result of interactions with baroclinic disturbances appears unrelated to significant tropical or midlatitude atmospheric anomalies and thus should be considered the random component of seasonal hurricane activity, at least until further insights are gained. Indeed, when prediction algorithms are developed to forecast the annual number of Atlantic hurricanes, best hindcast skill results from models that assume a simple average for baroclinically influenced storms. These regression-based forecast models are only marginally better than climatology.

Full access
R. L. DeSOUZA
,
C. I. ASPLIDEN
,
M. GARSTANG
,
N. E. LaSEUR
, and
Y. HSUEH

Abstract

A temporary mesoscale network of pilot balloon stations on a tropical island (Barbados, West Indies) revealed the existence of a low-level jet at 700 m above mean sea level, with a maximum wind near 40 m/s and a duration of at least 2 hr. The phenomenon appears to be associated with the Venturi effect produced in the low levels by a traveling gravity wave at the inversion. It is suggested that jets of this kind probably exist over other tropical islands.

Full access