117:(WMO) defined that to be classified as a "squall", the wind must increase at least 8 metres per second (29 km/h; 18 mph) and must attain a top speed of at least 11 metres per second (40 km/h; 25 mph), lasting at least one minute in duration. In Australia, a squall is defined to last for several minutes before the wind returns to the long-term mean value. In either case, a squall is defined to last about half as long as the definition of sustained wind in its respective country. Usually, this sudden violent wind is associated with briefly heavy precipitation as
438:
45:, which lasts for only seconds. They are usually associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to the increase of the sustained winds over that time interval, as there may be higher gusts during a squall event. They usually occur in a region of strong sinking air or cooling in the mid-atmosphere. These force strong localized upward motions at the leading edge of the region of cooling, which then enhances local downward motions just in its wake.
538:
49:
313:
428:
rapid within the lower and mid-levels of a mature thunderstorm, one might believe that low pressure dominates in the mesoscale environment. However, this is not the case. With downdrafts ushering colder air from mid-levels, hitting ground and propagating away in all directions, high pressure is to be
51:
56:
54:
50:
374:
from an angle behind the frontal boundary. The strong winds at the surface are usually a reflection of dry air intruding into the line of storms, which when saturated, falls quickly to ground level due to its much higher density before it spreads out downwind. Significant squall lines with multiple
585:
associated with them may outrun the squall line itself and the synoptic scale area of low pressure may then infill, leading to a weakening of the cold front; essentially, the thunderstorm has exhausted its updrafts, becoming purely a downdraft dominated system. The areas of dissipating squall line
55:
560:
is another kind of mesoscale low-pressure area to the rear of a squall line near the back edge of the stratiform rain area. Due to the subsiding warm air associated with the system's formation, clearing skies are associated with the wake low. Severe weather, in the form of high winds, can be
448:
is an important aspect to measuring the potential of squall line severity and duration. In low to medium shear environments, mature thunderstorms will contribute modest amounts of downdrafts, enough to turn will aid in create a leading edge lifting mechanism – the gust front. In high shear
53:
411:
The main driving force behind squall line creation is attributed to the process of in-filling of multiple thunderstorms and/or a single area of thunderstorms expanding outward within the leading space of an advancing
520:
is frequently seen on the northern and southernmost reaches of squall line thunderstorms (via satellite imagery). This is where the northern and southern ends curl backwards towards the middle portions of the
52:
265:
and are characterized by heavy rains driven by blustery winds. Local fishermen at sea are often on the lookout for signs of impending squalls on the open water and rush to shore at its early signs.
334:. It is classified as a multi-cell cluster, meaning a thunderstorm complex comprising many individual updrafts. They are also called multi-cell lines. Squalls are sometimes associated with
449:
environments created by opposing low level jet winds and synoptic winds, updrafts and consequential downdrafts can be much more intense (common in supercell mesocyclones). The cold air
601:
From here, a general thinning of a squall line will occur: with winds decaying over time, outflow boundaries weakening updrafts substantially and clouds losing their thickness.
561:
generated by the wake low when the pressure difference between the mesohigh preceding it and the wake low is intense enough. When the squall line is in the process of decay,
895:
253:
is a term used offshore South Africa for a squall forming in fair weather. It is named for the appearance of the small isolated cloud marking the top of the squall.
624:
normally have squalls coincident with spiral bands of greater curvature than many mid-latitude systems due to their smaller size. These squalls can harbor
565:
can be generated near the wake low. Once new thunderstorm activity along the squall line concludes, the wake low associated with it weakens in tandem.
549:
The poleward end of the squall line is commonly referred to as the cyclonic end, with the equatorward side rotating anticyclonically. Because of the
613:'s gust front. From the time these low cloud features appear in the sky, one can expect a sudden increase in the wind in less than 15 minutes.
1014:
974:
994:
232:
is a short but furious rainstorm with strong winds, often small in area and moving at high speed, especially as a maritime term. A strong
783:
485:
As thunderstorms fill into a distinct line, strong leading-edge updrafts – occasionally visible to a ground observer in the form of a
829:
184:
is characterized by strong increases of the wind forced through sharp mountain valleys on the
Pacific Ocean side of the isthmus.
946:
899:
573:
As supercells and multi-cell thunderstorms dissipate due to a weak shear force or poor lifting mechanisms, (e.g. considerable
496:) is another sign of a squall line. In the winter, squall lines can occur albeit less frequently – bringing heavy snow and/or
138:, these are characterized as strong downsloped winds that move across the pampas, eventually making it to the Atlantic Ocean.
806:
587:
391:, including simplistic isolated thunderstorms unrelated to advancing cold fronts, to the more complex daytime/nocturnal
474:, condensing water and building a dark, ominous cloud to one with a noticeable overshooting top and anvil (thanks to
114:
721:
553:, the poleward end may evolve further, creating a "comma shaped" mesolow, or may continue in a squall-like pattern.
1077:
1039:
1094:
1063:
396:
392:
347:
466:
The leading area of a squall line is composed primarily of multiple updrafts, or singular regions of an
475:
370:. Squall lines require significant low-level warmth and humidity, a nearby frontal zone, and vertical
1064:"Wake Low Severe Wind Events in the Mississippi River Valley: A Case Study of Two Contrasting Events"
453:
leaves the trailing area of the squall line to the mid-level jet, which aids in downdraft processes.
172:
and a dramatic temperature drop, thus ultimately replacing and relieving the prior hot conditions.
991:
609:
Shelf clouds and roll clouds are usually seen above the leading edge of a squall, also known as a
594:, insufficient wind shear, or poor synoptic dynamics (e.g. an upper-level low filling) leading to
1068:
1011:
971:
20:
113:
The term "squall" is used to refer to a sudden wind-speed increase lasting minutes. In 1962 the
796:
450:
388:
958:
1081:
429:
found widely at surface levels, usually indicative of strong (potentially damaging) winds.
157:
8:
1085:
342:, but they can also occur independently. Most commonly, independent squalls occur along
647:
can be spawned by an intrusion of cold air aloft over a relatively warm surface layer.
301:
1110:
833:
441:
A summer squall line in
Southern Ontario, producing lightning and distant heavy rains.
802:
771:
225:
197:
1089:
872:
648:
621:
148:
437:
1018:
998:
978:
238:
153:
1129:
867:
550:
492:
Beyond the strong winds because of updraft/downdraft behavior, heavy rain (and
424:
Pressure perturbations within an extent of a thunderstorm are noteworthy. With
281:
233:
169:
1139:
1134:
1123:
513:
343:
670:
644:
610:
359:
331:
947:
Guide To
Singapore's Weather, archived by archive.org on November 1, 2013.
725:
665:
625:
595:
578:
522:
501:
486:
471:
400:
326:
317:
293:
209:
118:
1031:
660:
633:
582:
562:
479:
445:
413:
371:
367:
236:
outflow occurring in fjords and inlets is referred to by mariners as a
165:
61:
38:
312:
152:, which is an abrupt southerly wind change in the southern regions of
750:
695:
629:
526:
355:
335:
285:
161:
86:
78:
42:
537:
591:
557:
542:
517:
425:
289:
274:
934:
919:
636:
which exists in the vicinity of a tropical cyclone's outer bands.
525:, making a "bow" shape. Bow echoes are frequently featured within
512:
Following the initial passage of a squall line, light to moderate
64:(strong downdraft); after this video was shot, it started raining.
1109:
National
Weather Service Forecast Office, Springfield, Missouri.
574:
497:
467:
376:
363:
339:
297:
77:
By one version, the word appears to be Nordic in origin, but its
146:
In southeastern
Australia, the colloquial name for a squall is
1010:
Robert H. Johns and Jeffry S. Evans. Storm
Prediction Center.
60:
A video recorded nearing the end of a squall, caused by a dry
489:– may appear as an ominous sign of potential severe weather.
81:
is considered obscure. It probably has its roots in the word
27:
876:. National Library of Australia. 23 December 1901. p. 2
470:, rising from ground level to the highest extensions of the
164:, which approaches from the southeast, mainly on a hot day,
1095:
10.1175/1520-0434(1999)014<0581:WLSWEI>2.0.CO;2
493:
351:
196:
is a squall emanating from tropical thunderstorms near the
857:. Oxford University Press. 10Rev Ed edition (7 April 2005)
273:"Barat" is a term for a northwest squall in Manado Bay in
320:
such as this one can be a sign that a squall is imminent
478:
winds). Because of the chaotic nature of updrafts and
304:. Gusts can reach up to 28 m/s (100 km/h).
219:
73:
There are different versions of the word's origins:
772:squall: Definition and Much More from Answers.com
261:In most parts of the country, squalls are called
1121:
500:and lightning – usually over inland lakes (i.e.
1061:
801:. Oxford University Press. 2011. p. 1400.
358:, dangerous straight line winds, and possibly
256:
929:
927:
96:By another version, it is an alteration of
1093:
924:
784:Georoots News V.1#5: Changes in the Wind.
419:
382:
939:
536:
482:, pressure perturbations are important.
436:
311:
108:
47:
1122:
1055:
972:EUMeTrain: Case Study on Squall Line.
745:
743:
690:
688:
686:
651:can be in the form of a snow squall.
616:
586:thunderstorms may be regions of low
724:The Weather Channel. Archived from
604:
16:Short, sharp increase in wind speed
13:
753:. Australian Bureau of Meteorology
740:
683:
268:
175:
14:
1151:
798:Concise Oxford English Dictionary
702:. American Meteorological Society
639:
307:
220:Pacific Northwest (North America)
124:
115:World Meteorological Organization
41:lasting minutes, as opposed to a
1062:David M. Gaffin (October 1999).
632:due to the significant vertical
577:or lack of daytime heating) the
516:precipitation is also common. A
1103:
1040:American Meteorological Society
1024:
1004:
984:
964:
951:
913:
888:
827:
245:
37:is a sudden, sharp increase in
1111:Storm Spotter Online Training.
933:Golden Gate Weather Services.
860:
848:
821:
789:
776:
765:
714:
568:
203:
1:
676:
507:
432:
296:that form over the island of
945:National Environment Agency
456:
406:
397:mesoscale convective complex
180:Offshore Central America, a
141:
129:
68:
7:
992:Meteorology Online: Squall.
654:
461:
393:mesoscale convective system
387:There are several forms of
10:
1156:
832:. Eumetcal. Archived from
532:
257:Philippines (West Pacific)
25:
18:
855:Oxford English Dictionary
300:and move east across the
1113:Retrieved on 2006-11-19.
1021:Retrieved on 2006-11-19.
1001:Retrieved on 2006-11-19.
981:Retrieved on 2006-11-19.
961:Retrieved on 2006-11-19.
898:. WGN-TV. Archived from
786:Retrieved on 2006-12-30.
375:bow echoes are known as
346:, and may contain heavy
330:is an organized line of
26:Not to be confused with
1069:Weather and Forecasting
1036:Glossary of Meteorology
216:is a name for a squall
187:
89:word meaning literally
21:Squall (disambiguation)
959:What is a Squall Line?
957:Weatherquestions.com.
722:"Weather Glossary: S."
546:
442:
420:Pressure perturbations
383:Squall line life cycle
321:
65:
540:
440:
389:mesoscale meteorology
315:
109:Character of the wind
59:
284:" is a term used in
19:For other uses, see
1086:1999WtFor..14..581G
896:"Weather Words – B"
529:mesoscale systems.
1017:2010-05-27 at the
997:2007-02-05 at the
977:2006-10-19 at the
868:"SOUTHERLY BUSTER"
547:
443:
322:
302:Straits of Malacca
66:
970:Wilfried Jacobs.
808:978-0-19-960108-0
728:on August 1, 2008
649:Lake-effect snows
622:Tropical cyclones
617:Tropical cyclones
251:Bull's Eye Squall
226:Pacific Northwest
134:Known locally as
57:
1147:
1114:
1107:
1101:
1099:
1097:
1059:
1053:
1051:
1049:
1047:
1028:
1022:
1008:
1002:
988:
982:
968:
962:
955:
949:
943:
937:
931:
922:
917:
911:
910:
908:
907:
892:
886:
885:
883:
881:
873:Wellington Times
864:
858:
852:
846:
845:
843:
841:
836:on March 3, 2016
825:
819:
818:
816:
815:
793:
787:
780:
774:
769:
763:
762:
760:
758:
747:
738:
737:
735:
733:
718:
712:
711:
709:
707:
692:
605:Signs in the sky
166:bringing in cool
149:southerly buster
58:
1155:
1154:
1150:
1149:
1148:
1146:
1145:
1144:
1120:
1119:
1118:
1117:
1108:
1104:
1060:
1056:
1045:
1043:
1030:
1029:
1025:
1019:Wayback Machine
1009:
1005:
999:Wayback Machine
989:
985:
979:Wayback Machine
969:
965:
956:
952:
944:
940:
935:Names of Winds.
932:
925:
918:
914:
905:
903:
894:
893:
889:
879:
877:
866:
865:
861:
853:
849:
839:
837:
826:
822:
813:
811:
809:
795:
794:
790:
782:Georoots News.
781:
777:
770:
766:
756:
754:
751:"Weather Words"
749:
748:
741:
731:
729:
720:
719:
715:
705:
703:
694:
693:
684:
679:
657:
642:
619:
607:
571:
535:
510:
464:
459:
435:
422:
409:
403:thunderstorms.
385:
310:
288:and Peninsular
271:
269:South-East Asia
259:
248:
222:
206:
190:
178:
176:Central America
154:New South Wales
144:
132:
127:
111:
71:
48:
31:
24:
17:
12:
11:
5:
1153:
1143:
1142:
1137:
1132:
1116:
1115:
1102:
1054:
1023:
1012:Derecho Facts.
1003:
983:
963:
950:
938:
923:
912:
887:
859:
847:
820:
807:
788:
775:
764:
739:
713:
681:
680:
678:
675:
674:
673:
668:
663:
656:
653:
641:
640:Winter weather
638:
618:
615:
606:
603:
570:
567:
551:coriolis force
534:
531:
509:
506:
476:synoptic scale
463:
460:
458:
455:
434:
431:
421:
418:
408:
405:
384:
381:
309:
308:Severe weather
306:
282:Sumatra squall
270:
267:
258:
255:
247:
244:
221:
218:
205:
202:
189:
186:
177:
174:
170:severe weather
143:
140:
131:
128:
126:
125:Regional terms
123:
110:
107:
106:
105:
100:influenced by
94:
70:
67:
15:
9:
6:
4:
3:
2:
1152:
1141:
1138:
1136:
1133:
1131:
1128:
1127:
1125:
1112:
1106:
1096:
1091:
1087:
1083:
1079:
1075:
1071:
1070:
1065:
1058:
1041:
1037:
1033:
1027:
1020:
1016:
1013:
1007:
1000:
996:
993:
987:
980:
976:
973:
967:
960:
954:
948:
942:
936:
930:
928:
921:
916:
902:on 2007-03-18
901:
897:
891:
875:
874:
869:
863:
856:
851:
835:
831:
824:
810:
804:
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799:
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785:
779:
773:
768:
752:
746:
744:
727:
723:
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697:
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689:
687:
682:
672:
669:
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664:
662:
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637:
635:
631:
627:
623:
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612:
602:
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584:
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483:
481:
477:
473:
469:
454:
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447:
439:
430:
427:
417:
415:
404:
402:
398:
394:
390:
380:
378:
373:
369:
365:
361:
360:funnel clouds
357:
353:
349:
348:precipitation
345:
341:
337:
333:
332:thunderstorms
329:
328:
319:
314:
305:
303:
299:
295:
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287:
283:
278:
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266:
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217:
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139:
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99:
95:
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76:
75:
74:
63:
46:
44:
40:
36:
29:
22:
1105:
1073:
1067:
1057:
1044:. Retrieved
1035:
1026:
1006:
990:Thinkquest.
986:
966:
953:
941:
915:
904:. Retrieved
900:the original
890:
878:. Retrieved
871:
862:
854:
850:
840:November 15,
838:. Retrieved
834:the original
823:
812:. Retrieved
797:
791:
778:
767:
757:November 15,
755:. Retrieved
732:November 15,
730:. Retrieved
726:the original
716:
706:November 15,
704:. Retrieved
699:
671:White squall
645:Snow squalls
643:
620:
611:thunderstorm
608:
600:
572:
555:
548:
545:is a mesolow
511:
491:
484:
465:
444:
423:
410:
386:
325:
323:
294:squall lines
279:
272:
262:
260:
250:
249:
246:South Africa
237:
229:
223:
213:
207:
193:
191:
182:gully squall
181:
179:
147:
145:
135:
133:
112:
101:
97:
90:
82:
72:
34:
32:
1080:: 581–603.
666:Squall line
626:waterspouts
596:frontolysis
579:squall line
569:Dissipation
563:heat bursts
523:squall line
502:Great Lakes
487:shelf cloud
472:troposphere
401:squall line
368:waterspouts
354:, frequent
344:front lines
327:squall line
318:shelf cloud
210:East Indies
204:East Indies
200:of Bayamo.
119:squall line
1124:Categories
1032:"Wake Low"
920:Wind Names
906:2006-11-19
814:2014-12-30
677:References
661:Rogue wave
634:wind shear
583:gust front
514:stratiform
508:Bow echoes
480:downdrafts
446:Wind shear
433:Wind shear
414:cold front
399:(MCC), to
395:(MCS) and
372:wind shear
336:hurricanes
168:, usually
62:microburst
39:wind speed
1046:March 21,
630:tornadoes
527:supercell
504:region).
457:Evolution
407:Formation
364:tornadoes
356:lightning
338:or other
286:Singapore
234:Katabatic
162:Australia
142:Australia
130:Argentina
91:to squeal
87:Old Norse
79:etymology
69:Etymology
43:wind gust
1015:Archived
995:Archived
975:Archived
880:27 March
830:"Squall"
700:Glossary
696:"Squall"
655:See also
592:humidity
558:wake low
543:wake low
518:bow echo
462:Updrafts
426:buoyancy
377:derechos
340:cyclones
290:Malaysia
275:Sulawesi
239:squamish
158:Victoria
136:pamperos
1082:Bibcode
575:terrain
533:Mesolow
498:thunder
468:updraft
451:outflow
298:Sumatra
263:subasko
224:In the
208:In the
1076:(10).
1042:. 2009
805:
590:, low
230:squall
194:bayamo
98:squeal
83:skvala
35:squall
1130:Storm
828:WMO.
214:brubu
198:Bight
28:squaw
1140:Rain
1135:Wind
1048:2018
882:2015
842:2018
803:ISBN
759:2018
734:2018
708:2018
628:and
588:CAPE
494:hail
366:and
352:hail
292:for
228:, a
188:Cuba
156:and
102:bawl
1090:doi
1078:AMS
581:or
85:an
1126::
1088:.
1074:14
1072:.
1066:.
1038:.
1034:.
926:^
870:.
742:^
698:.
685:^
598:.
556:A
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416:.
379:.
362:,
350:,
324:A
316:A
277:.
242:.
212:,
192:A
160:,
121:.
33:A
1100:.
1098:.
1092::
1084::
1052:.
1050:.
909:.
884:.
844:.
817:.
761:.
736:.
710:.
280:"
104:.
93:.
30:.
23:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
