Search Results

You are looking at 1 - 10 of 18 items for

  • Author or Editor: Mark A. Lander x
  • Refine by Access: All Content x
Clear All Modify Search
Mark A. Lander

Abstract

No abstract available

Full access
Mark A. Lander

Abstract

In its simplest description, the large-scale low-level circulation of summer over the western North Pacific Ocean can be described in terms of low-latitude southwesterlies, a monsoon trough, and a subtropical ridge. When the axis of the monsoon trough is in its normal orientation (NW-SE), tropical cyclones tend to move northwestward on tracks close to those expected from climatology. As an episodic event, the axis of the monsoon trough extends farther north and east than normal and acquires a reverse (SW-NE) orientation. When the monsoon trough becomes reverse oriented, tropical cyclones within it tend to exhibit north-oriented motion and other specific unusual motions such as eastward motion at low latitude and binary interactions with other tropical cyclones along the trough axis. Approximately 80% of the tropical cyclones that are associated with a reverse-oriented monsoon trough move on north-oriented tracks. A tropical cyclone track type, defined herein as the “S”-shaped track, is primarily associated with reverse orientation of the monsoon trough: 23 of 35 cases (66%) of S motion during the period 1978–94 occurred in association with a well-defined reverse-oriented monsoon trough.

Full access
Mark A. Lander

Abstract

No abstract available.

Full access
Mark A. Lander

Abstract

The evolution of the pattern of the deep convective cloud is presented for three selected cases of tropical cyclone twins symmetrical with respect to the equator. In each case, the pattern evolution is similar and can be separated into four distinct stages.

Full access
Mark A. Lander

Abstract

No abstract available.

Full access
Mark A. Lander

Abstract

No abstract available.

Full access
Mark A. Lander

Abstract

El Niño-Southern Oscillation (ENSO)-related variations in the observed character (e.g., annual storm totals, preferred genesis region, etc.) of the tropical cyclone activity in the western North Pacific are sought. With respect to annual storm totals, no ENSO signal is found; with respect to genesis region, a strong relationship is found between ENSO indices and the zonal displacement of the annual mean genesis locations. ENSO indices during the first half of the calendar year were found to be weakly predictive of the number and genesis locations of tropical cyclones occurring from July through December.

Full access
Mark A. Lander

Abstract

This paper describes the character and evolution of the low-level wind, sea level pressure, and satellite-observed cloudiness over the western North Pacific (WNP) during August 1991 when the low-level monsoon circulation there became organized as a monsoon gyre. The specific configuration of the monsoon circulation, which herein is called a monsoon gyre, is an episodic event—occurring roughly once per year, for two or three weeks during July, August, or September. As a monsoon gyre, the low-level circulation of the WNP becomes organized as a large cyclonic vortex associated with a nearly circular 2500-km-wide depression in the contours of the sea level pressure. A cyclonically curved band of deep convective clouds rims the southern through eastern periphery of this large vortex. Once this pattern is established, it becomes a prolific generator of mesoscale vortices that emerge from the downstream end of the major peripheral cloud band. These mesoscale vortices form the seed disturbances for midget or small-sized tropical cyclones. The large area encompassed by the outermost closed isobar of the monsoon gyre of August 1991 (the centroid of which moved slowly westward along 20°N) was the site of genesis for two tropical depressions, two tropical storms, and two typhoons during its 20-day westward journey. Initially, small tropical cyclones formed in the peripheral circulation of the gyre and later, the gyre itself evolved into a very large tropical cyclone; this is suggestive of two distinct modes of tropical cyclogenesis: one mode operates to produce small tropical cyclones in the eastern periphery of the gyre, and the other mode operates to accelerate the winds of the monsoon gyre until it becomes a giant tropical cyclone.

Full access
John A. Rupp
and
Mark A. Lander

Abstract

The authors develop a technique that applies models of the radial profile of the wind in tropical cyclones to historical best-track databases of tropical cyclones, in order to estimate the wind (at 1-h intervals) experienced at any selected tropical location for any or all of the historical tropical cyclones affecting the location. When these estimated winds are condensed into a time series of the highest annual tropical cyclone-related wind, extreme value analysis can be applied in order to calculate the recurrence intervals of extreme wind speeds.

The island of Guam, located at a low latitude in the western North Pacific, was selected as a site for testing the technique. Guam has historical measurements of tropical cyclone-related wind, from which an independent estimate of the recurrence intervals of extreme wind speeds was obtained. In addition, wind traces during the passage of three major typhoons that affected Guam were used to assess the ability of the technique to reproduce an accurate hourly time series of the winds experienced during the passage of these typhoons.

For Guam, the recurrence intervals calculated from the time series of wind yielded by the authors’ technique closely match those computed from the wind measurements. The technique also reproduces a reasonable wind trace for the three major typhoons affecting Guam. Given its successful validation when applied to Guam, we believe that this technique can be used to make useful estimates of the recurrence intervals of tropical cyclone-related high wind speeds at any coastal tropical location where in situ wind measurements may he lacking, but where an historical best-track archive of tropical cyclone track and intensity exists.

Full access
Mark A. Lander
and
Michael D. Angove

Abstract

This paper is designed to be an annual summary of the Eastern Hemisphere tropical cyclones of 1995. The tropical cyclone statistics presented are those of the Joint Typhoon Warning Center, Guam. The text focuses primarily upon the tropical cyclones that occurred in the western North Pacific during 1995; however, since the area of responsibility of the Joint Typhoon Warning Center covers the entire Eastern Hemisphere, brief summaries of the tropical cyclone activity within the north Indian Ocean, south Indian Ocean, and the southwest Pacific are also presented. Overall, 1995 was a relatively quiet year in the Eastern Hemisphere: the 22 tropical cyclones of the Southern Hemisphere were only one shy of the record low of 21, and for the first time since 1988 the number of tropical storms and typhoons in the western North Pacific was below normal. In the western North Pacific, there was a marked shift to the west of the preferred region for the genesis and development of tropical cyclones. This is consistent with the end of persistent large-scale circulation anomalies characteristic of the warm phase of the El Niño–Southern Oscillation (ENSO) and the onset (during 1995) of weak ENSO cold-phase anomalies (i.e., La Niña conditions).

Full access