435:, and 2019, were the result of entrenched highs that became detached from the jet stream for a prolonged period of time and allowed warm, dry air to build in place. In many cases such as the 1999 US drought, the heat wave was preceded by prior months of below normal precipitation that prevented temperatures from cooling. The 2003 heat wave in Europe occurred, conversely, during a year that North America experienced markedly below normal temperatures and higher than normal precipitation, especially during the spring months. The high amount of rain in North America increased the energy levels in the polar jet, driving it far to the north in Europe and resulting in a prolonged, static high pressure ridge that drove up hot air from the Sahara Desert into Europe.
447:
97:
162:
293:
31:
300:
Blocking of atmospheric systems near the surface of the Earth occurs when a well-established poleward high pressure system lies near or within the path of the advancing storm system. The thicker the cold air mass is, the more effectively it can block an invading milder air mass. The depth of the
319:
In the middle latitudes of the
Northern Hemisphere, areas on the eastern side of blocking anticyclones or under the influence of anomalous flows from colder continental interiors related to blocks experience severe winters, a phenomenon which has been known since the discovery of the
233:
in the last week of
September 2022 drifted northward and its remnants became detached from the jet stream, resulting in a stationary low pressure system spinning off the Northeastern US and bringing several days of precipitation until a front finally moved through on October 6.
419:. Unlike other midlatitude regions of the Northern Hemisphere, however, cold winters in Europe (e.g. 1916/17, 1962/63) are often very mild over Central Asia, which can gain warm air advection from subtropical cyclones pushed to the south under negative NAO conditions.
81:
Oceans. Whilst these events are linked to the occurrence of extreme weather events such as heat waves, particularly the onset and decay of these events is still not well captured in numerical weather forecasts and remains an open area of research.
65:. These blocks can remain in place for several days or even weeks, causing the areas affected by them to have the same kind of weather for an extended period of time (e.g. precipitation for some areas, clear skies for others). In the
124:
lead to a stronger polar vortex during the winter for as long as two years afterwards. The strength and position of the cyclone shapes the flow pattern across the hemisphere of its influence. An index which is used in the
212:
retreating poleward, leaving the then cut-off system behind. Whether or not the system is of high- or low-pressure variety dictates the weather that the block causes. Precisely this situation occurred over the southern
277:
that usually develop further south than normal. They stay virtually unmoving for a lengthy period (i.e. several days to weeks) and thus block the regular easterly motion of weather systems across southern
Australia.
173:
Rex blocks (or dipole blocks) consist of a high situated poleward (north in the
Northern Hemisphere; south in the Southern Hemisphere) of a low. Very often both the high and the low are closed, meaning that the
324:(NAO) in the 1840s. These blocking patterns also have a tendency to produce anomalously mild conditions at very high latitudes, at least in those regions exposed to anomalous flow from the ocean as in
1027:
1057:
396:
104:
Polar cyclones are climatological features which hover near the poles year-round. They are weaker during summer and strongest during winter. When the polar vortex is strong, the
1002:
262:. A blocking high in the southern Tasman Sea directs low pressure systems and troughs towards eastern Australia, whereby providing rainfall on the east coast of Australia.
217:
during late spring and early summer of 2007, when a cut-off-low system hovering over the region brought unusually cool temperatures and an extraordinary amount of rain to
296:
When warm air ahead of an oncoming storm system overrides cool air trapped east of a mountain range, cloudiness and precipitation can occur for prolonged periods of time
229:), and a cut-off-high near the coast of Georgia that caused a drought in the Southeast that same year. Rainy, cooler weather results if the block is a low in the US.
606:
Woollings, Tim; Barriopedro, David; Methven, John; Son, Seok-Woo; Martius, Olivia; Harvey, Ben; Sillmann, Jana; Lupo, Anthony R.; Seneviratne, Sonia (2018-09-01).
1217:
205:
108:
increase in strength. When the polar cyclone is weak, the general flow pattern across mid-latitudes buckles and significant cold outbreaks occur.
1019:
1119:
van Loon, Harry and Rogers, Jeffrey C.; ‘The Seesaw in Winter
Temperatures Between Greenland and Northern Europe: Part I: General Description’;
182:
lines) defining the high–low close to form a circle. Rex blocks are named after meteorologist Daniel F. Rex, who first identified them in 1950.
1049:
242:
If the block is a high, it will usually lead to dry, warm weather as the air beneath it is compressed and warmed, as happened in southeastern
735:
1096:
773:
661:
380:
376:
1138:
999:
301:
cold air mass is normally shallower than the mountain barrier which created the cold air damming, or CAD. Some events across the
885:
535:
834:
1158:
Hirschi, Joël J.-M. and Sinha, Bablu; ‘Negative NAO and cold
Eurasian winters: how exceptional was the winter of 1962/1963?’;
431:. Some unusually intense summers such as 1936 in the United States, 1999, 2002, and 2011, and in Europe summers such as 1976,
1090:
767:
970:
948:
427:
Heat waves in summer are the result of similar blocking patterns, typically involving the placement of the semi-permanent
383:
are almost always associated with high latitude
Atlantic blocking and an equatorward shift of the polar jet stream to
511:
305:
can last for ten days. Pollutants and smoke can remain suspended within the stable air mass of a cold air dam.
861:
348:
259:
255:
149:
contours with which they are associated in the
Northern Hemisphere resemble an Ω, the uppercase Greek letter
480:
344:
17:
321:
906:
Rex, D. F. (1950). "Blocking Action in the Middle
Troposphere and its Effect upon Regional Climate".
868:
226:
1121:
364:
266:
1080:
757:
1236:
109:
1020:"What caused the 'rain bomb'? How the unprecedented Queensland and NSW 2022 floods unfolded"
1135:
915:
810:
695:
619:
570:
485:
247:
201:
142:
50:
1136:
Downstream
Weather Impacts Associated with Atmospheric Blocking over the Northeast Pacific
8:
683:
465:
360:
197:
179:
146:
126:
66:
919:
814:
699:
623:
574:
927:
826:
727:
648:
583:
558:
475:
302:
130:
1192:
1175:
1197:
1160:
1086:
1000:
Widespread rain to fall in all states as two storms form in Australia's east and west
881:
763:
731:
719:
711:
653:
635:
588:
527:
507:
428:
352:
795:
1187:
923:
830:
818:
703:
643:
627:
578:
395:, unusually cold winters like 1899/1900, 1929/30 and 1930/31, 1944/45, 1954/55 and
287:
153:. They typically have a low-high-low pattern, arranged in the west–east direction.
446:
53:
field that are nearly stationary, effectively "blocking" or redirecting migratory
1221:
1142:
1006:
974:
968:
865:
368:
337:
274:
70:
27:
Large-scale patterns in the atmospheric pressure field that are nearly stationary
944:
506:
Glossary of Meteorology, Second Edition; American Meteorological Society, 2000;
452:
400:
372:
356:
208:, it is known as being "cut off". The usual pattern which leads to this is the
631:
1230:
715:
639:
592:
404:
230:
214:
166:
113:
35:
1174:
Mitchell, Dann; Kornhuber, Kai; Huntingford, Chris; Uhe, Peter (July 2019).
1050:"Stalled weather: how stuck air pressure systems drive floods and heatwaves"
607:
1201:
723:
657:
392:
343:
Such cold winters over the contiguous United States and southern Canada as
333:
254:
it can cause torrential rains in eastern Australia, as in the cases of the
175:
91:
822:
460:
416:
191:
46:
707:
270:
251:
209:
105:
986:
Victoria. Department of Crown Lands and Survey (Victoria, Australia);
470:
408:
325:
314:
243:
363:
directing very cold Arctic air with a long trajectory as far as the
96:
557:
Stefanon, Marc; D’Andrea, Fabio; Drobinski, Philippe (2012-03-01).
412:
384:
329:
222:
78:
858:
559:"Heatwave classification over Europe and the Mediterranean region"
755:
388:
121:
117:
74:
54:
367:, as did the Western cold waves of 1889/90 and January 1950. In
1173:
605:
355:
and 1978/79, 1993/94, and 2017/18 resulted from blocks in the
218:
161:
150:
100:
Polar vortex and weather impacts due to stratospheric warming
30:
432:
375:, cold winters such as 1683/84, 1739/40, 1794/95, 1829/30,
292:
759:
Polar lows: mesoscale weather systems in the polar regions
1082:
Mountain Meteorology : Fundamentals and Applications
556:
204:-pressure system becomes stuck in place due to a lack of
939:
937:
407:
westwards to push the very cold air from the Siberian "
112:
which occlude and migrate into higher latitudes create
1176:"The day the 2003 European heatwave record was broken"
859:
Arctic Oscillation (AO) time series, 1899 – June 2002.
934:
442:
265:
In Australia, blocking highs generally occur in the
250:. However, when a blocking high is situated in the
69:, extended blocking occurs most frequently in the
1078:
1228:
1134:Carrera, M.L.; Higgins, R.W. and Kousky, V.E.; ‘
165:An example of a Rex block off the West coast of
608:"Blocking and its Response to Climate Change"
85:
793:
762:. Cambridge University Press. p. 174.
1009:by Ben Deacon from ABC News. 20 March 2021
756:Erik A. Rasmussen and John Turner (2003).
688:Annals of the New York Academy of Sciences
502:
500:
34:An example of an omega block over western
1191:
1115:
1113:
647:
582:
308:
185:
1085:. Oxford University Press. p. 166.
291:
246:in 2006 and 1967 with resultant extreme
160:
95:
29:
684:"Atmospheric blocking events: a review"
522:
520:
497:
14:
1229:
1110:
399:are associated with blocking near the
379:, 1916/17, 1941/42, February 1947 and
141:Omega blocks are so-named because the
1030:from the original on 28 February 2022
681:
538:from the original on 6 December 2017
517:
905:
281:
24:
928:10.1111/j.2153-3490.1950.tb00339.x
874:
682:Lupo, Anthony R. (November 2021).
25:
1248:
1211:
1060:from the original on 3 March 2022
796:"Volcanic Eruptions and Climate"
445:
237:
49:are large-scale patterns in the
1167:
1152:
1128:
1099:from the original on 2023-09-16
1072:
1042:
1012:
993:
980:
962:
951:from the original on 2017-10-22
899:
888:from the original on 2017-10-22
840:from the original on 2016-03-04
776:from the original on 2023-09-16
738:from the original on 2023-09-16
664:from the original on 2023-09-16
136:
988:The Victorian Drought, 1967/68
851:
787:
749:
675:
612:Current Climate Change Reports
599:
563:Environmental Research Letters
550:
129:to gauge its magnitude is the
13:
1:
1193:10.1016/S2542-5196(19)30106-8
882:"Brief page about Rex blocks"
491:
422:
156:
584:10.1088/1748-9326/7/1/014023
481:Ridiculously Resilient Ridge
7:
1180:The Lancet Planetary Health
438:
10:
1253:
1218:What Is a Greenland Block?
1149:, 17 (2004), pp. 4823–4839
1079:C. David Whiteman (2000).
871:. Retrieved on 2009-03-02.
322:North Atlantic Oscillation
312:
285:
189:
116:within the polar vortex.
89:
86:Impact of the polar vortex
1125:, 106 (1978), pp. 296–310
632:10.1007/s40641-018-0108-z
57:. They are also known as
869:University of Washington
794:Alan Robock (May 2000).
532:theweatherprediction.com
227:June 2007 Texas flooding
433:2003 European heat wave
1122:Monthly Weather Review
945:"Atmospheric Blocking"
857:Todd Mitchell (2004).
411:" outward towards the
359:or to the east of the
309:Midlatitude cold waves
297:
267:Great Australian Bight
186:Cut-off highs and lows
170:
110:Extratropical cyclones
101:
39:
1005:24 March 2021 at the
803:Reviews of Geophysics
313:Further information:
295:
275:high-pressure systems
273:, which are powerful
164:
99:
63:blocking anticyclones
33:
1164:62 (2007); pp. 43–48
1026:. 28 February 2022.
823:10.1029/1998rg000054
486:Trough (meteorology)
196:When an upper-level
51:atmospheric pressure
920:1950Tell....2..275R
815:2000RvGeo..38..191R
700:2021NYASA1504....5L
624:2018CCCR....4..287W
575:2012ERL.....7a4023S
466:Geopotential height
361:Mackenzie Mountains
180:geopotential height
147:geopotential height
127:northern hemisphere
67:Northern Hemisphere
1147:Journal of Climate
1141:2019-08-01 at the
973:2015-09-23 at the
864:2003-12-12 at the
708:10.1111/nyas.14557
476:High-pressure area
303:Intermountain West
298:
171:
131:Arctic oscillation
102:
40:
1092:978-0-19-803044-7
769:978-0-521-62430-5
528:"The Omega Block"
429:subtropical ridge
260:2022 flood events
206:steering currents
120:eruptions in the
73:over the eastern
16:(Redirected from
1244:
1206:
1205:
1195:
1186:(7): e290–e292.
1171:
1165:
1156:
1150:
1132:
1126:
1117:
1108:
1107:
1105:
1104:
1076:
1070:
1069:
1067:
1065:
1056:. 3 March 2022.
1054:The Conversation
1046:
1040:
1039:
1037:
1035:
1016:
1010:
997:
991:
990:; published 1968
984:
978:
966:
960:
959:
957:
956:
941:
932:
931:
903:
897:
896:
894:
893:
878:
872:
855:
849:
848:
846:
845:
839:
800:
791:
785:
784:
782:
781:
753:
747:
746:
744:
743:
679:
673:
672:
670:
669:
651:
603:
597:
596:
586:
554:
548:
547:
545:
543:
524:
515:
504:
455:
450:
449:
288:Cold air damming
282:Cold air damming
21:
1252:
1251:
1247:
1246:
1245:
1243:
1242:
1241:
1227:
1226:
1222:Accuweather.com
1220:– Jim Andrews,
1214:
1209:
1172:
1168:
1157:
1153:
1143:Wayback Machine
1133:
1129:
1118:
1111:
1102:
1100:
1093:
1077:
1073:
1063:
1061:
1048:
1047:
1043:
1033:
1031:
1018:
1017:
1013:
1007:Wayback Machine
998:
994:
985:
981:
975:Wayback Machine
967:
963:
954:
952:
943:
942:
935:
904:
900:
891:
889:
880:
879:
875:
866:Wayback Machine
856:
852:
843:
841:
837:
798:
792:
788:
779:
777:
770:
754:
750:
741:
739:
680:
676:
667:
665:
604:
600:
555:
551:
541:
539:
526:
525:
518:
505:
498:
494:
451:
444:
441:
425:
338:Interior Alaska
317:
311:
290:
284:
240:
194:
188:
169:in January 2007
159:
139:
94:
88:
28:
23:
22:
15:
12:
11:
5:
1250:
1240:
1239:
1225:
1224:
1213:
1212:External links
1210:
1208:
1207:
1166:
1151:
1127:
1109:
1091:
1071:
1041:
1011:
992:
979:
961:
933:
914:(4): 275–301.
898:
873:
850:
786:
768:
748:
674:
618:(3): 287–300.
598:
549:
516:
495:
493:
490:
489:
488:
483:
478:
473:
468:
463:
457:
456:
453:Weather portal
440:
437:
424:
421:
403:extending the
401:Ural Mountains
373:Western Europe
365:American South
357:Gulf of Alaska
310:
307:
286:Main article:
283:
280:
239:
236:
190:Main article:
187:
184:
158:
155:
138:
135:
114:cold-core lows
90:Main article:
87:
84:
59:blocking highs
26:
9:
6:
4:
3:
2:
1249:
1238:
1235:
1234:
1232:
1223:
1219:
1216:
1215:
1203:
1199:
1194:
1189:
1185:
1181:
1177:
1170:
1163:
1162:
1155:
1148:
1144:
1140:
1137:
1131:
1124:
1123:
1116:
1114:
1098:
1094:
1088:
1084:
1083:
1075:
1059:
1055:
1051:
1045:
1029:
1025:
1021:
1015:
1008:
1004:
1001:
996:
989:
983:
976:
972:
969:
965:
950:
946:
940:
938:
929:
925:
921:
917:
913:
909:
902:
887:
883:
877:
870:
867:
863:
860:
854:
836:
832:
828:
824:
820:
816:
812:
808:
804:
797:
790:
775:
771:
765:
761:
760:
752:
737:
733:
729:
725:
721:
717:
713:
709:
705:
701:
697:
693:
689:
685:
678:
663:
659:
655:
650:
645:
641:
637:
633:
629:
625:
621:
617:
613:
609:
602:
594:
590:
585:
580:
576:
572:
569:(1): 014023.
568:
564:
560:
553:
537:
533:
529:
523:
521:
513:
512:1-878220-34-9
509:
503:
501:
496:
487:
484:
482:
479:
477:
474:
472:
469:
467:
464:
462:
459:
458:
454:
448:
443:
436:
434:
430:
420:
418:
414:
410:
406:
405:Siberian High
402:
398:
394:
390:
386:
382:
378:
374:
370:
366:
362:
358:
354:
350:
346:
341:
339:
335:
334:chinook winds
331:
327:
323:
316:
306:
304:
294:
289:
279:
276:
272:
268:
263:
261:
257:
253:
249:
245:
238:Blocking high
235:
232:
231:Hurricane Ian
228:
224:
220:
216:
215:United States
211:
207:
203:
199:
193:
183:
181:
178:(or constant
177:
168:
167:North America
163:
154:
152:
148:
144:
134:
132:
128:
123:
119:
115:
111:
107:
98:
93:
83:
80:
76:
72:
68:
64:
60:
56:
52:
48:
44:
37:
36:North America
32:
19:
1237:Anticyclones
1183:
1179:
1169:
1159:
1154:
1146:
1130:
1120:
1101:. Retrieved
1081:
1074:
1062:. Retrieved
1053:
1044:
1032:. Retrieved
1024:The Guardian
1023:
1014:
995:
987:
982:
964:
953:. Retrieved
911:
907:
901:
890:. Retrieved
876:
853:
842:. Retrieved
806:
802:
789:
778:. Retrieved
758:
751:
740:. Retrieved
691:
687:
677:
666:. Retrieved
615:
611:
601:
566:
562:
552:
540:. Retrieved
531:
426:
417:Caspian Seas
393:Central Asia
342:
318:
299:
264:
241:
195:
172:
140:
137:Omega blocks
103:
92:Polar vortex
62:
58:
42:
41:
694:(1): 5–24.
461:Anticyclone
351:, 1949/50,
192:Cut-off low
47:meteorology
38:in May 2006
18:Omega block
1103:2016-09-27
977:see p. 116
955:2008-02-19
892:2006-01-31
844:2012-02-24
809:(2): 171.
780:2016-09-27
742:2022-04-07
668:2022-04-07
492:References
423:Heat waves
332:, or from
271:Tasman Sea
252:Tasman Sea
210:jet stream
157:Rex blocks
106:Westerlies
732:229931718
716:0077-8923
640:2198-6061
593:1748-9326
471:Heat dome
409:cold pole
387:and even
326:Greenland
315:Cold wave
244:Australia
1231:Category
1202:31296455
1139:Archived
1097:Archived
1058:Archived
1028:Archived
1003:Archived
971:Archived
949:Archived
886:Archived
862:Archived
835:Archived
774:Archived
736:Archived
724:33382135
662:Archived
658:30956938
536:Archived
439:See also
385:Portugal
369:Northern
330:Beringia
269:and the
248:droughts
223:Oklahoma
118:Volcanic
79:Atlantic
55:cyclones
1161:Weather
1064:3 March
1034:3 March
916:Bibcode
831:1299888
811:Bibcode
696:Bibcode
649:6428232
620:Bibcode
571:Bibcode
542:27 July
397:1968/69
391:. Over
389:Morocco
381:1962/63
377:1894/95
353:1977/78
349:1935/36
345:1911/12
176:isobars
143:isobars
122:tropics
75:Pacific
1200:
1089:
908:Tellus
829:
766:
730:
722:
714:
656:
646:
638:
591:
510:
336:as in
71:spring
43:Blocks
838:(PDF)
827:S2CID
799:(PDF)
728:S2CID
225:(see
219:Texas
200:- or
151:omega
1198:PMID
1087:ISBN
1066:2022
1036:2022
764:ISBN
720:PMID
712:ISSN
692:1504
654:PMID
636:ISSN
589:ISSN
544:2019
508:ISBN
415:and
413:Aral
371:and
328:and
258:and
256:2021
221:and
198:high
77:and
1188:doi
1145:’;
924:doi
819:doi
704:doi
644:PMC
628:doi
579:doi
202:low
145:or
61:or
45:in
1233::
1196:.
1182:.
1178:.
1112:^
1095:.
1052:.
1022:.
947:.
936:^
922:.
910:.
884:.
833:.
825:.
817:.
807:38
805:.
801:.
772:.
734:.
726:.
718:.
710:.
702:.
690:.
686:.
660:.
652:.
642:.
634:.
626:.
614:.
610:.
587:.
577:.
565:.
561:.
534:.
530:.
519:^
499:^
347:,
340:.
133:.
1204:.
1190::
1184:3
1106:.
1068:.
1038:.
958:.
930:.
926::
918::
912:2
895:.
847:.
821::
813::
783:.
745:.
706::
698::
671:.
630::
622::
616:4
595:.
581::
573::
567:7
546:.
514:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
