A north-south Isobaric configuration, with practically no field curvature, developed 

 to the west of the cyclone center and was maintained till after 1200Z on 20 February. 

 The coastal winds off the Mid-Atlantic states were light (10-15kts) and variable 

 until the frontal system passed the coast (OOOOZ, 19 February). The cyclone began 

 to rapidly intensify after passing over New England. The center fell to 984 mb at 

 OOOOZ on 20 February. The deepening of the cyclone led to an intensification of 

 the pressure gradient which increased surface wind speeds behind the frontal system. 

 These winds affected the coastal areas from Maine to Cape Hatteras, N« C 



4.2 A Closer Look at the Wind Field 



The National Weather Records Center in Ashville, N. C. was able to supply 

 enough additional data to allow a more detailed look at the structure of the wind 

 field. These data are presented in Figure 7. The notation "A" at the base of an 

 arrow indicates the data were taken with an anemometer. All anemometer winds 

 at sea were gathered by lightships and have been reduced to an equivalent 10 meter 

 wind assuming a logarithmic profile and the drag coefficient data of DeLeonibus 

 (in preparation). This 10 meter height corresponds to the same level that visual esti- 

 mates taken from shipboard are purported to represent. It was not worthwhile to 

 similarly reduce winds taken at land stations for obvious reasons. Considering the 

 many different ships reporting, the winds were remarkably uniform. A wind speed 

 of 30-35 kts (15.4 - 18.0 m/sec) and direction of 335°T is typical of the values 

 reported. The plane track is shown on each map and was essentially oriented parallel 

 to the wind direction . 



The relative steadiness of the wind field is apparent from an inspection of the 

 above illustrations. In addition, Figure 8 shows a time history of the wind force and 

 direction at selected near shore stations where anemometers were used. Since the 

 data were only available in terms of Beaufort force, no attempt has been made to 

 correct for different anemometer heights. However, all of the anemometers were at 

 a height of 18 to 19.5 meters above the sea surface, so the data were taken at 

 essentially the same elevation. Since the air mass associated with this storm was 

 very unstable*, it is to be expected that some variability due to gustiness will be 

 present in these figures. Even with this variability the constancy of the nearshore 

 wind field through the measurement time was reasonably goodo 



It was not possible to obtain similar anemometer wind information for the 

 region far from shore „ However, estimates of the wind in this area through accurate 

 plane positioning were obtained. By locating the plane every five minutes via 

 LORAN A (Section 3.3), the ground speed was estimated. Since the true air speed 



* Air-sea temperature differences as reported by the light ships were between -6° 

 and -10°C. 



15 



