|Dropsonde Scientist||Franklin, Kaplan|
This document is divided into 3 sections (Each section is written by the Chief Scientist):
This was a NHC tasked mission to do a single plane synoptic flow pattern to map the environmental flow ahead of Hurricane Edouard. The pattern would drop 20 ODWs to document the synoptic features N of the storm (these represent the last ODWs). The track is attached. 43RF would depart from MacDill AFB at 1800 UTC recovering in Miami.
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N43RF took off at 1823 UTC. The first half of the mission, 1929-2230 UTC, went smoothly as we sampled the region NW of the storm, making 8 of 9 ODW drops with good winds and pressure, temperature, and humidity. Scheduled drop #2 was omitted due to problems getting a sonde baselined in time. We passed through the ridge axis at 2120 UTC (37 N, 73.5 W) and entered NW flow along the E-W track along the N portion of our track. The only possible problem may be the flight level dew point, which was bad prior to 2102 UTC.
At 2245 UTC (37.9 N, 66 W) we were at our farthest NE point in the vicinity of a ENE-WSW lines of convective cells. There were a number of cells near the turn point and the ODW was dropped S of cells as the flow switched from WNW to WSW, reaching 30 kts just S of the convection. After the turn to the W at 2322 UTC (35 N, 66 W) the drops got more difficult to place as we were in and out of precipitation. At 2340 UTC (35 N, 67.75 W) we passed into a region of stratiform rain below the aircraft flight level (400 mb) as we entered the N rain shield around the storm. From 2340-0102 UTC the plane was in precipitation at and below the aircraft. Only 3 of the next 5 ODWs worked. However, the Doppler winds should be really interesting. The radar indicated a number of high vertical shear regions in the precipitation region. The plane even experience a dramatic 180 degree wind shift (135°-315°) between 0036 and 0040 UTC as we passed 140 nm due N of the storm center.
From 0102-0202 UTC we tracked SW along the NW periphery of the storm dropping the four working ODWs we had. After drop 19 no more sondes were left so we climbed to ferry to Miami. Of the 20 scheduled drops, 17 were transmitted in time to meet NCEP's operational analysis deadline.
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This was a successful mission (historic as well as, THERE ARE NO MORE ODWs). It was very interesting to see how the flow to the N of the storm varied as it interacted with the baroclinic zone. The ODW drops were positioned nicely to document the ridge and the trough to the N of the storm, indicating that the trough was lifting out leaving Edouard behind to continue tracking N. A hidden benefit of this mission may be the Doppler and microphysics data sets collected in the rainbands N of the center and in the frontal zone.
Early indications are that the data from the drops may have had a positive influence on the operational forecast guidance, by reducing the spread in the guidance and focusing on the landfall threat to New England.
1. Problem with the dew point prior to 2102 UTC. The flight director reset it at 2102 UTC and it seemed to work fine afterwards.
2. Radar DAT drive #1 ate one of the DAT tapes, switched to DAT drive #2.
3. Three of the scheduled drops were not transmitted to NCEP. Drop #2 was skipped due to operator problems; .drop #16 was bad and could not be backed up due to the limited sonde supply; and drop #20 was omitted due to a lack of sondes. Drop 19 had to be terminated early to meet the NCEP Aviation run analysis deadline.
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