Two Flavors of Record Heat: Deadhorse and Houston

If you glance at a temperature map for North America, as shown below, you might get the impression that we’re in the midst of a fairly typical midsummer week. The north central United States and south central Canada are basking in relative comfort, thanks to a strong upper-level low and an accompanying surface high moving across the northern tier of U.S. states. Readings on Thursday morning dipped into the 50s and 60s Fahrenheit across the Northern Plains. This air will be sliding eastward over the next several days, bringing a refreshing “mild-down” across the Midwest and Northeast. What’s noteworthy right now isn’t at the core of the continent: it’s along the fringes, where some exceptional heat has been produced in recent days.


Figure 1. Temperature anomalies (departures from normal) for Thursday, July 15, 2016, as extrapolated from the 00Z Thursday GFS model output. Image credit: Climate Reanalyzer/University of Maine.


Big heat in northernmost Alaska
A pulse of warm air invaded the North Slope of northern Alaska on Wednesday, bringing some of the warmest air ever recorded there. Even with the 24-hour sunlight it receives during most of July, the North Slope typically experiences highs only in the 50s and lows in the 30s. Much warmer air can filter into the region on occasion, though, typically as a mild air mass sweeps in aloft and then warms further as it descends (the same process that can produce very mild winter conditions along the east slopes of the Rockies via “chinook” winds). On Wednesday, the tiny town of Deadhorse, AK--located about 200 air miles southeast of Barrow, and just 10 miles from the Arctic Ocean--rocketed to a high of 85°F, which is an all-time high for the Deadhorse/Prudhoe Bay area. Records there only go back to 1968, but climatologist Brian Brettschneider adds that the Deadhorse reading was the highest ever reported at any location within 50 miles of Alaska’s Arctic coast. The COOP station in Kuparuk, a few miles west of Deadhorse, also reported 85°F, according to Brettschneider. Meanwhile, Barrow topped out at 66°F on Wednesday, well short of the daily record of 79°F—which also happens to be its all-time record high, set in 1993. Update: On Thursday, July 14, Kuparuk topped its all-time record set just the day before, soaring to 86°F.


Figure 2. Temperatures at 4 PM AKDT Wednesday, July 13, 2016, along the Arctic Ocean coast of northernmost Alaska. Image credit: Brett Brettschneider.

Hot nights in Houston
The eye-opener this month in southeast Texas isn’t that it got up into the 80s—it’s that the temperature has had trouble getting below that range. Last week, on July 5, Houston’s Bush Intercontinental Airport tied its all-time warm minimum with a steamy low of just 83°F. This came midway through a five-day stretch of lows at or above 80°F, all of them setting daily records. Weather records at the airport began only in 1969, but the only higher daily minimum in the city’s official record is the 84°F low notched more than a century ago, on July 29, 1895. For this month through Wednesday, July 13, Houston has scored a remarkable nine days with low temperatures at or above 80°F. The most such lows in a single month is 14, in August 1964, so the city has a reasonable shot at breaking that record, as noted by Eric Berger at Space City Weather. Houston’s average temperature for the month through Wednesday (counting both highs and lows) is a sweltering 88.3°F, which is running almost a degree higher than the warmest July on record (87.5°F, set in 1980).

Further west, extreme heat has also been plaguing the High Plains of eastern New Mexico and west Texas for days on end. The town of San Jon, NM, set an all-time record high of 111°F on Wednesday, beating the previous record of 110°F set on June 24, 1990 (records in San Jon go back to 1907). Portales, NM, beat its July record and tied its all-time record high of 109°F from June 25, 2011 (records in Portales go back to 1905). In Lubbock, TX, the average high temperature this month has been a blazing 100.3°F, more than 7 degrees above average. On July 7, Lubbock tied its all-time monthly record of 109°F.

Torrid conditions for the heartland next week
After being shunted to the far sides of the continent, record or near-record heat will invade the center of North America next week, perhaps for an extended period. Long-range computer models continue to insist that a very strong and large ridge of high pressure will develop next week, encompassing most of the contiguous U.S. by the weekend of July 23-24. Temperatures will soar well into the 90s across most of the central U.S., with large areas above 100°F possible by late next week, especially over the Great Plains. Some runs of the GFS and ECMWF models have predicted that the height of the 500-mb pressure surface (roughly the vertical midpoint of the atmosphere) will exceed 600 decameters (6 km, or about 3.7 miles) near the center of the ridge. This would be a noteworthy event, typically seen only during the most intense U.S. heat waves. Because warm air expands, a deep layer of warm air at low levels pushes the 500-mb height upward.


Figure 3. Temperature anomalies (departures from average) in degrees C, projected by the GFS model run from 06Z Thursday, July 14, 2016, for 18Z (2:00 pm EDT) Thursday, July 21, 2016. For readings in degrees Fahrenheit, multiply the Celsius readings shown by 1.8. Image credit: tropicaltidbits.com.

Seemingly endless parade of storms continues in the Eastern Pacific
The Eastern Pacific is in the midst of an extraordinary period of July activity, thanks to favorable genesis conditions created by the presence of the Madden-Julian Oscillation (MJO), which has created rising air and low pressure over the region. Beginning on July 2, Tropical Storm Agatha formed, and since then, three hurricanes have joined the parade: Category 4 Hurricane Blas (now dissipated), Category 2 Hurricane Celia (now a tropical storm), and Category 1 Hurricane Darby (predicted to stay below Category 2 strength through the weekend, then weaken.)


Figure 4. VIIRS visible satellite image of ex-Hurricane Blas, Hurricane Celia, Tropical Storm Darby, and Invest 98E taken on Wednesday afternoon, July 13, 2016. Image credit: NASA.

Estelle on the way--and perhaps Frank
Tropical Storm Estelle is also likely on the way--both the European and GFS models indicate that an area of disturbed weather several hundred miles southwest of Acapulco, Mexico (Invest 98E) will develop into a tropical depression by Saturday, and become Tropical Storm Estelle early next week. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave 98E 2-day and 5-day odds of development of 50% and 90%, respectively. Future Estelle is expected to follow a path similar to Agatha, Blas, Celia and Darby--generally west to west-northwest, away from Mexico. If the Eastern Pacific manages to spit out a Tropical Storm Frank before the end of the month--which is quite possible, given the latest long-range forecasts from the GFS and European models--this would give us six named storms for the month, one short of the July record of seven named storms for Eastern Pacific set in 1985, according to NHC hurricane scientist Eric Blake.

The Atlantic remains quiet
As is usually the case when the Eastern Pacific is active, the Atlantic is quiet. This anti-correlation in activity occurs because rising air over the tropical Eastern Pacific typically creates a compensating area of sinking air over the tropical Atlantic. This sinking air creates surface high pressure and dry weather--the antithesis of conditions needed for tropical cyclone formation. There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. Don't expect to see a serious threat area develop in the Atlantic until the Eastern Pacific's burst of activity slows down.

Bob Henson (heat), Jeff Masters (tropical)