Su Campu

Pressure drops by 1 hPa for every 8 m increase in altitude (roughly, in the lower troposphere - it's less higher up). The average ISA 850 hPa height is 1,450 m, with a surface pressure of 1,013.25 hPa. In very cold airmasses the pressure fall with height is greater because the air is denser and the pressure levela are spaced closer together, and vice versa for warm airmasses. In the case of low pressure (or depression, i.e. a depression in the pressure level surfaces through the lower atmosphere) all of the pressure levels are brought down towards the ground, so the 950 hPa level, which would normally be at around 500 m, could now be at the surface, and the 850 hPa level will be lowered by roughly the same amount (so now at around 950 m!). Given this 500 m drop, the 850 hPa temperature can now afford to be warmer than we'd normally look for for snow, and we should really be looking at a new level 500 m higher up for our "850hPa uppers" (i.e. 500/8 m = ~63 hPa higher, or the 787 hPa level - roughly!). People blindly look at the 850 hPa level for their "uppers" when in fact there is a lot more to it than that. In any case, the 850 hPa chart will also give the height of that level too, but a rough calculation of it is to take the difference between the pressure at the surface and 850 hPa and multiply by 8 m. e.g. 960 at the surface so 850 hPa level is now at roughly (960-850)x8 m = 880 m.

Konstantinos, have a look at this excellent tutorial on polar lows. http://www.eumetrain.org/resources/mfc_2013_s9.html

Mace Head, on the western Galway coast, reported max sustained winds of 32 m/s (72 mph) and a gust of 40 m/s (90 mph). 03963 164// /2530 10073 20049 39673 49700 57040 60142 87/// 333 10110 87/17 90710 91140 91232=

Maximum sustained winds at Mace Head this evening were 32 m/s (62 kts/72 mph). Gust 40 m/s (78 kts/90 mph). 03963 164// /2530 10073 20049 39673 49700 57040 60142 87/// 333 10110 87/17 90710 91140 91232=

Malin Head reached 15.3 °C today

It is a bone-chilling temperature alright, but let's not get carried away. This was at 14,000 ft, so our comparison of this temperature to the coldest recorded in say Siberia is a little misleading. If there were a 14,000-ft block of ice in the Arctic in the depths of solar night then we could be seeing similar temperatures there. Even Ojmjakon (2,600 ft) in northeastern Siberia has recorded -71.2 °C, and often gets to -60 °C in mid-winter. Raise that city, which is located in a similar hollow between mountains, a few more thousand feet and subject it to 24 hours of net cooling through a thin and frigid atmosphere and Antarctica won't be so outlandish.

Even as far west as Donegal Airport, at sea-level on the NW coast of Ireland, reported 42 gust 66 knots at 06:18. SPECI EIDL 050616Z AUTO 26042G66KT 6000 +DZ SCT018 BKN024 OVC028 10/07 Q1014=

South Uist Range is 50 gust 65 knots (58 gust 75 mph) at 0600, but with a gust of 77 knots (89 mph) in the last hour. AAXX 05064 03023 17543 /2950 10076 20039 39962 49967 55042 60082 723// 333 20060 3/005 70088 83/20 90710 91177 91065= Lerwick has fallen 15.4 hPa in 3 hours.

Jesus Smithy you're tough going. Convection will be very shallow due to a large mid-level inversion and surface pressure building, so although you may have your -8 C T850s at a push, that is no guarantee of precipitation.

The eye passed Port Blair earlier, with 41-knot southwesterly winds, gusting to 70 knots. The 3 am synop is interesting, reporting tornadoes/whirlwinds (unless it's a mistake - it also reports sudden drops in relative humidity (999-groups), which looks unlikely, given the constant temp/dewpoint readings). AAXX 25034 43333 21493 82541 10246 20246 49971 76398 8672/ 333 20222 56599 59139 6213/ 84712 85617 88458 91025 91954 99957 91070 91941 99957= The 91954 and 91941 groups mean whirlwinds of "moderate intensity to the south" and "slight intensity to the northeast", respectively. Maybe there were?

148 mm have fallen in the last 24 hours at Port Blair. Pressure now 999.8 hPa, wind just 14 knots. http://www.ogimet.com/cgi-bin/gsynres?ind=43333〈=en&decoded=yes&ndays=2&ano=2013&mes=11&day=24&hora=21

-5.2 C at Gurteen this morning, with -10 C on the grass. 100 m visibility in freezing fog. AAXX 2206103966 17901 /1201 11050 21057 30139 40238 53005 60002 73431 333 21052 3/110=

"...over the Arabian Sea..."?! I think they mean the Bay of Bengal!

Yes, mm, not m. The NAE also shows it developing a warm core before becoming frontal as it moved eastwards. http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&CONT=itit&MODELL=nae&MODELLTYP=1&VAR=pstp&WMO=&ZOOM=0&RES=0&PERIOD=&PANEL=0&ARCHIV=0&BASE=201311190600%26HH%3D0 And what is the threshold minimum pressure before a low can be called a "cyclone"? Any closed cyclonic circulation is called a cyclone, it's just that the type needs to be specified (tropical, extra-tropical, etc.). http://glossary.ametsoc.org/wiki/Cyclone

Cyclone Cleopatra, as it was named, was porobably a hybrid tropical-like cyclone that developed a warm core, according to this analysis. http://www.meteogiornale.it/notizia/30115-1-alluvione-in-sardegna-ciclone-evoluto-in-tlc-alcuni-indizi A station in Villasor recorded a max rain-rate of 208 m/h. Several official stations in the east (Dorgali Filitta, Oliena and Villanova Strisaili) recorded totals near 400 m in a few hours Monday evening. http://www.sar.sardegna.it/servizi/dati/datistazioni7gg.asp?stazione=Dorgali%20Filitta

These idiots who write this stuff are nothing short of criminals and should be locked up. Remember, an anagram of tabloids is "Is Bad Lot".

Tacloban Airport NOTAM RPLL-C0828/13 A) RPVA D Z ROMUALDEZ B ) 2013 NOV 10 13:48 C) 2013 NOV 30 09:30 EST E) TACLOBAN AP OPEN TO MIL AND HUMANITARIAN FLTS, AND LTD COMMERCIAL OPS FM SUNRISE TO SUNSET. RMK: ONLY C-130, TURBOPROP (ATR, Q4, Q3, ETC) AND AND BLW ACFT CAT.

Its windfield has completely collapsed and it's just a rain-maker now, with 343 mm having fallen in 24 hours at Beihai, along the Chinese coast. http://www.ogimet.com/cgi-bin/gsynop?lang=en&esc=2&nav=Yes&lat=20N&lon=105E&proy=orto&base=bluem&ano=2013&mes=11&day=11&hora=6&min=0&vr4=R4

Yes, there is. SSE 39 gust 64 knots. Pressure shooting back up by 11.5 hPa in 3 hours. AAXX 10211 48839 21496 82020 10240 20237 39909 49973 52115 76262 8672/ 222// 00249 2//// 333 59124 60047 86894 88499 91133 91520 96162= Just making landfall in NE Vietnam.http://www.ogimet.com/cgi-bin/gsynop?lang=en&esc=2&nav=Yes&lat=20N&lon=105E&proy=orto&base=bluem&ano=2013&mes=11&day=10&hora=21&min=0&vwi=Wi

Scenes resembling the tsunamis of 2004 and 2012. Nothing will stand in the way of nature.

Yeah thanks Steve, no idea what I was at posting that link!

Haiyan's centre is passing very close to, or just over, Bach Long Vi, a tiny isolated island between Hainan and northeastern Vietnam, in the next couple of hours. http://www.ogimet.com/cgi-bin/gsynres?lang=en&ind=59023&ano=2013&mes=11&day=10&hora=15&min=0&ndays=30 There are 3-hourly manned synop reports from the island's station (8 m amsl). The last one at 1500Z showed 41 gust 70 kt winds, pressure dropping 11.5 hPa in 3 hours to 983.7 hPa. 69 mm of rain in 3 hours. The 1800Z report will be interesting. AAXX 10151 48839 21495 80521 10242 20240 39774 49837 57115 76566 8672/ 222// 00240 2//// 333 59292 60697 86894 88499 91136 91536 96165=

Severe turbulence, by definition, could be hazardous to modern aircraft. It is defined as turbulence which causes at least temporary loss of control of the aircraft. Aircraft that are involved in such an encounter must be checked for damage after landing. There are many turbulence incidents reported monthly but in the majority of these it is passengers seated without seatbelts or crew who are injured. Nobody should be seated without their seatbelt fastened, but how many people actually listen to the preflight safety briefing? Too busy reading the Kindle to pay heed. http://avherald.com/ There are good turbulence forecasts provided to pilots in the Sigwx charts fourtimes a day. Both CAT and Cb areas and levels are hightlighted. http://brunnur.vedur.is/flugkort/PGDE14_EGRR_1200.PNG

It puts Sky News to shame. To think that they had 24-hour continuous coverage of the St. Jude gale in England and this devastation only got a mention after the event. At least CNN were on the ball with it, even if it's "only" 1,200 dead so far in the Phillipines. At least it wasn't a western country where lives are worth more... Anyway, rant over, now some weather. Yaxian, on the southern tip of Hainan Island, is reporting 37 gust 59 knots at 2100Z as Haiyan to the southeast starts to make its presence felt. It will be a good station to keep an eye on as the storm gets closer, though it only reports every 3 hours. Sanhu Dao, well to the southeast, is reporting 35 gust 57 knots and pressure 990 hPa. http://www.ogimet.com/cgi-bin/gsynop?lang=en&esc=2&nav=Yes&lat=15N&lon=110E&proy=orto&base=bluem&ano=2013&mes=11&day=9&hora=21&min=0&vwi=Wi Sanya Airport (ZJSY) is another one to watch http://www.ogimet.com/cgi-bin/gmetar?lang=en&esc=4&nav=Yes&lat=15N&lon=105E&proy=orto&base=bluem&ano=2013&mes=11&day=09&hora=22&min=00&vwi=Wi

The much slower forward speed of this weekend's system will mean lower speeds on its southern flank. An interesting setup though.