NATIONAL WEATHER SUMMARY

SEPTEMBER 2023

Aug. 27-Sep. 2: Just after daybreak on August 30, Idalia became the first major hurricane in modern history to make landfall in the Big Bend of Florida. While moving ashore at 7:45 am EDT, Category 3 Idalia was packing maximum sustained winds near 125 mph and had a central barometric pressure of 949 millibars (28.02 inches).

The Western showers accompanied the end of a warm spell, which boosted weekly temperatures at least 5°F above normal in numerous locations from the Four Corners region to the northern Plains. Persistent heat (temperatures averaging as much as 5°F above normal) also gripped the western and central Gulf Coast States, an area ravaged by a summer-long heat wave and lack of rainfall.

In contrast, weekly readings averaging as much as 5°F below normal in the eastern Corn Belt. With a gradual eastward shift in hot weather, multiple areas across the western and central U.S. reported triple-digit (100-degree) temperatures. Some of the hottest weather occurred late in the week across the nation’s mid-section, where temperatures rose to 100°F or higher as far north as South Dakota. As the week began, however, some of the hottest weather in recorded history gripped the western and central Gulf Coast States. August 27 was the hottest day on record in New Orleans, LA, where the high of 105°F smashed the mark of 102°F originally set on August 22, 1980. On the 27th in Texas, Houston set an all-time station record (109°F; previously, 108°F on September 4, 2000), while College Station (112°F) tied a record that had been achieved on September 4, 2000, and August 20, 2023. Elsewhere in Texas, Lufkin (111°F) broke a station record that had first been set on August 19, 1909, while Austin (110°F) tied a monthly standard. Extreme heat lingered for a few more days in the western Gulf Coast region, where Palacios, TX (102°F on August 30) set a monthly record. The lateAugust heat capped the hottest month on record in various towns and cities, with Louisiana locations such as Baton Rouge (90.1°F) and Lafayette (90.3°F) reporting a monthly average temperature above the 90-degree mark for the first time. Hottest-month-on-record standards were eclipsed as far east as Florida locations such as Tallahassee (86.4°F), Orlando (85.9°F), and Daytona Beach (85.0°F). In late August, extreme heat also resurfaced in the West, where triple-digit, daily-record highs for the 28th reached 104°F in Hermiston, OR, and 103°F in Pasco, WA. Palm Springs, CA, posted a pair of daily-record highs of 118°F on August 28 and 29. Similarly, Phoenix, AZ, tallied a trio of daily-record highs (114, 117, and 116°F) from August 27-29. With 22 days of 115-degree heat during the first 8 months of the year, Phoenix has already surpassed its 2020 annual record of 14 such days. During the mid- to late-week period, heat began to creep into the nation’s mid-section, where Rapid City, SD, collected a daily-record high (102°F) for August 30. The last day of August featured daily-record highs in Colorado locations such as Pueblo (101°F) and Grand Junction (98°F). Pueblo logged another daily-record high of 101°F on September 1. In Nebraska, North Platte registered three consecutive daily-record highs (100, 102, and 101°F) from September 1-3. Borger, TX, noted daily-record highs (103, 103, 104, and 105°F) on each of the first 4 days of September. Farther east, however, cool Midwestern weather lingered through the end of August, when Moline, IL, measured a daily-record low of 45°F on the 31st.

 

3-9:  Quiet weather prevailed nearly nationwide. Noteworthy rainfall was confined to a few areas, including the lower Mississippi Valley, parts of the East, and northern sections of the Rockies and Plains.

As the week began, locally heavy showers shifted northeastward from the Great Basin and Intermountain West. A few days later, rain reached the upper Great Lakes region. During the second half of the week, showers and thunderstorms were mostly focused along a slow-moving cold front, which eventually reached the Atlantic Coast.

10-16: Showers extended to other areas, including the central and southern Rockies. However, rainfall was spotty in most other areas of the country, including the Midwest, where corn and soybeans continued to mature at an ahead-of-normal pace— especially from the Mississippi Valley westward. Completely dry weather prevailed from the Pacific Coast States to the northern Rockies and northern High Plains. Elsewhere, showers dotted the East. 

Officially, Lee was a post-tropical cyclone with sustained winds near 70 mph while making landfall on Long Island, Nova Scotia, Canada, on the afternoon of September 16, less than 50 miles eastsoutheast of Eastport, ME. Impacts in eastern Maine included heavy rain, high winds, and pounding surf. Meanwhile, the temperature regime featured warmerthan-normal weather surrounding cool conditions, with weekly readings averaging more than 5°F above normal in parts of southern Texas, New England, and the Northwest. In contrast, temperatures broadly averaged at least 5°F below normal across portions of the central and southern Plains, as well as the mid-South and lower Midwest. As the week progressed, record-setting heat generally shifted eastward across the Deep South. September 10 featured daily-record highs in Arizona locations such as Phoenix (113°F) and Tucson (111°F). That marked the 55th day this year in Phoenix with a high temperature of 110°F or greater, compared to the previous record of 53 such days in 2020. Tucson also extended its record for 110-degree days in a year (18 such days in 2023, compared the former standard of 10 days in 1990 and 1994). Farther east, intense heat continued to grip southern Texas, with McAllen noting a high of 100°F or greater on each of the first 16 days of September. With 89 days of 100-degree heat so far this year, McAllen neared its annual record of 90 triple-digit days, set in 2016. Elsewhere in southern Texas, Brownsville continued to set multiple heat records, including 100-degree days in a year (40 days through September 16; previously, 12 days in 2019) and tripledigit days in September (10 days; previously, 6 days in 1900). Triple-digit heat extended as far north as Corpus Christi, TX, where a daily-record high of 101°F occurred on September 14. Meanwhile in Florida, Punta Gorda closed the week with four consecutive daily-record highs (97, 96, 96, and 97°F) from September 13-16. In southern Florida, monthly records were tied or broken Key West (95°F on September 14) and Marathon (97°F on September 16 and 17). Late in the week, heat intensified in the Northwest, while cool air spread southward across the eastern U.S. Northwestern daily-record highs included 97°F (on September 15) in Roseburg, OR, and 97°F (on September 16) in Lewiston, ID. On the 16th, daily-record lows in the Carolinas dipped to 53°F in Wilmington, NC, and 54°F in North Myrtle Beach, SC.

17-23: Warmth preceded and accompanied the increasing shower activity, with weekly temperatures broadly averaging 5 to 10°F above normal from Texas and southeastern New Mexico to the northern Plains and upper Midwest. In contrast, readings averaged at least 5°F below normal in many locations across the central and southern Appalachians, as well as the middle and southern Atlantic States. Separately, temperatures averaged as much as 5°F below normal from parts of California to the interior Northwest. Freezes were observed in traditionally colder locations across the Rockies, northern Great Basin, and Intermountain West. Heat across the nation’s mid-section expanded and intensified as the week progressed. Early in the week, unusually hot conditions were mostly limited to southern Florida, where Marathon tied a monthly record on September 17 with a high of 97°F. During the mid- to lateweek period, heat steadily built across the south-central U.S. El Paso, TX, posted daily-record highs of 99, 97, and 98°F, respectively, on September 20, 22, and 23. From September 21-23, Del Rio, TX, closed the week with a trio of daily-record highs (101, 102, and 105°F). Elsewhere in Texas, a pair of daily-record highs occurred on September 22 and 23 in Wichita Falls (101 and 104°F). Triple-digit, daily-record highs for September 23 included 103°F in Lawton, OK; 103°F in San Angelo, TX; 102°F in Midland, TX; 101°F in Roswell, NM; and 100°F in Alexandria, LA. Farther north, scattered daily records included 83°F (on September 21) in Brainerd, MN, and 90°F (on September 23) in Joplin, MO. In contrast, high temperatures on September 23 rose only to 59°F in Martinsburg, WV, and 61°F in Danville, VA—lowest on record for the date in both locations.

24-30: Early in the week, the remnants of Tropical Storm Ophelia produced rain from the middle Atlantic Coast to southern New England. Even after Ophelia’s dissipation, persistent easterly flow led to low clouds and showers along the Atlantic Seaboard, with rain lingering in some areas

.Cool weather accompanied the Northwestern storminess, leading to some high-elevation snow accumulations. Late in the week, showery weather began to make a southward and eastward push into northern California, the Great Basin, and the Intermountain West. Farther east, a few showers in the eastern Plains  and neighboring regions locally boosted topsoil moisture but were insufficient to alleviate drought concerns in the Mississippi River basin. In fact, water levels from Cairo, IL, downstream to Greenville, MS, approached records set just last year, in October 2022. Concurrently, warm, dry weather in many key summer production areas of the nation’s mid-section favored crop maturation and harvesting. However, the late-season heat also maintained significant stress on pastures and immature summer crops in some of the nation’s hardest-hit drought areas, including the western and central Gulf Coast States. Weekly temperatures averaged at least 5 to 10°F above normal from the Plains to the Mississippi Valley, as well as the upper Great Lakes region. The warmest weather, relative to normal, covered portions of the central Plains and western Corn Belt. Meanwhile, readings averaged as much as 5°F below normal in California and the Pacific Northwest. Similarly cool weather was observed along the East Coast, especially from Georgia to southern New England. Record-setting heat was largely confined to the south-central U.S. early in the week, but soon expanded to other areas. In Del Rio, TX, a string of seven triple-digit days from September 19-25 included a daily-record high of 107°F on the 24th. Other triple-digit, daily-record highs in Texas on September 24 included 103°F in Austin and San Angelo, and 102°F in Waco, College Station, and Dallas-Fort Worth. Elsewhere in Texas, Brownsville achieved a high of 98 or 99°F each day from September 20- 27. Heat made a brief appearance in the Desert Southwest, where tripledigit, daily-record highs for September 26 reached 104°F in Tucson and 101°F in Nogales. Tucson notched another daily record, 103°F, on September 27. Farther east, Alexandria, LA, collected consecutive daily-record highs (98 and 99°F, respectively) on September 26-27. On the same 2 days, Vicksburg, MS, also reported a pair of daily records (95 and 96°F). Late in the week, heat made a significant northward surge. By September 29, daily-record highs surged to the 95-degree mark or higher in locations such as Concordia, KS (96°F); Lincoln, NE (96°F); and Sioux City, IA (95°F). For Sioux City, the only later observance of a high of 95°F or greater occurred on October 3, 1938. In addition, Sioux City tallied a trio of daily-record highs (95, 94, and 92°F) from September 29 – October 1. The last day of September featured a vast array of daily-record highs, stretching from Brownsville, TX (97°F), to Minneapolis-St. Paul, MN (88°F). The following day, on the 1st, Minneapolis-St. Paul logged its highest-ever October temperature, with a reading of 92°F (previously, 90°F on October 10, 1928, and October 3, 1997). Other daily-record highs on September 30 included 100°F in College Station, TX; 98°F in Hill City, KS; 96°F in Lincoln, NE; and 94°F in Quincy, IL. In contrast, scattered Western daily-record lows dipped to 41°F (on September 27) in Ramona, CA, and 25°F (on September 28) in Klamath Falls, OR.

 

 

Jim G. Munley, jr.
http://www.jimmunleywx.com