There are several areas to watch in the Northern Hemisphere tropics today, but the Atlantic and East Pacific both do not have a tropical cyclone active – the first occurrence of such event since July 7. In the Atlantic, a tropical wave has a chance to develop into the Atlantic’s next tropical cyclone, and could end up as a long-tracked storm. In the Eastern Pacific, Invest 91E has become slightly better organized today, but is not very likely to develop into anything significant since conditions are expected to become unfavorable later this week. In the Western Pacific, Typhoon Noru is holding on, and is likely to pose a major threat to Southern Japan and perhaps Eastern South Korea as a strong typhoon.

Atlantic tropical wave has potential to develop into 2017’s first long tracked storm

A tropical wave, currently located near the coast of western Africa, is producing some disorganized showers and thunderstorms. This wave is expected to emerge into the eastern Atlantic Ocean tonight, and has potential to slowly develop over the next several days. NHC gives this wave a 10 percent chance of development within 48 hours, and a 30 percent chance of development within five days. The wave is expected to be in an environment of light to moderate wind shear, and will likely be able to remain south of the strongest Saharan Air Layer (SAL) for the next few days. In addition, a Convectively Coupled Kelvin Wave (CCKW) is currently passing through the Atlantic and this could help the wave’s development. There do not appear to be any major large-scale factors that could suppress development, but the intensity forecast remains very uncertain. The 12z Wednesday ECMWF, UKMET and CMC runs, as well as the 18z Wednesday GFS run, predicted development of this system within the next five days. Over 50% of the 18z GEFS and 12z EPS ensemble members predicted at least slight development. Based on the strong model support and fairly favorable conditions, I give this system a 20 percent chance of development within 48 hours, and a 60 percent chance of development within five days. It is now August, and Atlantic hurricane activity typically sharply rises during this month.

It is too soon to determine that if development occurs where this system will end up in the long range. Quicker development would likely favor a recurve out to sea. Slower development would likely result in the cyclone being closer to the Lesser Antilles islands in about 7-8 days or so. Models disagree on when development will occur. The GFS is slightly slower with development and predicts the wave to develop into a tropical depression in about 96 hours or so. The ECMWF is much faster with development and has the wave rapidly developing into a tropical depression in 48-72 hours. The UKMET model is somewhat in between the two scenarios and develops the wave around 72 hours out.

In addition to this wave, the ECMWF and GFS models have been hinting at the possibility of a broad area of low pressure to develop over the Northwestern Caribbean Sea in about 5-6 days, which could possibly emerge into the Bay of Campeche or Western Gulf of Mexico where tropical cyclogenesis could occur. Many 12z EPS ensemble members also predicted development in this region, with a couple members even showing a hurricane. Although this area has not yet been mentioned in the NHC’s Tropical Weather Outlook, it is worth watching closely early next week. The next two names on the Atlantic naming list are Franklin and Gert.

91E only has a low chance of developing

Invest 91E, an area of showers and thunderstorms over the Eastern Pacific, has become slightly better organized today, but it has some hurdles in developing into a tropical cyclone. As of 18:00 UTC Wednesday, Invest 91E was centered near 12.5°N 99.2°W and was moving west-northwestward at about 15 mph. Maximum sustained winds were 25 knots (30 mph), with an estimated minimum pressure of 1009 mb. 91E has a narrow opportunity of developing into a weak tropical cyclone before conditions are expected to become unfavorable later this week. The disturbance is currently in light to moderate wind shear of about 10-15 knots, over warm sea surface temperatures of near 29°C (84.2°F), and in a moist environment with mid-level relative humidity values of over 75 percent.  However, wind shear is expected to increase to over 20 knots by Friday afternoon, along with cooling sea surface temperatures as the disturbance enters a drier and more stable environment. None of the most recent GFS, ECMWF, or UKMET model runs predicted any development with this system. It is possible that 91E could spin up into a tropical depression or minimal tropical storm by Friday, but anything more seems unlikely. After 91E, global models seem to predict that the East Pacific could be quiet for an extended period of time, which is a positive for development in the Atlantic basin. The next name on the East Pacific naming list is Jova.

Large-eyed Typhoon Noru a major threat to southern Japan this weekend

Typhoon Noru, which has been an active for nearly two weeks now, is posing a major threat to Japan. As of 00:00 UTC Thursday, Typhoon Noru was centered near 27.5°N 134.8°E, and was moving north-northwestward at about 7 mph. Maximum 1-minute sustained winds were estimated at 95 knots (110 mph) with an estimated minimum pressure of 953 mb, equivalent to a strong category 2 hurricane on the Saffir-Simpson Scale. Maximum 10-minute sustained winds from the Japan Meteorological Agency (JMA) at 18:00 UTC Wednesday were slightly lower, at 85 knots (100 mph) with an estimated minimum pressure of 945 mb. The ECMWF and GFS models both predict that Noru will make landfall on Sunday as a strong typhoon. Noru may also pose a threat to Eastern portions of South Korea. While the ECMWF and GFS models both show Noru rapidly intensifying to a super typhoon prior to landfall, the global models are likely overdoing the strength due to their tendency to over-deepen tropical cyclones at high latitudes. Noru’s current structure, consisting of a very large eye, may also limit any rapid intensification before landfall. The official Joint Typhoon Warning Center (JTWC) forecast predicts Noru will make landfall as a Category 3 typhoon, and I think this is far more reasonable.

I will be back tomorrow for another post. Lots to talk about in the coming days!