Mission Plan :

42 will conduct an EMC-tasked TDR mission for Sunday 1630L (2030Z) takeoff, targeting the 00Z HWRF forecast cycle. The track (Fig.1) is an initial rotated Figure-4 pattern at 8,000 ft radar altitude, with the IP on the west side, 105 nmi legs, final point on the south side. Then climb to >20 kft (as high as possible), counterclockwise circumnavigation at 70 nmi from the center. A total of 13 dropsondes is proposed with the endpoint sondes (4), center (1), drop every 45 deg. azimuth of circumnav. (8). No AXBTs.

Figure 2. GOES-16 channel 13 brightness temperature at 2106 UTC, July 8, 2018.

Figure 3. 250 to 850 hPa deep layer mean (left) and deep shear (right) from CIMSS analysis. 2018.

Figure 4.TS Chris track and intensity forecasts initiated at 18Z, July 8 2018.

NHC advisory at 2100 UTC for the storm position is at 32.7°N, 74.6°W with estimated minimum central pressure 1008 mb and the max sustained winds 45 kt with gusts to 55 kt. Satellite presentation of the storm shows the storm is getting better organized, the strongest convection mostly located in the east-northeast of the storm (Fig. 2).

Chris remains in between two mid-level highs and a mid- to upper-level trough to its northeast (Fig.3) that caused the cyclone is nearly stationary. The currents are forecast to remain light, so little motion is anticipated during the next 2 days. Chris is embedded within an environment of medium to low shear (Fig. 3) and is expected to be over a pool of warm water for the next 2 days. A mid-level trough forecast to swing eastward across the eastern United States will provide enough forcing to kick Chris northeastward with increasing forward speed over the Atlantic beyond 72 hours.

An earlier Air Force reconnaissance plane reported flight-level winds of 51 kt on the eastern semicircle. NHC's initial intensity is set at 45 kt in this advisory. Most of the model guidance on track forecasts remains similar within 48 h, but spreads a bit after 72 h, largely due to the forecast difference in the forward motion of the cyclone (Fig. 4). The intensity guidance from most of the models forecasts that the cyclone remains to be a tropical storm within 24 h. After 24 h, NHC and some of the models (e.g. SHIPS, HMON) brought the cyclone to a hurricane strength. After 48 h, majority of the model guidance forecasts the cyclone to be a hurricane.

Mission Summary :

Take off (at 2332 UTC) was delayed due to engine #2 deice valve problem and oil leak. This left us only about 3 h max on station time, with one hour and half for ferry each way.

Figure 5. Actual flight track for mission 20180708H2. Flight-level winds (barbs) and wind speeds (shaded, kt) indicated (courtesy of www.tropicaltidbits.com).

When we arrived at IP, the strongest convection shifted to northeast. While inbound in the first leg of the track, 57 kt inbound flight-level wind was reported. We then did center hunting during the first leg of the figure-4, where a circle near the center of the cyclone was flown. Center fix showed the storm motion was 135 degree at 2 kt. While at the inbound of the second leg, 105 nm north of the storm center, we noticed a big convective band ~70 nmi north of the center. Some lightning was seen as we penetrated that major convective band. Radar reported echo tops >16 km. Due to the shortened mission, we only completed a single figure-4 pattern (Fig. 5) for the TDR mission. In total, 6 dropwindsondes (2 center, 4 endpoints) were deployed during the mission.

Figure 6. Wind speed at 0.5 km (left) and 2.5 km (right).

Figure 7. Reflectivity at 2 km (left) and wind speed at 2 km and 5 km (right), respectively.

Despite the shortened mission, we were still able to get a decent coverage of the cyclone sampling. Radar wind analysis showed the strongest wind speed was located north of the center (Fig. 6), although there could be some undersampling in the NE quadrant of the cyclone. The strongest reflectivity was in the NE quadrant of the cyclone (Fig. 7). Radar analysis after the second center pass also indicated the system became well aligned vertically (Fig. 7). Chris will be on a slowly strengthening trend. We also obtained a good recording of WSRA sea surface significant wave height data (Fig. 8).

Figure 8. WSRA surface wave height in plain view (left) and storm relative (right).

Mission Evaluation/Problems:

AOC crew were extremely supportive. They fixed the plane engine deice issue and oil leak in a very timely manner that enabled us to collect vital data for analysis and model assimilation. We were able to collect a single figure-4 pattern that still gave us a decent 3D view of the cyclone.

MMR was operating during the mission but the settings for the radar made situation awareness very difficult using the MMR. So the flight director used primarily the nose radar for situation awareness throughout the course of the mission.

We found radar processing parameters in the plane were not set correctly. Paul Reasor was able to assist the radar scientists to reset the parameters. During the second TDR analysis, the terminal in the Linux computer was also not responsive. We had to close the rsync terminal to re-transmit the data. We ended up needing to do that for all subsequent analyses during the Chris missions. Paul Reasor worked with John Gamache and John Hill at AOC to try to resolve the issue. John Hill made some changes on the AOC data server that alleviated part of the issue, but Paul and John will need to look at their real-time scripts to decide how to fix the remaining issues.

Hui Christophersen
19 July 2018

Pass #1 Timeseries wind, rain rate, and pressure plots		Pass #2 Timeseries wind, rain rate, and pressure plots
Timeseries wind, SFMR wind, rain rate, altitude and pressure plots

Flight track	Temperature and Moisture	Wind and Atlitude
Flight track

Flight Director's log | Flight Director's manifest NetCDF data | serial data | 1 second data

LPS#1 log | LPS#2 log | Radar log | Drop log

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