Category: Posts EN

El Nino Watch Posted For This Fall and Winter

Written by Team Morecast

 

Forecasters with the Climate Prediction Center (CPC) have issued an El Nino Watch for later this year. They predict a 50% chance of El Nino development by the fall, ramping up to 65% by the winter.

El Nino is the positive or warm phase of the El Nino-Southern Oscillation (ENSO). ENSO is a fluctuation in sea surface temperature anomalies in the Pacific which have well-recognized impacts on global weather patterns. Model guidance has continued to come into better agreement about the progression from the current ENSO-neutral conditions to an El Nino. The graph below shows ENSO forecast values, with +1 considered the threshold for declaring an El Nino status. As you can see, threshold values are threatened within a few months of the new year.

 

 

The most significant impacts from El Nino tend to occur during the winter months in the Northern Hemisphere. However, there are warm season patterns associated with the El Nino, even a relatively minor event like the one reflected by the forecast values shown above. The graphic below shows typical warm-season influences on the weather from El Nino. The warm, dry pattern in the Caribbean is correlated with decreased tropical cyclone activity in the Atlantic basin during El Nino conditions. The El Nino phase is typically associated with stronger upper-level winds across the Atlantic basin which tend to disrupt and deter cyclone development.

 

 

Meteorologists have responded to El Nino forecasts in the last several weeks by issuing new tropical season forecasts. In April the consensus expectation was for an above-normal tropical storm season in the Atlantic. However, recent updates predict a more average or normal season. Residents of the US East and Gulf coasts as well as Central America shouldn’t breathe easy just yet, though. Some of the most infamous hurricane strikes of past years, like Hugo and Andrew, occurred in otherwise quiet El Nino-suppressed seasons. Lead photo courtesy Pixabay contributor inspirexpressmiami.

Heat Wave Will Spread to the US Eastern Seaboard By Early Next Week

Written by Team Morecast

 

Residents in the east have been lucky so far this spring and early fall. Temperatures well above normal a few months ago have trended downward over the past few weeks (see graphic below). Comfortably mild temperatures have dominated so far this spring, but look for a rapid onset of summer this weekend into early next week.

 

 

Heat watches and warnings are already in effect in the Midwest, where highs this weekend should approach 100 degrees with heat index values at dangerous levels. The strong ridge of high pressure responsible for the heat will spread to the East Coast by Sunday into Monday. Highs on Monday are expected to exceed 90 degrees well into the New England states (at least away from the cooling ocean influence). It would be the warmest temperatures in many months if the forecasts are correct. In Worcester, MA, for instance, highs only touched 90 degrees once in summer 2017, on June 12th. This blazing heat will be accompanied by high humidity, leading to health-threatening heat index values well above 100 degrees, even topping 110 degrees in the Mid-Atlantic.

 

 

Heat index values above 105 degrees are defined as dangerous with an increased risk for heat cramps and heat exhaustion. Prolonged exposure to these conditions, especially under direct sunlight which can increase the effective heat index as much as 15 degrees, can lead to heat stroke. This is a potentially deadly illness responsible for 600 deaths on average per year in the U.S. If you have outdoor plans this weekend into early next week, drink plenty of fluids, use sunscreen, and take frequent indoor breaks. Lead photo courtesy Air Force Sgt. Sheila DeVera.

Severe Storms to Straddle the US-Canada Border Thursday!

Written by Team Morecast

 

Plenty of warm, moist air will surge north into the Northern Plains on Thursday. This unstable air mass will meet a fairly strong jet stream near the international border. The combination will produce a strong threat for severe storms from Thursday afternoon into early Friday.

 

 

 

Highs will reach well into the 90s on Thursday over portions of the Central Plains, even as far north as South Dakota (see graphic above). Extreme instability will develop in this environment by early to mid-afternoon. Severe storms are expected to develop near or just north of the border after 2 pm CT. These storms will spread south and east through the afternoon, persisting as they move east well into the overnight hours.

 

 

The strongest cells will be capable of producing very large hail up to 2.5″ (6 cm) in diameter as well as isolated tornadoes through the afternoon and evening hours. Damaging wind gusts to 75 mph (120 kph) will also occur, especially if storms consolidate into an overnight squall line.

Bud Weakening, Still a Major Flooding Threat!

Written by Team Morecast

 

Tropical Storm Bud was a major hurricane as recently as Tuesday morning, when it boasted a peak sustained wind of 130 mph (210 kph). However, over the past 24 hours the storm has quickly entered much cooler ocean waters that have resulted in rapid weakening (see graphic below). Bud will continue to weaken, but will still pose a threat for heavy rain and flooding from the Baja California into northwest Mexico and the U.S. Desert Southwest.

 

Bud is now located about 190 miles (305 km) south-southeast of Cabo San Lucas, Mexico, moving north-northwest at 6 mph (9 kph). Trends suggest the storm will continue to move generally north into the southern Baja California, then northeast towards northwest Mexico near Obregon. While gusty winds could be a minor concern for some coastal spots, heavy rain will be the much more widespread and dangerous threat.

 

 

The heaviest rains of 3-6 inches (75-150 mm) are expected from the southern Baja California into the adjacent part of mainland Mexico, especially in the west-facing slopes and foothills of the central Sierra Madre range. Localized amounts higher than six inches are likely. Expect serious flash flooding in this area, along with mudslides in steeper terrain. Lesser amounts of 1-3 inches (25-75 mm) will occur elsewhere, including into parts of southeast Arizona and New Mexico.