Tropical Troubles For Gulf?

Saturday Morning Update:
The NHC has given this tropical wave a 40% chance to develop over the next five days.

Friday Evening Update:
The tropics may begin to heat up “close to home” next week as a tropical wave eventually encounters more favorable conditions for intensification. Currently, the tropical wave is sitting south and east of Florida (near the island of Hispaniola) and has a 10% chance of development over the next five days according to the National Hurricane Center (see Fig. 1).

Fig. 1: NHC monitoring tropical wave
The tropical wave will move north and westward into the eastern Gulf of Mexico by early next week. At this point, the tropical wave may begin to organize and intensify into a tropical cyclone. Wind shear is currently preventing organization (see Fig. 2) but this should lessen by mid next week across the Gulf (see Fig. 3). Numerical guidance is struggling with the evolution and movement of the tropical wave. The European is currently stronger and shows the wave intensifying potentially into a tropical cyclone (see Fig. 4). The GFS, however, keeps this as an open wave. The strength will play a role in the movement of the wave. An open wave would likely track towards the northwestern Gulf whereas a tropical cyclone would likely move towards the north-central Gulf.

Fig. 2: Current wind shear (Friday)

Fig. 3: Future wind shear (Wednesday morning)

Fig. 4: European 850mb winds (Wednesday morning)
Regardless of intensity, tropical moisture will aid in heavy rainfall for much of the Gulf. Heavy rainfall and gusty winds will impact parts of Florida as soon as this holiday weekend followed by rain chances increasing for the northeast and north-central Gulf by early to mid next week. Several inches are possible across the northern Gulf next week (see Fig. 5).

Fig. 5: 7-day rainfall totals
This tropical wave needs to be closely monitored over the weekend. Updates on potential track and intensity will be provided as uncertainty decreases.

First Winter Weather Advisory Of The Season Issued In The Lower-48

Winter weather will grace parts of the northern Rockies early this upcoming week as snow levels drop to around 9,000 feet. The Billings National Weather Service (NWS) issued the first Winter Weather Advisory (WWA) of the season for parts of southern Montana (see Fig. 1).

Fig. 1: Current WWAs for Montana

2-7″ with isolated higher amounts are likely for the Beartooth and Absaroka Mountains (see Fig. 2). This will cause hazardous travel conditions where the heaviest snow falls. Snow will not be limited to Montana. Northwestern Wyoming and Northwestern Colorado will see snow in the higher elevations (see Fig. 3).

Fig. 2: Latest message from the NWS

Fig. 3: NAM snowfall forecast

Late-August snow is not unheard of for the northern Rockies. The jet-stream begins to dip slightly southward this time of the year, which can cause snow levels to drop. It’s just a matter of time before more areas in the lower-48 pickup their first snow of the season.

Western Relief (From Heat & Smoke) And Snow!

Much of the West has been plagued by heat and smoke but a change in the weather pattern will lead to cooler conditions and better air quality by as early as tomorrow (Thursday). A trough will build into the West through the end of this week into the weekend (see Fig. 1). This will allow cooler air to advect into the region. The greatest impacts will be felt across the Pacific Northwest (PNW) but impacts will not be limited to the Pacific Northwest–the Southwest will cool down as well.

Fig. 1: Trough building into the PNW

Temperatures will fall a good 15 to 30 degrees across parts of the PNW with more subtle cooling across parts of the Southwest but still allowing for below normal temperatures (see Fig. 2). For the PNW, high temperatures will be in the 60s to low 70s in the low elevations with higher elevations remaining in the 40s. There is even the possibility of snow for the highest elevations in the Cascades and northern Rockies where a few inches may fall. If you have plans to go up to Mount Rainer, snow will be likely from late week through the weekend. An increase in precipitation is likely for the region, too.

Fig. 2: Climate Prediction Center temperature probabilities (days 6-10)

Along withe the cooler temperatures and increase in precipitation chances, the air quality will improve as the trough builds in (see Fig. 3 and 4). It should be noted, this pattern change will change the direction of the surface winds, which will impact fire movement for wildfires that are not contained.

Fig. 3: Near-surface smoke (this morning)

Fig. 4: Near-surface smoke (Friday)

Hurricane Lane Likely To Directly or Indirectly Impact Hawaii Later This Week

Hurricane Lane is currently a powerful category 4 hurricane with maximum sustained winds of around 150 mph, making it a borderline category 5 storm. Earlier model projections had Lane skirting to the south of the Hawaiian islands, but over time, model guidance has begun to trend northward, increasing the likelihood that Hawaii with either be indirectly or directly impacted by Lane. Hopefully, the residents of Hawaii have undertaken procedures to protect their homes such as installing High Impact Windows.

When a hurricane strengthens, the wind flow in the mid and upper-levels of the atmosphere becomes increasingly important, since those winds have a strong influence on the steering of the storm. Over the last several days, Lane has remained positioned to the south of a mid-level high pressure system that has extended as far west as the Hawaiian islands. Given that the flow around a high pressure feature in the Northern Hemisphere is clockwise and given Lane’s previous position relative to the high, the hurricane has generally been on a westward track. The issue is that as Lane continues westward, the high is going to weaken over/near Hawaii, which will eventually put Lane on the western periphery of that feature. This means that Lane will likely begin to make a northwestward turn towards the Big Island in a day or so.

There is generally a consensus between the operational European and GFS models that Hurricane Lane is going to begin making a turn northwestward towards Hawaii by mid-week. The GFS projects that the Big Island will be directly impacted by the storm, while the European model brings the storm a bit farther westward and directly has it impacting the smaller Hawaiian islands to the west.

GFS hurricane lane forecast

European hurricane lane forecast

Hurricane Lane is currently in an environment with low vertical wind shear and sufficiently warm sea surface temperatures. This has played a significant role in Lane’s recent strengthening. Lane is expected to encounter strengthening southwesterly wind shear as it approaches the islands, but the issue is that this probably won’t occur until Lane is already impacting the islands. The low-level flow is generally from east-to-west, which would be much more influential on Lane’s motion if it were weaker. In this scenario, Lane would be steered more westward. However, as long as Lane remains adequately strong which is now the most likely scenario, it will begin moving dangerously close to the islands later this week.

The Central Pacific Hurricane Center is going with a consensus between the GFS and European models in their latest track projection and has issued hurricane watches for the eastern half of the islands. Note that the Big Island, along with several of the smaller islands to the west are now in the cone of uncertainty. The forecast will have to be fine-tuned over the next couple of days, as far as whether or not there will be an actual landfall or where that could occur. However, given the size of Lane, impacts will most likely occur to Hawaii even if Lane does not technically make landfall on any of the islands. Once Lane begins to interact with Hawaii’s mountainous terrain and becomes more heavily influenced by increasing vertical wind shear, it will begin to weaken and steer westward. Since Lane will gain a lot of latitude over the next several days, this increases the odds that a large part of the island will at least be impacted, to some extent.

Hurricane Lane Track

If you are planning to be in Hawaii this week, please continue to monitor these forecasts closely. If you have plans to travel to the island and can change those plans, I encourage you to keep an eye on the latest forecasts through today and tomorrow and change plans, if necessary. Please continue to follow Firsthand Weather on Facebook and Twitter, as we will be continuously posting updates on social media.

Developing Low Pressure System Will Usher In Fall-Like Temperatures

Around this time of year, the majority of us begin to wonder when we’re about to get a little cooler weather. Sometimes, parts of the United States manage to get a few days of fall-like temperatures in later August, and luckily, a feature currently moving across the Central Plains is going to make that happen.

A potent shortwave has begun to swing southeastward into the Central Plains, which has made conditions favorable for the development of a surface low pressure system across eastern Kansas. This low has certainly tapped into Gulf of Mexico moisture, and given favorable dynamics, a shield of rain and thunderstorms currently aligns from Arkansas up through the Central Plains. Persistent cloudiness managed to keep most of those areas under stable conditions today, but enhanced low-level shear and better instability has allowed some storms to become briefly tornadic across southern Missouri and northwestern Arkansas.

The surface low will continue advancing northeastward overnight tonight and tomorrow. There will be a chance for severe thunderstorms across the middle Mississippi Valley, western Tennessee Valley, and as far northward as eastern Iowa, southern Illinois, and southwestern Indiana tomorrow. Once the severe weather threat passes for that region, the current airmass will be replaced with less humid and slightly cooler air by Tuesday morning. The passage of the cold front will continue to advance less humid and cooler air all the way to the East Coast and Gulf coast by Wednesday and Wednesday evening. Eastern Ohio, western Pennsylvania, and regions just south of there may have to be monitored for severe weather chances on Tuesday, given that dynamics will become more conductive and diurnal heating could increase instability.

Surface map for Thursday morning

With the eastward advancement of the Central Plains shortwave combined with another shortwave digging southeastward from Canada, this will result in a longwave trough temporarily becoming established across the eastern United States mid-to-late this week. Thanks to this pattern, a cooler airmass will be further reinforced across the region, and temperatures will get all the way down into the 50s Wednesday and Thursday nights as far south as the northern Gulf coast states and along and just southeast of the Appalachian mountains. Lows in the 50s don’t seem all that impressive in the fall, but during the summer, it’s not too shabby!

Low temperatures Thursday morning

Low temperature anomalies Thursday morning

Make sure you enjoy the cooler weather while it lasts, because a warming trend is expected after this brief taste of fall!

Hector To Impact Hawaii

Hurricane Hector appears it will move close enough to Hawaii to bring gusty winds and heavy rainfall from Tuesday night into early Thursday for parts of the islands (see Fig. 1). At this hour, Hector is a major hurricane (Category 4) with maximum sustained winds of 130 mph. As Hector continues its westward movement, it should remain a hurricane as it approaches the Big Island. This is due to the favorable environmental conditions including the anomalously warm waters in the region (see Fig. 2).

Fig. 1: National Hurricane Center Forecast For Hector

Fig. 2: Current Sea-Surface Temperature Anomalies (Tropical Tidbits)

While Hector is moving westward at this hour. A northerly component to its forward motion is expected early this upcoming week. This is because Hector is moving along the southern periphery of an upper-level high (forcing the westward motion) but the high should slowly weaken as a trough builds southward allowing the northerly component (see Fig. 3). How far north Hector will track is unknown. In the latest advisory, the National Hurricane Center believes the center of Hector will remain just south of the Big Island. With that said, it is possible Hector could make landfall in Hawaii. The average track errors are still close to 150 miles this far out.

Fig. 3: 500mb Geopotential Heights (Tropical Tidbits)

Regardless of landfall, Hector will cause tropical storm conditions for parts of the Big Island and possibly Maui, Moloka’i and O’ahu. Gusty winds of 30-45mph, heavy rain showers, and rough seas are likely. Please remain on high-alert if you’re in Hawaii or have plans to travel to Hawaii this week as just a small northerly jog could bring more severe impacts.

102-Year Sea-Surface Temperature Record Broken

Crowds have been flocking to Southern California beaches this summer, and for good reason. The water temperatures are anomalously warm (see Fig. 1). Ocean temperatures have been well above-average along the Southern California coastline for much of the summer. 80°F+ water temperatures have been reported (San Diego Bay).

Fig. 1: Current SST Anomalies (TropicalTidbits.com)

Earlier this week, the sea-surface temperature (SST) at the Scripps Pier in San Diego, California hit its highest reading in the pier’s 102-year history. According to Scripps Institution of Oceanography, UC San Diego, the SST at the pier was measured was 78.6°F, which broke the previous record of 78.4°F (1931). Scripps Institution of Oceanography, UC San Diego, has measured the SSTs at the pier since 1916 as a part of its scientific research.