• Austin G. R., R. M. Rauber, H. T. Ochs III, and L. J. Miller, 1996: Trade wind clouds and Hawaiian rainbands. Mon. Wea. Rev.,124, 2126–2151.

  • Barnes, G. M., and K. Sieckman, 1984: The environment of fast- and slow-moving tropical mesoscale convective cloud lines. Mon. Wea. Rev.,112, 1782–1794.

  • Betts, A. K., C. S. Bretherton, and E. Klinker, 1995: Relation between mean boundary layer structure and cloudiness at the R/V Valdivia during ASTEX. J. Atmos. Sci.,52, 2752–2762.

  • Blanchard, D. C., 1953: Raindrop size distribution in Hawaiian rains. J. Meteor.,10, 457–473.

  • Brill, K., and B. Albrecht, 1982: Diurnal variation of the trade-wind boundary layer. Mon. Wea. Rev.,110, 601–603.

  • Brown, R. A., 1970: A secondary flow model for the planetary boundary layer. J. Atmos. Sci.,27, 742–757.

  • Carbone, R. E., J. D. Tuttle, W. A. Cooper, V. Grubisic, and W.-C. Lee, 1998: Trade-wind rainfall near the windward coast of Hawaii. Mon. Wea. Rev.,126, 2847–2863.

  • Chen, Y.-L., and J.-J. Wang, 1994: Diurnal variation of surface thermodynamic fields on the island of Hawaii. Mon. Wea. Rev.,122, 2125–2138.

  • Fox, T., 1969: An Example of a Medium Level Westerly Wave over South and Central Africa. Lusaka Meteor. Notes, Ser. A, 2 pp.

  • Giambelluca, T. W., M. A. Nullet, and T. A. Schroeder, 1986: Rainfall Atlas of Hawaii. Rep. R 76, State of Hawaii, Dept. of Land and Natural Resources, 267 pp.

  • Han-Shun-Cheong, K. S., 1970: Rainfall over Oahu and location of 300-mb trough during trade wind regime. Hawaii Inst. Geophys. Rep. HIG 70-28, 14 pp. [NITS COM-71-00335].

  • Hill, H. W., 1964: The weather of lower latitudes of the southwest Pacific associated with passages of disturbances in the middle latitude westerlies. Proc. Symp. on Tropical Meteorology, Rotorua, New Zealand, New Zealand Meteor. Serv., 352–360.

  • Klossel, K. A., and B. A. Albrecht, 1989: Low-level inversions over the tropical Pacific. Thermodynamic structure of the boundary layer and the above-inversion moisture structure. Mon. Wea. Rev.,117, 87–101.

  • Larson, R. N., 1978: Summer trade wind rainfall in the Hawaiian islands. M.S. thesis, Dept. of Meteor., University of Hawaii, 84 pp.

  • LeMone, M. A., and W. T. Pennell, 1976: The relation of trade wind cumulus distribution to subcloud layer fluxes and structure. Mon. Wea. Rev.,104, 524–539.

  • Leopold, L. B., 1949: The interaction of trade wind and sea breeze, Hawaii. J. Meteor.,6, 312–320.

  • Lyons, S. W., 1982: Empirical orthogonal function analysis of Hawaiian rainfall. J. Appl. Meteor.,21, 1713–1729.

  • MacDonald, G. A., and A. T. Abbott, 1970: Volcanoes in the Sea. University of Hawaii Press, 441 pp.

  • Malkus, J. S., 1963: Cloud patterns over tropical oceans. Science,141, 767–778.

  • Mordy, W. A., and L. E. Eber, 1954: Observations of rainfall from warm clouds. Quart. J. Roy. Meteor. Soc.,80, 48–57.

  • Ramage, C. S., S. J. S. Khalsa, and B. N. Meisner, 1981: The central Pacific near-equatorial convergence zone. J. Geophys. Res.,86, 6580–6598.

  • Raymond, D. J., and S. A. Lewis, 1995: Rotating convective disturbances in the trades. Quart. J. Roy. Meteor. Soc.,121, 271–299.

  • Riehl, H., 1979: Climate and Weather in the Tropics. Academic Press, 611 pp.

  • ——, T. C. Yeh, J. S. Malkus, and N. E. Laseur, 1951: The northeast trade of the Pacific Ocean. Quart. J. Roy. Meteor. Soc.,77, 598–626.

  • Sanderson, M., Ed., 1993. Prevailing Trade Winds, Weather and Climate in Hawaii. University of Hawaii Press, 126 pp.

  • Smolarkiewicz, P. K., R. M Rasmussen, and T. L. Clark, 1988: On the dynamics of Hawaiian cloud bands: Island forcing. J. Atmos. Sci.,45, 1872–1905.

  • Seck, A., 1962: The Heng or dry rainy season in Senegal. Ann. Geogr.,385, 225–246.

  • Siler, R. K., 1962: Synoptic patterns for wet and dry trades on the island of Hawaii. Mon. Wea. Rev.,90, 103–106.

  • Southern, R. L., W. R. Kininmonth, and M. R. Prescod., 1969: Derivation of convective forecasting models for northern Australia from a climatology of lightning discharges. Proc. Conf. on the Summer Monsoon of Southeast Asia. Honolulu, HI, Naval Weather Research Facility, 239–254.

  • Takahashi, T., 1973: Numerical simulation of maritime warm cumulus. J. Geophys. Res.,78, 6233–6247.

  • ——, 1977a: Rainfall at Hilo, Hawaii. J. Meteor. Soc., Japan, 55, 121–129.

  • ——, 1977b: A study of Hawaiian warm rain showers based on aircraft observations. J. Atmos. Sci.,34, 1773–1790.

  • Winner, D. C., 1968: Climatological estimates of clock-hour rainfall rates. Air Weather Service Tech. Rep. 202, 30 pp.

  • Woodcock, A. H., 1975: Anomalous orographic rains of Hawaii. Mon. Wea. Rev.,103, 334–343.

  • Worthley, L. E., 1968: Rainfall patterns in Hawaii associated with upper-level cyclones. Hawaii Inst. Geophys. Rep. HIG 68–13, 88 pp.

  • Zipser, E. J., 1977: Mesoscale and convective-scale downdrafts as distinct components of squall-line structure. Mon. Wea. Rev.,105, 1568–1589.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 76 76 8
PDF Downloads 54 54 5

Trade Wind Rainfall atop Mount Waialeale, Kauai

View More View Less
  • 1 Durham, North Carolina
  • | 2 Department of Meteorology, School of Ocean and Earth Sciences, University of Hawaii at Manoa, Honolulu, Hawaii
© Get Permissions
Restricted access

Abstract

Very large coast to mountain rainfall gradients have been observed in the trade winds and winter monsoons. Since the surface moist layer is usually capped by a subsidence inversion near 2 km, the rain is “warm.” On the top of a mountainous island, which is generally below the inversion, such as Kauai, trade wind rainfall can be very great and the coast to top rainfall gradient very large. Autographic rainfall measurements at the top of Mount Waialeale (1598 m MSL, one of the wettest spots on the earth) on Kauai together with surface and upper-air measurements made at Lihue, 20 km to the southeast, and weather satellite images confirm and expand on earlier descriptions of the nature of mountain rainfall in the trade winds.

Significant rain results from moderate or fresh trade winds being lifted up the eastern escarpment of Waialeale, but only when a band or area of cumulus extends upwind of the mountain. Small wind shear in the vertical and a sharp upper limit to the moist layer reduce entrainment and facilitate growth of cloud droplets. At the mountaintop rain is usually light or moderate, with drops smaller than 2 mm, but persisting long enough to produce large accumulations. Along the windward coast, drops usually evaporate before reaching the ground. Divergence and upward motion east of an upper-tropospheric trough barely affect the moist trade wind layer. Cloud lines associated with shear line extensions of cold fronts or with dying tropical cyclones to the south account for much of the rain though short-lived mesoscale cloud systems are also important.

Thunderstorms are very rare with surface flow from a trade wind direction. The wind then curves cyclonically on the northwest sides of sharp troughs or small cyclones. Upper-tropospheric southwesterlies usually prevail. The nocturnal rainfall maximum at Waialeale probably stems largely from radiational cooling at the top of the moist layer causing clouds over and upwind of the island to increase. Other trade wind islands of about the same size and height as Kauai, but with no mountaintop rain gauges, probably also have large coast to mountaintop rainfall gradients.

Corresponding author address: Dr. C. S. Ramage, 1420 Acadia Street, Durham, NC 27701-1302.

Abstract

Very large coast to mountain rainfall gradients have been observed in the trade winds and winter monsoons. Since the surface moist layer is usually capped by a subsidence inversion near 2 km, the rain is “warm.” On the top of a mountainous island, which is generally below the inversion, such as Kauai, trade wind rainfall can be very great and the coast to top rainfall gradient very large. Autographic rainfall measurements at the top of Mount Waialeale (1598 m MSL, one of the wettest spots on the earth) on Kauai together with surface and upper-air measurements made at Lihue, 20 km to the southeast, and weather satellite images confirm and expand on earlier descriptions of the nature of mountain rainfall in the trade winds.

Significant rain results from moderate or fresh trade winds being lifted up the eastern escarpment of Waialeale, but only when a band or area of cumulus extends upwind of the mountain. Small wind shear in the vertical and a sharp upper limit to the moist layer reduce entrainment and facilitate growth of cloud droplets. At the mountaintop rain is usually light or moderate, with drops smaller than 2 mm, but persisting long enough to produce large accumulations. Along the windward coast, drops usually evaporate before reaching the ground. Divergence and upward motion east of an upper-tropospheric trough barely affect the moist trade wind layer. Cloud lines associated with shear line extensions of cold fronts or with dying tropical cyclones to the south account for much of the rain though short-lived mesoscale cloud systems are also important.

Thunderstorms are very rare with surface flow from a trade wind direction. The wind then curves cyclonically on the northwest sides of sharp troughs or small cyclones. Upper-tropospheric southwesterlies usually prevail. The nocturnal rainfall maximum at Waialeale probably stems largely from radiational cooling at the top of the moist layer causing clouds over and upwind of the island to increase. Other trade wind islands of about the same size and height as Kauai, but with no mountaintop rain gauges, probably also have large coast to mountaintop rainfall gradients.

Corresponding author address: Dr. C. S. Ramage, 1420 Acadia Street, Durham, NC 27701-1302.

Save