Jul 17, 2013

Anatomy of a Heat Wave

Today will be the 4th consecutive day of 90°+ heat for Albany; we'll likely hit 90 or better on Thursday and Friday of this week, too. This is the longest hot spell for Albany since July 20-23, 2011; The last 5 day heat wave for Albany in 2011 (from the 5th through 9th) and the last 6 day heat wave was Aug 11th-16th, 2002.

Albany is currently in the midst of its 171st heat wave going back to 1820 when temperature records first started to be kept for the city (daily temperature & precipitation records started in 1874).

Remember a heat wave for us is defined as a stretch of 3 or more days in a row with an afternoon high temperature of 90° or higher.

Here is a breakdown of Heat Waves past for Albany
  • The longest heat wave EVER was 10 days spanning from Aug 27th through Sept 5th, 1953
  • This heat wave featured 2 days with an afternoon high of 100° on Set. 2nd and 3rd. (BTW- this was the last time Albany hit the Century mark).
  • The longest heat wave EVER was 10 days spanning from Aug 27th through Sept 5th, 1953
  • 10 and 9 day heat waves have occurred once each
  • 8 and 7 day heat waves have happened 3 times each
  • A 6 day heat waves have happened 10 times
  • A 5 day heat wave has happened 5 times in the past
  • A 4 day heat wave has occurred 32 times
  • A heat wave of 3 days has occurred 102 times in the past
Long duration heat waves have similar weather patterns. Of the 10 past, 6 day long heat waves for Albany I have randomly chosen 3 of  them and compositeted the surface map for them
Composite surface map for 6 day heat wave 6/29-7/4, 1887
Composite surface map for 6 day heat wave July 7-12, 1944
Composite surface map for 6 day heat wave July 24-29,1963

The dark contoured areas indicate regions of lower pressure. All 3 composite maps indiacte this thermal or heat induced low across the Southwest States and Intermountain West. The brighter shaded areas off both the Pacific and East Coast of the U.S. are the subtropical HIGH pressure areas. All these maps show the Pacific subtropical high to be very strong and situated to the north of its normal position. The Atlantic subtropical  (Bermuda) high is close to its normal position but features and "extension" to the northwest, that is towards the Ohio Valley and Great Lakes region. This northwest extension of the high allow for a westerly wind flow. Sinking air  is associated with a high pressure area. Sinking allows for the air to heat up, the addition of the westerly flow around the "extension" of the Bermuda high allows for additional localized warming of the air to occur across the valleys of the Northeast due to additional compression. Keep in mind when air sinks it both compresses and warms .

Any relief on the way?

Probably over the weekend a cold front will press slowly southeastward across the Northeast States. Once the front clears the area by later Sunday, less humid and cooler (more seasonable) weather will follow. This relief may come with a price - the cold front may cause strong even severe weather for the Northeast U.S. during the weekend.