Daily Weather Maps Research Articles

Event-Based Climatology of Tropical Cyclone Rainfall in Houston, Texas and Miami, Florida

Tropical cyclone (TC) rainfall amounts are compared from 1950–2017 for Houston, Texas and Miami, Florida to estimate the risk of TC rain in both cities. Following the wake of Hurricanes Harvey and Irma in 2017, concern has risen over the future of raininess in these locations. Per-event rainfall amounts are aggregated using tracks taken from HURDAT, time-of-rain gathered from National Weather Service daily weather maps, and rainfall totals taken from airport monitoring stations. Risk analysis tools include descriptive statistics, time series, and return frequencies for Houston and Miami, and spatially interpolated surfaces for Hurricanes Harvey and Irma. The season duration is longer in Miami than in Houston. The uppermost rainfall events in the distribution for Houston show a significant increase through time, suggesting the most intense rainfall events are becoming worse for Houston. The expected return frequency for a Harvey-like event (940 mm) in Houston is every 230 years, on average, and the 90th percentile rain of 286 mm is expected once every 17 years (11–29; 90% significance). The expected return frequency for an Irene-like event (261 mm—maximum for location) in Miami is every 173 years, on average, and the 90th percentile rain of 167 mm is expected once every 11 years (7–17; 90% significance). Results show a substantial difference between Houston and Miami TC rainfall climatologies similar to the differences of Hurricanes Harvey and Irma. Though emergency management must be tailored for each TC, management for inland TC rainfall may be more applicable in Houston than in Miami.

Relationship between glacier melting and atmospheric circulation in the southeast Siberia

The interaction between climate and cryosphere is a key issue in recent years. Changes in surface mass balance of mountain glaciers closely correspond to differential changes in atmospheric circulation. Mountain glaciers in southeast Siberia located on East Sayan, Baikalsky and Kodar ridges have been continuously shrinking since the end of the Little Ice Age. In this study we used daily synoptic weather maps (Irkutsk Center of Hydrometeorology and Environmental Monitoring), 500 hPa, 700 hPa and 850 hPa geopotential height and air temperature data of NCEP/NCAR reanalysis to assess relationships between atmospheric circulation patterns and the sum of positive temperature (SPT), a predictor of summer ice/snow ablation. Results show that increased SPT (ablation) is generally associated with anticyclones and anticyclonic pressure fields (with cloudless weather conditions) and warm atmospheric fronts. Decreased SPT (ablation) is strongly correlated with cyclones and cyclonic type pressure fields, cold atmospheric fronts and air advections. Significant correlations have been found between ablation and cyclonic/anticyclonic activity. Revealed decreasing trends in the SPT in three glaciarized ridges at the beginning of the 21st century led to changes of air temperature and snow/ice melt climates.

Seasonal patterns and trends of fastest 2‐min winds at coastal stations in the conterminous USA

ABSTRACTWeather extremes have a substantial societal impact, particularly in increasingly densely populated coastal areas. This research uses ‘fastest 2‐min wind’ records at land‐based coastal automated weather stations in the conterminous United States to characterize seasonal patterns of ‘extreme’ wind speed. The records also are examined for evidence of trends in the fastest winds that may be indicative of changes in cyclone activity over the available period of record (13–19 years).Fastest 2‐min winds at stations along the Pacific, western Gulf, and northern Atlantic coasts have a winter maximum and a summer minimum, similar to the seasonal variation in mean wind speeds. In contrast, the fastest winds at southern Atlantic and eastern Gulf coast stations show a winter minimum and a summer maximum that is opposite what is observed for mean speeds. Over the period of available record, many coastal stations show positive trends in the fastest 2‐min wind speeds in winter, spring and summer. Negative trends are most frequent in the autumn. On an annual basis, the trends in fastest 2‐min winds are consistent with the results of satellite‐derived near‐coastal oceanic wind speed assessments. Examination of daily weather maps and synoptic composites supports the interpretation that extratropical cyclone activity is the primary driver of the fastest wind speeds at most stations, with tropical systems and mesoscale features such as thunderstorms producing some of the fastest winds during the summer and autumn.

Earth’s Atmosphere Prevailing Surface Winds Based on Effectiveness of Mbane Biouele Formula Derived in 2009

Any system designed to simulate the earth's atmosphere general circulation, must necessarily be based on the spatial-or temporal average conditions. Irregularities in the profiles of air motions that we observe on daily weather maps often make lose any real meaning to the general circulation. As complicated and inconsistent that is the daily traffic of air particles, it is interesting to define a general circulation characteristic of the average air transportation around the globe. Indeed, this transport responds to a need to transfer heat from the equator (heat source) to the poles (cold sources). Mbane Biouele formula (2009), derived from Clausius-Clapeyron relation (1832), now allows faithful and unique representation of the tricellular general circulation: Hence, the possibility of access to the earth’s atmosphere prevailing surface winds in summer as well as winter.

Identifying extreme hottest days from large scale upper air data: a pilot scheme to find California Central Valley summertime maximum surface temperatures

A pilot scheme uses upper air data from a few extreme hottest days to identify those and other extreme hottest days measured by 3 stations sampling the California Central Valley (CV). Prior work showed that CV extreme heat wave onsets have characteristic large scale patterns in many upper-air variables; those patterns also occur for the hottest days. A pilot scheme uses areas of two upper-air variables with high significance and consistency to forecast extreme surface temperatures. The scheme projects key parts of composite patterns for one or more variables onto daily weather maps of the corresponding variables resulting in a ‘circulation index’ for each day. The circulation index measures how similar the pattern on that day is to the composite patterns in areas dynamically relevant to a CV extremely hot day, with a larger value for a stronger match and larger amplitude. The scheme is tested on the development period (1979–1988) and on the subsequent 18 year ‘independent’ period (1989–2006). The pilot scheme captures about half of the rare events in the development period, with similar skill for the independent period. Based only on 16 days of extreme heat in the first 10 years, the scheme is not intended to represent the general distribution; however the circulation index has similar kurtosis, variance, and skewness as the observed maximum temperatures. Properties of the high end tail of the distribution are notably improved by adding the second predictor. The scheme outperforms simply using 850 hPa temperature above the CV.

Retrospect: April 14, 1935: Black Sunday

U.S. Weather Bureau Daily Weather Map for 8:00 a.m. EST, April 14, 1935. Massive dust storms, spawned by the passage of a dry cold front, created blackout conditions during what became known as “Bl...

Retrospect: November 11, 1935: Explorer II Stratospheric Balloon Flight

U.S. Weather Bureau Daily Weather Map for 8:00 a.m. EST (6:00 a.m. MST), November 11, 1935. An area of high pressure is centered over Minnesota, southeastern North Dakota, and eastern South Dakota....

The Relation Between Jet Stream Location and Cyclones Over the Western Iran

Daily rain data for the selected stations were obtained from the Meteorological Organization of Iran for the 1985-1999 period. The consecutive rain days of length 1 to 5 days and widespread over the study area were extracted. The jet tracks and speed surges were extracted from the daily weather maps of IRIMO for the 54 selected rainy periods. The results showed that the wind speed does not affect the rain intensity. The jet tracks show negative curvature during the non and low rain days but strong positive curvature during the maximum rain day. The establishment of a deep trough during the intensive rain days caused the jet tracks to concentrate close to the study area.

The Relationship between El Niño and the Duration and Frequency of the Santa Ana Winds of Southern California

This study examines the variability of the duration and frequency of Santa Ana winds due to El Niño over a thirty-three-year period. Daily Weather Maps and NCEP/NCAR Reanalysis were used to study large-scale upper-level and surface circulation patterns during wind events. A Student's t-test was used to determine statistically significant changes in the winds during March of El Niño winters. A significant decrease in the duration and frequency of wind events was found in March during El Niño. This can be attributed to the decrease in strength and frequency of the Great Basin high pressure and the increase in wintertime cyclones in southern California.

The Santa Ana Winds of California

Abstract A 33-yr, numerical dataset of the occurrence of Santa Ana winds for the period 1968–2000 has been created and validated. Daily Weather Maps were examined to identify the days when a surface high pressure system existed over the Great Basin simultaneously with a surface low pressure system offshore of southern California, and the prevailing wind over southern California was from the northeast quadrant. The dates of these occurrences, as well as the wind speed, temperature, and dewpoint temperature among other variables, were extracted and tabulated. The frequency of Santa Ana events derived from the weather maps was compared to events defined by wind direction only and there is agreement between the two. Preliminary results show that the Santa Ana event is limited to the period September–April and that the month of peak occurrence is December. The average frequency of events is 20 yr–1 and the average duration of an event is 1.5 days. Humidity levels are not uniform across Santa Ana events; the dr...

The Influence of Large-Scale Flow on Fall Precipitation Systems in the Great Lakes Basin

Abstract A synoptic climatology is presented of the precipitation mechanisms that affect the Great Lakes Basin. The focus is on fall because increasing precipitation in this season has contributed to record high lake levels since the 1960s and because the causes can be synoptically evaluated. Precipitation events were identified for the period 1935–95 from NOAA Daily Weather Maps. Precipitation days were classified as one of nine types. Trends in the precipitation classifications, 24-h precipitation totals, and the frequency and intensity of precipitation days and events were analyzed. It was found that the precipitation increased 15% over the basin and 35% at Grand Rapids, Michigan, from 1935–65 to 1966–95. The increased precipitation was driven by an increase in the amount of precipitation per day (from low pressure systems and warm, stationary, and occluded fronts) and an increase in the frequency of precipitation days (from troughs and cold, warm, stationary, and occluded fronts). All classifications ...

Near-resonant topographically forced envelope Rossby solitons in a barotropic flow

In this paper, a parametrically excited nonlinear Schrödinger (NLS) equation is proposed to describe the near-resonant interaction between dipole envelope Rossby soliton and wave number-two topography under the LG-type dipole near resonance condition in a weak background westerly wind. Based on this equation, the existence and stability of steady soliton are discussed. It is found that the stability of the steady forced soliton depends on the latitude and setting of the background westerly wind. The numerical method is applied to solve the forced NLS equation. It is found that under favourable conditions small-amplitude envelope Rossby soliton in the topographic trough can be amplified through the near-resonant forcing of wavenumber-two topography. In a moderate parameter range, the forced amplified envelope soliton is stable. In particular, in the soliton amplification process the maximum soliton amplitude exhibits aperiodic oscillation. However, in some parameter range, the amplified soliton is unstable and developes finally into a cnoidal wave after a long time. In addition, the time sequences of the instantaneous total stream function field are found to bear a remarkable resemblance to the initiation, maintenance and decay of localized dipole blockings in the north Atlantic ocean observed from the daily weather maps. Thus, in the weak nearly resonant background westerly wind, the near-resonant interaction between dipole envelope Rossby soliton and wave number-two topography seems to be a possible mechanism for dipole blockings observed in the two oceans.

Preliminary climatology of southern Africa extreme weather: 1973?1992

Preliminary climatological statistics of extreme weather events over the southern Africa region are established through analysis of daily weather maps of the South African Weather Bureau for a twenty year peiod, 1973–1992. Influences of global warming and inter-annual variability imposed by El Nino events, amongst others, are sought. Notable trends include a decrease in the frequency of station days with rainfall > 70 mm and an increase in station days with temperature > 38°C. Correlations offer some insights to extreme climate associations. Lows over the land in the west and over the sea to the east display consistent interannual variability, despite opposing rainfall regimes. Agreement in extreme temperature statistics in all regions suggest that drought is widespread over southern Africa. Rainfall in the north is negatively related to lows over the sea to the south. A potential mechanism underlying the inverse relationship between midlatitude and sub-tropical storminess is the development of a vorticity dipole associated with the westerly jet stream. This is investigated in an El Nino-influenced case study.

Within- and Among-Year Effects of Cold Fronts on Migrating Raptors at Hawk Mountain, Pennsylvania, 1934-1991

ABsTRAcr.--Cold-front passage has long been associated with south-bound raptor migration in northeastern North America. We used Hawk Mountain Sanctuary's 55-year database to calculate abundance indices of 14 raptor species at the site. These indices, together with data taken from coincidental U.S. Department of Commerce daily weather maps, were used to investigate the extent to which raptor migration at Hawk Mountain is associated with the passage of cold fronts. Daily abundance indices for 12 of 14 raptor species exhibited significant increases during one or more of the three days following frontal passage. Three basic patterns emerged, which differed in the number of days after frontal passage on which peak migration occurred. The patterns fit the flight behavior of the species involved. We failed to detect a long-term linear trend in numbers of fall-season cold fronts at the site. Stepwise multipleregression analyses revealed that annual-abundance indices were not influenced by annual variation in the numbers of cold fronts passing the Sanctuary at the time of fall migration. Overall, our analyses confirm the results of earlier, short-term studies demonstrating withinyear effects of frontal passage on raptor migration. Our failure to detect among-year effects of frontal passage rates on annual counts of raptors migrating past the site supports the notion that cold fronts enhance fall migration rather than simply making the birds more visible to observers at such times by forcing them closer to the watch site. Received 6 December 1994, accepted 25 April 1995.

Recent developments in hydrologic data assimilation

Data assimilation is a term that is most closely associated with the atmospheric sciences. It arises from the meteorological custom of constructing daily weather maps which show how environmental variables such as pressure and wind velocity vary over space (see Daley [1991] for a good historical review). Such maps are useful both for short‐term forecasting, where they provide initial conditions for numerical weather prediction models, and for more long‐term climatic analysis, where they can be used to reveal regional trends [Bengtson and Shukla, 1988; National Research Council, 1991; Shubert et al, 1993].For many years weather maps were derived from a limited number of measurements collected from surface stations and radiosondes. The mapping process required a good understanding of atmospheric physics and was typically carried out by hand, using the methods of ‘subjective analysis’. In the first half of the twentieth century efforts were made to standardize and automate meteorological mapping. The quantitative procedures which grew out of these efforts were commonly called ‘objective analysis’ methods [Gandin, 1963]. Objective analysis algorithms provide spatially distributed descriptions of atmospheric conditions which are consistent both with observed data and with kinematic (‘diagnostic’) principles (such as the geostrophic requirement that the pressure gradient and Coriolis force must balance). These algorithms produce ‘snapshots’ portraying conditions everywhere in a given region at a particular time.

The early summer seasonal change of Large-Scale circulation over east asia and its relation to change of the frontal features and frontal rainfall environment during 1991 summer

By using the rawinsonde data, upper cloud amount data and objective analysis data for global domain which all were produced by Numerical Prediction Division,JMA and by using daily and mean weather map issued byJMA and daily rainfall data over the Huaihe River Basin from China, an observational study to the early summer seasonal change of large-scale circulation over East Asia and its relation to change of the frontal features and environment for the frontal rainfall has been carried out. Following reaults have been obtained: (1) The early summer seasonal change of large-scale circulation was occurred during 20–23 May 1991, which was about 10 days earlier than the normal. During the period the subtropical westerly jet and tropical easterlies abruptly moved northward; (2) The northward movement of the tropical easterlies was not uniform, it was earlier at 100 hPa level and about 24 hrs late at 200 hPa level. The phenomenon was associated with earlier disappearence of the subtropical westerly jet at 100 hPa level; (3) During the seasonal change there were two westerly jets in the upper level and changed their intensity with the time. Before 18 May 1991, the southern one was more intense and then changed to more intense for the northern one and disappearence of the southern one, the phenomenon seemed to be appeared as northward movement of the southern jet; (4) A faster temperature(T) rising in the upper level over the Tibetan Plateau was associated with the seasonal change. From theT rising theT maximum moved onto the plateau, changing theT gradient from positive to nega-tive to the south flank of the plateau, the effect to reduce and disappear the southern westerlies. Also theT rising was associated with change of the frontal features over East Asia; (5) The seasonal change type during 1991 was same as that during 1992 and 1993, but different from that during 1990; (6) The environment for the frontal rainfall was change in the season, the differences were in the baroclinity in upper level and vertical wind speed and direction shear.

Surface Weather Analysis at the National Meteorological Center: Current Procedures and Future Plans

The preparation of surface weather analyses at the National Meteorological Center (NMC) is currently under review. The availability of advanced graphics workstations and consideration of revisions to conceptual models of cyclogenesis and frontal analysis present challenges and opportunities for improving surface analysis at NMC. In this paper, current procedures and surface analysis products are reviewed. The adaptation of workstation technology to one surface weather analysis product, the Daily Weather Maps, Weekly Series, is described and presented as a preliminary experiment for assessing the utility of performing surface analyses on interactive workstations. Finally, issues that will impact the future of surface analysis at NMC, such as workstation development, utilization of gridded datasets and their manipulation for improving objective analyses, possible revisions to frontal symbology, incorporation of mesoscale symbology, and changes to sea-level pressure computations, are discussed.

Daily weather mapping from 1781:

An account is given of the preparation of daily weather maps within the historical-instrumental period, with details concerning the detection and location of source material and its subsequent examination, collection and reduction to provide a workable synoptic network of comparable meteorological observations over the eastern North Atlantic-European sector. The application of the Lamb British Isles weather types and Grosswetterlagen for the statistical analysis of circulation patterns derived from these charts is discussed. An objective test was devised whereby the frequency of monthly extremes of nine variables was examined with the following important conclusions: An account is given of the impact of climate on the affairs of man in the 1780s, highlighting some specific historical case studies and discussing agriculture and industry in general.

Use of Cluster Analysis to Define Periods of Similar Meteorology and Precipitation Chemistry in Eastern North America. Part I: Transport Patterns

Abstract Cluster analysis has been applied to transport vectors, derived from three years of daily backwards trajectories, in order to define a synoptic climatology of representative three-day periods of air mass movement. The resulting clusters represent groups whose mean air mass transport fields are statistically different from one another and correspond to the types of high and low pressure patterns seen on daily weather maps. Seasonal differences were evident in the frequency of occurrence of each cluster. The clusters were relatively insensitive to changes in number of sites or years used; however, different clustering methods yielded somewhat different clusters. Ward's method yielded clusters with more or less equal numbers while other methods tended to produce one large cluster and a series of “outlier” clusters. Cluster analysis was useful in the computer-assisted classification of spatial patterns of weather data and should be considered for use along with more widely used synoptic climatologica...

北海道石狩湾上の降雪雲のレーダーエコーの特徴(レーダーエコー気候学;その1)

The characteristics of radar echoes of the precipitating snow clouds over the Ishikari Bay, Hokkaido, Japan were investigated statistically during four months, February and March of 1983 and 1984. In this analysis, the precipitating snow clouds were divided into three types: typical monsoon, final period of monsoon type and low pressure type based on the daily weather maps. Examined elements in this analysis were as follows; Size distributions of radar echo population, percentage occupied by the strong echo areas as against total precipitating echo areas, time changes of echo areas, locations of the center of individual large echo areas, life time of the echoes, and so on. Highly interesting characteristics were obtained; the log-normal distribution was obtained for the size ranges of radar echoes of all snowfall types; the percentage occupied by the echoes stronger than level 2 accounted for less than 40% of all echo areas; the total echo area showed sharp fluctuations; the locations at which the radar echo areas when the snow clouds invading the plain reached their maximal sizes were along the coast line; the average echo area having a life time of 1 hour was approximately 25km2 etc.