Category: Tropical Weather

June is a little more than a week away, and while that marks the start of meteorological summer, it also marks the start of Hurricane season in the Atlantic Basin (North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico).

Hurricane season in the Atlantic runs from June 1 through November 30, but it got off to an extraordinarily early start in 2016 when Hurricane Alex formed back in January. Alex became the first January tropical system in the Atlantic when it acquired subtropical characteristics south of the Azores on January 13. It became a full-fledged hurricane on January 14, the first January hurricane in the Atlantic since Alice in 1955. Alex crossed the Azores as a strong tropical storm on January 15, and eventually head out in the open Atlantic transitioning to an extratropical cyclone on January 17. The next storm that forms will be given the name Bonnie.

Is the early start a harbinger for an active hurricane season? Not necessarily. What will be more of a factor is the developing La Nina in the Pacific Ocean. In an El Nino, such as the one we had in 2015, the subtropical jet stream is stronger, which inhibits storm development as the jet stream effectively cuts the tops off of storms before they can develop. In a La Nina, the subtropical jet is weaker, allowing easterly winds to dominate, which allows the storms to develop.

The presence of El Nino or La Nina is just one of many factors that go into whether a hurricane season is active or quiet, but most predictions are for activity to be more common than in 2015 and above normal. In a normal season, the Atlantic Basin sees 12 named storms, of which 6 become hurricanes and 3 become major hurricanes (Category 3 or higher on the Saffir-Simpson Scale). While there are plenty of hurricane forecasts out there, these were pioneered by Dr. William Gray, who recently passed away after over 50 years in the field. His research team at Colorado State University continues his work, and for this season is calling for 14 named storms, of which 8 could become hurricane, and 3 major hurricanes.

An active season doesn’t guarantee that a storm will make landfall in the United States though. In 2010, there were 19 named storms, 12 hurricanes, and 5 major hurricanes. Only 1 storm, Tropical Storm Bonnie, made landfall in the United States. On the flip side, 1992 was a quiet season, with just 7 named storms, 4 hurricanes, and 1 major hurricane, with the first named storm not forming until August 16. Of course, that first storm was Andrew, which slammed into South Florida on August 24 as a Category 5 hurricane, one of just 3 Category 5 storms to ever make landfall in the United States.

The peak of the season usually occurs from mid-August through late September, but an early start isn’t unusual. On average, the first name storm of the season occurs on July 9, with the first hurricane forming around August 10. In 2015, there were two tropical storms during May and June (Ana and Bill), while 2012 saw 4 named systems (Alberto, Beryl, Chris, and Debby) with 1 hurricane (Chris) forming before the end of June.

An upper level low pressure system will slowly move into the Southwest over the next few days. Between Thursday through Saturday, plenty of moisture will be streaming in from the south, resulting in 2 to 3 inches of rain falling in portions of the Great Plains. Mechanisms helping this along include the strong low level jet from the south with an intensity that is 2 to 4 standard deviations above normal at times. Favorable upper level jet dynamics, in the form of the right rear quadrant of the upper level jet, will be above the region, allowing for strong large scale lift. Moisture in the atmosphere, in the form of precipitable water, will also be 2 to 4 standard deviations above normal. The one important part of the movement of this system is the fact that the low pressure system gets picked up by a trough to the northwest and directed north, meaning that the main forcing gets directed north while the bulk of the moisture stays south. At the same time, however, the precipitation is directed into the same area in northeastern Texas Thursday night to Sunday morning as a cold front runs into a surface trough. All in all, while severe storms are possible with this setup, flooding seems the most problematic outcome with a continuous flow of moisture paired with dry hard-packed soil that will suck up little rainfall in portions of the Southern Great Plains. The rain should shutoff early Sunday as a ridge of high pressure enters. The ridge of high pressure lasts until Tuesday, when another cold front comes in.

Meanwhile, in the Tropics, the Atlantic remains quiet. However, in the Eastern Pacific, Tropical Depression Twenty-E is centered about 235 miles southeast of Puerto Escondido, Mexico as of Tuesday evening. This low pressure system will be directed to the west-southwest by a mid-level ridge just to its north, over the Gulf of Mexico. The ridge is forecast to move eastward so the low pressure system is then steered to the north between an approaching front to the west and the high pressure ridge to its east. Guidance also seems to be in agreement that a landfall in western Mexico should occur around Saturday as a hurricane. An increasing intensity has been indicated by the previous text in this paragraph and this fits with the large scale environment being conducive for development. The main contributors are very warm sea surface temperatures and light shear adjacent to the storm. Even still, two areas with negative impacts on the storm are possible with dry air entrainment into the storm from strong winds through the Isthmus of Tehuantepec and an uncertain inner core strength. If the inner core does get strong enough, dry air entrainment will become less of a problem. It is thought that the positive factors will outweigh the negative factors so intensification is forecast with the storm becoming a Tropical Storm between now and early Wednesday. In the Central Pacific, Hurricane Olaf is located 1060 miles east-southeast of Hilo, Hawaii and 1275 miles east-southeast of Honolulu Hawaii. Hurricane Olaf does have 15 nautical-mile wide eye and a concentric ring of convection. A recurving track is forecast for Olaf as it moves around a ridge of high pressure to its north. Then a disturbance picks up Olaf and brings it northeast. This track keeps the bulk of the hurricane’s main impacts away from the Islands, but a strong swell is still possible this weekend. Shear is expected to remain weak until later Wednesday and the system does move over warm sea surface temperatures so strengthening is possible in the near term. Next, shear is expected to increase water temperatures are expected to decrease so weakening is possible starting Friday.

The US is littered with all sorts of weather for this weekend. The most hazardous weather has already been addressed in a previous blog post entitled, “Much Colder Air Headed for the Great Lakes and Northeast” and is all about the cooler temperatures and, combined with the scattered precipitation across the Northeast, snow; especially in the northern and western areas of the Northeast and higher elevations. A warm up is expected after the cooler air aloft moves offshore and warmer air moves in beginning this coming Tuesday.

Furthermore, a cold front moves onshore in the Western United States bringing showers and inland thunderstorms to an area that has been very dry this summer and has had numerous wildfires sprout. Between Saturday and Tuesday, a 3-day rainfall total of up to 3 inches is expected in portions of the Rockies with under an inch possible in other lower elevations. Still, southwestern California may remain dry as plenty of dry air remains around the region and may allow for evaporation before the rain reaches the ground. Some flash flooding is possible in the Southwest as the warm, moist flow continues to enhance showers and storms.  Some drought relief is possible this winter as a strong El Nino is developing. On average, California receives plenty of precipitation during El Nino events, so a dent may be made in its drought situation. In the 1997 strong El Nino, California received plenty of rain, but it was spread out over a long time period, which is the best case scenario, because it means less flood problems as opposed to when it comes all at once with ground that dry and stiff. A few quick events can help to moisten and open up the ground for future event and allow for some absorption of the water into the ground. With many of the smaller events, snow can still accumulate in the higher elevations, which helps the drinking water problem because of melt-water runoff once the winter is over. Of course not every El Nino is the same so it’ll be worth watching this winter.

Over the oceans, the Atlantic remains quiet with only one area that could develop tropical characteristics. Even still the chance that that happens is low. It is near the Yucatan Peninsula and is associated with an area of low pressure nearby. Its proximity to land is not helping its development chances at all during the next day or so. Some tropical development is possible as it crosses back over onto water late this weekend or Monday. Even without tropical development, heavy rain is expected over Central America from the system. In the Eastern Pacific, Tropical Storm Olaf resides 1660 miles west-southwest of the southern tip of the Baja Peninsula. It has been affected by an area of high pressure, but that is set to weaken, which should allow a gradually slowing of speed and move more northward. Pressure centers and resultant stream flow allow for a continuation of a northward movement of Olaf especially by Tuesday, though gradually increasing northward movement is also possible starting today. In terms of intensity, shear currently around the storm is affecting it, but it isn’t understood how much. It’s thought that the shear is slowing the intensification so with shear expected to diminish by around Monday, intensification should occur to a major hurricane in the early work week. Another area of showers and storms needs to be watch especially by 5 days out or midweek next week for tropical development into a tropical depression as it moves westward away from the Americas. Further development of this system is likely.

A large majority of the nation is enjoying quiet weather this Sunday. The biggest exception is in the Southeast thanks to a developing low pressure system east of Georgia. The persistent easterly flow north of the system, combined with a strong high pressure area to the north, along with astronomically high tides. is producing flooding along the coast from the Mid-Atlantic states southward to Florida. A second area of low pressure is centered across the Gulf of Mexico. This will bring showers and thunderstorms to much of the Gulf Coast, and Deep South. Some of these storms could produce locally heavy rainfall as well.

Meanwhile, strong winds are noted across the Northern Plains ahead of a cold front. Wind gusts have exceeded 30-40 mph across portions of the region today. The front will cross the region tonight, with only a few showers expected in places. However, as the front moves farther to south and east in the coming days, expect showers and possible thunderstorms along it as it runs into warm/moist air. The place that looks the most conducive to severe weather tomorrow should be from the Western Plains into the Central Rockies.

In the Atlantic, an area of disturbed weather about 425 miles southwest of Bermuda is being monitored for tropical development. Conditions are favorable for additional development for the next day or two, but should become unfavorable beyond that. Another area that is being monitored for possible tropical development is located over the northeast Yucatan Peninsula this afternoon. This system is interacting with an upper-level low pressure system in the western Gulf of Mexico, producing scattered showers and thunderstorm. This system is expected to move north toward the northern Gulf over the next couple of days, but upper level winds are only marginally conducive for development. Whether or not tropical development occurs with this storm, it will likely produce heavy rainfall across the Gulf Coast and parts of the Southeast over the next several days.  Elsewhere in the Atlantic, Tropical Depression Ida dissipated about 1000 miles east of the Leeward islands this afternoon.

In the Eastern Pacific. Tropical Storm Marty is centered about 235 miles west-southwest of Acapulco, Mexico this afternoon, drifting toward the north at 3 mph. Some slight strengthen is expected over the next day or so before a weakening trend will likely commence. The forecast track for Marty contains some uncertainty, but due to its proximity to the Mexican coast, a Tropical Storm Watch has been issued from Acapulco to Lazaro Cardenas. Another area of storms about 1000 miles southwest of Cabo San Lucas, Mexico is being monitored for development this afternoon. Conditions aren’t favorable for development at this time, but as it drifts northward or northeastward over the next few days, some development is possible.

A cold front is the major weather-maker today as it settles into the Southern Plains and Southeast. The front will continue to push through the Southern Plains on Monday producing additional showers and thunderstorms. The main threat for those storms will be gusty winds, hail and heavy rain. As the front stalls out across the Southeast over the next few days, it will have ample opportunity to create showers and storms with the possibility of heavy rain, wind, and possibly some hail. This is not to say that showers and thunderstorms are expected the entire time, as cloud cover and dry air will both remain in place nearby. So watching for when energetic disturbances move into those regions will be key for storm initiation. One such disturbance looks to push through today in Texas while an upper level low serves as a center for storms on Monday in the Southeast.

Meanwhile, in the tropics there are a few areas that bear watching. The strongest is in the Atlantic Ocean as Tropical Storm Ida continues its northwestward movement at 17 mph. As an area of high pressure strengthens to the north of Ida, it should slow down the storm’s forward motion and models indicate that it may become stationary as well. Ida’s low-level center remains exposed because of the westerly shear. This shear is expected to weaken in the next day or two, allowing for the possibility of strengthening. However, the shear is expected to pick back up as an upper level trough helps to increase it. This may stall or even decrease the intensity of the storm. Another area of interest in the Atlantic resides about 325 miles east of northeast Florida. Because it is not showing signs of being tropical or even subtropical, the reconnaissance mission into the storm that was scheduled for today was canceled. The storm resides in an area that is not conducive to development while its low level center remains exposed. All of these factors give low tropical formation chances within the next few days.

In the Eastern Pacific, an area of storms located west of the Baja Peninsula has been tagged as Tropical Depression Sixteen-E. As it moves north-northwestward at 14 mph, it looks to enter an area less conducive to development tonight with cooler waters and strong upper level winds. It will also spread heavy rain into the Baja Peninsula and northwestern Mexico today and into portions of southern California and Arizona on Monday and Tuesday. Once again, be aware of flash floods and mud slides in mountainous areas of Mexico and the Southwest.

In the Central Pacific, Tropical Depression five-C continues to battle shear on its western side, shifting all the convection to the eastern side and exposing the low level center. The depression is moving toward the north-northeast and is expected to increase its speed today as steering flow increases. As it moves along its track, a shift from a northeastward movement to more northward and then northwestward movement is expected as it gets caught in the upper level pattern. Some model disagreement occurs with the intensity of the storm itself, but it is expected to increase in intensity from a tropical depression to a tropical storm later tonight, even as shear increases. However, the system should transition into an extratropical storm over the next 2-3 days. Tropical Storm watches and warnings are in effect for some of the Central Pacific islands located well to the west of the Hawaiian Islands.

Drought conditions persist across the Western United States, in some places the drought is extreme. Because of the dryness, along with lightning from thunderstorms among other causes, wildfires have been sparked all over the region. A few wildfires have burned property including the well-known “Valley Fire” in California, which has even claimed lives.

Some welcome relief was also seen this past week as a low pressure system and cold front moved onto the United States from the Pacific Ocean. This produced rainfall from the San Francisco Bay Area northward to Washington State. A report detailing the fire situation quoted an official with Cal Fire saying, “Crews have made continued good progress on several fires burning in California. A little bit of rain has helped along with cooler temperatures and higher humidity.” Of course, as a cold front pushes through an area where a wildfire is ongoing, forecasters and firefighters are also aware of increasing winds and wind direction changes that may help to spread the fire even further.

Elsewhere, as we get into the climatological peak of hurricane season, the tropics are becoming active again. In the Atlantic there are three areas that are being monitored. Tropical storm Ida is centered a little more than 1100 miles west of the Cape Verde Islands and is moving west-northwest at 14 mph. It has maximum sustained winds at 40 mph. Ida should remain a tropical storm for the next few days while crossing the Central Atlantic.

A little farther to the west. Tropical Depression Nine dissipated late Saturday afternoon. Conditions are not favorable for the storm to redevelop over the Central Atlantic. The third area being watched is an area of disturbed weather a few hundred miles off the Southeast coast.. There, conditions are marginally favorable for tropical development during the next few days. The system should move off tho the northeast, staying off the East Coast, with some strengthening possible.

In the Eastern Pacific Ocean, an area of disturbed weather located about 275 miles south-southwest of the Cabo San Lucas, Mexico is being monitored for development. Some development is possible over the next few days, but the main threat from this system will be heavy rainfall across northwestern Mexico and southern portions of Arizona and California as the system moves toward the north-northwest.

In the Central Pacific Ocean, Tropical Depression Five-C is centered about 360 miles northwest of Johnston Island, moving toward the north-northeast at 15 mph. Top winds are near 35 mph, and some strengthening is possible over the next day or two. After that, gradual weakening is expected as the system moves across open waters.