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Weather, Time and Sky |
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Weather |
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The weather had a profound effect on U-boat operations. A U-boat's
low conning tower made it a poor observation platform and darkness and
bad weather only made that worse. On the other hand the low silhouette
of a U-boat enabled it to take advantage of darkness and lighting conditions
to maneuver unseen on the surface surprisingly close to the enemy.
Cold weather and heavy seas took a heavy toll on watchstanders who were
far more exposed to the elements than on surface ships. In heavy
seas the U-boat's deck gun was unusable and anti-aircraft weapons were
greatly reduced in effectiveness, the transfer of fuel from other U-boats
was made more difficult or impossible as was the downloading of torpedoes
from deck containers. In extremely heavy seas, a U-boat's torpedoes
could not maintain depth and a destroyer's depth charges and guns could
not be brought to bear. In those conditions the U-boat War came
to a temporary stop while both sides simply rode it out. |
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The center column of each KTB page was titled "Account of Position,
Wind, Weather, Sea state, Humidity, Visibility, Moonlight, etc."
Weather was entered in the KTB every four hours when the boat was on the
surface. Some COs simply noted the bare facts with a few abbreviations
and numbers, others were much more descriptive. The standard items
found in these weather notations are described below in the order they
are usually seen in KTBs: |
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| Observation |
Examples |
Notes |
| Wind direction and force |
ENE 6 |
The Beaufort scale was used. |
| Cloud cover |
6/10, C 6, Teilweise bewölkt |
Most often expressed as 10ths of cloud coverage
but several sets of descriptive words appear in KTBs. The
project has adopted the rules in the table below to convert descriptive
words into 10ths of cloud cover. |
| Sea state |
See 2, Seeg. 2 |
It is believed that U-boats used the Douglas
Sea Scale to report Sea state and Swell |
| Visibility |
Sicht. 5 sm, 500m, gute Sicht |
Usually in nautical miles or in meters if
the visibility is low, some COs referred to visibility in descriptive
terms: good, medium, bad or very bad. |
| Weather |
Niesel, Regen Schauer, Schnee |
A description of conditions such as drizzle,
rain showers, snow, etc. |
| The conditions below were sometimes
noted |
| Swell |
D 2, 2, leichte Dg. |
It is believed that U-boats used the Douglas
Sea Scale to report Sea state and Swell |
| Darkness |
Helle Nacht |
Descriptive terms were used, reported only
when the night was particularly light or dark |
| Temperature |
-3 Grad, plus 7° C
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Reported only when the temperature was particularly
cold |
| Barometric pressure |
1013mb abflauend |
Reported only when it was rising or falling
as during storms |
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Sea state refers to the height and character of waves on a large body
of water (not what is observed at the shore where waves interact with
the bottom). These waves are locally generated by wind acting on
the surface of the water. Swells are generated remotely sometimes
traveling long distances. It is quite possible for the wind to be
calm with no waves but a significant swell will be experienced.
It is also possible for swells to arrive from two directions at once.
During WWII wind force was reported using the Beaufort Wind Scale and
sea state and swells were reported using the Douglas Sea scale.
The Beaufort Wind Scale is still in use today. The Douglas Sea Scale
has been replaced by the World Meteorological Organization Sea State Code.
For more information on these scales see the links below. |
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Click the icons to
proceed to the associated websites |
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Wikipedia page on the Beaufort Wind Scale |
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Wikipedia page on the Douglas Sea Scale |
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The
project has adopted the rules in the table below to convert the three
sets of descriptive words found in U-boat KTBs to the modern official
values for cloud cover. |
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Terms for Sky conditions
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Modern
Official Terms/Values |
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(Used in
translated KTBs) |
| Descriptive term |
Literal translation |
Term |
Tenths coverage |
| Ganz bedeckt (bed.) |
completely overcast (ovc.) |
overcast |
10/10 |
| Fast ganz bed. |
nearly completely ovc. |
broken |
8/10 |
| Zum grossen Teil bed. |
for the most part ovc. |
scattered |
6/10 |
| Halb bed. |
partial ovc. |
few |
4/10 |
| Unbedeckt or Klar |
clear |
clear |
0/10 |
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| Sehr stark bewölkt (bew.) |
very strongly cloudy |
overcast |
10/10 |
| Stark bew. |
strongly cloudy |
broken |
8/10 |
| Mittel or Teilweise bew. |
medium or partly cloudy |
scattered |
6/10 |
| Leicht, Wenig, Kaum, Geringe, Schwach bew.
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lightly, or a little cloudy |
few |
4/10 |
| Nicht bew. |
not cloudy |
clear |
0/10 |
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overcast |
10/10 |
| Mehrere Wolken |
several clouds |
broken |
8/10 |
| Einzelne Wolken |
few clouds |
scattered |
6/10 |
| Fast wolkenlos Vereinzelte Wolken |
nearly cloudless |
few |
4/10 |
| Wolkenlos |
cloudless |
clear |
0/10 |
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Distances for Visibility conditions (from the Wetterkurzschlussel) |
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| Descriptive Term |
Distance |
| Sehr schlechte |
Very bad |
As a result of precipitation or dust |
Up to 1/2 nm |
| Schlechte |
Bad |
Horizon still completely obscured, as a result of precipitation, dust or mist |
Up to 1-1/2 nm |
| Geringe |
Poor |
Horizon indistinct, as a result of precipitation, dust or mist |
Up to 3 nm |
| Mäßige |
Moderate |
Horizon just barely visible |
Up to 5 nm |
| Gute |
Good |
Horizon easily distinguished |
Up to 10 nm |
| Sehr gute |
Very good |
Ships, the coast and other things well distinguished at appropriate distances |
Over 10 nm |
| Außergewöhnlich klare Luft |
Exceptionally clear air |
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Over 20 nm |
| Sehr dichter Nebel |
Very thick fog |
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Under 50 meters |
| Dichter Nebel |
Thick fog |
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Up to 200 meters |
| Mäßiger Nebel |
Moderate fog |
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Up to 1/2 nm |
| Nebel |
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| Starker Seerauch |
Heavy sea smoke |
(a type of fog that forms in cold air above warm water) |
Under 1/2 nm |
| Leichter Seerauch |
Light sea smoke |
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Over 1/2 nm |
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Height/Length of Swells (from the Wetterkurzschlussel) |
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| Descriptive Term |
Height/Length |
| Niedrig |
Low |
Under 2 meters |
| Mäßige hoch |
Moderate |
2-4 meters |
| Hoch |
High |
Over 4 meters |
| Kurz |
Short |
Up to 40 meters |
| Mittellang |
Medium |
40-150 meters |
| Lang |
Long |
Over 50 meters |
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Time
and Sky |
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Times in KTBs are in DGZ (Deutsche Gesetzliche Zeit/German Legal Time),
which was usually MEZ/CET (Mitteleuropäische Zeit/Central European
Time) = Universal Time/GMT +1 hour. |
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During WWII, DGZ was changed to MESZ/CEST (Mitteleuropäische Sommerzeit/Central
European Summer Time) = Universal Time/GMT +2 hours between the following
dates: |
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01.04.1940
02:00 MEZ to 02.11.1942 03:00 MESZ |
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29.03.1943
02:00 MEZ to 04.10.1943 03:00 MESZ |
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03.04.1944
02:00 MEZ to 02.10.1944 03:00 MESZ |
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02.04.1945
02:00 MEZ to 16.09.1945 03:00 MESZ |
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As a result of maintaining the ship's clocks and KTB in German Legal Time,
sunrise and sunset became more and more offset from normal experience
as the boat moved further east or west from base. For example, off
the east coast of the US in the winter months, the sun might rise at 14:00
and set at 24:00 according to the ship's clocks. |
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Invisibility is the primary tactical advantage of a U-boat. The
vast majority of attacks took place during the hours of darkness for only
then could the boat use high speed to maneuver into attack position without
being detected. Ideally the boat would maneuver to attack from the
dark side (into the sunrise, sunset or moon) silhouetting the target against
the dim light. The phase of the moon and the degree of sky cover
were key factors in determining how dark the night would be.
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The time of sun and moonset, rise and transit are important for navigation
using the sextant. A fix could also be generated by sighting the
sun or the moon. If the tactical situation permitted the boat was
likely to surface when stars are visible and the horizon was distinct
(between civil twilight and sunrise or sunset) or during the sun or moon
transit. |
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For all the above reasons, Sun and Moon Data have been provided for each
day of the KTB. To generate this data, the 1200 DGZ (Universal Time
+ 1 or 2 hours) position, given in the Kriegsmarine Quadrant system is
converted to Latitude and Longitude (see the Navigation page for links
to Quadrant converters). The resulting position and the date are
entered into the US Naval Observatory's webpage form and the data is formatted
for use on the U-boat Archive website. |
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Click the icon to proceed to
the US Naval Observatory website page for Sun and Moon Data |
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Weather, Time and Sky Vocabulary |
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| Abenddämmerung |
Dusk |
| Abendrot |
Red sunset, afterglow |
| Abflauend |
Subsiding abating |
| Abnehmende |
Decreasing |
| Achterlicher Wind |
Following wind |
| Angünstiger |
Adverse/unfavorable |
| Anhaltend |
Steady |
| Arktische Kaltluft |
Polar air |
| Atmosphärendruck |
Barometric pressure |
| Aufbrechend |
Breaking up |
| Auffrischend (Auffr.) |
Freshening increasing |
| Aufgerissen |
Broken |
| Aufklaren |
To clear up/Clean up (ship) |
| Aufklärend |
Clearing up |
| Aufreißende |
Broken replace Auffressend |
| Außenluft-Thermometer |
Free-air thermometer |
| Barometer (Bar.) |
Barometer |
| Barometrisch Gefälle |
Pressure gradient |
| Bathythermograph |
Bathythermograph - device for measuring water temperature at various depths |
| Bebelbänke |
Fog bank |
| Bedeckt (bed.) |
Overcast |
| Beleuchtung |
Illumination |
| Bessernd |
Improving |
| Betriebszeit |
Operational time |
| Bewegte See |
Choppy sea |
| Bewölk (bew.) |
Cloudy |
| Bewölkungszunahme |
Increasing cloudiness |
| Bezogen |
Overcast |
| Bleiflaute |
Dead calm |
| Bodennebel |
Ground fog |
| Bodenwind |
Surface wind |
| Böen |
Squall |
| Böig |
Gusty |
| Böiges Wetter |
Squally weather |
| Bölinie |
Squall line |
| Brandung |
Surf |
| Brise |
Breeze |
| Cirruswolke |
Cirrus cloud |
| Dämmerung |
Twilight |
| Deutsche Gesetzliche Zeit (DGZ) |
German Legal Time |
| Dichter Nebel |
Thick fog |
| Diesig |
Hazy misty |
| Diesigkeit (d.) |
Haze |
Druckänderung |
Pressure change |
| Dunkel (dkl.) |
Dark |
| Dunkelheit |
Darkness |
| Dunst |
Haze |
| Dunstig |
Hazy |
| Dunstschicht |
Haze/mist layer |
| Dünung (Dün. or D.) |
Swell |
| Durcheinanderlaufen |
Confused (sea/swell) |
| Durchzug |
Passage (of a weather front) |
| Dwarssee |
Beam sea |
| Dwarswind |
Beam wind |
| Einheitszeit |
Standard time |
| Einzelne Wolken |
Few clouds |
| Eisansatz |
Accumulation of ice |
| Eisberg |
Iceberg |
| Eiskristalle |
Ice crystals |
| Eisregen |
Sleet, ice pellets |
| Eisscholle |
Ice flow |
| Eisstücke |
Broken ice |
| Eisverhältnisse |
Ice conditions |
| Etwas |
Somewhat |
| Fast ganz bedeckt |
Nearly completely overcast |
| Fast wolkenlos |
Nearly cloudless |
| Federwolke |
Cirrus cloud |
| Ferngewitter |
Isolated thunderstorm |
| Feuchter Dunst |
Mist |
| Feuchtigkeit |
Humidity |
| Feuersichtige |
Good visibility |
| Finsternis |
Darkness |
| Flau |
Calm (wind) |
| Flaut ab |
Wanes (wind) |
| Flaute |
Calm |
| Fliegerwetter |
Good flying weather |
| Flugwetter |
Flying weather (good weather) |
| Frost |
Freezing |
| Ganz bedeckt |
Completely overcast |
| Gegenwind |
Headwind |
| Gering (ger.) |
Small/ few/poor/slight |
| Gesichtskreis |
Horizon/field of view |
| Gewitter |
Thunderstorm |
| Gischt |
Foam, spray |
| Glasartige Vereisung |
Clear ice, glaze |
| Glatte See |
Smooth sea |
| Gleichbleibend (glbl.) |
Steady/unchanged |
| Grad |
Degrees |
| Graupel |
Sleet |
| Greenwich-Normalzeit |
Greenwich Civil Time |
| Hagel |
Hail |
| Halb bedeckt |
Partial overcast |
| Halbmond |
Crescent moon |
| Haufenwolke |
Cumulus cloud |
| Heiter |
Sunny, fair (weather) |
| Heller |
Bright |
| Hellwerden |
Getting light |
| Hohe |
High |
| Höhentemperatur |
Temperature at various altitudes |
| Horizontale Sichtweite |
Horizontal visibility |
| In der Umgebung |
In the vicinity |
| Kalt |
Cold |
| Kälte |
Cold |
| Kaltluftfront |
Cold front |
| Kaum |
Scarcely |
| Keine Kimm |
No visual horizon |
| Keine Veränderungen |
No changes |
| Kimm |
Visual horizon |
| Klar |
Clear |
| Klareis |
Clear ice, glaze |
| Klima |
Climate |
| Kumuluswolke |
Cumulus cloud |
| Kurzzeitig |
Temporary |
| Lang (lg.) |
Long |
| Leicht bewölkt |
Lightly cloudy |
| Leichte (l.) (lcht.) |
Slight, light |
| Linienbö |
Line squall |
| Links drehender |
Shift counter-clockwise |
| Linkslaufend |
Counterclockwise |
| Luftdruckmesser |
Barometer |
| Luftmeer |
Atmosphere |
| Luftschicht |
Atmospheric layer |
| Lufttemperatur (L.) |
Dry-bulb temperature |
| Mässig (Mäss.) |
Moderate |
| Meeresleuchten (Meeresl.) |
Marine phosphorescence |
| Mehrere Wolken |
Several clouds |
| Meßgerät |
Measuring instrument (weather instruments) |
| Mittel |
Medium, typical |
| Mittel bewölkt |
Partly cloudy |
| Mitteleuropäische Sommerzeit (MESZ) |
Central European Summer Time (CEST) |
| Mitteleuropäische Zeit (MEZ) |
Central European Time (CET) |
| Mittlere Wolkenhöhe (m) |
Medium-high ceiling |
| Mond |
Moon |
| Mondhelligkeit |
Bright moonlight |
| Mondlose Nacht |
Moonless night |
| Mondnacht |
Moonlit night |
| Mondschein |
Moonshine |
| Monduntergang |
Moonset |
| Morgendämmerung |
Dawn |
| Müller Mond |
Miller's moon (full moon) |
| Nachmittag (nachm.) |
Afternoon |
| Nebel |
Fog, mist |
| Nebelbank |
Fog bank |
| Nebelschwaden |
Patches of fog/wafts of mist |
| Nebelverhältnisse |
Fog conditions |
| Niederschlag |
Precipitation |
| Niedrig |
Low |
| Niedrige Wolkendecke |
Low cloud layer |
| Niesel |
Drizzle |
| Nordlicht |
Northern lights |
| Ölige See |
Oily sea (flat calm) |
| Orkan |
Hurricane, tropical cyclone |
| Ortszeit |
Local time |
| Packeis |
Pack ice |
| Passat |
Trade wind |
| Passatwetter |
Tradewind weather |
| Rechts drehender |
Shift clockwise |
| Rechtsläufig |
Clockwise |
| Rechtzeitig |
Punctual, in time |
| Regen |
Rain |
| Regenbö |
Thick squall |
| Regenbogen |
Rainbow |
| Regenguss |
Rain storm, downpour |
| Regenschauer |
Rain shower |
| Regenwolke |
Rain cloud |
| Reif |
Rime ice, frost |
| Ruhiges Wetter |
Quiet weather , calm weather
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| Schatten |
Shadow |
| Schattenriß |
Silhouette |
| Schauer |
Showers |
| Schauerwetter |
Showery weather |
| Schaum |
Foam |
| Scheitelpunkt |
Zenith |
| Scheußliches Wetter |
Atrocious weather |
| Schichtwolke |
Stratocumulus cloud |
| Schlechte (Schl.) |
Poor |
| Schlechtes Wetter |
Bad weather |
| Schlechtwetter |
Bad weather |
| Schlechtwetterwolken |
Bad weather clouds |
| Schnee |
Snow |
| Schneeregen |
Snow/rain mix |
| Schneetreiben |
Driving snow |
| Schnell zunehmende Kälte |
Quickly growing cold |
| Schroff |
Abrupt, rough, steep |
| Schwach bewölk |
Lightly cloudy |
| Schwache |
Slight, weak |
| Schwere |
Heavy |
| Seegang (Seegg.) |
Literally swell but used in KTBs for sea state |
| Seerauch |
Sea smoke (a type of fog that forms in cold air above warm water) |
| Sehr stark bewölkt |
Very strongly overcast |
| Seitenwind |
Cross wind |
| Sicht |
Visibility |
| Sichtverbesserung |
Visibility improvement |
| Sichtverschlechterung |
Deteoriating visibility |
| Sichtweite (sicht. or S.) |
Visual range |
| Sonnenaufgang |
Sunrise |
| Sonnenglast |
Sun glare/Sunshine |
| Sonnenglaz |
Sun glitter |
| Sonnenschein |
Sunshine |
| Sonnenuntergang |
Sunset |
| Spiegelglatte |
Flat calm |
| Sprühregen |
Drizzle, spray |
| Sprühregen |
Mist/drizzle |
| Stark bewölkt |
Strongly overcast |
| Stark Dünung |
Heavy swell |
| Staub |
Dust |
| Staubregen |
Dust rain |
| Staubsturm |
Dust storm |
| Stehend |
Steady |
| Steigend |
Rising |
| Steile |
Steep |
| Sterne |
Starry |
| Sternklar |
Starlit |
| Stirnwind |
Headwind |
| Strichweise |
Scattered |
| Stunde (Std.) |
Hour |
| Stündlich |
Hourly |
| Sturzsee |
Heavy sea breaking on deck |
| Sturzwellen |
Breakers |
| Sturzwellenbekommen |
Ship heavy seas |
| Tagesanbruch |
Daybreak |
| Taghell |
As bright as day |
| Talnebel |
Ground fog |
| Taupunkt |
Dew point |
| Teilweise |
Partial |
| Temperaturgradient |
Temperature gradient |
| Thermometer |
Thermometer |
| Tief hängende Wölken |
Low hanging clouds |
| Tiefschwarz Nacht |
Inky black night |
| Tiefziehende Wolken |
Low pressure area clouds |
| Trombe |
Cyclone, tornado |
| Übersättigung |
Supersaturation |
| Uhr |
Watch, clock |
| Uhrvergleich |
Synchronization of watches |
| Uhrzeit |
Clock time such as 13.45; as opposed to Zeit, time, in sense of time length |
| Umspringen |
Veer |
| Unbedeckt |
Clear |
| Unbekannt |
Unknown |
| Ungetrübt |
Unclouded |
| Ungeübte |
Confused (seas) |
| Unsichtig |
No visibility |
| Unsichtigkeit |
Poor visibility |
| Unstetiges Wetter |
Changeable weather |
| Unverändert |
Unchanged |
| Veränderungen |
Changes |
| Vereinzelt |
Isolated |
| Vereinzelte |
Scattered/isolated |
| Vereisen |
To ice up |
| Verschwommene Kimm |
Hazy/blurred horizon |
| Völlig |
Completely |
| Vollmond |
Full-moon (period) |
| Vollmondnacht |
Night of a full moon |
| Voraussage |
Prediction, forecast |
| Vortag |
Previous day |
| Vorübergehend |
Temporarily |
| Warmluftfront |
Warm front |
| Wechselnd |
Variable/shifting |
| Wechselnd (Wech.) |
Changing |
| Wenig bewölkt |
Lightly cloudy |
| Wetter |
Weather |
| Wetterbeobachtung |
Weather observation |
| Wetterbeobachtungsschiff |
Weather observing vessel |
| Wetterbericht |
Weather report |
| Wetterbesserung |
Weather improvement |
| Wetterdienst |
Weather Service |
| Wetterfunkegerätesee (WFS.) |
Automatic German weather buoy |
| Wetterfunkgeräteland (WFL.) |
Automatic German weather sation |
| Wetterfunkmeldung |
Weather message |
| Wetterkunde |
Meteorology |
| Wetterlage |
Weather conditions |
| Wetterleuchten |
Summer lightening |
| Wettermessung |
Meteorological measurement |
| Wetterstelle |
Weather station |
| Wettertemperatur (W.) |
Wet-bulb temperature |
| Wetterumschlag |
Break in the weather |
| Wetterverhältnisse |
Weather conditions |
| Wetterverschlechterung |
Weather degradation |
| Windmesser |
Anemometer |
| Windmessgerät |
Anemometer |
| Windseite |
Windward |
| Windstärke |
Wind velocity |
| Windstill |
Calm |
| Windstoß |
Wind squall |
| Wirbelsturm |
Hurricane |
| Witterung |
Atmospheric conditions, weather |
| Wnsichtiges Wetter |
Poor visibility |
| Wolken |
Clouds |
| Wolkendecke |
Cloud cover |
| Wolkenhimmel |
Overcast sky |
| Wolkenhöhe |
Ceiling |
| Wolkenlos |
Cloudless |
| Wolkenuntergrenze |
Height of cloud base |
| Wolkiges Wetter |
Cloudy weather |
| Zeitig |
Early |
| Zeitraum |
Period of time |
| Zeitweise (ztw.) |
Occasionally |
| Zeitzonen |
Timezones |
| Zerrissene Wolkendecke |
Broken cloud layer |
| Zonenzeit |
Standard time |
| Zum grossen teil bedeckt |
For the most part overcast |
| Zum teil |
Partially |
| Zunehmend (zun.) |
Increasing/growing |
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