Blog Post 2 (author: Sydney Hopkins)

On March 31 00Z, a broad area of low pressure can be seen centered over North Carolina and Virginia moving eastward (Figure 1). The low-pressure system, with cyclonic circulation, is producing an associated cold front that runs down the southeast, oriented southeast to northeast. Further northward, another low-pressure system can be observed just north of Maine producing an associated cold front that runs down the east coast appearing to almost connect with the front further south. The combination of these low-pressure systems and their associated fronts are producing precipitation and storms up and down the east coast. The pressure gradient does not appear to be very strong, indicating milder storms and weather.

Figure 1: Surface Analysis, April 1 00Z


The system in focus can be seen moving over the east coast of the US in the infrared image below, taken on March 31 23Z. The whitest shades of the image can be seen over Georgia and the Carolinas. These white shades indicate cold cloud temperatures, which usually correspond to higher clouds with associated convection and storms (Figure 2). On the radar image below, taken shortly after on April 1 01Z, highest reflectivity can be seen over Georgia and the Carolinas, corresponding to the whitest regions on the infrared image. These areas of high reflectivity indicate high levels of precipitation (Figure 3).


Figure 2: Infrared Satellite Image, March 31 23Z


Figure 3: Radar Image, April 1 01Z


In figure 4 below, showing 250 hPa windspeeds and 500-1000 hPa thickness, the low-pressure system centered over North Carolina appears to be in the right entrance region of the jet. This is an area of positive vorticity advection, which results in upward vertical motion and is favorable for the strengthening of extratropical cyclones. This would suggest our system should continue to strengthen as it moves off the east coast. Additionally, the lows can be observed to be centered in a region of an upstream trough and downstream ridge (Figure 5). This is an area with ageostrophic divergence, which results in upward vertical motion and is favorable for the intensification of the cyclonic system being discussed. The highest areas of divergence and upward vertical motion can be seen in figure 5 along the southeast coast.


Figure 4: 1000-500 hPa thickness, 250 hPa wind speed, April 1 00Z


Figure 5: 300-200 hPa PV, irro. Wind, 600-400 hPa ascent, April 1 00Z


This low-pressure system will continue to produce precipitation along the east coast throughout the day on April 1. The 12-hr. precipitation probability map shows moderate probability of rain along the east coast (Figure 6). This precipitation should not be associated with too much severe weather activity. Figure 7 shows that only low levels of CAPE can be observed over Florida and southeast Georgia. This indicates a lower probability for intense storms associated with this system.


Figure 6: 12 hr. probability of precipitation, April 1 00Z


Figure 7: 850 hPa heights, temp, CAPE, 1000-500 hPa shear, April 1 00Z