FORECAST DISCUSSION: Tuesday, August 6, 1996
*** Weekend Update *** Over the past few days, a high pressure area centered in the mid-Atlantic and Great Lakes region has established itself in the east. It has and will continue to pump very warm, moist air into the eastern half of the U.S. and northward into Canada. Under these typical summer conditions, daytime skies are usually partly sunny or partly cloudy and there is that ever-present chance of afternoon and evening showers and thunderstorms, with the chance of rain depending on the closeness of a front, where the surface winds are converging together that day, etc. Sunday's and Monday's situations are good examples of how this matters to the development of blue mold and why the importance of being attentive to your local area weather is so often stressed.
With the exception of the SE NC source region, all other source areas on Sunday would have received a Low Risk rating. Forecast trajectories went off to the north at moderate speeds, skies were expected to be partly to mostly sunny, and the chance of showers was slight (20% or less). Those growers who didn't get any rain are probably under minimal threat of disease development. However, the threat jumps upward for those growers who DID receive a shower. The rain likely deposited some surviving live spores and created an environment favorable for infection. Thus, even though a source area has only one general risk assessment, the THREAT from that source can vary, depending on the actual amount of cloud cover during transport and the location and timing of any shower activity.
As for the SE NC source region on Sunday, forecast trajectories flowed to the west and then northwest later Sunday night. Near-coastal counties almost certainly had live spores deposited.....and the source was a Moderate risk to areas in SE and south-central NC. On Monday, all source areas were Moderate risks. Going with the clockwise flow of the high pressure area, forecasts pathways were to the W and then NW from the E NC sources and to the north from the other source areas. Movement was generally slow for those sources in the U.S. and moderate from the Canadian site. The most threatened places were the southern Appalachian mountain region and counties near to and NW of the SE NC source, since showers and thunderstorms were most prevalent in those areas.
*** Today's Summary *** Source regions are mostly Moderate risks Tuesday and Wednesday. The general scenario described above holds true; conditions are not favorable enough to warrant any High Risk assessments, yet it's certainly possible for development to occur from any of the source areas. The region of highest concern is the southern Appalachian mountains, where weak winds, partly cloudy skies, and a pretty good chance of afternoon showers may combine to produce some localized disease development. TK
HIGH-RISK SOURCES: None
***** NOTE: These forecasts/outlooks only apply to disease development from airborne transport of spores!!! We do not have the capability to ascertain blue mold development by other means, such as transplanting of infected seedlings, nor will we attempt to do so. Please consult the Extension Service personnel in your area if you have concerns about these matters! *****
This service is provided by the North Carolina State University departments of Plant Pathology and Marine, Earth, and Atmospheric Sciences.
Web page last updated by Thomas Keever on 6 August 1996.