# Presentation: 271238

## Beyond QuikSCAT

- TPC/NHC Requirements for Satellite Retrievals of Ocean Surface Vector Winds
- Richard Knabb
- 6 June 2006

## Needs vs Wants

## Key Forecast Parameters

- Tropical Cyclone Intensity:  Maximum sustained surface wind (1 minute average, 10 m altitude, unobstructed exposure), associated with the circulation of the tropical cyclone at a given point in time.
- Tropical Cyclone Wind Radius:  Largest distance from the center of the tropical cyclone of a particular sustained surface wind speed threshold (e.g., 34, 50, 64 kt) somewhere in a particular quadrant (NE, SE, SW, NW) surrounding the center and associated with the circulation at a given point in time.

## Advisory Forecast Cycle

| Time (UTC) | Event | Activities/Comments |
| --- | --- | --- |
| 1200 | Forecast cycle begins | Review late models, synoptic obs, microwave data, scatterometer, etc.; begin determining wind radii |
| 1230 | Receive fix information | Analyze recon or satellite fix data, update the best track, determine compute parameters (initial position, motion, intensity, size) |
| 1245 | Submit computes | Review model fields [submit invest computes, 2nd storm?] |
| 1250 | Retrieve guidance | Examine guidance, re-evaluate initial radii, make track, intensity, radii forecasts, fill out worksheet |
| 1340 | Prepare for conference call | Watches/warnings, begin writing forecast discussion, [make aircraft tasking requests for following day] |
| 1400-1410 | Conference call | Coordinate forecast, watches/warnings. |
| 1410-1430 | Prepare products | [New fix], Write Public Advisory, Discussion |
| 1430-1500 | edit/xmit products | Also update web graphics |

**Advisory Forecast Cycle**

## Advisory Forecast Cycle

| Time (UTC) | Event | Activities/Comments |
| --- | --- | --- |
| 1500 | Clean up workspace | Enter fixes, file paperwork |
| 1510-1530 | Prepare ATL TWO | Examine models (0-36 h), imagery, scatterometer, microwave |
| 1530-1600 | Prepare for Long-Range Coordination call | Examine models (120-168 h) |
| 1600 | LRCC-HPC | Look out for tours! |
| 1630-1650 | Prepare EPAC TWO | Examine models, imagery, microwave, scatterometer |
| 1715-1745 | Prepare intermediate advisory? |  |
| 1745-1800 | Examine 12Z model fields |  |
| 1800 | Begin next forecast cycle |  |

**Advisory Forecast Cycle**

## HOW DO WE ESTIMATE INTENSITY?

**Satellites**
**Geostationary IR and VIS (Dvorak technique)**
**AMSU**
**QuikSCAT           **
**Surface observations**
**ships, buoys, land stations (limited)**
**WSR-88D (near land)**

**Aircraft reconnaissance**
**flight-level winds**
**GPS dropsondes**
**Stepped Frequency Microwave Radiometer (SFMR)**
**Airborne doppler radar**

## Slide 8

## 105 kt

**RECON  FLIGHT-LEVEL  WINDS**
**HURRICANE  GEORGES  9/20/98 20-23Z**

**105 kt**

**90 kt**

**90 kt**

**95 kt**

## QuikSCAT Limitations

- Rain contamination
- Rain-induced bias in retrieved wind speeds that varies with rain rate and actual wind speeds
- Lack of collocated rain rate data
- Inability to measure max winds in most hurricanes
- Rain attenuation, signal saturation, resolution
- Directional ambiguities
- TC center fixing and identification
- Availability and timeliness

## Requirements

- Greatly reduced or even non-existent sensitivity to rain
- Provide accurate wind speed and direction retrievals regardless of rain rate (no rain, light rain, or heavy rain)

## Requirements

- Capability to measure entire range of sustained surface wind speeds in TCs
- 0 to 165 kt, accurate to within 1-2 kt
- Finer horizontal resolution (1-4 km), and increased sensitivity at extreme wind speeds
- Fill in some gaps left by aircraft recon
- Does not fly into every major hurricane (e.g., east Atlantic, east Pacific)
- Provides data only along a line during each flight leg
- Recon gaps even in “well-sampled” storms

## Requirements

- Elimination of the directional ambiguity problem
- Need much more accurate position fixing for TCs
- Determining if closed circulation exists (key factor in determining if cyclogenesis has occurred)

## Requirements

- More timely data
- Reduce time between satellite overpass and receipt of data to a few minutes

## Requirements

- More continuous monitoring of systems
- Especially needed in the Tropics where gaps in POES data are largest
- Increase frequency of retrievals over each system of interest
- At least 3-hourly to ensure data is timely for next advisory