Most climate fronts that attain the Northwest coast are typically wimpy.
Solely a slight change in temperature, a minor wind shift, and a modest change in humidity.
Fairly a distinction to the customarily sturdy fronts of the central and jap U.S.
The explanation for our typically unexceptional fronts is two-fold.
First, the fronts reaching our coast are typically aged, declining occluded fronts, in comparison with the prime, lively fronts of the western Pacific. Cyclones and fronts are pushed by giant temperature gradients (modifications of temperature over distance) and a powerful jet stream, one thing that exists over the western Pacific, the place chilly air from Siberia meets the nice and cozy water of the Kuroshio present. Not true off our coast.
Frontal Picture Produced by Dall-E Machine Studying
Second, the temperature modifications throughout our fronts are typically weak as a result of they’ve traveled throughout hundreds of miles of temperate ocean, which progressively warms the chilly air following the fronts (see Pacific sea floor temperature under). Temperature contrasts weaken as a entrance crosses the Pacific, and temperature contrasts, in flip, drive strain and wind contrasts. Thus, our fronts have unremarkable modifications in these parameters.
The outcome: wimpy fronts.
Tomorrow: An Distinctive Entrance
However often, circumstances produce a powerful, landfalling entrance on the Northwest coast and that may occur tomorrow (Wednesday) morning. Let me present you.
A really sturdy entrance will attain the Northwest coast early subsequent morning.
Beneath is the forecast radar picture for 1 AM Wednesday morning. You see the slim, corrugated line off the coast (I put in a crimson arrow to assist)? That’s the entrance. Meteorologists name this a slim chilly frontal rainband, and it possesses intense precipitation and wind shifts.
Three hours later, the entrance will probably be on the coast (see under).
This entrance will probably be related to a well-defined floor trough of low strain and an abrupt shift in winds from southwesterly to northwesterly, as illustrated by the forecast sea degree strain and winds under at 1 AM.
The entrance will savage the coast after which be weakened on the lee (jap) aspect of the Olympics, sparing Puget Sound the worst.
However Puget Sound pays the piper later as sturdy winds push down the Strait creating one other line of heavy rain and wind shift that may transfer into the Sound in the course of the afternoon (see forecast radar picture for two PM under). A Puget Sound convergence zone will then arrange round Seattle after that.
Why is that this entrance going to be so sturdy? As a result of an unusually sturdy slug of very chilly air has been quickly pushed southeastward out of Siberia and Alaska in the direction of our area, drawn southward by a powerful trough of low strain.
Here’s a forecast map of the temperature and winds Wednesday morning at round 10,000 ft (700 hPa strain, blues and purples are the coldest temperatures). You possibly can actually see the chilly, arctic air pushing off our coast. The Arctic will probably be paying us a go to!
The uber-cold air is obvious within the seen satellite tv for pc picture this afternoon (under). The mottled, pop-corn space signifies the chilly air.
Apparently, the temperature distinction with the entrance is stronger at 10,000 ft than on the surface–a actual basic round right here as a result of moderating results of the delicate ocean waters.
Count on a moist/windy day tomorrow west of the Cascade crest, with noticeably cooling temperatures. I could not bike to the UW….
