Three Letters To Describe The Pacific Northwest Weather: H O T

Continued hot weather is in the forecast for the Pacific Northwest (PNW) through the rest of July as a strong upper-level ridge builds into the region. The Climate Prediction Center (CPC) has high probabilities of above average temperatures across the entire West Coast stretching into Alaska (see Fig. 1). High temperatures will be 6-18°F above average, which will rival the intensity and duration of the heat wave of mid-July. The warmest temperatures in Washington and Oregon will occur over the weekend as the upper-level ridge strengthens.

Fig. 1: CPC Temperature Anomaly Map For Days 6-10

So how hot will it get in the major cities of the PNW (see Fig. 2, 3, 4)?

Seattle: upper-80s to 90
Tacoma: low-90s
Olympia: low-90s
Portland: mid-90s
Eugene: mid to upper-90s
Medford: low-100s
Twin Falls: upper-90s
Boise: low-100s

The Coastal areas will escape the oppressive heat, due to the marine layer, which will keep highs in the upper-60s to low-70s.

Fig. 2: NAM Tuesday Forecast Highs

Fig. 3: NAM Wednesday Forecast Highs

Fig. 4: NAM Thursday Forecast Highs

Heat indices should remain close to the air temperature since humidity levels will remain low but the low humidity levels will increase the fire risk due to the ongoing abnormally dry conditions (see Fig. 5). Currently, there are a few fires burning in the PNW; this paired with a stagnant high-pressure, will allow a decrease in air quality in urban areas and valleys. People with breathing impairments should limit time outside.

Fig. 5: Current Drought Monitor

Overall, dry conditions can be expected in this region; however, a few isolated thunderstorms may develop during the afternoon hours across the higher-terrain. This convection will have minimal precipitation but contain gusty-winds due to evaporation and lightning. This could aid in sparking fires across northern California, southern Oregon, southern Idaho and northern Nevada.

Above average temperatures are in the forecast for the Southwest, too. A few records are possible in California. Coastal waters are well-above average in southern California making for a pleasant swimming environment (see Fig. 6).

Fig. 6: Current SST Anomalies

A break from the heat may begin next week as the upper-level ridge shifts eastward.

Winter 2018-2019 Discussion and Modoki El Niño

July and August are important months for climatologists and meteorologists to begin analyzing certain trends and variables to start the preliminary process of obtaining an idea of what may come during the winter season. There are certain areas around the World we can look to, to aid in providing a ‘snapshot’ of what the winter season may look like for the U.S. One area that is important to look at is the equatorial Pacific. The state of this region can play one of the puzzle-pieces (an important puzzle-piece) into how the winter will shape up. There are three very important variables to analyze when looking at the equatorial Pacific: I) sea-surface temperature (SST) anomalies, II) the positioning of the anomalously warm or cool SSTs, and III) the depth of the anomalously warm or cool SSTs.

As of mid-July, the state of the equatorial Pacific is trending anomalously warm which is signaling El Nino conditions developing (see Fig. 1). This is supported and is expected to continue per the majority of the models (see Fig. 2). We are currently in a neutral condition (not El Niño or La Niña); however, due to this region continuing to warm since March, the chances of El Niño developing are increasing. The Climate Prediction Center has increased the odds of El Niño developing in the winter to 65%.

Fig. 1: Current SST anomalies (Tropical Tidbits)

Fig. 2: Models ENSO predictions (IRI and CPC)

So what is El Niño? El Niño is simply a climate pattern that occurs when SSTs (in the equatorial Pacific) are above-normal for a long period of time. This climate pattern is a cycle (ENSO) in which below-normal SSTs can occur, too, in which the development of La Niña can occur. This climate cycle play an important role in shaping weather patterns around the entire World. Of significance, are the impacts of this cycle on the winter in the U.S. During an El Niño, the storm-track tends to shift significantly southward (see Fig. 3). This causes an increase in cloud-cover and precipitation for the southern U.S. In return, due to the cloud-cover and precipitation, temperatures tend to be below-average in this region. It can also lead to above-average temperatures in northern parts of the U.S. The impacts on temperatures and precipitation, however, are dependent upon the strength of the El Niño and the positioning of the warm SSTs.

Fig. 3: El Niño winter pattern in North America (CPC)

Based on the current trends and available data, it appears a weak to moderate Modoki El Niño may develop by late fall/winter. I am sure you’re wondering what differences, if any, are there between Modoki El Niño and El Niño. And yes, there are differences. An Modoki El Niño is slightly different than the conventional El Niño (see Figures: 4 and 5). Modoki El Niño features stronger warming, and at a great depth, of the central equatorial Pacific and cooling in the eastern and western tropical Pacific. This is what is occurring based on the latest SST anomalies (see Fig. 1). Also, notice the cooler temperatures along the West Coast of South America. This is a signature, when paired with the central warming, of Modoki El Niño.

Fig. 4: El Niño SST anomalies (JAMSTEC)

Fig. 5: Modoki El Niño SST anomalies (JAMSTEC)

This type of warming and cooling pattern in the tropical Pacific alters the normal winter pattern in the U.S. and has different implications than the typical El Niño on temperatures and precipitation (see Figures: 6, 7, 8 and 9). Instead of the Southwest seeing an increase in rainfall, as expected with El Niño, Modoki El Niños can cause an increase in temperatures and lack of precipitation in this region. An increase in storminess and cool temperatures can occur for South-central and Southeastern parts of the U.S. during a Modoki El Niño.

Fig. 6: El Niño temperatures (JAMSTEC)

Fig. 7: Modoki El Niño temperatures (JAMSTEC)

Fig. 8: El Niño precipitation (JAMSTEC)

Fig. 9: Modoki El Niño precipitation (JAMSTEC)

Updates will be needed as we head into August and September, but I wanted to give some insight into what I am currently analyzing for the winter season in the U.S. Please note, this is only one puzzle-piece in a medium to long range forecast. Other teleconnections can influence fall and winter patterns that have big implications on temperatures and precipitation.

If you’re tired of the extreme heat, you’re in luck (for a while) if you live across parts of the Southeast, Northeast, Plains and Midwest. For the Plains, below-normal temperatures will arrive by late this weekend, followed by below-normal temperatures arriving for the Midwest, Northeast and parts of the Southeast by mid-week–and overall continuing for the rest of the second half of July.

The drier/cooler air is due to a big dip in the jet-stream across central and eastern parts of the U.S. This “dip” will allow for periodic frontal passages to dive south and eastward, ushering in below-normal temperatures and lower dewpoints for the second half of July. The Climate Prediction Center (CPC) concurs that an upper-air pattern change will occur, ushering in near to below-normal temperatures (see Fig. 1 and Fig. 2). The gray to blue colors indicate probabilities of temperatures near (gray color) to below-normal (blue colors).

Fig. 1: CPC 6-10 Day Temperature Outlook

Fig. 2: CPC 8-14 Day Temperature Outlook

While it won’t feel cold outside, temperatures will fall to below-normal values. Highs will be in the 80s for parts of the Southeast and 70s/low-80s for the Plains, Midwest and Northeast; with lows dipping into the 50s for these areas and mid-60 degree lows as far south as northern Mississippi, northern Alabama and northern Georgia. It is possible a brief return to above-normal temperatures will occur by the weekend before another cold front ushers in below-normal temperatures for the following week.

Which Day Is The Warmest Day Of The Year?

It’s a very warm day across much of the country today so I am sure many of you are wondering when the warmest day of the year is for your area. According to National Centers For Environmental Information (NECI), the average warmest day for the lower-48 varies from June through September (see Fig. 1). Parts of the Southwest and Midwest have already experienced the warmest day on average.

Fig. 1: NECI Map Of Average Warmest Day

For areas that have yet to see the warmest day of the year, it is upon you over the next month. Much of the, South, Southeast, North-central, and Northwest parts of the U.S. will see the warmest day between July 15th and August 15th (depending on the area).

Just a friendly reminder, Autumn is only 51 days away!

(Please keep in mind, this map is based on long-term averages {1981-2010} and certain weather features can cause the warmest day to occur later in the year than what is shown on this map.)

Tropical Depression Three

5:30PM Eastern Update

Tropical Depression Three (TD3) has officially developed off of the coast of North Carolina. TD3 has maximum sustained winds of 30 mph and moving to the NNW at 5 mph (see Fig. 1). TD3 is expected to strengthen into a weak Tropical Storm by Saturday followed by further intensification into a hurricane by late Sunday or early Monday.

Fig. 1: National Hurricane Center Forecast

While intensification of TD3 is likely due to the warm sea-surface temperatures and a low environmental shear, landfall across the Carolinas does not look likely at this time. TD3 is slowly moving towards the NNW but should begin to meander (or nearly become stationary) over the weekend due to weak steering currents. By early next week, it appears a trough will pick-up the tropical cyclone and shunt it off the NE, thus, landfall is not expected across the Carolinas. Due to the Carolinas being on the west side of the tropical cyclone, no direct impacts are likely. The majority of the rain and wind associated with the system should remain offshore (however, there is an outside chance the outerbanks see scattered showers/storms).

With that said, if you live along the coast from Virginia down to South Carolina, it is wise to keep a close eye on the forecast. The National Hurricane Center does include the outerbanks of North Carolina in the official cone of uncertainty. Any small changes to certain upper-level features may make landfall more possible. Rip currents are a guaranteed hazard with this system along the East Coast so be careful if you’re headed to the beach.

Firsthand Weather will have updates as needed!

Tropical Update (Carolinas Need To Remain Alert)

Things have heated up in the Atlantic this week. Firsthand Weather is closely monitoring two systems: I) Invest 96 L and 2) Hurricane Beryl.

Invest 96 L
At this hour, we are keeping a close eye on a well-defined low that is spinning off of the coast of the Carolinas (see Fig. 1). Looking at the 850 mb vorticity, which shows the structure of the storm (see Fig. 2), shows Invest 96 L is compact and circular which is a positive sign for further development into a tropical cyclone (tropical depression or tropical storm) in the near future. The atmosphere has moistened paired with upper-level divergence (see Fig. 3), which has led to a substantial increase in convection associated with Invest 96 L (see Fig. 4). The National Hurricane Center (NHC) has given this low a 70% chance of development into a tropical cyclone over the next 48 hours and an 80% chance of development over the next five days.

Fig. 1: National Hurricane Center Forecast

Fig. 2: Current Vorticity Map (University of Wisconsin)

Fig. 3: Upper-Level Divergence Map (University of Wisconsin)

Fig. 4: Current Satellite Imagery

As Invest 96 L develops into a tropical cyclone (tropical depression or tropical storm) over the next couple of days, the system will track slowly north and westward towards the outerbanks of North Carolina. At the same time, a potent cold front will move into the Carolinas along with an approaching shortwave by Saturday night. Depending on the intensity of the low, it is possible it will get absorbed by the frontal system and eventually dissipate. Another possible scenario is the low intensifies and meanders just off of the coast of the Carolinas before either moving out-to-sea or towards land.

Right now, it is too early to determine if landfall will occur or if an out-to-sea scenario will occur. This situation needs to be closely monitored. If the low sits off of the coast of the Carolinas, it is possible (being on the western side) that rain and wind impacts may be minimal to nonexistent, but it is also possible that impacts may be felt if the system gets closer to the coast. Regardless, if you have beach plans in this area, it is best to stay out of the water. Rip currents will be a guaranteed hazard with this system.

Hurricane Beryl
We are also monitoring Hurricane Beryl (see Fig. 5). Beryl quickly strengthened into a hurricane and has maximum sustained winds of 80 mph with higher gusts and is moving to the west at 14 mph. Beryl should continue to strengthen over the next 24-36 hours with maximum sustained winds increasing to 100 to 110 mph. As Beryl approaches the Lesser Antilles by late this weekend, it should feel the influence of the shear over the eastern Caribbean (see Fig. 6) and weakening back into a tropical storm looks likely.

Fig. 5: National Hurricane Center Forecast

Fig. 6: Shear Map (University of Wisconsin)
Beryl should impact the islands as a tropical storm. Regardless of weakening, an increase in rain chances and gusty winds will occur for the Lesser Antilles followed by an increase in rain chances for Puerto Rico and the U.S. Virgin Islands early next week.

Please keep checking back for updates!

Tropical Storm Beryl

Satellite imagery indicates Tropical Depression Two has strengthened into a Tropical Storm. Tropical Storm Beryl developed in the central Tropical Atlantic and has maximum sustained winds of 50 mph with higher gusts. Beryl is moving to the W at 16 mph.

Fig. 1: National Hurricane Center Forecast

Shear is currently high ahead of the storm over the eastern Caribbean (see Fig. 2), which should prevent significant strengthening. However, Beryl should slowly increase in intensity over the next 24-48 hours. Right now, it appears Beryl should reach weak-hurricane status with strengthening up to around 75 mph by Saturday morning. As Beryl approaches the Lesser Antilles by late this weekend, it should feel the influence of the shear over the eastern Caribbean and weakening looks likely. Regardless of weakening, an increase in rain chances will occur for the Lesser Antilles followed by an increase in rain chances for Puerto Rico and the U.S. Virgin Islands on Sunday into Monday.

Fig. 2: Current Shear Map (University of Wisconsin)

Fig. 3: Sunday Morning Shear Map (Tropical Tidbits)

Updates will be provided as needed!

Tropical Depression Two Forms

Tropical Depression Two (TD2) formed in the central Tropical Atlantic this morning. TD2 will track westward through this week into the weekend (see Fig. 1). At this hour, TD2 has maximum sustained winds of 35 mph and moving to the W at 16 mph. TD2 is expected to strengthen into a weak Tropical Storm by Friday morning.

Fig. 1: National Hurricane Center Forecast

Shear is currently high ahead of the storm over the eastern Caribbean (see Fig. 2). As TD2 continues its trek westward, shear values are forecast to remain high in this region (see Fig. 3), which appears to keep TD2 from strengthening any further than a weak Tropical Storm. Right now, it appears TD2 may reach 50 mph intensity. As TD2 (likely as a Tropical Storm) approaches the Lesser Antilles by this weekend, it should feel the influence of the shear and it is possible weakening will occur. Regardless of weakening, an increase in rain chances will occur for the Lesser Antilles followed by an increase in rain chances for Puerto Rico and the U.S. Virgin Islands on Sunday into Monday.

Fig. 2: Current Shear Map (University of Wisconsin)

Fig. 3: Sunday Morning Shear Map (Tropical Tidbits)

This is a fluid situation so please keep checking back for updates from Firsthand Weather!

Big Cool Down On The Way!

Tired of the heat? You’re in luck if you live across the parts of the South, Northeast, and Midwest. A big break in the recent heat will begin to take place late this week into the weekend. The upper-level high that has kept the east very hot, will begin to weaken and shift westward late this week. The retrograding of this high will allow a trough to dip into the Northeast, which will send a cold front southward into areas east of the Mississippi this weekend. The air behind the cold front will be much drier and cooler. Temperatures will drop 5-15 degrees in some areas (especially across the Midwest and Northeast).

Friday High Temperature Anomalies

Saturday High Temperature Anomalies

Sunday High Temperature Anomalies

While it won’t be cold outside, or even chilly, temperatures fall to near to slightly below normal for parts of the South, Midwest, and Northeast. This will end the Excessive Heat Warnings and Heat Advisories. Temperatures should moderate by early next week.

2018 Atlantic Hurricane Season Revisions

Revisions have been made to the 2018 Atlantic Hurricane Season according to Colorado State University (CSU). CSU is expecting the season to be less active than originally thought, which would lead to a below-average hurricane season for the Atlantic. This is according to an updated outlook (July 2nd, 2018) from CSU.

The main variable in the predicted reduction of named storms is due to cooler Sea-Surface Temperatures (SSTs) across the tropical Atlantic (see Fig. 1). Below-average SSTs have persisted throughout the early hurricane season and has expanded since May. Below-average SSTs in this region tends to lead to a less-active hurricane season.

Fig. 1: Sea-Surface Temperature Anomaly Map From Tropical Tidbits

Another variable that may influence the hurricane season is the potential return of El Nino conditions later this year. The waters near the equator across the eastern Pacific and central Pacific have warmed to above-average (see Fig. 2). While not technically reaching the El Nino threshold yet, wind shear has been abnormally strong over the southern Gulf of Mexico and Caribbean Sea thus far during the hurricane season. This along with the equatorial-Pacific waters warming, typically is indicative of the development of El Nino.

Fig. 2: Sea-Surface Temperature Anomaly Map From Tropical Tidbits

The new outlook from CSU now includes 11 named storms, which includes already named Subtropical Storm Alberto, for the 2018 season (see Fig. 3). Of the 11 named storms, four hurricanes are expected with one of the hurricanes reaching major status (Category 3 or higher). The previous outlook from CSU called for 14 named storms (6 hurricanes with 2 being major hurricanes).

Fig. 3: Updated 2018 Atlantic Hurricane Season Outlook

Firsthand Weather is also forecasting an average to below-average season for the Atlantic. Regardless of the number of named storms in a hurricane season, it only takes one storm making landfall to cause significant impacts.