Harvey_Boston

Current: Record breaking temperatures and dry conditions across MA today. Looking at water vapor and visible satellite imagery from unysis, some upper level clouds are moving into the area currently. With the dry conditions and cool ocean temperatures still present, a sea breeze has actually set up in Boston which will keep the moisture higher and max temp lower. Further inland, record breaking temperatures are already being recorded according to the NWS in Taunton. In some of the hottest areas, the afternoon relative humidities will be in the mid 20s % which is the justification for the Red Flag Warning currently in place. Precipitation is not expected with these dry conditions.

Surface Observations from http://weather.rap.ucar.edu/surface showing the easterlies associated with the sea breeze in Boston

Short Range: A cold front associated with a surface low in the Great Lakes will move through overnight tonight bringing slightly cooler temperature tomorrow. Again with the dry conditions, precip is not expected with this frontal passage. Temperatures tomorrow are expected to be slightly cooler, however they are still projected to be well above average into the lower 80s. The winds will be westerly behind the front which will eliminate the possibility of Boston seeing another sea breeze. Temperature tomorrow night will be much cooler with overnight closer to average with an upper-level trough settling in the region. Model guidance from ncep is in fairly good agreement with strength and timing of the trough. Wednesday's high temperature will be the coolest of the week with highs in the lower 60s (this is still above average). Thursday will be warmer again as a weak ridge starts to move in into the area.

NAM 850 temp from http://mag.ncep.noaa.gov showing the frontal passage tonight into tomorrow morning

Long Range: The weak ridge keeps temperature warm for the remainder of the week and dry conditions are expected to continue. By the end of the week, a stronger system will move into the eastern U.S. bringing the first chance of rain for MA. Behind it a deep trough is expected to settle in with much colder temperatures. Model confidence is still fairly high this far out with the GEFS showing the the deep trough in somwhat the same position. A few runs keep the trough further west, but the majority move it into the region by 12Z Sunday.

GEFS for 12Z Sunday from http://mag.ncep.noaa.gov

Verification: Even with the weak sea breeze, Boston still broke their record high on the 16th with a temperature of 87F according to the NWS. The sea breeze reached Boston at approximately 14Z on the 16th when the winds changed from predominately S/SW to easterly. As predicted, temperatures inland were warmer than Boston, although just slightly, with some stations reporting highs in the 90s. With dewpoints as low as 45F in the afternoon, relative humidities were around 25% which coupled with fairly strong surface winds especially gusts as high as 30 kts verifies the fire weather hazards that were in place. This information was viewed using the Utah's Mesowest site. The following day Boston reached 84F which was a little warmer than forecasted and no sea breeze was observed. The dry air behind the front which moved through the Boston around 10Z on the 17th warmer up substantially resulting with the highs into the lower 80s. With the very dry air in place behind the cold front, the overnight low temperatures dropped significantly into the lower 50s on the coast and upper 40s inland. Temperatures were also much colder on the 18th and as expected there was no precipitation reported throughout the 16th, 17th and 18th.

Image from mesowest.utah.edu showing the easterlies associated with the sea breeze