donsutherland1

From the WPC: Storm Summary Number 12 for Heavy Rain and Wind Gusts Associated with Hurricane Dorian NWS Weather Prediction Center College Park MD 500 AM EDT Sat Sep 07 2019 ...Rain and gusty winds continue over coastal southeast Massachusetts and is beginning to impact the shores of Maine as Hurricane Dorian tracks northeast... A Tropical Storm Warning remains in effect for coastal portions of southeastern Massachusetts and Downeast Maine. For a detailed graphical depiction of the latest watches, warnings and advisories, please see www.weather.gov At 400 AM EDT...National Weather Service radar and surface observations show periods of rain are impacting coastal areas of far southeast New England. Tropical storm force winds have been reported in Cape Cod and the nearby islands. Rain has also begun to fall along the coast of Maine. Below are preliminary rainfall and wind observations associated with Dorian. For more information regarding the location and forecast track of Dorian, please refer to www.nhc.noaa.gov ...Selected preliminary Storm Total Rainfall in inches from 700 AM EDT Sun Sep 01 through 400 AM EDT Sat Sep 07... ...MASSACHUSETTS... MARTHA'S VINEYARD AIRPORT 1.53 CHATHAM MUNI ARPT 1.19 HYANNIS/BARNSTABLE MUNI ARPT 1.17 ...Selected preliminary Peak Wind gusts in miles per hour earlier in the event... ...DELAWARE... LEWES 49 ...FLORIDA... NEW SMYRNA BEACH 69 SAINT AUGUSTINE BEACH 1 NNE 62 JUNEAU BEACH PIER 61 DAYTONA BEACH 55 JACKSONVILLE 55 GOVERNMENT CUT 52 ST. LUCIE PLANT 49 POMPANO BEACH 48 PORT CANAVERAL 47 MERRITT ISLAND 46 MIAMI OPA LOCKA 43 ...GEORGIA... RACCOON BLUFF 22 E - NDBC 67 SECESSIONVILLE 2 ESE 62 NORTH TYBEE ISLAND 60 FORT PULASKI 57 BRUNSWICK 40 ...MASSACHUSETTS... NANTUCKET SHOALS BUOY 76 WELLFLEET 55 PROVINCETOWN 50 ...NEW JERSEY... RUTGERS 50 ...NORTH CAROLINA... CEDAR ISLAND FERRY TERMINAL 110 BUXTON (HATTERAS HIGH SCHOOL) 101 OREGON INLET CG 101 JEANETTES PIER 99 PAMLICO SOUND 95 CAPE LOOKOUT 94 FORT MACON 89 OCRACOKE 89 DUCK PIER 87 FORT MACON NEAR ATLANTIC BEACH 85 BALD HEAD ISLAND 32 SSE 72 CHERRY POINT 72 ALLIGATOR RIVER BR 71 ELIZABETH CITY 70 FEDERAL POINT 64 EDENTON 59 OAK ISLAND 55 CALABASH 54 FAYETTEVILLE ARPT/HOPE MILLS 4 ENE 52 NORTH RIVER 50 ...RHODE ISLAND... CHARLESTOWN 51 ...SOUTH CAROLINA... CENTENARY 39 SSE - NDBC 98 DEWEES ISLAND 6 ESE - NDBC 92 FRIPP ISLAND 5 ESE - NDBC 92 WINYAH BAY 76 CHARLESTON INTL AIRPORT 69 FOLLY BEACH 67 HILTON HEAD AIRPORT 67 FORT SUMTER 65 ISLE OF PALMS 63 GEORGETOWN 62 BEAUFORT 61 NORTH MYRTLE BEACH 61 PALMS PIER 61 MCCLELLANVILLE 45 SSE - NDBC 58 MURRELLS INLET 56 CHARLESTON HARBOR 55 ...VIRGINIA... CHESAPEAKE LIGHT TOWER 83 CAPE HENRY 70 NORFOLK 64 VIRGINIA BEACH 52 SUFFOLK 50 ...Selected preliminary Storm Total Rainfall in inches where the event has ended... ...DELAWARE... BETHANY BEACH 1.70 SELBYVILLE 1.63 ...FLORIDA... PALM COAST 4.5 SSW 5.68 DELAND 0.6 SSE 4.54 LAKE MARY 3.92 FLAGLER BEACH 2.3 SSE 3.71 PALM VALLEY 5.9 SSW 3.47 PAISLEY 3.36 WINTER HAVEN GILBERT ARPT 3.34 ST AUGUSTINE AIRPORT 2.68 CAPE CANAVERAL 2.66 APOPKA 3.5 ESE 2.62 NASA SHUTTLE FACILITY 2.59 DAYTONA BEACH INTL ARPT 2.58 ORLANDO/SANFORD ARPT 2.53 VERO BEACH 2.5 S 2.38 MELBOURNE 2.31 ...GEORGIA... DARIEN 9.0 ENE 2.83 SAVANNAH 9.6 E 2.38 JEKYLL ISLAND 0.6 E 1.84 ...MARYLAND... OCEAN CITY 1.78 ...NORTH CAROLINA... WILMINGTON 7.3 NE 13.10 LUMBER RIVER 10.96 WILMINGTON 10.67 CASTLE HAYNE 10.25 CALABASH 2.5 E 9.86 KINGSTON 4.7 ESE 8.77 TAR RIVER 8.05 MOUNT OLIVE 2.4 SW 8.00 NAGS HEAD 7.75 NEW BERN 5.3 SW 7.36 MARINERS'S WARF PARK 7.33 CHAPANOKE 7.25 CLINTON 5.8 SW 6.90 BEAUFORT 0.6 SSE 6.82 PINE LEVEL 6.40 HOPE MILLS 8.0 SSE 6.35 DUPLIN COUNTY ARPT 6.31 SAMPSON CO ARPT 6.03 GRANDY 0.6E 6.00 CLINTON 5.69 HOMINY SWAMP 5.46 SOULES SWAMP 5.35 SUNSET BEACH 5.10 SHILOH 5.07 CALABASH 1.2 NNW 5.05 ...SOUTH CAROLINA... PAWLEYS ISLAND 5.6 NNE 15.21 MYRTLE BEACH 5.2 SW 12.77 CONWAY 11.86 MCCLELLANVILLE 0.2 ESE 10.70 NORTH MYRTLE BEACH 10.45 MOUNT PLEASANT 4.4 NE 10.12 MYRTLE BEACH INTL ARPT 8.87 CHARLESTON 5.4 SSE 8.24 GEORGETOWN COUNTY ARPT 6.19 CHARLESTON INTL ARPT 5.54 ...VIRGINIA... VIRGINIA BEACH 3.64 CHESAPEAKE 2.34 NORFOLK INTL ARPT 1.86 GREENBRIER 1.10 For the latest rainfall forecast and Excessive Rainfall Outlooks associated with Dorian, please refer to www.wpc.ncep.noaa.gov The next Storm Summary will be issued by the Weather Prediction Center at 1100 AM EDT. Please refer to your local National Weather Service office for additional information on this event.

Storm total rainfalls from Hurricane Dorian include: North Myrtle Beach, SC: 10.75" (yesterday had a daily record 10.39") Wilmington, NC: 10.05" Today, Elizabeth City, NC has picked up 4.34" rain through 7:45 am. The previous daily record was 2.60", which was set in 1968.

Extreme heat continued in parts of Colorado today. Pueblo reached 102°, which tied that city's September record, which was set on September 2, 2019. Today was also Pueblo's 3rd 100° day this month. Prior to 2019, Pueblo had only 5 100° or above readings in September. Records go back to 1888. Denver also had a high temperature of 98°, which was just above the daily record of 97° from 1899 and 2013. On September 2, Denver had its first-ever 100° reading in September. Denver has now had 3 high temperatures of 98° or above this month. Prior to 2019, the monthly record had been 97°. Records go back to 1872. A cold front is now moving through the state. Temperatures should be lower tomorrow.

Hurricane Dorian is bringing heavy rain and high winds as it moves ashore in eastern North Carolina. Through 8:30 pm, North Myrtle Beach, NC had picked up 9.98" rain. That is the second highest daily precipitation amount on record for the Myrtle Beach area. Dorian is now starting to accelerate to the northeast. Dorian will likely pass far enough to the east tomorrow into Saturday to avoid having a significant impact on the greater New York City region, though it will very likely lead to rough surf and strong rip currents. Parts of Long Island and eastern New England could still receive some periods of rain or heavier showers and gusty winds associated with Dorian. The storm will likely eventually make landfall in Nova Scotia and then in Newfoundland before racing out into the far northern Atlantic. In the wake of Dorian, the weekend will feature a preview of autumn. Afterward, a return to normal and then above normal temperatures could be slow. Even as Dorian will help usher in a cool air mass in the Northeast, parts of Florida saw near record to record heat following Dorian's offshore passage. High temperatures included: Apalachicola: 97° (tied September record); Pensacola: 99° (highest September temperature since September 25, 1925 when the temperature reached 100°); and, Tallahassee: 99° (highest September temperature since September 19, 2005 when the temperature also hit 100°). The ENSO Region 1+2 anomaly was -0.4°C and the Region 3.4 anomaly was -0.2°C for the week centered around August 28. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.45°C and the ENSO Region 3.4 anomaly has averaged +0.20°C. Neutral-warm ENSO conditions are in place in Region 3.4 with neutral-cool conditions in place in Region 1+2. There remains uncertainty about the ENSO evolution later this fall. The CFSv2 has recently shifted toward a warm-neutral/borderline weak El Niño signal for the winter. The SOI was -12.54 today. Today, the preliminary Arctic Oscillation (AO) figure was +0.832. Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall. Therefore, a warmer than normal September and fall appear likely, though the persistence of Dorian's impact on the larger circulation has reduced the probability of a warmer than normal September, though a warm monthly anomaly remains the base case. The potential for autumn 2019 to rank among the 30 warmest cases on record is on the table. On September 4, the MJO was in Phase 5 at an amplitude of 1.151 (RMM). The September 3-adjusted amplitude was 1.079. Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal September is near 50%.

The record I'm citing is the daily record for September 5, not the all-time record for daily precipitation. Sorry about any confusion my post might have created.

With 0.78" rain over the past 40 minutes, Wilmington's daily rainfall has reached 4.44". That surpasses the daily record of 4.41", which was set in 1996 as Hurricane Fran was moving toward landfall.

Hurricane Fran. I should have mentioned it.

With 2.23" rain in the past hour, Wilmington has now received 3.66" rain today. The daily rainfall record is 4.41", which was set in 1996.

Over the past 3 hours, Myrtle Beach has picked up 3.98" rain. That, alone, exceeds the daily rainfall record of 3.61", which was set in 2008.

Hurricane Dorian is currently bringing rain to portions of the Georgia, South Carolina, and North Carolina. As Dorian moves northeastward across easternmost North Carolina, it will likely bring heavy rain and damaging winds to parts of Georgia, South Carolina, North Carolina and Virginia tonight and tomorrow. Afterward, Dorian will likely pass far enough to the east to avoid having a significant impact on the greater New York City region, though it will very likely lead to rough surf and strong rip currents. Parts of Long Island and eastern New England could still receive some periods of rain or heavier showers and gusty winds associated with Dorian. The storm will likely eventually make landfall in Newfoundland. On account of Dorian's strong circulation, an unseasonably cool air mass could push into the region for the latter part of this week. Beyond that, the timing for a return to normal and then above normal temperatures could be slow. Ahead of a frontal passage, temperatures rose into the 80s and 90s in the Middle Atlantic and southern New England areas. High temperatures included: Baltimore: 96° (tied record set in 1937); Harrisburg: 89°; New York City: 87°; Newark: 90°; Philadelphia: 92°; and, Washington, DC: 96° (old record: 95°, 1985, 2008, and 2018). The ENSO Region 1+2 anomaly was -0.4°C and the Region 3.4 anomaly was -0.2°C for the week centered around August 28. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.45°C and the ENSO Region 3.4 anomaly has averaged +0.20°C. Neutral-warm ENSO conditions are in place in Region 3.4 with neutral-cool conditions in place in Region 1+2. There remains uncertainty about the ENSO evolution later this fall. The CFSv2 has recently shifted toward a warm-neutral/borderline weak El Niño signal for the winter. The SOI was -14.79 today. Today, the preliminary Arctic Oscillation (AO) figure was +0.901. Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall. Therefore, a warmer than normal September and fall appear likely, though the persistence of Dorian's impact on the larger circulation has reduced the probability of a warmer than normal September, though a warm monthly anomaly remains the base case. The potential for autumn 2019 to rank among the 30 warmest cases on record is on the table. On September 3, the MJO was in Phase 4 at an amplitude of 1.069 (RMM). The September 2-adjusted amplitude was 1.030. The MJO has now been in Phase 4 for 9 consecutive days. The last time the MJO was in Phase 4 for at least 9 consecutive days was August 20-29, 2018 when the MJO was in Phase 4 for 10 consecutive days. Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal September is 51%. 　

Utqiagvik (formerly Barrow) has seen a dramatic increase in the number of days each year where the temperature stays above freezing. Much of the increase has come recently, as summer Arctic sea ice has declined markedly from prior levels. The change in the 30-year moving averages (to remove the noise of interannual variability) for the number of such days provides further illustration of the dramatic warming that is underway in the Arctic region. For the 1961-90 base period, the 30-year moving average was 43.9 days. For the latest 30-year period (1989-2018), the moving average has increased to 63.4 days. That's a nearly 20-day increase over a remarkably short period of time. Through September 3, Utqiagvik has had 76 days with temperatures above freezing. The last time Utqiagvik had fewer than 50 days above freezing was 2003. In 2007, the minimum Arctic sea ice extent fell below 5 million square kilometers for the first time (JAXA data set). Since then, only 2009 has had a minimum extent of 5 million square kilometers (5.054 million square kilometers). As of September 3, Arctic sea ice extent was 4.175 million square kilometers. During the "low ice" era that commenced in 2007, Utquiavik has averaged 76.8 days per year (2007-18) with above freezing temperatures. Through September 3, Utqiagvik had a record 70 consecutive days where the temperature has stayed above freezing. The old record was 68 consecutive days from July 1-September 6, 2009. Prior to 2009, there were no cases with 60 or more consecutive days above freezing.

I included a chart for AO-/EPO- summers (averages are based on all days that met both criteria). That historically warm pattern has also grown warmer.

Dorian has moved slowly away from the Bahamas and is now moving northwestward off the Florida Peninsula. Tomorrow, Dorian will gradually accelerate and eventually add an easterly component to its motion. In addition to Florida's east coast, portions of the Georgia's, South Carolina's, North Carolina's, and Virginia's coastlines will likely experience heavy rain and at least some damaging winds. Coastal flooding is very likely. Afterward, Dorian will likely pass far enough to the east to avoid having a significant impact on the greater New York City region, though it will very likely lead to rough surf and strong rip currents. Parts of Long Island and eastern New England could still receive some periods of rain or heavier showers and gusty winds associated with Dorian. The storm will likely eventually make landfall in Newfoundland. Dorian's principal impact might be the amplification of the larger circulation. As a result, an unseasonably cool air mass could push into the region for the latter part of this week. Beyond that, the timing for a return to normal and then above normal temperatures could be slow. Some of the guidance is signaling a rebound to notably warmer conditions after mid-month. The ENSO Region 1+2 anomaly was -0.4°C and the Region 3.4 anomaly was -0.2°C for the week centered around August 28. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.45°C and the ENSO Region 3.4 anomaly has averaged +0.20°C. Neutral-warm ENSO conditions are in place in Region 3.4 with neutral-cool conditions in place in Region 1+2. There remains uncertainty about the ENSO evolution later this fall. The CFSv2 has recently shifted toward a warm-neutral/borderline weak El Niño signal for the winter. The SOI was -16.70 today. Today, the preliminary Arctic Oscillation (AO) figure was +0.835. Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall. Therefore, a warmer than normal September and fall appear likely, though the persistence of Dorian's impact on the larger circulation has reduced the probability of a warmer than normal September, though a warm monthly anomaly remains the base case. The potential for autumn 2019 to rank among the 30 warmest cases on record is on the table. On September 2, the MJO was in Phase 4 at an amplitude of 1.031 (RMM). The September 1-adjusted amplitude was 0.879. Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal September is 53%.

Let me rephrase things a little. The pattern was not forecast to be especially unfavorable to ice reduction. The forecast showed fluctuations in the NAM, not a persistent anomaly. One would have needed a fairly extraordinary development to lead to an unprecedented early end to melt season. The MAN had been forecast to slide back toward neutral during the first week of September. All other things being equal, that suggested reductions in Arctic sea ice would continue probably for another week and perhaps two.

As you noted correctly, had there been an August minimum, it would have been unprecedented. Since 8/31, Arctic sea ice extent has continued to decline. That a piece of guidance would suggest an unprecedented situation, moreso when the upper air pattern had been forecast to grow more favorable for continued reductions in sea ice, raises some questions about the model itself. I'm not sure what the track record of the model in question is, but this is a high profile miss. Overall, forecasting of sea ice minimums remains a fairly low skill endeavor at present.

Hurricane Dorian will continue to gradually weaken tonight and tomorrow as continues its slow turn to the north. Nevertheless, Dorian will remain a powerful hurricane. Dorian will likely pass just off the Florida Peninsula. As Dorian comes northward and gradually takes a more eastward turn, portions of the Florida, Georgia, and the Carolinas' coastlines will likely experience heavy rain and at least some damaging winds. Coastal flooding is very likely. Afterward, Dorian will likely pass far enough to the east to avoid having a significant impact on the greater New York City region, though it will very likely lead to rough surf and strong rip currents. Parts of Long Island and eastern New England could still receive some periods of rain or heavier showers and gusty winds associated with Dorian. Dorian's principal impact might be the amplification of the larger circulation. As a result, an unseasonably cool air mass could push into the region for the latter part of this week. Beyond that, the timing for a return to normal and then above normal temperatures could be slow. Some of the guidance is signaling a rebound to notably warmer conditions after mid-month. Across the Atlantic Ocean, the most recent round of excessive heat continues to dissipate in Europe. Nevertheless, as the area of warmth headed north and east, a number of records were set. Select records included: Kecskemet, Hungary: 91°, Kirkenes Lufthavn, Norway: 72° (tied September record); Kruunupyy, Finland: 73°; Murmansk, Russia: 75° (new September record); Oulu, Finland: 75°; Pecs, Hungary: 90°; Rovaniemi, Finland: 72°; Szolnok, Hungary: 91°; and, Vadso, Norway: 68°. In the United States, Denver recorded a 100° high temperature, its latest 100° reading on record. The prior latest such temperature occurred on August 16, 2002. Pueblo, CO also saw the temperature set a new September record at 102°. The ENSO Region 1+2 anomaly was -0.4°C and the Region 3.4 anomaly was -0.2°C for the week centered around August 28. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.45°C and the ENSO Region 3.4 anomaly has averaged +0.20°C. Neutral-warm ENSO conditions are in place in Region 3.4 with neutral-cool conditions in place in Region 1+2. There remains uncertainty about the ENSO evolution later this fall. The CFSv2 has recently shifted toward a warm-neutral/borderline weak El Niño signal for the winter. The SOI was -20.86 today. Today, the preliminary Arctic Oscillation (AO) figure was +0.419. Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall. Therefore, a warmer than normal September and fall appear likely, though the persistence of Dorian's impact on the larger circulation has reduced the probability of a warmer than normal September, though a warm monthly anomaly remains the base case. The potential for autumn 2019 to rank among the 30 warmest cases on record is on the table. On September 1, the MJO was in Phase 4 at an amplitude of 0.881 (RMM). The August 31-adjusted amplitude was 1.039. Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal September is 48%.

Numerous monthly records were set in Colorado and Wyoming today.

With Hurricane Dorian's historic intensification, it is a good time to point to an article in the American Meteorological Society's Journal of Climate from last fall. The article noted that one can expect more intense storms on account of climate change. Abstract: As one of the first global coupled climate models to simulate and predict category 4 and 5 (Saffir–Simpson scale) tropical cyclones (TCs) and their interannual variations, the High-Resolution Forecast-Oriented Low Ocean Resolution (HiFLOR) model at the Geophysical Fluid Dynamics Laboratory (GFDL) represents a novel source of insight on how the entire TC intensification distribution could be transformed because of climate change. In this study, three 70-yr HiFLOR experiments are performed to identify the effects of climate change on TC intensity and intensification. For each of the experiments, sea surface temperature (SST) is nudged to different climatological targets and atmospheric radiative forcing is specified, allowing us to explore the sensitivity of TCs to these conditions. First, a control experiment, which uses prescribed climatological ocean and radiative forcing based on observations during the years 1986–2005, is compared to two observational records and evaluated for its ability to capture the mean TC behavior during these years. The simulated intensification distributions as well as the percentage of TCs that become major hurricanes show similarities with observations. The control experiment is then compared to two twenty-first-century experiments, in which the climatological SSTs from the control experiment are perturbed by multimodel projected SST anomalies and atmospheric radiative forcing from either 2016–35 or 2081–2100 (RCP4.5 scenario). The frequency, intensity, and intensification distribution of TCs all shift to higher values as the twenty-first century progresses. HiFLOR’s unique response to climate change and fidelity in simulating the present climate lays the groundwork for future studies involving models of this type. The article also covers the likely increase in the most extreme tropical cyclones: The increased probability of higher-intensity TCs becomes more tangible when focusing on the number of TCs that exceed 165 kt in each simulation, which is the fastest wind speed ever recorded during a TC landfall (Typhoon Haiyan; Takagi and Esteban 2016). In the 70-yr HiFLOR CTL experiment, nine TCs achieve awind speed of greater than 165 kt. The number of TCs that exceed this threshold grows to 32 for the 2016–35 simulation and 72 for the 2081–2100 simulation. https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0898.1

Hurricane Dorian may begin to gradually weaken later tonight or tomorrow as its forward motion continues to slow and then it eventually begins to turn to the north. Even as Dorian will likely pass offshore, portions of the Florida, Georgia, and the Carolinas' coastlines could still experience heavy rain and at least some damaging winds. Enough EPS members suggest the possibility of landfall to avoid completely ruling out such a scenario in Florida and especially in eastern North Carolina. Afterward, Dorian will likely pass far enough to the east to avoid having a significant impact on the greater New York City region, though it will very likely lead to rough surf and strong rip currents. Parts of Long Island and eastern New England could still receive some periods of rain or heavier showers and gusty winds associated with Dorian. Dorian's principal impact might be the amplification of the larger circulation. As a result, an unseasonably cool air mass could push into the region for the latter part of this week. Beyond that, the timing for a return to normal and then above normal temperatures could be slow. Some of the guidance is signaling a rebound to notably warmer conditions after mid-month. Across the Atlantic Ocean, the latest round of heat that toppled records in large parts of Europe will be concluding Europe. Earlier today, a number of daily and even monthly records were registered in Norway and Sweden. Select records included: Bardufoss, Norway: 73°; Bodo Vi, Norway: 73° (tied September record); Evenes, Norway: 75° (new September record); Kirkenes Lufthavn, Norway: 68°; Leknes, Norway: 72° (new September record); Liepaja, Latvia: 84°; Linkoping, Sweden: 81° (new September record); Murmansk, Russia: 68°; Norrkoping, Sweden: 82° (new September record); Pori, Finland: 77°; Stockholm: 79° (tied September record); Svolvaer, Norway: 68° (new September record); Vadso, Norway: 64°; Vassa, Finland: 77°; Vasteras, Sweden: 79°; and, Visby Flygplats, Sweden: 82° (new September record). The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was 0.0°C for the week centered around August 21. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.27°C. Neutral-warm ENSO conditions are in place in Region 3.4 with neutral-cool conditions in place in Region 1+2. There is considerable uncertainty about the ENSO evolution later this summer into the fall. Some of the guidance continues to show the development of neutral-cool ENSO conditions. The SOI was -14.32 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.186. The AO has averaged -1.062 for August. Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall. Therefore, a warmer than normal September and fall appear likely, though the persistence of Dorian's impact on the larger circulation has reduced the probability of a warmer than normal September, though a warm monthly anomaly remains the base case. The potential for autumn 2019 to rank among the 30 warmest cases on record is on the table. On August 31, the MJO was in Phase 4 at an amplitude of 1.058 (RMM). The August 30-adjusted amplitude was 1.185. Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal September is 46%.

On August 31, Arctic sea ice extent was 4,259,262 square kilometers on JAXA. Based on sensitivity analysis, the following are implied probabilities for various minimum extent figures: 4.25 million square kilometers or below: 99% 4.00 million square kilometers or below: 59% 3.75 million square kilometers or below: 0.6% 75th percentile: 4.041 million square kilometers 25th percentile: 3.916 million square kilometers Minimum extent figures based on historic 2010-2018 data: Mean decline: 3.979 million square kilometers Median decline: 4.016 million square kilometers Minimum decline: 4.078 million square kilometers Maximum decline: 3.757 million square kilometers Summary: After a pause likely due to storminess over the Polar region, Arctic sea ice extent has again begun to decline. Arctic sea ice extent will likely decline with some momentary increases over the next 1-2 weeks. A minimum extent figure below 4.000 million square kilometers still remains possible, but the probability of that outcome has declined markedly over the past week.

Notes: This post was prepared in scientific style to provide links to key points in the section on climate change. All temperature data is from the National Climatic Data Center. The EPO data is through August 29. OVERVIEW Prior to 2019, July 2016 was Anchorage, Alaska's warmest month on record. Summer 2019 was even warmer than July 2016. A warm synoptic pattern that occurred within the context of increased anthropogenic greenhouse gas forcing resulted in exceptional and persistent record-breaking warmth this summer. During June-August 2019, Anchorage experienced its warmest summer on record by 2.0°F (1.1°C). Its summer mean temperature (62.815°F/17.119°C) exceeded that of its warmest month on record prior to 2019 (62.694°F/17.052°C in July 2016). Summer 2019 saw Anchorage record its warmest-ever June, July, and August. Anchorage tied its all-time record high minimum temperature on two consecutive days. Anchorage reached 90°F (32.2°C) for the first time on record. The duration of the excessive warmth and extreme temperatures recorded during the summer would have been very unlikely, if not improbable, without human-induced climate change. PREDOMINANT SYNOPTIC PATTERN Summer 2019 featured a remarkable coupling of atmosphere and ocean. A persistent upper air ridge that promoted warm and dry conditions was anchored over the waters with the highest sea surface temperature anomalies. These conditions promoted a synoptic pattern where the East Pacific Oscillation (EPO) was negative. The negative EPO combined with a negative Arctic Oscillation (AO) to form a negative Arctic Oscillation-negative EPO pattern (AO-/EPO-) that predominated during the summer. During summer 2019, the AO was negative on 81/92 (88%) days. The EPO was negative on 64% of days. An AO-/EPO- pattern is typically a warm one in Anchorage. For the current climate reference period (1981-2010), the average summer temperature in Anchorage was 56.9°F (13.8°C). During AO-/EPO- patterns, the average was 57.6°F (14.2°C). Climate change has led to summers becoming warmer and also warm synoptic patterns (AO-/EPO-) becoming warmer. ROLE OF CLIMATE CHANGE The observed global warming since the 1950s is unequivocal with anthropogenic greenhouse gas emissions being the dominant driver of that warming (IPCC Climate Change Synthesis Report 2014). The warming is a global phenomenon with 98% of the world having experienced its warmest 51 years during the current 2,000 years (Neukom, et al. 2019). Since 1880, Arctic temperatures have been increasing at more than twice the rate of global temperatures (GISTEMP Data Set). In recent decades, the rate at which the Arctic has been warming relative to worldwide temperatures has increased. From 1980 through 2018, the Arctic has warmed at a decadal rate of 1.51°F (0.84°C), which is just over 3.5 times the global rate (GISTEMP Data Set). Multiple lines of evidence corroborate the rapid warming that is taking place in the Arctic. Increases in humidity, precipitation, river discharge, glacier equilibrium line altitude and land ice wastage; warming of near-surface permafrost; and, decreases in sea ice thickness and extent, and spring snow cover extent and duration are consistent with rising temperatures (Box, et al. 2019). Consistent with the Arctic warming, Alaska has recently experienced temperatures that are warmer than they have been at any time in the past century (Thoman et al., 2019). As Alaska has warmed, Anchorage has also experienced rising temperatures. A disproportionate share of Anchorage's warmest months has occurred in 2000 or later. During the 1961-1990 base period, Anchorage had a summer (June 1-August 31) mean temperature of 56.4°F (13.6°C). During the current climate reference period (1981-2010), Anchorage's average summer temperature had risen to 56.9°F (13.8°C). For the most recent 30-year period (1989-2018), Anchorage's average summer temperature had increased further to 57.6°F (14.2°C). The last time Anchorage had a cooler than normal summer (mean temperature below the 1981-2010 reference period) was 2012 when the average summer temperature was 56.0°F (13.3°C). Without climate change, the extreme summer 2019 warmth would have been improbable. However, the combination of a rising average summer temperature and increasing variability (1961-1990: mean temperature 56.4°F/13.6°C; standard deviation: 1.4°F/0.8°C vs. 1989-2018: mean temperature: 57.6°F/14.2°C; standard deviation: 1.6°F/0.9°C) has made summers like 2019 approximately 190 times more likely than they had been. The long duration of the AO-/EPO- synoptic pattern led to the relentless persistence of above to much above normal temperatures in Anchorage that allowed monthly warm temperature records to be set in June, July, and August. Rapid Arctic warming has contributed to an increasing frequency of long-duration upper air patterns (Francis, et al. 2018). Should the world warm 3.6°F (2.0°C) above its pre-industrial temperatures, the persistence of boreal summer weather will likely increase further (Pfleiderer, et al. 2019). Based on the above evidence, human-driven climate change played a key role in bringing about Anchorage's historic summer warmth. Without anthropogenic warming, the combination of the exceptional heat and remarkable duration of the warmth in Anchorage would have been very unlikely, if not improbable. DATA AND RECORDS Summer 2019 Temperature Thresholds: Lows 60°F (15.6°C) or above: 9 days (previous summer and annual record: 4, 2016) Highs 70°F (21.1°C) or above: 49 days (previous summer record: 40, 2004; previous annual record: 42, 2013) Highs: 80°F (26.7°C) or above: 8 days (previous summer and annual record: 4 days, 2015) Highs: 90°F (32.2°C) or above: 1 day (none prior to 2019) Daily Record High Minimum Temperatures: June 8: 54°F (12.2°C) (old record: 53°F/11.7°C, 1978) June 24: 58°F (14.4°C) (tied record set in 1984) June 28: 57°F (13.9°C) (old record: 56°F/13.3°C, 2015 and 2016) June 29: 60°F (15.6°C (old record: 58°F/14.4°C, 1984 and 1990) June: 3 new records and 1 tied record July 2: 57°F (13.9°C) (tied record set in 1970) July 3: 58°F (14.4°C (tied record set in 1979 and tied in 1999 and 2014) July 5: 61°F (16.1°C) (old record: 60°F/15.6°C, 1984) July 6: 59°F (15.0°C) (tied record set in 2015) July 8: 61°F (16.1°C) (old record: 59°F/15.0°C, 1968, 2003, and 2004) July 9: 62°F (16.7°C) (old record: 59°F/15.0°C, 2003) July 12: 60°F (15.6°C) (old record: 59°F/15.0°C, 1977) July 13: 59°F (15.0°C) (tied record set in 1972 and tied in 2013) July 20: 59°F (15.0°C) (old record: 58°F/14.4°C, 1973, 1983, 2003, 2004, and 2016) July 22: 58°F (14.4°C) (tied record set in 1984 and tied in 1996, 2013, and 2016) July 24: 59°F (15.0°C) (tied record set in 1984) July: 5 new records and 6 tied records August 7: 61°F (16.1°C) (old record: 58°F/14.4°C, 1979 and 1983) August 13: 63°F (17.2°C) (old record: 57°F/13.9°C, 2003) ***tied all-time record*** August 14: 63°F (17.2°C) (old record: 58°F/14.4°C), 2001) ***tied all-time record*** August 16: 58°F (14.4°C) (tied record set in 1967) August 17: 57°F (13.9°C) (old record: 56°F/13.3°C, 1984) August: 4 new records and 1 tied record Summer: 12 new records and 8 tied records Daily Record High Maximum Temperatures: June 23: 78°F (25.6°C) (old record: 75°F/23.9°C, 1974) June 24: 75°F (23.9°C (old record: 74°F/23.3°C, 2015) June 27: 79°F (26.1°C) (old record: 78°F/25.6°C, 1997) June 28: 81°F (27.2°C) (old record: 80°F/26.7°C, 1997) June 29: 82°F (27.8°C) (old record: 77°F/25.0°C 1968, 1989, and 1990) June: 5 new records July 3: 80°F (26.7°C) (tied record set in 2018) July 4: 90°F (32.2°C) (old record: 77°F/25.0°C), 1999) ***all-time record*** July 5: 81°F (27.2°C) (old record: 77°F/25.0°C, 1999) July 6: 81°F (27.2°C) (tied record set in 2015) July 7: 85°F (29.4°C) (old record: 79°F/26.1°C, 2009) July 8: 85°F (29.4°C) (old record: 84°/28.9°C, 2003) July: 4 new records and 2 tied records August 7: 77°F (25.0°C) (tied record set in 2015) August 10: 77°F (25.0°C) (old record: 75°F/23.9°C, 1960, 1972, and 2004) August 12: 77°F (25.0°C) (tied record set in 2005) August 13: 77°F (25.0°C) (old record: 75°F/23.9°C, 1963, 1977, 2007) August 14: 75°F (23.9°C) (old record: 74°F/23.3°C, 1990) August 15: 77°F (25.0°C) (old record: 76°F/24.4°C, 1984) August: 4 new records and 2 tied records Summer: 13 new records and 4 tied records CONCLUSION Anchorage experienced a historically warm summer. The all-time record high temperature was established, the all-time record warm minimum temperature was tied on two consecutive days, and numerous daily record high maximum and minimum temperatures were set or tied. June 2019 was the warmest June on record. July 2019 was the warmest July and month on record. August 2019 was the warmest August on record. Ocean-atmosphere coupling produced a persistent pattern associated with warmer than normal temperatures. Anthropogenic climate change, that has driven global and Arctic warming and led to increasing temperature variability in the Arctic region, has dramatically increased the probability of persistent warmth and extreme high temperatures. Absent the contribution of climate change, the kind of warmth seen during summer 2019 was extremely unlikely, if not improbable. Going forward, the ongoing warming is likely to continue on account of a continuing rise in the atmospheric concentration of greenhouse gases. Although summer warmth equivalent to 2019 will likely remain rare over the next decade or two, the probability of such occurrences will very likely increase.

Hurricane Dorian will likely remain a dangerous Category 4 hurricane through much of tomorrow. Later this weekend, the steering currents will likely break down leaving Dorian drifting on its approach to Florida. The probability that Dorian will avoid destructive landfall has increased. Most EPS members now show Dorian's remaining offshore. Nevertheless, the Florida coastline will still experience heavy rain and damaging winds. Afterward, it remains uncertain whether Dorian or its remnants will have a direct impact on the greater New York City region, though it will very likely lead to rough surf and strong rip currents. Its impact on the larger circulation could drive an unseasonably cool air mass into the region for the latter part of next week. Across the Atlantic Ocean, Europe continues to experience record-breaking warmth. This latest round of heat will shift into eastern Europe beginning tomorrow before dissipating. Select daily records included: Cannes, France: 88°; Cape Mele, Italy: 93°; Clermont-Ferrand, France: 93°; Copenhagen: 79°; Fassberg, Germany: 88°; Genoa, Italy: 91°; Istres, France: 91°; Lille, France: 88°; Malmo, Sweden: 79°; Meppen, Germany: 86°; Nimes, France: 91°; Roenne, Denmark: 79°; Ronchi Dei Legionari, Italy: 95°; Soenderborg Lufthavn, Denmark: 79°; St. Dizier, France: 91°; Trieste, Italy: 95°; and, Wittmundhaven, Germany: 86°. Anchorage has experienced its warmest summer on record with a mean temperature of 62.8°. That temperature exceeds what had previously been the warmest monthly temperature on record prior to July 2019 by nearly one-tenth of a degree while smashing the prior summer of 60.8° from 2016. In addition, Anchorage experienced its warmest August on record. That follows a record warm June and a record warm July (and month). 2019 is the only year with three consecutive monthly records (cold or warm). San Francisco experienced its warmest August on record with a mean temperature of 68.4°. The old record was 68.0°, which was set 2015. Summer 2019 was also the warmest summer on record with a mean temperature of 66.1°. Although that rounded figure tied the average from summer 2014, it was nearly five hundredths of a degree warmer. The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was 0.0°C for the week centered around August 21. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.27°C. Neutral-warm ENSO conditions are in place in Region 3.4 with neutral-cool conditions in place in Region 1+2. There is considerable uncertainty about the ENSO evolution later this summer into the fall. Some of the guidance continues to show the development of neutral-cool ENSO conditions. The SOI was -11.90 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.579. The AO has averaged -1.062 for August. Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall. Therefore, a warmer than normal September and fall appear likely, though the persistence of Dorian's impact on the larger circulation has reduced the probability of a warmer than normal September. The potential for autumn 2019 to rank among the 30 warmest cases on record is on the table. On August 30, the MJO was in Phase 4 at an amplitude of 1.183 (RMM). The August 29-adjusted amplitude was 1.109. Finally, New York City had an August mean temperature of 75.5°. that was 0.3° above normal.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 0.5 0.6 0.4 0.2 1.4 1.3 0.6 1.5 2.1

Hurricane Dorian will likely continue to intensify in coming days. Late this weekend, the steering currents could break down leaving Dorian drifting on its approach to Florida. That might give it some opportunity to avoid a destructive landfall. Afterward, it remains uncertain whether Dorian or its remnants will ever have a direct impact on the greater New York City region, though it will very likely lead to rough surf and strong rip currents. Across the Atlantic Ocean, Europe continues to experience record-breaking warmth. This latest round of heat will shift into eastern Europe late this weekend before dissipating. Select daily records included: Berlevag, Norway: 75°; Carcassonne, France: 97°; Istres, France: 93°; Ivalo, Finland: 72°; Kuusamo, Finland: 72°; Mehamn, Norway: 75°; Montpelier France: 91°; Murmansk, Russia: 72°; Nimes, France: 99° (old record: 88°); Orange, France: 97°; Trieste, Italy: 90°; and, Vadso, Norway: 68°. The warmest summer on record is concluding in Anchorage. Based on sensitivity analysis applied to the latest guidance, Anchorage will likely finish summer 2019 with a mean temperature near 62.7°. That temperature would match what had previously been the warmest monthly temperature on record prior to July 2019. The summer record is 60.8°, which was set in 2016. In addition, Anchorage will set a new August record high mean temperature. The implied probability for its warmest August on record is near 100%. August would mark the third consecutive monthly record set this year. No single year holds three consecutive monthly records (cold or warm), much less during the same season, in Anchorage. Moreover, San Francisco will likely experience its warmest August on record and could match its warmest summer on record and perhaps surpassing it by a few hundredths of a degree. The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was 0.0°C for the week centered around August 21. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.43°C and the ENSO Region 3.4 anomaly has averaged +0.27°C. Neutral-warm ENSO conditions are in place in Region 3.4 with neutral-cool conditions in place in Region 1+2. There is considerable uncertainty about the ENSO evolution later this summer into the fall. Some of the guidance continues to show the development of neutral-cool ENSO conditions. The SOI was -20.70 today. Today, the preliminary Arctic Oscillation (AO) figure was -0.828. The AO has averaged -1.062 for August. Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September was 69.1° (69.8° after adjusting for ongoing warming) and 58.9° (59.6° adjusted) for September through November in New York City. The 1981-2010 baseline normal figures are 68.0° and 57.5° respectively. The majority of cases saw a warmer than normal September and all cases featured a warmer than normal fall. Therefore, a warmer than normal September and fall appear likely. The potential for autumn 2019 to rank among the 30 warmest cases on record is on the table. The MJO's recent high-amplitude passage through Phase 4 during the August 5-15 period has been followed by a range of solutions in the September 1-15 period during past cases. The coolest was 2001 with a mean temperature of 70.7° in New York City. The warmest was 1983 with a mean temperature of 77.2° in New York City. The 1981-2010 base normal for the September 1-15 period is 71.8°. A plausible outcome could see a few cooler than normal to near normal days during the first week of September followed by warming that would result in a warmer than normal September 1-15 average temperature. Dorian's impact on the larger synoptic pattern has increased uncertainty for the first 10 days of the month. The second half of the first week of September appears to offer one chance of above to much above normal readings. The second half of the month could be warmer relative to normal (not necessarily in absolute terms) than the first half. September 2019 could mark the fifth consecutive year of a 70.0° or higher monthly mean temperature in Central Park. The current 30-year period (1989-2018) is the warmest on record for September with a mean temperature of 69.0°. The most recent 10-year period (2009-2018) is also the warmest on record for September with a mean temperature of 70.1°. On August 29, the MJO was in Phase 4 at an amplitude of 1.107 (RMM). The August 28-adjusted amplitude was 0.949. Finally, New York City has an implied 76% probability of having a warmer than normal August.

The warmest anomalies will likely occur during the second half of September. Dorian's impact on the pattern has created some additional uncertainty for the first 10 days of the month.