The nowcasting and short and medium-range forecasting of extratropical cyclones and their associated weather patterns remains a challenging problem for operational meteorologists. This is especially true over the western United States which is impacted by many upper-level wave and storm systems that originate and track over the data sparse Pacific Ocean, limiting the accuracy of analyses and numerical model guidance of these events. Remotely sensed satellite data, such as visible and infrared imagery, have proven to be invaluable in supplementing meteorological information over this region. The work conducted in this one-year project focused on evaluating and operationally utilizing a new satellite-derived product, Microwave Sounding Unit (MSU) brightness-temperature images of the upper-troposphere/lower-stratosphere, to improve nowcasting and forecasting of cyclone events over the western United States.
The main premise for the research was the concept that tropopause undulations characterized by potential vorticity (PV) and temperature anomalies can play important roles in the structure and development of baroclinic systems. Accordingly, remotely sensed satellite observations that are able to define the tropopause structure may improve the analysis and prediction of extratropical cyclones, particularly over conventional data-sparse regions such as the ocean basins. The project involved four major activities:
1) the development of procedures and software to analyze and statistically compare six months of hemispheric satellite-sensed MSU brightness-temperature data
2) the development of procedures and software to collect, process, and analyze locally obtained MSU data and to make the final analyses available over the Internet
3) the identification and in-depth analysis of individual case studies
4) the evaluation of the MSU analysis product in real time.
The primary accomplishment of the project was a six-month climatological study which demonstrated that statistically relevant correlations exist across much of the Northern Hemisphere between the channel 3 MSU data and various conventional fields that have been shown to be dynamically linked to the upper-level temperature field and baroclinic development. In particular, strong correlations were found between the channel 3 MSU and the 400-100 mb thickness and the 200-mb temperature fields. Moreover, generally high correlations were found between the MSU and synoptic-scale mid- and upper-level geopotential height and PV features, especially over the storm tracks. These results suggest a high degree of reliability for tracking with the MSU synoptic-scale mid- and upper-level baroclinic waves that are associated with cyclogenesis.
Another significant accomplishment of this project was the development and implementation of a prototype local MSU collection, processing, and analysis procedure at the Naval Postgraduate School with commercially available hardware and software. Currently, channel 3 MSU brightness temperature analyses for the western U.S. and eastern Pacific Ocean generated from this procedure are being distributed in real time over the Internet via the world wide web (http://www.met.nps.navy.mil).