Tropical Feature: Weekly SSTA Analysis/Trend09/24/2018, 10:26 am EST
Madden Julian Oscillation Phase_1 May Activate Atlantic Tropics09/30/2018, 5:40 pm EST
Highlight: 2 Major Typhoons to Slam Japan Next 2 Weeks
Causes amplified “ridge bridge” Alaska to Siberia
North America result? Snow unloads on Canada
Canada becoming a large source region for early season chill
- Major typhoon 1 & 2 to Japan: Major Typhoon Trami strikes Japan Sep. 30. Another one follows and is expected to strike Japan Oct. 5.
Fig. 1: 2 major typhoons on their way to Japan late SEP/early OCT.
Fig. 2-3: The amplifying upper ridge across Alaska to Siberia caused by 2 West Pacific typhoons (left) and snowfall forecast across Canada the next 15 days beneath a cold upper trough (right).
Fig. 4: The case is made for a cold and snowy early autumn across Canada. Too early for these cold air masses to drop south into U.S.
- Population weight gas HDD forecast: Despite the early cold and snow in Canada and some influence of that cold on the North-Central U.S. the national gas population weight HDD forecast remains warm mainly due to high demand eastern U.S. areas staying warm well into October. The GFS OP indicates what would happen to national HDD count if the Canadian cold air mass released into the U.S. Oct. 5-11 (which is unlikely).
Fig. 5: All models and the gas population weight HDD forecast by CWG through Oct. 11.
- Tropical Disturbance 98L: 98L failed to evolve overnight and is a relatively small area of convection east of North Carolina. This system turns north and northeast the next 2-3 days staying off the U.S. Coastline with limited development potential. Risk of an emerging tropical cyclone is lowered from 50% to 30% by NOAA/NHC.
- NOAA/NHC re-energizes Kirk: Kirk has regained tropical storm status in the central North Atlantic tropics. Kirk moves west and gains some strength the next couple days but once reaching the Caribbean Sea will weaken and likely dissipate in the western Caribbean Sea in 6-7 days. The dissipation in the Caribbean is due to a strong upper atmosphere east wind as implied by a still strong negative phase of the quasi-biennial oscillation.
- Leslie: NOAA/NHC dismissed this subtropical storm in the central North Atlantic a couple days ago. However, a “perfect storm” develops over the next 10 days as the remains of Leslie intensifies due to a cold upper trough entraining tropical moisture. The GFS OP indicates 2 pulses of 970 MB low pressure this weekend and later next week for this likely huge central North Atlantic storm. North of the storm a large high pressure system develops causing a downstream, cold trough to cool off Europe. Another example of late season tropical/subtropical events causing northern hemisphere pattern change.
- Northeast corridor severe storms: NOAA/SPC indicates a severe weather risk across the Northeast Corridor today. Yesterday a streak of damaging wind moved across northern Illinois and through Chicago. A similar somewhat isolated event occurs in the Northeast Corridor today.
Fig. 6: Severe thunderstorms zone forecast across the Northeast Corridor today by NOAA/SPC.
- Frost advisories: The western Dakotas and western Nebraska are under a frost advisory this morning. A freeze warning is issued for northwest Nebraska.