US Weather Commentary

Sub-Tropical Storm Andrea classified off the Southeast U.S. Coast, 4 weeks before Hurricane Season officially starts.

Behind the Headline: In 2002, the National Hurricane Center decided to begin the process of naming Sub-Tropical Storms, which are hybrid storms that derive their energy from baroclinic processes (like Nor'Easters do), but are partially deriving their energy from barotropic processes (warm tropical waters).  The first and only Sub-Tropical Storm to be named, and remain that way throughout its life, was Nicole in October 2004.  Sub-Tropical Storm Ana in April of 2003 eventually transformed info a regular Tropical Storm, and Sub-Tropical Storm #16 was added during post-Season analysis wedged between Stan and Tammy.

Bigger Story:  Andrea was a borderline case to have even been classified in the first place, and she is already dissipating (recently downgraded to Sub-Tropical Depression status) as she meanders off the Georgia and northern Florida Coastlines.  Andrea is a very feeble system, with all her convection pushed off to her eastern flanks, so rains are practically a non-issue.  The most intense consequence from this storm has ironically been fire, not water, with gusty winds literally fanning the wildfire flames across Georgia and northern Florida (with noticeable ash blown all the way down to southwestern Florida).

Off-shore winds promote brief heat across coastal California

Behind the Headline: With a steady, easterly, down-sloping wind flow, subsidence spurred coastal California to warm up briefly this week (San Francisco hit 89°F on Monday and Los Angeles hit 91°F on Tuesday), before quickly dropping back yesterday (San Francisco only managed an afternoon max of 65°F and Los Angeles struggled up to 71°F).

Bigger Story: As has already been the observed case for several weeks now, the Pacific coast marine layer and sea-breeze mechanism will be quite formidable in 2007, providing a predominant cap on shore-line temperatures similar to what we witnessed in 2005 or even 2002 and 2001.  However, the entire State is contending with moderate to extreme drought, so when these rarer wind vectors set up (such as Santa Ana events), temperatures could easily spike substantially.  Another way to characterize this is that the median afternoon temperature throughout a month should be a lot cooler than the mean afternoon temperature throughout a given month.  And those occasionally coastal heat spikes (which inflate the mean) will undoubtedly exacerbate forest/wild/brush fires which their inland counterparts are contending with more routinely.

Forecasting the NWS Forecast:

Today's 8-14 day outlook maps will erode a lot of the below normal temperatures from the Northeast compared to its 6-10 day counterpart. The Gulf Coast is likely to be kept in neutral to below normal forecasts in the 8-14 day outlook. The West will continue to be painted in above normal temperatures.

Re-Included for pertinence:

Do Not confuse May Warmth with Summer Heat for Northern U.S. this year

Spring has sprung, and the temperatures are quite pleasant across much of the Nation, but for the Northern States we must separate above normal May temperatures (and even much above May temperatures), from true Summer heat that tallies up plentiful Cooling Degree Days.

Chilly oceans, lakes and rivers help provide a cap on afternoon temperatures for "coastal" zones along with creating some crisp nights (West Hampton NY fell to 27°F this morning), and Spring 2007 (with the extended Winter) is a textbook case of this. Additionally, soil moisture (regionally very high in 2007) and surface heat fluxes are poorly handled by computer models, as we were dramatically reminded this past Winter. So considering wet ground extracts large amounts of energy from the lower atmosphere (latent heat of Evaporation is 2,500 Joules/gram), it's no wonder that computer models have recently been going overboard, as you end up with a huge hemispheric parameter force largely ignored.

Thanks to a 2007 Winter Season extending into April, Spring will be abbreviated enough and Summer will arrive soon enough.  So focus your attention to the Southern U.S. for early signs of Summer heat for the time being, as others are not making the proper thermodynamic adjustments to the forecasts and quite frankly are anxious for weather headlines.

Regardless of how cool or warm May weather turns out to be for a particular region, remember that May temperatures and the ensuing Summer temperatures are independent of each other: http://www.weather2000.com/nyc.html 

Our Summer research summary highlights:

The combination of severe drought, severe flooding and anomalous hydro-meteorological conditions will make for a very complex mosaic of weather results across the U.S. over the next 6 months.  Unfortunately, the improper attribution of La Niña & El Niño to broad-brushed domestic temperature outcomes by other forecasters has already begun to mislead users in need of accurate climate science.  Our forecast discussions, tables, ENSO Reports and of course Site-Specific analyses, will again help safely guide you through the 2007 Summer chronology, details and warnings.  Below, are some highlights which our research has discovered and concluded to help with your early planning and seasonal mind-set:

• Main theme for 2007 U.S. Summer:  Hotter than Normal (geographic mosaic of Hot-Dry & Hot-Humid)
•  Regions warming the most compared to 2006 (last) Summer:  Mid-West and Mid-Atlantic/Northeast
• Regions cooling the most compared to 2006 (last) Summer: Coastal California and High/Western Plains
• Notable weather reminiscent of 2005:  Periodic cool waves for Northwest and Rockies
• Notable weather reminiscent of 2006:  Drought-induced Heat-spikes for Southeast
• Most undervalued, significant weather parameter for 2007 U.S. Summer:  Humidity/Heat Index

Severe Storms and Drought status:

2007 has impressively been producing both anomalously large Heating Degree Day tallies simultaneously with anomalously large Cooling Degree Day tallies (in the deep South), so when those air masses clash, sparks fly, and the result is (around) an astounding 750 preliminary U.S. tornadoes in 2007 to-date, double the average we're supposed to have at this juncture.  In other cases the severe weather takes the form of concentrated downpours & flash-flooding events (as we have witnessed across the Western Gulf Coast and Southern Plains region. But this often does not translate into widespread saturating rainfall (or the ground can not absorb downpours that fast).  As a consequence, Drought (and corresponding wild fire risk) continues to be an increasing area of concern for 3 main areas we have been monitoring: (1) California/Nevada/Arizona, (2) Wyoming/western Dakotas, and (3) Southeast/Florida Peninsula. Precise storm tracks, rainfall quantity, and intensifying/expanding drought areas will need to be analyzed on a weekly basis in April & May 2007, to determine how they will define or refine Summer weather outcomes.

Special Reports and Tropical Outlooks to look forward to

Please let us know if you'd ever like us to comment on, decipher, explain or debunk any Hurricane research or predictions you may come across from other weather sources, conferences or the Internet.

Later this month, the National Hurricane Center [NHC] will be issuing their own 2007 Atlantic Hurricane Season Outlook, and Colorado State University [CSU] will be issuing the May update to their own outlooks.  As usual, we'll do our best to anticipate what direction we believe they will going, as these outlooks typically garner media attention.

To incorporate some late-breaking Hydro-Meteorological data and research, our latest ENSO Report was released on Thursday May 3rd.  This report updated and detailed our month-by-month Temperature & Precipitation expectations for the upcoming Spring and Summer Seasons. 

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