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3-9: Significant shower activity was mostly limited to portions of the East, with the heaviest rain (locally 2 inches or more) observed in New England and across Florida’s peninsula.  Meanwhile, relentless, late-season heat accompanied widely scattered Western showers.  Some of the heaviest showers dotted the Desert Southwest.  Farther north, however, dozens of wildfires remained active from the Pacific Coast States to the northern Rockies, shrouding the sky with smoke and reducing air quality.  Extremely dry conditions also persisted across the drought-stricken northern High Plains, where some producers were planting winter wheat in dust.  By week’s end, Hurricane Irma began to turn toward Florida after devastating a string of islands across the northern Caribbean.  Among the islands suffering catastrophic damage were the northern U.S. Virgin Islands of St. John and St. Thomas, which were battered by Irma’s southern eyewall on September 6, when the then-Category 5 storm was packing sustained winds of 185 mph.  Puerto Rico and the U.S. Virgin Island of St. Croix were grazed by Irma, suffering significant but not historic damage.  Irma crossed the lower Florida Keys, just east of Key West, on the morning of September 10, with sustained winds near 130 mph.  This year marks the first time that two Category 4 storms (winds of 130 mph or greater) have made a U.S. landfall in the same year, as Harvey struck the middle Texas coast with a similar intensity late on August 25.  More details on Irma’s final landfall on Marco Island, FL, and well as other storm details, will appear next week. Meanwhile, daily-record totals topped an inch in a few Southern and Eastern locations, including Vicksburg, MS (1.24 inches on September 5), and Montpelier, VT (1.01 inch on September 3).  In the Desert Southwest, record-setting totals reached 1.20 inches (on September 9) in Palm Springs, CA, and 0.48 inch (on September 8) in Desert Rock, NV.  In California, Redding measured a daily-record sum (0.61 inch) for September 7.  Late-week rain clipped the southern tip of Texas, where Brownsville received a recordsetting amount (1.56 inches) for September 8.  Elsewhere in Texas, neither Galveston nor flood-weary Beaumont-Port Arthur received a drop of rain during the first 10 days of September, while Houston reported 0.06 inch.


10-16: Hurricane Irma tore across the Florida Keys on the morning of September 10, followed by a final landfall on Marco Island, FL, during the afternoon.  Irma was packing sustained winds near 130 mph upon reaching Cudjoe Key at 9:10 am EDT, marking the first time that two Category 4 hurricanes achieved a U.S. landfall in the same year.  (Hurricane Harvey had crossed the middle Texas coast near Rockport with winds near 130 mph on August 25.)  When Irma made landfall on Marco Island at 3:35 pm EDT, sustained winds had dropped to 115 mph— a Category 3 hurricane.  Although Irma traversed the western side of Florida’s peninsula, damage was reported nearly statewide.  Agricultural impacts in Florida included wind damage to citrus and sugarcane, as well widespread flooding (from 10- to 20-inch rainfall totals) and long-duration power outages.  Portions of Florida’s east coast also experienced storm-surge flooding.  Farther north, tropical storm force winds spread into Alabama, Georgia, and parts of the Carolinas, threatening open-boll cotton; pecans and other tree nuts; and forestry land.  Damage assessments from high winds, flooding, and loss of electricity continued throughout the week and beyond. Although many weather observations in Florida were lost due to power outages and extreme conditions, a wind gust to 142 mph was recorded on September 10 at the Naples Airport.  Other wind gusts reported by the National Weather Service included 130 mph on Marco Island; 120 mph on Big Pine Key; 99 mph in Miami; 89 mph in Fort Myers; 74 mph in St. Petersburg; and 70 mph in Sarasota-Bradenton.  Early on the 11th, gusts were clocked to 86 mph in Jacksonville, FL; 72 mph at Folly Beach, SC; and 70 mph at Fort Pulaski, GA.  September 10 was the wettest day on record in Florida locations such as Fort Pierce (13.08 inches); Melbourne (10.23 inches); and Sanford (9.24 inches).  Gainesville, FL, experienced its wettest 2-day period on record on September 10-11; the 12.40-inch total surpassed 11.81 inches during a hurricane strike on September 26-27, 1894.  St. Simons Island, GA, recorded 11.64 inches on September 10-11.  Elsewhere in Georgia, record-setting totals for September 11 included 5.72 inches in Alma; 4.74 inches in Savannah; and 4.10 inches in Augusta.  Other daily-record amounts for the 11th reached 5.51 inches in Charleston, SC, and 2.92 inches in Anniston, AL.  On September 11, the St. Johns River at Mayport, FL, climbed to its second-highest level on record—2.68 feet above flood stage—due to storm-surge flooding.  Mayport’s record, set on October 2, 1898, remains 4.70 feet above flood stage.  Farther inland, Florida crest records from September 1964 were broken on the 12th or 13th along the Santa Fe River at Worthington Springs (13.17 feet above flood stage) and the New River near Lake Butler (7.55 feet).  On September 13, crest records from April 1982 were achieved along the Ocklawaha River at Rodman Dam (4.70 feet above flood stage) and Eureka (3.49 feet).  The St. Johns River at Astor, FL, which climbed 1.63 feet above flood stage on September 13, has been higher only during a series of storms in September-October 1933.  Later, the focus for precipitation turned to the northern Plains.  Cut Bank, MT, reported 88 days (June 18 – September 13) with precipitation totaling 0.01 inch or less, breaking the record of 74 days set from October 22, 1908 – January 3, 1909.  Cut Bank’s streak ended with a 0.47-inch total on September 14-15.  Elsewhere, record setting totals for September 15 reached 1.96 inches in Grand Forks, ND, and 1.10 inches in Great Falls, MT.  In Iowa, Mason City collected 1.55 inches on September 16, a record for the date.


17-23: On September 20, Hurricane Maria slammed St. Croix (of the U.S. Virgin Islands) and Puerto Rico.  Just before 1 a.m. AST, Maria passed less than 20 miles south of St. Croix as a Category 5 hurricane with sustained winds near 175 mph.  Hours later, at 6:15 am, Maria directly struck Puerto Rico, making landfall as a high-end Category 4 storm with winds of 155 mph near Yabucoa.  Devastating impacts, including severe wind damage and record flooding, accompanied the hurricane, which struck just 2 weeks after Hurricane Irma grazed St. Croix and Puerto Rico—and caused great destruction on the other major U.S. Virgin Islands of St. Thomas and St. John.  Puerto Rican flooding persisted for days afterward, as massive runoff strained flood-control projects and other catchment basins. Surviving weather equipment on St. Croix and Puerto Rico painted a partial picture of the destruction.  In a 48-hour period from September 1921, several rainfall totals in excess of 20 inches were documented in Puerto Rico.  At one location in the municipality of Caguas, a total of 37.90 inches was reported.  Several wind gusts in excess of 100 mph were clocked on St. Croix and Puerto Rico, although most data was lost due to equipment destruction or power outages.  On St. Croix, a gust to 136 mph was recorded 5 miles east of Christiansted.  Many surviving river gauges on Puerto Rico experienced record-setting crests on September 20, during or just after Maria’s passage, erasing high-water marks that had been set during the memorable floods of September 1975 (Eloise); October 1985 (Isabel); and September 1998 (Georges).  One record that was not broken was the high-water mark of 21.40 feet above flood stage along Rio de la Plata near Toa Alta, where the standard was established during the “San Felipe Segundo” hurricane of September 1928.  Maria was the first Category 4 hurricane to make a Puerto Rican landfall since 1932; however, the “San Felipe Segundo” storm remains the only Category 5 storm (160 mph sustained winds) to directly strike the island.  Days after Maria’s departure, flood damage to Guajataca Dam in northwestern Puerto Rico resulted in the evacuation of downstream individuals due to the threat of imminent failure; however, use of a damaged auxiliary spillway helped to ease pressure on the dam itself. Early-week precipitation highlights were limited to the Northwest.  Daily-record precipitation totals included 0.86 inch (on September 18) in Stanley, ID, and 0.92 inch (on September 19) at Lake Yellowstone, WY.  From September 18-22, Stanley received exactly 2 inches of precipitation.  In Oregon, record-setting totals for September 20 included 0.75 inch in Meacham and 0.52 inch in Pendleton.  Meacham’s 3-day sum, from September 18-20, rose to 2.29 inches.  Similarly, Pocatello, ID, netted 2.09 inches of rain from September 19-22, aided by a daily-record total of 1.04 inches on the 21st.  Late in the week, significant snow developed across the Intermountain West, where Alta, UT, measured daily-record snowfall totals (3.4 and 11.0 inches, respectively) on September 22 and 24.  On September 23, precipitation reached the nation’s mid-section, where daily-record amounts included 2.46 inches in Huron, SD; 1.57 inches in Roswell, NM; and 1.39 inches in North Platte, NE.  Two-day (September 23-24) totals reached 4.04 inches in Huron and 3.42 inches in North Platte.


24-30: Warm, humid, showery conditions, hurricane recovery efforts continued in Puerto Rico and the U.S. Virgin Islands, following Irma on September 6 and Maria on September 20.  Maria’s direct strike on Puerto Rico as a Category 4 storm—the strongest hurricane to hit the island since 1928—left residents without electricity and other necessities, such as fresh food and running water. For several days, an axis of heavy rain stretched from southern sections of the Rockies and Plains into the upper Midwest.  Weekly rainfall topped 2 inches in several areas, while lingering rain in the south-central U.S. boosted totals to 4 to 8 inches or more—sparking local flooding—in parts of Texas.  Elsewhere, light showers were mostly limited to the Pacific Northwest, Intermountain West, and Northeast.  A few heavier showers dotted Florida. In areas not affected by tropical downpours, September ended with little rainfall along and east of a line from northeastern Texas to Lower Michigan.  Shreveport, LA, reported only a trace of rain (3.16 inches below normal), edging the September 2015 standard of 0.07 inch.  In Arkansas, Russellville’s monthly total of 0.04 inch was 3.26 inches below normal, breaking the September 2004 record of 0.07 inch.  In contrast, Melbourne, FL, completed its wettest September on record (20.94 inches, or 274 percent of normal), surpassing 19.68 inches in 1948.  Meanwhile, pounding, early-week rains stretched across the nation’s mid-section.  Record-setting rainfall totals for September 24 included 2.03 inches in North Platte, NE, and 1.47 inches in Goodland, KS.  In South Dakota, Huron netted 4.04 inches on September 23-24.  On September 25, daily-record totals in Kansas reached 3.92 inches in Medicine Lodge and 1.93 inches in Garden City.  The focus for heavy rain eventually shifted southward, resulting in a daily-record amount for September 26 in Laredo, TX (5.24 inches).  From September 25-28, rainfall totaled 8.17 inches in Laredo; 4.48 inches in Las Vegas, NM; and 4.36 inches in Lawton, OK.  Farther north, Havre, MT, received nearly an inch of September rainfall, but still completed its driest January-September period on record (4.56 inches, or 47 percent of normal).


Jim G. Munley, jr.

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