Desierto norte de Chile

Saturday, January 28, 2012

Woohoo, finally a nice forecast!

The GFS model has *finally*, for the first time this winter, given us a snow forecast here in Maryland that does not appear in the 200+ hr time period! This prediction is the first time the model has shown a solution like this, so we have to wait for subsequent model runs to look for consistency. For comparison, none of the other major models - at least in their a.m. runs from earlier today - showed a solution like this. Regardless, here's the prediction at 144 h, so we'll see how it pans out in 6 days.

Friday, January 20, 2012

Some wintry weather (finally)?

Robust cold air advection has finally set in (it's January 20!), and precipitation will begin falling here by midnight. The combination of the two should give us our first true accumulating wintry precipitation event: up to 1" of snow, then a quick changeover to sleet, then to freezing rain, then finally to rain. By 15Z (10 a.m.) we should be all rain in Annapolis. This will be an interesting event to watch, for several reasons: (1) sleet/freezing rain are less common here than snow or rain; (2) surface cold/dry air is more entrenched than NWP models are predicting (we're at 34F/12F in Annapolis now, which gives a wet-bulb temperature around 25F - plenty cold for freezing/frozen precipitation. Locations to our east and north are similar (34/12 at Cape May, NJ; 36/10 at Ocean City, MD), so it will take a while to advect in warmer air. Thus we'll have to see how things pan out.

Of course I have a flight tomorrow at 11:35 a.m. to New Orleans for the AMS meeting. I expect some delays, but hopefully not an outright cancellation (although with how tight Southwest's flight schedule is, given that my plane will have already likely made 2 take-offs & landings by the time it leaves BWI late-morning, nothing is certain). Here are NAM model predictions of 2m temp, accumulated snow, and composite reflectivity, all valid at 7 a.m.

Wednesday, January 18, 2012

Another paper submitted!

My student co-authors, Sean and Sarah, and I have been busy the past 9 months. Today we submitted the fruits of those labors, a paper to Atmospheric Environment presenting a clear connection between surface ozone and the Madden-Julian Oscillation. I think tonight I'll celebrate a little, but then tomorrow it's back on the treadmill (another grant proposal, meetings about summer activities, etc.) Still it feels good to submit the paper, especially considering the research is a good break from things I have done in the past (PhD, postdoc).

Thursday, January 12, 2012

Not much time below freezing this winter

This winter has been pretty warm. Except for one morning when the temperature plunged to 15F, Annapolis has spent most of the winter above freezing. Using the NOAA tidal gauge station 8575512 data from 01 Dec-12 Jan, Annapolis has been below freezing 50.7 hours (out of a possible 1008 hours), less than 5% of the time. Measuring days when the temperature went below 30F gives far fewer hours: only 27.8 hours below 30F in the past 41 days (an avg of 30 mins/day below 30F). We'll see how the next few days go (the prediction is for some colder air for the next week), but needless to say, the first 1/2 of "meteorological winter" (Dec, Jan, and Feb) has been noticeably warm.

No sign of any snow whatsoever

Since returning from the Dominican Republic a week ago, I've been regularly checking the middle- and long-range forecast models for any hint at winter precipitation. We received a surprise 1/2" of snow on Monday - falling from an upper-level environment clearly supportive of snow, but into a low-level thermal profile that, at least at first glance, wasn't that supportive (sfc temps at precip onset were 36F). Turns out low-level dry air advection (dew point temps 23-25F) allowed just enough wet bulb (evaporative) cooling to bring the surface closer to 33-34F. As soon as precip ended, temperatures returned to near 36F, providing some support for the evaporative cooling scenario.

For getting anything beyond that quick 1/2", though, the long-range forecast is bleak. Both GFS and ECMWF mid- and long-range predictions (out to 240h) bring several surface low pressure systems across the eastern U.S., but always to the west of the Appalachians, placing Annapolis in the "warm sector" of the cyclones and ensuring the precipitation falls as rain.

We'll have to see how the rest of the winter shapes up, but at least for the next 7-10 days, the outlook for significant accumulating snow in the non-mountain mid-Atlantic is bleak.

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