AMDAR Forecast Applications Mexico AMDAR Workshop November 2011

AMDAR Data Have Many Applications Aviation Convective inhibition Low-level wind shear Ceilings and visibilities Turbulence Fire Weather Mixing heights Relative humidity forecasts Marine Forecasts Small craft and gale warnings

Aviation Benefits AMDAR soundings in vicinity of airports allow meteorologists to monitor the atmosphere in real time. This allows for more accurate forecasts of low clouds/fog, low-level wind shear, convection and more. AMDAR flight level data provide important information in flight corridors. Some aircraft report turbulence data.

Aviation Applications of AMDAR Data Convective forecasts Wind speed forecasts Low level wind shear detection Low cloud/fog forecasts

Convective Forecasts The formation of thunderstorms often depends on reaching the convective temperature, and/or breaking a mid-level capping inversion. Meteorologists largely rely on model forecast soundings for determining whether thunderstorms will occur. When forecast soundings are not accurate, thunderstorms often are forecast mistakenly, or they occur when not forecast. Over forecasting of thunderstorms often cause needless delays or result in wasted fuel.

Examples of Convective Inhibition Thunderstorms were forecast in the 18UTC Monterrey TAF in a TEMPO group from 22UTC until 01UTC. TAF MMMY Z 1918/ KT P6SM SCT030 TX36/1922Z TN26/2012Z FM KT P6SM BKN040 TEMPO 1922/2001 5SM TSRA BKN030CB FM KT P6SM SCT020 FM KT P6SM BKN030 FM KT P6SM SCT040 BKN250

1717UTC Aircraft Sounding A sounding from 1717UTC shows a strong capping inversion above 850mb. With a surface dewpoint of 17°C, a surface temperature of about 40°C would be required to break the cap. The Level of Free Convection (LFC) suggests that there will be clouds around 12,000 AGL.

Surface Observations MMMY Z 13008KT 15SM FEW090 BKN100 33/15 A2987 MMMY Z 12012KT 15SM SCT100 SCT200 35/13 A2983 MMMY Z 13011KT 15SM FEW030 BKN100 BKN200 37/10 A2974 RMK DSNT CB/RA SSW CU/N MMMY Z 13008KT 15SM FEW040 SCT100 BKN200 37/10 A2974 RMK DSNT CB/SW MMMY Z 07006KT 15SM FEW070 SCT100 BKN200 36/14 A2974 CU/N MMMY Z 10019KT 15SM FEW070 SCT100 34/17 A2975 MMMY Z 09022KT 15SM SCT100 31/18 A2981 METARS show that scattered to broken clouds were reported at 10,000ft (though they were likely around 12,000ft) as suggested by the LFC. Surface temperatures of 37°F were too cool to break the mid-level capping inversion.

0140UTC Aircraft Sounding Surface heating had been insufficient to break the cap, so thunderstorms did not occur. Upon receipt of the 1717UTC TAMDAR sounding, the TAF probably could have been updated to take out mention of thunderstorms.

Low-Level Wind Shear AMDAR data can be useful in determining the presence of low-level wind shear (LLWS). Aircraft ascending or descending in the vicinity of an airport are in an ideal location for depicting LLWS.

Low-Level Wind Shear An example of this was noted by the WFO forecasters in Green Bay, WI on the evening of 29 October LLWS was forecast to begin after 0600 UTC in the TAF that night. TAMDAR soundings from around 0120 UTC showed that LLWS was already present.

Low-Level Wind Shear

The meteorologist was able to update the TAF and begin the LLWS more than 3 hours earlier than the prior forecast. This was mentioned in the Area Forecast Discussion that was issued around 0245UTC:

Ceilings and Visibilities AMDAR data are very useful in forecasting low ceilings and fog that greatly impact airports. Water vapor data is a very important element, but soundings even without it still can be useful.

Ceilings and Visibilities The WFO forecasters in Detroit, MI found TAMDAR data to be useful in predicting a dense fog event on the evening of February 4th, Soundings showed that there were light winds in the boundary layer, moisture near the surface and dry air above. These are normally suitable conditions for the formation of low clouds or fog.

Ceilings and Visibilities

Forecasters at Detroit amended their TAF for the 09 to 12UTC period, reducing visibilities to ½ mile. The METARS below show that actual visibilities dropped to below ½ mile. KDTW 0532z 00000kt 2sm br clr KDTW 0739z 17003kt 1 3/4sm br r04/1000v3500 KDTW 0936z 17004kt 1/4sm fg r04/0500v0600 KDTW 1154z 16004kt 1/4sm fg r04/2800v0600 Aircraft observations increasingly are being used to forecast the development of low clouds and fog.

Fire Weather Accurate fire weather forecasts require knowledge of stability, wind and moisture availability above the ground. The large spatial and temporal gaps in radiosonde data make this difficult. Places distant from radiosondes are at an even greater disadvantage. AMDAR data can fill many of these gaps, and is now used increasingly in fire weather forecasts.

Fire Weather Forecasters found AMDAR data useful in deciding to expand a *Red Flag Warning in effect for Northern and Central Wisconsin on the afternoon of July 15, Very dry air could be seen on TAMDAR soundings earlier in the day when the Red Flag Warning was issued. Later soundings showed there was sufficient dry air in other parts of the forecast area to expand the warning. * Temperature >75°F, RH <25%, winds of 25 mph or greater

Fire Weather AREA FORECAST DISCUSSION...UPDATED NWS GREEN BAY WI 200 PM CDT SAT JUL UPDATED...ADDED AREAL COVERAGE FOR THE RED FLAG HEADLINES. RH/S ALREADY IN THE 20 PCTS EARLY THIS AFTERNOON AND WINDS NEAR CRITERIA OVER NW WI. TAMDAR SOUNDING THIS AM FROM RHI SHOWS A VERY DRY AIR MASS TO MIX DOWN WITH NEAR CRITIERIA WINDS.

Fire Weather

Marine Applications Surface wind and resulting waves are influenced greatly by both winds aloft and stability. Unstable air helps mix down strong winds above the boundary layer, while stable conditions hinder mixing. AMDAR data are ideal for determining both winds aloft and atmospheric stability.

Marine Applications AMDAR has been used in the Great Lakes region and along the shorelines of the United States in marine forecasts. The following is an example from October 3, The NWS in Chicago used AMDAR data to determine that the atmosphere was sufficiently unstable to mix down 35 knot winds to the surface. Based on this information, they wisely decided to continue the Gale Warning that had been issued earlier in the day.

Marine Applications AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO IL 715 PM CDT SUN OCT MARINE...SHIP REPORTS OF GALES THIS EVENING FROM THE SOUTHWEST. SURFACE ANALYSIS AND USING THE ACARS SOUNDING FROM ORD AT 2230UTC SHOW STRONG WINDS ALOFT AND BEHIND THE FRONT. WILL KEEP THE GALE WARNING FOR OVERNIGHT. WHW

Marine Applications

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